diff --git a/docs/generators/ada-server.md b/docs/generators/ada-server.md
index 9a86032ec7e..7f804ddf0df 100644
--- a/docs/generators/ada-server.md
+++ b/docs/generators/ada-server.md
@@ -7,6 +7,16 @@ sidebar_label: ada-server
 | ------ | ----------- | ------ | ------- |
 |allowUnicodeIdentifiers|boolean, toggles whether unicode identifiers are allowed in names or not, default is false| |false|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
 |projectName|GNAT project name| |defaultProject|
 |sortModelPropertiesByRequiredFlag|Sort model properties to place required parameters before optional parameters.| |true|
diff --git a/docs/generators/ada.md b/docs/generators/ada.md
index 2b382b4c4fc..c5d73461dc2 100644
--- a/docs/generators/ada.md
+++ b/docs/generators/ada.md
@@ -7,6 +7,16 @@ sidebar_label: ada
 | ------ | ----------- | ------ | ------- |
 |allowUnicodeIdentifiers|boolean, toggles whether unicode identifiers are allowed in names or not, default is false| |false|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
 |projectName|GNAT project name| |defaultProject|
 |sortModelPropertiesByRequiredFlag|Sort model properties to place required parameters before optional parameters.| |true|
diff --git a/docs/generators/android.md b/docs/generators/android.md
index 4eeeec214b6..430500d9e6a 100644
--- a/docs/generators/android.md
+++ b/docs/generators/android.md
@@ -15,6 +15,16 @@ sidebar_label: android
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |groupId|groupId for use in the generated build.gradle and pom.xml| |null|
 |invokerPackage|root package for generated code| |null|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |library|library template (sub-template) to use|<dl><dt>**volley**</dt><dd>HTTP client: Volley 1.0.19 (default)</dd><dt>**httpclient**</dt><dd>HTTP client: Apache HttpClient 4.3.6. JSON processing: Gson 2.3.1. IMPORTANT: Android client using HttpClient is not actively maintained and will be depecreated in the next major release.</dd></dl>|null|
 |modelPackage|package for generated models| |null|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
diff --git a/docs/generators/apache2.md b/docs/generators/apache2.md
index cfa9756c7d5..8b92e02dd19 100644
--- a/docs/generators/apache2.md
+++ b/docs/generators/apache2.md
@@ -7,6 +7,16 @@ sidebar_label: apache2
 | ------ | ----------- | ------ | ------- |
 |allowUnicodeIdentifiers|boolean, toggles whether unicode identifiers are allowed in names or not, default is false| |false|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
 |sortModelPropertiesByRequiredFlag|Sort model properties to place required parameters before optional parameters.| |true|
 |sortParamsByRequiredFlag|Sort method arguments to place required parameters before optional parameters.| |true|
diff --git a/docs/generators/apex.md b/docs/generators/apex.md
index 06c54e3b972..80ac5bd24fb 100644
--- a/docs/generators/apex.md
+++ b/docs/generators/apex.md
@@ -10,6 +10,16 @@ sidebar_label: apex
 |buildMethod|The build method for this package.| |null|
 |classPrefix|Prefix for generated classes. Set this to avoid overwriting existing classes in your org.| |null|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |namedCredential|The named credential name for the HTTP callouts| |null|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
 |sortModelPropertiesByRequiredFlag|Sort model properties to place required parameters before optional parameters.| |true|
diff --git a/docs/generators/asciidoc.md b/docs/generators/asciidoc.md
index 66a175518bc..777a62080c7 100644
--- a/docs/generators/asciidoc.md
+++ b/docs/generators/asciidoc.md
@@ -16,6 +16,16 @@ sidebar_label: asciidoc
 |infoEmail|an email address to contact for inquiries about the application| |null|
 |infoUrl|a URL where users can get more information about the application| |null|
 |invokerPackage|root package for generated code| |null|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |licenseInfo|a short description of the license| |null|
 |licenseUrl|a URL pointing to the full license| |null|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
diff --git a/docs/generators/avro-schema.md b/docs/generators/avro-schema.md
index 13ca849949a..6f0621b7477 100644
--- a/docs/generators/avro-schema.md
+++ b/docs/generators/avro-schema.md
@@ -7,6 +7,16 @@ sidebar_label: avro-schema
 | ------ | ----------- | ------ | ------- |
 |allowUnicodeIdentifiers|boolean, toggles whether unicode identifiers are allowed in names or not, default is false| |false|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |packageName|package for generated classes (where supported)| |null|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
 |sortModelPropertiesByRequiredFlag|Sort model properties to place required parameters before optional parameters.| |true|
diff --git a/docs/generators/bash.md b/docs/generators/bash.md
index b91eb990a6d..3d626eff720 100644
--- a/docs/generators/bash.md
+++ b/docs/generators/bash.md
@@ -13,6 +13,16 @@ sidebar_label: bash
 |generateBashCompletion|Whether to generate the Bash completion script| |false|
 |generateZshCompletion|Whether to generate the Zsh completion script| |false|
 |hostEnvironmentVariable|Name of environment variable where host can be defined (e.g. PETSTORE_HOST='http://api.openapitools.org:8080')| |null|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
 |processMarkdown|Convert all Markdown Markup into terminal formatting| |false|
 |scriptName|The name of the script that will be generated (e.g. petstore-cli)| |null|
diff --git a/docs/generators/c.md b/docs/generators/c.md
index ee9b2586696..8ebc3221fae 100644
--- a/docs/generators/c.md
+++ b/docs/generators/c.md
@@ -8,6 +8,16 @@ sidebar_label: c
 |allowUnicodeIdentifiers|boolean, toggles whether unicode identifiers are allowed in names or not, default is false| |false|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |hideGenerationTimestamp|Hides the generation timestamp when files are generated.| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
 |sortModelPropertiesByRequiredFlag|Sort model properties to place required parameters before optional parameters.| |true|
 |sortParamsByRequiredFlag|Sort method arguments to place required parameters before optional parameters.| |true|
diff --git a/docs/generators/clojure.md b/docs/generators/clojure.md
index b2f3a6a4d91..e42936d9f86 100644
--- a/docs/generators/clojure.md
+++ b/docs/generators/clojure.md
@@ -8,6 +8,16 @@ sidebar_label: clojure
 |allowUnicodeIdentifiers|boolean, toggles whether unicode identifiers are allowed in names or not, default is false| |false|
 |baseNamespace|the base/top namespace (Default: generated from projectName)| |null|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
 |projectDescription|description of the project (Default: using info.description or &quot;Client library of &lt;projectName&gt;&quot;)| |null|
 |projectLicenseName|name of the license the project uses (Default: using info.license.name or not included in project.clj)| |null|
diff --git a/docs/generators/cpp-qt5-client.md b/docs/generators/cpp-qt5-client.md
index bc55db14523..9a043e53237 100644
--- a/docs/generators/cpp-qt5-client.md
+++ b/docs/generators/cpp-qt5-client.md
@@ -9,6 +9,16 @@ sidebar_label: cpp-qt5-client
 |contentCompression|Enable Compressed Content Encoding for requests and responses| |false|
 |cppNamespace|C++ namespace (convention: name::space::for::api).| |OpenAPI|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelNamePrefix|Prefix that will be prepended to all model names.| |OAI|
 |optionalProjectFile|Generate client.pri.| |true|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
diff --git a/docs/generators/cpp-qt5-qhttpengine-server.md b/docs/generators/cpp-qt5-qhttpengine-server.md
index 2b2cd4e9f15..574a019f13b 100644
--- a/docs/generators/cpp-qt5-qhttpengine-server.md
+++ b/docs/generators/cpp-qt5-qhttpengine-server.md
@@ -9,6 +9,16 @@ sidebar_label: cpp-qt5-qhttpengine-server
 |contentCompression|Enable Compressed Content Encoding for requests and responses| |false|
 |cppNamespace|C++ namespace (convention: name::space::for::api).| |OpenAPI|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelNamePrefix|Prefix that will be prepended to all model names.| |OAI|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
 |reservedWordPrefix|Prefix to prepend to reserved words in order to avoid conflicts| |r_|
diff --git a/docs/generators/cpp-tizen.md b/docs/generators/cpp-tizen.md
index f805721b577..16022f8f537 100644
--- a/docs/generators/cpp-tizen.md
+++ b/docs/generators/cpp-tizen.md
@@ -7,6 +7,16 @@ sidebar_label: cpp-tizen
 | ------ | ----------- | ------ | ------- |
 |allowUnicodeIdentifiers|boolean, toggles whether unicode identifiers are allowed in names or not, default is false| |false|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
 |reservedWordPrefix|Prefix to prepend to reserved words in order to avoid conflicts| |r_|
 |sortModelPropertiesByRequiredFlag|Sort model properties to place required parameters before optional parameters.| |true|
diff --git a/docs/generators/cwiki.md b/docs/generators/cwiki.md
index f2d5342f8f3..bf7949015bd 100644
--- a/docs/generators/cwiki.md
+++ b/docs/generators/cwiki.md
@@ -15,6 +15,16 @@ sidebar_label: cwiki
 |infoEmail|an email address to contact for inquiries about the application| |null|
 |infoUrl|a URL where users can get more information about the application| |null|
 |invokerPackage|root package for generated code| |null|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |licenseInfo|a short description of the license| |null|
 |licenseUrl|a URL pointing to the full license| |null|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
diff --git a/docs/generators/dart-dio.md b/docs/generators/dart-dio.md
index 05514b9a1e4..fd16331b9a1 100644
--- a/docs/generators/dart-dio.md
+++ b/docs/generators/dart-dio.md
@@ -9,6 +9,16 @@ sidebar_label: dart-dio
 |browserClient|Is the client browser based (for Dart 1.x only)| |null|
 |dateLibrary|Option. Date library to use|<dl><dt>**core**</dt><dd>Dart core library (DateTime)</dd><dt>**timemachine**</dt><dd>Time Machine is date and time library for Flutter, Web, and Server with support for timezones, calendars, cultures, formatting and parsing.</dd></dl>|core|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |nullableFields|Is the null fields should be in the JSON payload| |null|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
 |pubAuthor|Author name in generated pubspec| |null|
diff --git a/docs/generators/dart-jaguar.md b/docs/generators/dart-jaguar.md
index 5e81f82025f..995676b9a13 100644
--- a/docs/generators/dart-jaguar.md
+++ b/docs/generators/dart-jaguar.md
@@ -8,6 +8,16 @@ sidebar_label: dart-jaguar
 |allowUnicodeIdentifiers|boolean, toggles whether unicode identifiers are allowed in names or not, default is false| |false|
 |browserClient|Is the client browser based (for Dart 1.x only)| |null|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |nullableFields|Is the null fields should be in the JSON payload| |null|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
 |pubAuthor|Author name in generated pubspec| |null|
diff --git a/docs/generators/dart.md b/docs/generators/dart.md
index 993c31cf447..7cad220b66e 100644
--- a/docs/generators/dart.md
+++ b/docs/generators/dart.md
@@ -8,6 +8,16 @@ sidebar_label: dart
 |allowUnicodeIdentifiers|boolean, toggles whether unicode identifiers are allowed in names or not, default is false| |false|
 |browserClient|Is the client browser based (for Dart 1.x only)| |null|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
 |pubAuthor|Author name in generated pubspec| |null|
 |pubAuthorEmail|Email address of the author in generated pubspec| |null|
diff --git a/docs/generators/dynamic-html.md b/docs/generators/dynamic-html.md
index b252e414bdc..6d120dd987b 100644
--- a/docs/generators/dynamic-html.md
+++ b/docs/generators/dynamic-html.md
@@ -11,6 +11,16 @@ sidebar_label: dynamic-html
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |groupId|groupId in generated pom.xml| |null|
 |invokerPackage|root package for generated code| |null|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
 |sortModelPropertiesByRequiredFlag|Sort model properties to place required parameters before optional parameters.| |true|
 |sortParamsByRequiredFlag|Sort method arguments to place required parameters before optional parameters.| |true|
diff --git a/docs/generators/elixir.md b/docs/generators/elixir.md
index 14afa95bc9f..9dc1c27d189 100644
--- a/docs/generators/elixir.md
+++ b/docs/generators/elixir.md
@@ -8,6 +8,16 @@ sidebar_label: elixir
 |allowUnicodeIdentifiers|boolean, toggles whether unicode identifiers are allowed in names or not, default is false| |false|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |invokerPackage|The main namespace to use for all classes. e.g. Yay.Pets| |null|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |licenseHeader|The license header to prepend to the top of all source files.| |null|
 |packageName|Elixir package name (convention: lowercase).| |null|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
diff --git a/docs/generators/fsharp-functions.md b/docs/generators/fsharp-functions.md
index a7e28602b33..456a7daaa42 100644
--- a/docs/generators/fsharp-functions.md
+++ b/docs/generators/fsharp-functions.md
@@ -7,6 +7,16 @@ sidebar_label: fsharp-functions
 | ------ | ----------- | ------ | ------- |
 |allowUnicodeIdentifiers|boolean, toggles whether unicode identifiers are allowed in names or not, default is false| |false|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |licenseName|The name of the license| |NoLicense|
 |licenseUrl|The URL of the license| |http://localhost|
 |packageAuthors|Specifies Authors property in the .NET Core project file.| |OpenAPI|
diff --git a/docs/generators/groovy.md b/docs/generators/groovy.md
index 32699d5a12c..dbdec260313 100644
--- a/docs/generators/groovy.md
+++ b/docs/generators/groovy.md
@@ -25,6 +25,16 @@ sidebar_label: groovy
 |hideGenerationTimestamp|Hides the generation timestamp when files are generated.| |false|
 |invokerPackage|root package for generated code| |org.openapitools.api|
 |java8|Option. Use Java8 classes instead of third party equivalents|<dl><dt>**true**</dt><dd>Use Java 8 classes such as Base64</dd><dt>**false**</dt><dd>Various third party libraries as needed</dd></dl>|false|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |licenseName|The name of the license| |Unlicense|
 |licenseUrl|The URL of the license| |http://unlicense.org|
 |modelPackage|package for generated models| |org.openapitools.model|
diff --git a/docs/generators/haskell-http-client.md b/docs/generators/haskell-http-client.md
index 41163e8fa88..9b9a848ae68 100644
--- a/docs/generators/haskell-http-client.md
+++ b/docs/generators/haskell-http-client.md
@@ -24,6 +24,16 @@ sidebar_label: haskell-http-client
 |generateModelConstructors|Generate smart constructors (only supply required fields) for models| |true|
 |hideGenerationTimestamp|Hides the generation timestamp when files are generated.| |true|
 |inlineMimeTypes|Inline (hardcode) the content-type and accept parameters on operations, when there is only 1 option| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelDeriving|Additional classes to include in the deriving() clause of Models| |null|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
 |requestType|Set the name of the type used to generate requests| |null|
diff --git a/docs/generators/haskell.md b/docs/generators/haskell.md
index 2e35a073d89..6bb19ea0f86 100644
--- a/docs/generators/haskell.md
+++ b/docs/generators/haskell.md
@@ -8,6 +8,16 @@ sidebar_label: haskell
 |allowUnicodeIdentifiers|boolean, toggles whether unicode identifiers are allowed in names or not, default is false| |false|
 |apiPackage|package for generated api classes| |null|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelPackage|package for generated models| |null|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
 |serveStatic|serve will serve files from the directory 'static'.| |true|
diff --git a/docs/generators/html.md b/docs/generators/html.md
index 78cef65b33b..dd8c9fa9d65 100644
--- a/docs/generators/html.md
+++ b/docs/generators/html.md
@@ -15,6 +15,16 @@ sidebar_label: html
 |infoEmail|an email address to contact for inquiries about the application| |null|
 |infoUrl|a URL where users can get more information about the application| |null|
 |invokerPackage|root package for generated code| |null|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |licenseInfo|a short description of the license| |null|
 |licenseUrl|a URL pointing to the full license| |null|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
diff --git a/docs/generators/html2.md b/docs/generators/html2.md
index 51d39c72a7d..7201bdc2496 100644
--- a/docs/generators/html2.md
+++ b/docs/generators/html2.md
@@ -15,6 +15,16 @@ sidebar_label: html2
 |infoEmail|an email address to contact for inquiries about the application| |null|
 |infoUrl|a URL where users can get more information about the application| |null|
 |invokerPackage|root package for generated code| |null|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |licenseInfo|a short description of the license| |null|
 |licenseUrl|a URL pointing to the full license| |null|
 |packageName|C# package name| |null|
diff --git a/docs/generators/java-inflector.md b/docs/generators/java-inflector.md
index f34df4d7a13..4d9c6bfe7e4 100644
--- a/docs/generators/java-inflector.md
+++ b/docs/generators/java-inflector.md
@@ -27,6 +27,16 @@ sidebar_label: java-inflector
 |hideGenerationTimestamp|Hides the generation timestamp when files are generated.| |false|
 |invokerPackage|root package for generated code| |org.openapitools.controllers|
 |java8|Option. Use Java8 classes instead of third party equivalents|<dl><dt>**true**</dt><dd>Use Java 8 classes such as Base64</dd><dt>**false**</dt><dd>Various third party libraries as needed</dd></dl>|false|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |licenseName|The name of the license| |Unlicense|
 |licenseUrl|The URL of the license| |http://unlicense.org|
 |modelPackage|package for generated models| |org.openapitools.model|
diff --git a/docs/generators/java-msf4j.md b/docs/generators/java-msf4j.md
index 27017264e1c..bedc76b14d8 100644
--- a/docs/generators/java-msf4j.md
+++ b/docs/generators/java-msf4j.md
@@ -28,6 +28,16 @@ sidebar_label: java-msf4j
 |implFolder|folder for generated implementation code| |src/main/java|
 |invokerPackage|root package for generated code| |org.openapitools.api|
 |java8|Option. Use Java8 classes instead of third party equivalents|<dl><dt>**true**</dt><dd>Use Java 8 classes such as Base64</dd><dt>**false**</dt><dd>Various third party libraries as needed</dd></dl>|false|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |library|library template (sub-template)|<dl><dt>**jersey1**</dt><dd>Jersey core 1.x</dd><dt>**jersey2**</dt><dd>Jersey core 2.x</dd></dl>|jersey2|
 |licenseName|The name of the license| |Unlicense|
 |licenseUrl|The URL of the license| |http://unlicense.org|
diff --git a/docs/generators/java-pkmst.md b/docs/generators/java-pkmst.md
index c8df6eb8872..95b92bbb111 100644
--- a/docs/generators/java-pkmst.md
+++ b/docs/generators/java-pkmst.md
@@ -29,6 +29,16 @@ sidebar_label: java-pkmst
 |hideGenerationTimestamp|Hides the generation timestamp when files are generated.| |false|
 |invokerPackage|root package for generated code| |com.prokarma.pkmst.controller|
 |java8|Option. Use Java8 classes instead of third party equivalents|<dl><dt>**true**</dt><dd>Use Java 8 classes such as Base64</dd><dt>**false**</dt><dd>Various third party libraries as needed</dd></dl>|false|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |licenseName|The name of the license| |Unlicense|
 |licenseUrl|The URL of the license| |http://unlicense.org|
 |modelPackage|package for generated models| |com.prokarma.pkmst.model|
diff --git a/docs/generators/java-play-framework.md b/docs/generators/java-play-framework.md
index 3066a14a722..6801838e4a4 100644
--- a/docs/generators/java-play-framework.md
+++ b/docs/generators/java-play-framework.md
@@ -31,6 +31,16 @@ sidebar_label: java-play-framework
 |hideGenerationTimestamp|Hides the generation timestamp when files are generated.| |false|
 |invokerPackage|root package for generated code| |org.openapitools.api|
 |java8|Option. Use Java8 classes instead of third party equivalents|<dl><dt>**true**</dt><dd>Use Java 8 classes such as Base64</dd><dt>**false**</dt><dd>Various third party libraries as needed</dd></dl>|false|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |licenseName|The name of the license| |Unlicense|
 |licenseUrl|The URL of the license| |http://unlicense.org|
 |modelPackage|package for generated models| |apimodels|
diff --git a/docs/generators/java-undertow-server.md b/docs/generators/java-undertow-server.md
index 34544a236c3..94bf4e39cc1 100644
--- a/docs/generators/java-undertow-server.md
+++ b/docs/generators/java-undertow-server.md
@@ -27,6 +27,16 @@ sidebar_label: java-undertow-server
 |hideGenerationTimestamp|Hides the generation timestamp when files are generated.| |false|
 |invokerPackage|root package for generated code| |org.openapitools.handler|
 |java8|Option. Use Java8 classes instead of third party equivalents|<dl><dt>**true**</dt><dd>Use Java 8 classes such as Base64</dd><dt>**false**</dt><dd>Various third party libraries as needed</dd></dl>|false|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |licenseName|The name of the license| |Unlicense|
 |licenseUrl|The URL of the license| |http://unlicense.org|
 |modelPackage|package for generated models| |null|
diff --git a/docs/generators/java-vertx-web.md b/docs/generators/java-vertx-web.md
index cd6c3ee4e9e..a3fff510386 100644
--- a/docs/generators/java-vertx-web.md
+++ b/docs/generators/java-vertx-web.md
@@ -27,6 +27,16 @@ sidebar_label: java-vertx-web
 |hideGenerationTimestamp|Hides the generation timestamp when files are generated.| |false|
 |invokerPackage|root package for generated code| |org.openapitools.vertxweb.server|
 |java8|Option. Use Java8 classes instead of third party equivalents|<dl><dt>**true**</dt><dd>Use Java 8 classes such as Base64</dd><dt>**false**</dt><dd>Various third party libraries as needed</dd></dl>|false|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |licenseName|The name of the license| |Unlicense|
 |licenseUrl|The URL of the license| |http://unlicense.org|
 |modelPackage|package for generated models| |org.openapitools.vertxweb.server.model|
diff --git a/docs/generators/java-vertx.md b/docs/generators/java-vertx.md
index 58c68915ade..13e7bb94c42 100644
--- a/docs/generators/java-vertx.md
+++ b/docs/generators/java-vertx.md
@@ -27,6 +27,16 @@ sidebar_label: java-vertx
 |hideGenerationTimestamp|Hides the generation timestamp when files are generated.| |false|
 |invokerPackage|root package for generated code| |org.openapitools|
 |java8|Option. Use Java8 classes instead of third party equivalents|<dl><dt>**true**</dt><dd>Use Java 8 classes such as Base64</dd><dt>**false**</dt><dd>Various third party libraries as needed</dd></dl>|false|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |licenseName|The name of the license| |Unlicense|
 |licenseUrl|The URL of the license| |http://unlicense.org|
 |modelPackage|package for generated models| |org.openapitools.server.api.model|
diff --git a/docs/generators/java.md b/docs/generators/java.md
index 8cdcd9dc4e3..289ad440509 100644
--- a/docs/generators/java.md
+++ b/docs/generators/java.md
@@ -29,6 +29,16 @@ sidebar_label: java
 |hideGenerationTimestamp|Hides the generation timestamp when files are generated.| |false|
 |invokerPackage|root package for generated code| |org.openapitools.client|
 |java8|Option. Use Java8 classes instead of third party equivalents|<dl><dt>**true**</dt><dd>Use Java 8 classes such as Base64</dd><dt>**false**</dt><dd>Various third party libraries as needed</dd></dl>|false|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |library|library template (sub-template) to use|<dl><dt>**jersey1**</dt><dd>HTTP client: Jersey client 1.19.x. JSON processing: Jackson 2.9.x. Enable Java6 support using '-DsupportJava6=true'. Enable gzip request encoding using '-DuseGzipFeature=true'. IMPORTANT NOTE: jersey 1.x is no longer actively maintained so please upgrade to 'jersey2' or other HTTP libaries instead.</dd><dt>**jersey2**</dt><dd>HTTP client: Jersey client 2.25.1. JSON processing: Jackson 2.9.x</dd><dt>**jersey2-experimental**</dt><dd>HTTP client: Jersey client 2.25.1. JSON processing: Jackson 2.9.x</dd><dt>**feign**</dt><dd>HTTP client: OpenFeign 9.x (deprecated) or 10.x (default). JSON processing: Jackson 2.9.x.</dd><dt>**okhttp-gson**</dt><dd>[DEFAULT] HTTP client: OkHttp 3.x. JSON processing: Gson 2.8.x. Enable Parcelable models on Android using '-DparcelableModel=true'. Enable gzip request encoding using '-DuseGzipFeature=true'.</dd><dt>**retrofit**</dt><dd>HTTP client: OkHttp 2.x. JSON processing: Gson 2.x (Retrofit 1.9.0). IMPORTANT NOTE: retrofit1.x is no longer actively maintained so please upgrade to 'retrofit2' instead.</dd><dt>**retrofit2**</dt><dd>HTTP client: OkHttp 3.x. JSON processing: Gson 2.x (Retrofit 2.3.0). Enable the RxJava adapter using '-DuseRxJava[2]=true'. (RxJava 1.x or 2.x)</dd><dt>**resttemplate**</dt><dd>HTTP client: Spring RestTemplate 4.x. JSON processing: Jackson 2.9.x</dd><dt>**webclient**</dt><dd>HTTP client: Spring WebClient 5.x. JSON processing: Jackson 2.9.x</dd><dt>**resteasy**</dt><dd>HTTP client: Resteasy client 3.x. JSON processing: Jackson 2.9.x</dd><dt>**vertx**</dt><dd>HTTP client: VertX client 3.x. JSON processing: Jackson 2.9.x</dd><dt>**google-api-client**</dt><dd>HTTP client: Google API client 1.x. JSON processing: Jackson 2.9.x</dd><dt>**rest-assured**</dt><dd>HTTP client: rest-assured : 4.x. JSON processing: Gson 2.x or Jackson 2.10.x. Only for Java 8</dd><dt>**native**</dt><dd>HTTP client: Java native HttpClient. JSON processing: Jackson 2.9.x. Only for Java11+</dd><dt>**microprofile**</dt><dd>HTTP client: Microprofile client X.x. JSON processing: Jackson 2.9.x</dd></dl>|okhttp-gson|
 |licenseName|The name of the license| |Unlicense|
 |licenseUrl|The URL of the license| |http://unlicense.org|
diff --git a/docs/generators/javascript-apollo.md b/docs/generators/javascript-apollo.md
index 44cad073fd8..51a0421dcd7 100644
--- a/docs/generators/javascript-apollo.md
+++ b/docs/generators/javascript-apollo.md
@@ -11,6 +11,16 @@ sidebar_label: javascript-apollo
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |hideGenerationTimestamp|Hides the generation timestamp when files are generated.| |true|
 |invokerPackage|root package for generated code| |null|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |licenseName|name of the license the project uses (Default: using info.license.name)| |null|
 |modelPackage|package for generated models| |null|
 |modelPropertyNaming|Naming convention for the property: 'camelCase', 'PascalCase', 'snake_case' and 'original', which keeps the original name| |camelCase|
diff --git a/docs/generators/javascript-closure-angular.md b/docs/generators/javascript-closure-angular.md
index 89b3bd9b0ff..4cf42f33a9c 100644
--- a/docs/generators/javascript-closure-angular.md
+++ b/docs/generators/javascript-closure-angular.md
@@ -8,6 +8,16 @@ sidebar_label: javascript-closure-angular
 |allowUnicodeIdentifiers|boolean, toggles whether unicode identifiers are allowed in names or not, default is false| |false|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |hideGenerationTimestamp|Hides the generation timestamp when files are generated.| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
 |sortModelPropertiesByRequiredFlag|Sort model properties to place required parameters before optional parameters.| |true|
 |sortParamsByRequiredFlag|Sort method arguments to place required parameters before optional parameters.| |true|
diff --git a/docs/generators/javascript-flowtyped.md b/docs/generators/javascript-flowtyped.md
index 6ecd6654d10..8efe8bba9be 100644
--- a/docs/generators/javascript-flowtyped.md
+++ b/docs/generators/javascript-flowtyped.md
@@ -9,6 +9,16 @@ sidebar_label: javascript-flowtyped
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |enumNameSuffix|Suffix that will be appended to all enum names. A special 'v4-compat' value enables the backward-compatible behavior (as pre v4.2.3)| |v4-compat|
 |enumPropertyNaming|Naming convention for enum properties: 'camelCase', 'PascalCase', 'snake_case', 'UPPERCASE', and 'original'| |PascalCase|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelPropertyNaming|Naming convention for the property: 'camelCase', 'PascalCase', 'snake_case' and 'original', which keeps the original name. Only change it if you provide your own run-time code for (de-)serialization of models| |original|
 |npmName|The name under which you want to publish generated npm package. Required to generate a full package| |null|
 |npmRepository|Use this property to set an url your private npmRepo in the package.json| |null|
diff --git a/docs/generators/javascript.md b/docs/generators/javascript.md
index 1181fffa500..139499823d6 100644
--- a/docs/generators/javascript.md
+++ b/docs/generators/javascript.md
@@ -12,6 +12,16 @@ sidebar_label: javascript
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |hideGenerationTimestamp|Hides the generation timestamp when files are generated.| |true|
 |invokerPackage|root package for generated code| |null|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |licenseName|name of the license the project uses (Default: using info.license.name)| |null|
 |modelPackage|package for generated models| |null|
 |modelPropertyNaming|Naming convention for the property: 'camelCase', 'PascalCase', 'snake_case' and 'original', which keeps the original name| |camelCase|
diff --git a/docs/generators/jaxrs-cxf-cdi.md b/docs/generators/jaxrs-cxf-cdi.md
index ccd6d823c1e..13378c21444 100644
--- a/docs/generators/jaxrs-cxf-cdi.md
+++ b/docs/generators/jaxrs-cxf-cdi.md
@@ -31,6 +31,16 @@ sidebar_label: jaxrs-cxf-cdi
 |interfaceOnly|Whether to generate only API interface stubs without the server files.| |false|
 |invokerPackage|root package for generated code| |org.openapitools.api|
 |java8|Option. Use Java8 classes instead of third party equivalents|<dl><dt>**true**</dt><dd>Use Java 8 classes such as Base64</dd><dt>**false**</dt><dd>Various third party libraries as needed</dd></dl>|false|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |library|library template (sub-template)|<dl><dt>**&lt;default&gt;**</dt><dd>JAXRS spec only, to be deployed in an app server (TomEE, JBoss, WLS, ...)</dd><dt>**quarkus**</dt><dd>Server using Quarkus</dd><dt>**thorntail**</dt><dd>Server using Thorntail</dd><dt>**openliberty**</dt><dd>Server using Open Liberty</dd><dt>**helidon**</dt><dd>Server using Helidon</dd></dl>|&lt;default&gt;|
 |licenseName|The name of the license| |Unlicense|
 |licenseUrl|The URL of the license| |http://unlicense.org|
diff --git a/docs/generators/jaxrs-cxf-client.md b/docs/generators/jaxrs-cxf-client.md
index 0d1c841f153..052caa1f292 100644
--- a/docs/generators/jaxrs-cxf-client.md
+++ b/docs/generators/jaxrs-cxf-client.md
@@ -27,6 +27,16 @@ sidebar_label: jaxrs-cxf-client
 |hideGenerationTimestamp|Hides the generation timestamp when files are generated.| |false|
 |invokerPackage|root package for generated code| |org.openapitools.api|
 |java8|Option. Use Java8 classes instead of third party equivalents|<dl><dt>**true**</dt><dd>Use Java 8 classes such as Base64</dd><dt>**false**</dt><dd>Various third party libraries as needed</dd></dl>|false|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |licenseName|The name of the license| |Unlicense|
 |licenseUrl|The URL of the license| |http://unlicense.org|
 |modelPackage|package for generated models| |org.openapitools.model|
diff --git a/docs/generators/jaxrs-cxf-extended.md b/docs/generators/jaxrs-cxf-extended.md
index b83a1d55e4f..28756d164f8 100644
--- a/docs/generators/jaxrs-cxf-extended.md
+++ b/docs/generators/jaxrs-cxf-extended.md
@@ -34,6 +34,16 @@ sidebar_label: jaxrs-cxf-extended
 |implFolder|folder for generated implementation code| |src/main/java|
 |invokerPackage|root package for generated code| |org.openapitools.api|
 |java8|Option. Use Java8 classes instead of third party equivalents|<dl><dt>**true**</dt><dd>Use Java 8 classes such as Base64</dd><dt>**false**</dt><dd>Various third party libraries as needed</dd></dl>|false|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |licenseName|The name of the license| |Unlicense|
 |licenseUrl|The URL of the license| |http://unlicense.org|
 |loadTestDataFromFile|Load test data from a generated JSON file| |false|
diff --git a/docs/generators/jaxrs-cxf.md b/docs/generators/jaxrs-cxf.md
index d3dd5e44826..343374b3c24 100644
--- a/docs/generators/jaxrs-cxf.md
+++ b/docs/generators/jaxrs-cxf.md
@@ -33,6 +33,16 @@ sidebar_label: jaxrs-cxf
 |implFolder|folder for generated implementation code| |src/main/java|
 |invokerPackage|root package for generated code| |org.openapitools.api|
 |java8|Option. Use Java8 classes instead of third party equivalents|<dl><dt>**true**</dt><dd>Use Java 8 classes such as Base64</dd><dt>**false**</dt><dd>Various third party libraries as needed</dd></dl>|false|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |licenseName|The name of the license| |Unlicense|
 |licenseUrl|The URL of the license| |http://unlicense.org|
 |modelPackage|package for generated models| |org.openapitools.model|
diff --git a/docs/generators/jaxrs-jersey.md b/docs/generators/jaxrs-jersey.md
index 9183a75d65f..ef5a852acf6 100644
--- a/docs/generators/jaxrs-jersey.md
+++ b/docs/generators/jaxrs-jersey.md
@@ -28,6 +28,16 @@ sidebar_label: jaxrs-jersey
 |implFolder|folder for generated implementation code| |src/main/java|
 |invokerPackage|root package for generated code| |org.openapitools.api|
 |java8|Option. Use Java8 classes instead of third party equivalents|<dl><dt>**true**</dt><dd>Use Java 8 classes such as Base64</dd><dt>**false**</dt><dd>Various third party libraries as needed</dd></dl>|false|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |library|library template (sub-template)|<dl><dt>**jersey1**</dt><dd>Jersey core 1.x</dd><dt>**jersey2**</dt><dd>Jersey core 2.x</dd></dl>|jersey2|
 |licenseName|The name of the license| |Unlicense|
 |licenseUrl|The URL of the license| |http://unlicense.org|
diff --git a/docs/generators/jaxrs-resteasy-eap.md b/docs/generators/jaxrs-resteasy-eap.md
index 3a7623db679..1d5f312382e 100644
--- a/docs/generators/jaxrs-resteasy-eap.md
+++ b/docs/generators/jaxrs-resteasy-eap.md
@@ -29,6 +29,16 @@ sidebar_label: jaxrs-resteasy-eap
 |implFolder|folder for generated implementation code| |src/main/java|
 |invokerPackage|root package for generated code| |org.openapitools.api|
 |java8|Option. Use Java8 classes instead of third party equivalents|<dl><dt>**true**</dt><dd>Use Java 8 classes such as Base64</dd><dt>**false**</dt><dd>Various third party libraries as needed</dd></dl>|false|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |licenseName|The name of the license| |Unlicense|
 |licenseUrl|The URL of the license| |http://unlicense.org|
 |modelPackage|package for generated models| |org.openapitools.model|
diff --git a/docs/generators/jaxrs-resteasy.md b/docs/generators/jaxrs-resteasy.md
index 724c15e9289..60e52043dc4 100644
--- a/docs/generators/jaxrs-resteasy.md
+++ b/docs/generators/jaxrs-resteasy.md
@@ -29,6 +29,16 @@ sidebar_label: jaxrs-resteasy
 |implFolder|folder for generated implementation code| |src/main/java|
 |invokerPackage|root package for generated code| |org.openapitools.api|
 |java8|Option. Use Java8 classes instead of third party equivalents|<dl><dt>**true**</dt><dd>Use Java 8 classes such as Base64</dd><dt>**false**</dt><dd>Various third party libraries as needed</dd></dl>|false|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |licenseName|The name of the license| |Unlicense|
 |licenseUrl|The URL of the license| |http://unlicense.org|
 |modelPackage|package for generated models| |org.openapitools.model|
diff --git a/docs/generators/jaxrs-spec.md b/docs/generators/jaxrs-spec.md
index 3bd0accada9..98cbb0c96c3 100644
--- a/docs/generators/jaxrs-spec.md
+++ b/docs/generators/jaxrs-spec.md
@@ -31,6 +31,16 @@ sidebar_label: jaxrs-spec
 |interfaceOnly|Whether to generate only API interface stubs without the server files.| |false|
 |invokerPackage|root package for generated code| |org.openapitools.api|
 |java8|Option. Use Java8 classes instead of third party equivalents|<dl><dt>**true**</dt><dd>Use Java 8 classes such as Base64</dd><dt>**false**</dt><dd>Various third party libraries as needed</dd></dl>|false|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |library|library template (sub-template)|<dl><dt>**&lt;default&gt;**</dt><dd>JAXRS spec only, to be deployed in an app server (TomEE, JBoss, WLS, ...)</dd><dt>**quarkus**</dt><dd>Server using Quarkus</dd><dt>**thorntail**</dt><dd>Server using Thorntail</dd><dt>**openliberty**</dt><dd>Server using Open Liberty</dd><dt>**helidon**</dt><dd>Server using Helidon</dd></dl>|&lt;default&gt;|
 |licenseName|The name of the license| |Unlicense|
 |licenseUrl|The URL of the license| |http://unlicense.org|
diff --git a/docs/generators/jmeter.md b/docs/generators/jmeter.md
index 142f826d793..e8cbb38e5fd 100644
--- a/docs/generators/jmeter.md
+++ b/docs/generators/jmeter.md
@@ -7,6 +7,16 @@ sidebar_label: jmeter
 | ------ | ----------- | ------ | ------- |
 |allowUnicodeIdentifiers|boolean, toggles whether unicode identifiers are allowed in names or not, default is false| |false|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
 |sortModelPropertiesByRequiredFlag|Sort model properties to place required parameters before optional parameters.| |true|
 |sortParamsByRequiredFlag|Sort method arguments to place required parameters before optional parameters.| |true|
diff --git a/docs/generators/k6.md b/docs/generators/k6.md
index 4ff51c7527f..2f6d321b14f 100644
--- a/docs/generators/k6.md
+++ b/docs/generators/k6.md
@@ -7,6 +7,16 @@ sidebar_label: k6
 | ------ | ----------- | ------ | ------- |
 |allowUnicodeIdentifiers|boolean, toggles whether unicode identifiers are allowed in names or not, default is false| |false|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
 |sortModelPropertiesByRequiredFlag|Sort model properties to place required parameters before optional parameters.| |true|
 |sortParamsByRequiredFlag|Sort method arguments to place required parameters before optional parameters.| |true|
diff --git a/docs/generators/markdown.md b/docs/generators/markdown.md
index 2cba7bc698e..465504f6944 100644
--- a/docs/generators/markdown.md
+++ b/docs/generators/markdown.md
@@ -7,6 +7,16 @@ sidebar_label: markdown
 | ------ | ----------- | ------ | ------- |
 |allowUnicodeIdentifiers|boolean, toggles whether unicode identifiers are allowed in names or not, default is false| |false|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
 |sortModelPropertiesByRequiredFlag|Sort model properties to place required parameters before optional parameters.| |true|
 |sortParamsByRequiredFlag|Sort method arguments to place required parameters before optional parameters.| |true|
diff --git a/docs/generators/nim.md b/docs/generators/nim.md
index 61ba1d00f1f..0340561b620 100644
--- a/docs/generators/nim.md
+++ b/docs/generators/nim.md
@@ -7,6 +7,16 @@ sidebar_label: nim
 | ------ | ----------- | ------ | ------- |
 |allowUnicodeIdentifiers|boolean, toggles whether unicode identifiers are allowed in names or not, default is false| |false|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
 |sortModelPropertiesByRequiredFlag|Sort model properties to place required parameters before optional parameters.| |true|
 |sortParamsByRequiredFlag|Sort method arguments to place required parameters before optional parameters.| |true|
diff --git a/docs/generators/nodejs-express-server.md b/docs/generators/nodejs-express-server.md
index 76b0893f9a3..8cc7b8af1fc 100644
--- a/docs/generators/nodejs-express-server.md
+++ b/docs/generators/nodejs-express-server.md
@@ -7,6 +7,16 @@ sidebar_label: nodejs-express-server
 | ------ | ----------- | ------ | ------- |
 |allowUnicodeIdentifiers|boolean, toggles whether unicode identifiers are allowed in names or not, default is false| |false|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
 |serverPort|TCP port to listen on.| |null|
 |sortModelPropertiesByRequiredFlag|Sort model properties to place required parameters before optional parameters.| |true|
diff --git a/docs/generators/nodejs-server-deprecated.md b/docs/generators/nodejs-server-deprecated.md
index 84a3b131943..b2b09ce303c 100644
--- a/docs/generators/nodejs-server-deprecated.md
+++ b/docs/generators/nodejs-server-deprecated.md
@@ -9,6 +9,16 @@ sidebar_label: nodejs-server-deprecated
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |exportedName|When the generated code will be deployed to Google Cloud Functions, this option can be used to update the name of the exported function. By default, it refers to the basePath. This does not affect normal standalone nodejs server code.| |null|
 |googleCloudFunctions|When specified, it will generate the code which runs within Google Cloud Functions instead of standalone Node.JS server. See https://cloud.google.com/functions/docs/quickstart for the details of how to deploy the generated code.| |false|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
 |serverPort|TCP port to listen on.| |null|
 |sortModelPropertiesByRequiredFlag|Sort model properties to place required parameters before optional parameters.| |true|
diff --git a/docs/generators/ocaml.md b/docs/generators/ocaml.md
index d8cda30ed80..ab9a3bd7fd1 100644
--- a/docs/generators/ocaml.md
+++ b/docs/generators/ocaml.md
@@ -7,6 +7,16 @@ sidebar_label: ocaml
 | ------ | ----------- | ------ | ------- |
 |allowUnicodeIdentifiers|boolean, toggles whether unicode identifiers are allowed in names or not, default is false| |false|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
 |sortModelPropertiesByRequiredFlag|Sort model properties to place required parameters before optional parameters.| |true|
 |sortParamsByRequiredFlag|Sort method arguments to place required parameters before optional parameters.| |true|
diff --git a/docs/generators/openapi-yaml.md b/docs/generators/openapi-yaml.md
index 7eda9d44be0..3d7b5af1603 100644
--- a/docs/generators/openapi-yaml.md
+++ b/docs/generators/openapi-yaml.md
@@ -7,6 +7,16 @@ sidebar_label: openapi-yaml
 | ------ | ----------- | ------ | ------- |
 |allowUnicodeIdentifiers|boolean, toggles whether unicode identifiers are allowed in names or not, default is false| |false|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |outputFile|Output filename| |openapi/openapi.yaml|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
 |sortModelPropertiesByRequiredFlag|Sort model properties to place required parameters before optional parameters.| |true|
diff --git a/docs/generators/openapi.md b/docs/generators/openapi.md
index 5d46dccf4fd..7625d70cb8b 100644
--- a/docs/generators/openapi.md
+++ b/docs/generators/openapi.md
@@ -7,6 +7,16 @@ sidebar_label: openapi
 | ------ | ----------- | ------ | ------- |
 |allowUnicodeIdentifiers|boolean, toggles whether unicode identifiers are allowed in names or not, default is false| |false|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
 |sortModelPropertiesByRequiredFlag|Sort model properties to place required parameters before optional parameters.| |true|
 |sortParamsByRequiredFlag|Sort method arguments to place required parameters before optional parameters.| |true|
diff --git a/docs/generators/php-laravel.md b/docs/generators/php-laravel.md
index 57b9191b601..e2bbcaaab03 100644
--- a/docs/generators/php-laravel.md
+++ b/docs/generators/php-laravel.md
@@ -10,6 +10,16 @@ sidebar_label: php-laravel
 |artifactVersion|The version to use in the composer package version field. e.g. 1.2.3| |null|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |invokerPackage|The main namespace to use for all classes. e.g. Yay\Pets| |null|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelPackage|package for generated models| |null|
 |packageName|The main package name for classes. e.g. GeneratedPetstore| |null|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
diff --git a/docs/generators/php-lumen.md b/docs/generators/php-lumen.md
index 2414dda65c7..1e69867a13a 100644
--- a/docs/generators/php-lumen.md
+++ b/docs/generators/php-lumen.md
@@ -10,6 +10,16 @@ sidebar_label: php-lumen
 |artifactVersion|The version to use in the composer package version field. e.g. 1.2.3| |null|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |invokerPackage|The main namespace to use for all classes. e.g. Yay\Pets| |null|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelPackage|package for generated models| |null|
 |packageName|The main package name for classes. e.g. GeneratedPetstore| |null|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
diff --git a/docs/generators/php-silex.md b/docs/generators/php-silex.md
index 81f5e6cb38c..2557c8f1516 100644
--- a/docs/generators/php-silex.md
+++ b/docs/generators/php-silex.md
@@ -7,6 +7,16 @@ sidebar_label: php-silex
 | ------ | ----------- | ------ | ------- |
 |allowUnicodeIdentifiers|boolean, toggles whether unicode identifiers are allowed in names or not, default is false| |false|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
 |sortModelPropertiesByRequiredFlag|Sort model properties to place required parameters before optional parameters.| |true|
 |sortParamsByRequiredFlag|Sort method arguments to place required parameters before optional parameters.| |true|
diff --git a/docs/generators/php-slim-deprecated.md b/docs/generators/php-slim-deprecated.md
index 98381616b95..16b5a34e761 100644
--- a/docs/generators/php-slim-deprecated.md
+++ b/docs/generators/php-slim-deprecated.md
@@ -10,6 +10,16 @@ sidebar_label: php-slim-deprecated
 |artifactVersion|The version to use in the composer package version field. e.g. 1.2.3| |null|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |invokerPackage|The main namespace to use for all classes. e.g. Yay\Pets| |null|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelPackage|package for generated models| |null|
 |packageName|The main package name for classes. e.g. GeneratedPetstore| |null|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
diff --git a/docs/generators/php-slim4.md b/docs/generators/php-slim4.md
index b0e79e02ae7..86f9a6efbc5 100644
--- a/docs/generators/php-slim4.md
+++ b/docs/generators/php-slim4.md
@@ -10,6 +10,16 @@ sidebar_label: php-slim4
 |artifactVersion|The version to use in the composer package version field. e.g. 1.2.3| |null|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |invokerPackage|The main namespace to use for all classes. e.g. Yay\Pets| |null|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelPackage|package for generated models| |null|
 |packageName|The main package name for classes. e.g. GeneratedPetstore| |null|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
diff --git a/docs/generators/php-symfony.md b/docs/generators/php-symfony.md
index 1d3e71d3926..e645d1c0a2d 100644
--- a/docs/generators/php-symfony.md
+++ b/docs/generators/php-symfony.md
@@ -15,6 +15,16 @@ sidebar_label: php-symfony
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |hideGenerationTimestamp|Hides the generation timestamp when files are generated.| |true|
 |invokerPackage|The main namespace to use for all classes. e.g. Yay\Pets| |null|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelPackage|package for generated models| |null|
 |packageName|The main package name for classes. e.g. GeneratedPetstore| |null|
 |phpLegacySupport|Should the generated code be compatible with PHP 5.x?| |true|
diff --git a/docs/generators/php-ze-ph.md b/docs/generators/php-ze-ph.md
index 93a1d3f6adf..6afc5d2a291 100644
--- a/docs/generators/php-ze-ph.md
+++ b/docs/generators/php-ze-ph.md
@@ -10,6 +10,16 @@ sidebar_label: php-ze-ph
 |artifactVersion|The version to use in the composer package version field. e.g. 1.2.3| |null|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |invokerPackage|The main namespace to use for all classes. e.g. Yay\Pets| |null|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelPackage|package for generated models| |null|
 |packageName|The main package name for classes. e.g. GeneratedPetstore| |null|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
diff --git a/docs/generators/php.md b/docs/generators/php.md
index 413996804eb..ba90aa92d7c 100644
--- a/docs/generators/php.md
+++ b/docs/generators/php.md
@@ -11,6 +11,16 @@ sidebar_label: php
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |hideGenerationTimestamp|boolean, toggles whether unicode identifiers are allowed in names or not, default is false| |true|
 |invokerPackage|The main namespace to use for all classes. e.g. Yay\Pets| |null|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelPackage|package for generated models| |null|
 |packageName|The main package name for classes. e.g. GeneratedPetstore| |null|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
diff --git a/docs/generators/python-aiohttp.md b/docs/generators/python-aiohttp.md
index ee337d2e5bb..0904e15e29c 100644
--- a/docs/generators/python-aiohttp.md
+++ b/docs/generators/python-aiohttp.md
@@ -9,6 +9,16 @@ sidebar_label: python-aiohttp
 |controllerPackage|controller package| |controllers|
 |defaultController|default controller| |default_controller|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |packageName|python package name (convention: snake_case).| |openapi_server|
 |packageVersion|python package version.| |1.0.0|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
diff --git a/docs/generators/python-blueplanet.md b/docs/generators/python-blueplanet.md
index 0382237eef5..ba1613ebe21 100644
--- a/docs/generators/python-blueplanet.md
+++ b/docs/generators/python-blueplanet.md
@@ -9,6 +9,16 @@ sidebar_label: python-blueplanet
 |controllerPackage|controller package| |controllers|
 |defaultController|default controller| |default_controller|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |packageName|python package name (convention: snake_case).| |openapi_server|
 |packageVersion|python package version.| |1.0.0|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
diff --git a/docs/generators/python-flask.md b/docs/generators/python-flask.md
index c8ab554adeb..a09e1dd8894 100644
--- a/docs/generators/python-flask.md
+++ b/docs/generators/python-flask.md
@@ -9,6 +9,16 @@ sidebar_label: python-flask
 |controllerPackage|controller package| |controllers|
 |defaultController|default controller| |default_controller|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |packageName|python package name (convention: snake_case).| |openapi_server|
 |packageVersion|python package version.| |1.0.0|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
diff --git a/docs/generators/ruby.md b/docs/generators/ruby.md
index 2475a797ec6..9bc917daa98 100644
--- a/docs/generators/ruby.md
+++ b/docs/generators/ruby.md
@@ -17,6 +17,16 @@ sidebar_label: ruby
 |gemSummary|gem summary. | |A ruby wrapper for the REST APIs|
 |gemVersion|gem version.| |1.0.0|
 |hideGenerationTimestamp|Hides the generation timestamp when files are generated.| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |library|HTTP library template (sub-template) to use|<dl><dt>**faraday**</dt><dd>Faraday (https://github.com/lostisland/faraday) (Beta support)</dd><dt>**typhoeus**</dt><dd>Typhoeus &gt;= 1.0.1 (https://github.com/typhoeus/typhoeus)</dd></dl>|typhoeus|
 |moduleName|top module name (convention: CamelCase, usually corresponding to gem name).| |OpenAPIClient|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
diff --git a/docs/generators/scala-akka-http-server.md b/docs/generators/scala-akka-http-server.md
index ecd656979e3..5b293ffbc32 100644
--- a/docs/generators/scala-akka-http-server.md
+++ b/docs/generators/scala-akka-http-server.md
@@ -14,6 +14,16 @@ sidebar_label: scala-akka-http-server
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |groupId|groupId in generated pom.xml| |org.openapitools|
 |invokerPackage|root package for generated code| |org.openapitools.server|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelPackage|package for generated models| |null|
 |modelPropertyNaming|Naming convention for the property: 'camelCase', 'PascalCase', 'snake_case' and 'original', which keeps the original name| |camelCase|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
diff --git a/docs/generators/scala-akka.md b/docs/generators/scala-akka.md
index ad8c5d485cf..d023156775e 100644
--- a/docs/generators/scala-akka.md
+++ b/docs/generators/scala-akka.md
@@ -9,6 +9,16 @@ sidebar_label: scala-akka
 |apiPackage|package for generated api classes| |null|
 |dateLibrary|Option. Date library to use|<dl><dt>**joda**</dt><dd>Joda (for legacy app)</dd><dt>**java8**</dt><dd>Java 8 native JSR310 (prefered for JDK 1.8+)</dd></dl>|java8|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |mainPackage|Top-level package name, which defines 'apiPackage', 'modelPackage', 'invokerPackage'| |org.openapitools.client|
 |modelPackage|package for generated models| |null|
 |modelPropertyNaming|Naming convention for the property: 'camelCase', 'PascalCase', 'snake_case' and 'original', which keeps the original name| |camelCase|
diff --git a/docs/generators/scala-gatling.md b/docs/generators/scala-gatling.md
index 0e1e748245e..1b711480df2 100644
--- a/docs/generators/scala-gatling.md
+++ b/docs/generators/scala-gatling.md
@@ -9,6 +9,16 @@ sidebar_label: scala-gatling
 |apiPackage|package for generated api classes| |null|
 |dateLibrary|Option. Date library to use|<dl><dt>**joda**</dt><dd>Joda (for legacy app)</dd><dt>**java8**</dt><dd>Java 8 native JSR310 (prefered for JDK 1.8+)</dd></dl>|java8|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelPackage|package for generated models| |null|
 |modelPropertyNaming|Naming convention for the property: 'camelCase', 'PascalCase', 'snake_case' and 'original', which keeps the original name| |camelCase|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
diff --git a/docs/generators/scala-httpclient-deprecated.md b/docs/generators/scala-httpclient-deprecated.md
index febeca9a690..a6ee24cc447 100644
--- a/docs/generators/scala-httpclient-deprecated.md
+++ b/docs/generators/scala-httpclient-deprecated.md
@@ -9,6 +9,16 @@ sidebar_label: scala-httpclient-deprecated
 |apiPackage|package for generated api classes| |null|
 |dateLibrary|Option. Date library to use|<dl><dt>**joda**</dt><dd>Joda (for legacy app)</dd><dt>**java8**</dt><dd>Java 8 native JSR310 (prefered for JDK 1.8+)</dd></dl>|java8|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelPackage|package for generated models| |null|
 |modelPropertyNaming|Naming convention for the property: 'camelCase', 'PascalCase', 'snake_case' and 'original', which keeps the original name| |camelCase|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
diff --git a/docs/generators/scala-lagom-server.md b/docs/generators/scala-lagom-server.md
index 99b43af7d58..da97ad1ee7d 100644
--- a/docs/generators/scala-lagom-server.md
+++ b/docs/generators/scala-lagom-server.md
@@ -9,6 +9,16 @@ sidebar_label: scala-lagom-server
 |apiPackage|package for generated api classes| |null|
 |dateLibrary|Option. Date library to use|<dl><dt>**joda**</dt><dd>Joda (for legacy app)</dd><dt>**java8**</dt><dd>Java 8 native JSR310 (prefered for JDK 1.8+)</dd></dl>|java8|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelPackage|package for generated models| |null|
 |modelPropertyNaming|Naming convention for the property: 'camelCase', 'PascalCase', 'snake_case' and 'original', which keeps the original name| |camelCase|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
diff --git a/docs/generators/scala-play-server.md b/docs/generators/scala-play-server.md
index 57bdf5d70ed..ef8b2db4e74 100644
--- a/docs/generators/scala-play-server.md
+++ b/docs/generators/scala-play-server.md
@@ -10,6 +10,16 @@ sidebar_label: scala-play-server
 |basePackage|Base package in which supporting classes are generated.| |org.openapitools|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |generateCustomExceptions|If set, generates custom exception types.| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelPackage|package for generated models| |null|
 |modelPropertyNaming|Naming convention for the property: 'camelCase', 'PascalCase', 'snake_case' and 'original', which keeps the original name| |camelCase|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
diff --git a/docs/generators/scala-sttp.md b/docs/generators/scala-sttp.md
index 5c277bf9dcc..2d1584633b9 100644
--- a/docs/generators/scala-sttp.md
+++ b/docs/generators/scala-sttp.md
@@ -9,6 +9,16 @@ sidebar_label: scala-sttp
 |apiPackage|package for generated api classes| |null|
 |dateLibrary|Option. Date library to use|<dl><dt>**joda**</dt><dd>Joda (for legacy app)</dd><dt>**java8**</dt><dd>Java 8 native JSR310 (prefered for JDK 1.8+)</dd></dl>|java8|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |mainPackage|Top-level package name, which defines 'apiPackage', 'modelPackage', 'invokerPackage'| |org.openapitools.client|
 |modelPackage|package for generated models| |null|
 |modelPropertyNaming|Naming convention for the property: 'camelCase', 'PascalCase', 'snake_case' and 'original', which keeps the original name| |camelCase|
diff --git a/docs/generators/scalatra.md b/docs/generators/scalatra.md
index af71e32aa46..bb05a8f35e8 100644
--- a/docs/generators/scalatra.md
+++ b/docs/generators/scalatra.md
@@ -9,6 +9,16 @@ sidebar_label: scalatra
 |apiPackage|package for generated api classes| |null|
 |dateLibrary|Option. Date library to use|<dl><dt>**joda**</dt><dd>Joda (for legacy app)</dd><dt>**java8**</dt><dd>Java 8 native JSR310 (prefered for JDK 1.8+)</dd></dl>|java8|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelPackage|package for generated models| |null|
 |modelPropertyNaming|Naming convention for the property: 'camelCase', 'PascalCase', 'snake_case' and 'original', which keeps the original name| |camelCase|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
diff --git a/docs/generators/scalaz.md b/docs/generators/scalaz.md
index aa2f6121ca1..48ecb1bdfa7 100644
--- a/docs/generators/scalaz.md
+++ b/docs/generators/scalaz.md
@@ -9,6 +9,16 @@ sidebar_label: scalaz
 |apiPackage|package for generated api classes| |null|
 |dateLibrary|Option. Date library to use|<dl><dt>**joda**</dt><dd>Joda (for legacy app)</dd><dt>**java8**</dt><dd>Java 8 native JSR310 (prefered for JDK 1.8+)</dd></dl>|java8|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelPackage|package for generated models| |null|
 |modelPropertyNaming|Naming convention for the property: 'camelCase', 'PascalCase', 'snake_case' and 'original', which keeps the original name| |camelCase|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
diff --git a/docs/generators/spring.md b/docs/generators/spring.md
index 98b896d8f26..c2a43de8cea 100644
--- a/docs/generators/spring.md
+++ b/docs/generators/spring.md
@@ -35,6 +35,16 @@ sidebar_label: spring
 |interfaceOnly|Whether to generate only API interface stubs without the server files.| |false|
 |invokerPackage|root package for generated code| |org.openapitools.api|
 |java8|Option. Use Java8 classes instead of third party equivalents|<dl><dt>**true**</dt><dd>Use Java 8 classes such as Base64. Use java8 default interface when a responseWrapper is used</dd><dt>**false**</dt><dd>Various third party libraries as needed</dd></dl>|false|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |library|library template (sub-template)|<dl><dt>**spring-boot**</dt><dd>Spring-boot Server application using the SpringFox integration.</dd><dt>**spring-mvc**</dt><dd>Spring-MVC Server application using the SpringFox integration.</dd><dt>**spring-cloud**</dt><dd>Spring-Cloud-Feign client with Spring-Boot auto-configured settings.</dd></dl>|spring-boot|
 |licenseName|The name of the license| |Unlicense|
 |licenseUrl|The URL of the license| |http://unlicense.org|
diff --git a/docs/generators/swift2-deprecated.md b/docs/generators/swift2-deprecated.md
index fe739bc109a..34894b89301 100644
--- a/docs/generators/swift2-deprecated.md
+++ b/docs/generators/swift2-deprecated.md
@@ -8,6 +8,16 @@ sidebar_label: swift2-deprecated
 |allowUnicodeIdentifiers|boolean, toggles whether unicode identifiers are allowed in names or not, default is false| |false|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |hideGenerationTimestamp|Hides the generation timestamp when files are generated.| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |podAuthors|Authors used for Podspec| |null|
 |podDescription|Description used for Podspec| |null|
 |podDocsetURL|Docset URL used for Podspec| |null|
diff --git a/docs/generators/swift3-deprecated.md b/docs/generators/swift3-deprecated.md
index 7f1997eaef9..ed484208b2c 100644
--- a/docs/generators/swift3-deprecated.md
+++ b/docs/generators/swift3-deprecated.md
@@ -8,6 +8,16 @@ sidebar_label: swift3-deprecated
 |allowUnicodeIdentifiers|boolean, toggles whether unicode identifiers are allowed in names or not, default is false| |false|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |hideGenerationTimestamp|Hides the generation timestamp when files are generated.| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |lenientTypeCast|Accept and cast values for simple types (string-&gt;bool, string-&gt;int, int-&gt;string)| |false|
 |objcCompatible|Add additional properties and methods for Objective-C compatibility (default: false)| |null|
 |podAuthors|Authors used for Podspec| |null|
diff --git a/docs/generators/swift4.md b/docs/generators/swift4.md
index f4c589c02ea..4030c9a11f3 100644
--- a/docs/generators/swift4.md
+++ b/docs/generators/swift4.md
@@ -8,6 +8,16 @@ sidebar_label: swift4
 |allowUnicodeIdentifiers|boolean, toggles whether unicode identifiers are allowed in names or not, default is false| |false|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |hideGenerationTimestamp|Hides the generation timestamp when files are generated.| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |lenientTypeCast|Accept and cast values for simple types (string-&gt;bool, string-&gt;int, int-&gt;string)| |false|
 |nonPublicApi|Generates code with reduced access modifiers; allows embedding elsewhere without exposing non-public API calls to consumers.(default: false)| |null|
 |objcCompatible|Add additional properties and methods for Objective-C compatibility (default: false)| |null|
diff --git a/docs/generators/swift5.md b/docs/generators/swift5.md
index 52a75bd93b1..c7beb3e39ab 100644
--- a/docs/generators/swift5.md
+++ b/docs/generators/swift5.md
@@ -9,6 +9,16 @@ sidebar_label: swift5
 |apiNamePrefix|Prefix that will be appended to all API names ('tags'). Default: empty string. e.g. Pet =&gt; Pet.| |null|
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |hideGenerationTimestamp|Hides the generation timestamp when files are generated.| |true|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |lenientTypeCast|Accept and cast values for simple types (string-&gt;bool, string-&gt;int, int-&gt;string)| |false|
 |library|Library template (sub-template) to use|<dl><dt>**urlsession**</dt><dd>[DEFAULT] HTTP client: URLSession</dd><dt>**alamofire**</dt><dd>HTTP client: Alamofire</dd></dl>|urlsession|
 |nonPublicApi|Generates code with reduced access modifiers; allows embedding elsewhere without exposing non-public API calls to consumers.(default: false)| |null|
diff --git a/docs/generators/typescript-angular.md b/docs/generators/typescript-angular.md
index f382194df4a..4d9191a91f0 100644
--- a/docs/generators/typescript-angular.md
+++ b/docs/generators/typescript-angular.md
@@ -11,6 +11,16 @@ sidebar_label: typescript-angular
 |enumNameSuffix|Suffix that will be appended to all enum names. A special 'v4-compat' value enables the backward-compatible behavior (as pre v4.2.3)| |v4-compat|
 |enumPropertyNaming|Naming convention for enum properties: 'camelCase', 'PascalCase', 'snake_case', 'UPPERCASE', and 'original'| |PascalCase|
 |fileNaming|Naming convention for the output files: 'camelCase', 'kebab-case'.| |camelCase|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelFileSuffix|The suffix of the file of the generated model (model&lt;suffix&gt;.ts).| |null|
 |modelPropertyNaming|Naming convention for the property: 'camelCase', 'PascalCase', 'snake_case' and 'original', which keeps the original name. Only change it if you provide your own run-time code for (de-)serialization of models| |original|
 |modelSuffix|The suffix of the generated model.| |null|
diff --git a/docs/generators/typescript-angularjs.md b/docs/generators/typescript-angularjs.md
index fbfd828ba32..0c5f755640b 100644
--- a/docs/generators/typescript-angularjs.md
+++ b/docs/generators/typescript-angularjs.md
@@ -9,6 +9,16 @@ sidebar_label: typescript-angularjs
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |enumNameSuffix|Suffix that will be appended to all enum names. A special 'v4-compat' value enables the backward-compatible behavior (as pre v4.2.3)| |v4-compat|
 |enumPropertyNaming|Naming convention for enum properties: 'camelCase', 'PascalCase', 'snake_case', 'UPPERCASE', and 'original'| |PascalCase|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelPropertyNaming|Naming convention for the property: 'camelCase', 'PascalCase', 'snake_case' and 'original', which keeps the original name. Only change it if you provide your own run-time code for (de-)serialization of models| |original|
 |nullSafeAdditionalProps|Set to make additional properties types declare that their indexer may return undefined| |false|
 |prependFormOrBodyParameters|Add form or body parameters to the beginning of the parameter list.| |false|
diff --git a/docs/generators/typescript-aurelia.md b/docs/generators/typescript-aurelia.md
index 955079117b0..f5f0e764b66 100644
--- a/docs/generators/typescript-aurelia.md
+++ b/docs/generators/typescript-aurelia.md
@@ -9,6 +9,16 @@ sidebar_label: typescript-aurelia
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |enumNameSuffix|Suffix that will be appended to all enum names. A special 'v4-compat' value enables the backward-compatible behavior (as pre v4.2.3)| |v4-compat|
 |enumPropertyNaming|Naming convention for enum properties: 'camelCase', 'PascalCase', 'snake_case', 'UPPERCASE', and 'original'| |PascalCase|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelPropertyNaming|Naming convention for the property: 'camelCase', 'PascalCase', 'snake_case' and 'original', which keeps the original name. Only change it if you provide your own run-time code for (de-)serialization of models| |original|
 |npmName|The name under which you want to publish generated npm package. Required to generate a full package| |null|
 |npmVersion|The version of your npm package. If not provided, using the version from the OpenAPI specification file.| |1.0.0|
diff --git a/docs/generators/typescript-axios.md b/docs/generators/typescript-axios.md
index 5e65684a0e6..575d2e17bbc 100644
--- a/docs/generators/typescript-axios.md
+++ b/docs/generators/typescript-axios.md
@@ -9,6 +9,16 @@ sidebar_label: typescript-axios
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |enumNameSuffix|Suffix that will be appended to all enum names. A special 'v4-compat' value enables the backward-compatible behavior (as pre v4.2.3)| |v4-compat|
 |enumPropertyNaming|Naming convention for enum properties: 'camelCase', 'PascalCase', 'snake_case', 'UPPERCASE', and 'original'| |PascalCase|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelPropertyNaming|Naming convention for the property: 'camelCase', 'PascalCase', 'snake_case' and 'original', which keeps the original name. Only change it if you provide your own run-time code for (de-)serialization of models| |original|
 |npmName|The name under which you want to publish generated npm package. Required to generate a full package| |null|
 |npmRepository|Use this property to set an url of your private npmRepo in the package.json| |null|
diff --git a/docs/generators/typescript-fetch.md b/docs/generators/typescript-fetch.md
index 40e7ff4eb2c..2662e2adefa 100644
--- a/docs/generators/typescript-fetch.md
+++ b/docs/generators/typescript-fetch.md
@@ -9,6 +9,16 @@ sidebar_label: typescript-fetch
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |enumNameSuffix|Suffix that will be appended to all enum names. A special 'v4-compat' value enables the backward-compatible behavior (as pre v4.2.3)| |v4-compat|
 |enumPropertyNaming|Naming convention for enum properties: 'camelCase', 'PascalCase', 'snake_case', 'UPPERCASE', and 'original'| |PascalCase|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelPropertyNaming|Naming convention for the property: 'camelCase', 'PascalCase', 'snake_case' and 'original', which keeps the original name| |camelCase|
 |npmName|The name under which you want to publish generated npm package. Required to generate a full package| |null|
 |npmRepository|Use this property to set an url your private npmRepo in the package.json| |null|
diff --git a/docs/generators/typescript-inversify.md b/docs/generators/typescript-inversify.md
index 5d68c9f0839..6829b64eee8 100644
--- a/docs/generators/typescript-inversify.md
+++ b/docs/generators/typescript-inversify.md
@@ -9,6 +9,16 @@ sidebar_label: typescript-inversify
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |enumNameSuffix|Suffix that will be appended to all enum names. A special 'v4-compat' value enables the backward-compatible behavior (as pre v4.2.3)| |v4-compat|
 |enumPropertyNaming|Naming convention for enum properties: 'camelCase', 'PascalCase', 'snake_case', 'UPPERCASE', and 'original'| |PascalCase|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelPropertyNaming|Naming convention for the property: 'camelCase', 'PascalCase', 'snake_case' and 'original', which keeps the original name. Only change it if you provide your own run-time code for (de-)serialization of models| |original|
 |npmName|The name under which you want to publish generated npm package. Required to generate a full package| |null|
 |npmRepository|Use this property to set an url your private npmRepo in the package.json| |null|
diff --git a/docs/generators/typescript-jquery.md b/docs/generators/typescript-jquery.md
index 91d61cf31e1..262578ce207 100644
--- a/docs/generators/typescript-jquery.md
+++ b/docs/generators/typescript-jquery.md
@@ -10,6 +10,16 @@ sidebar_label: typescript-jquery
 |enumNameSuffix|Suffix that will be appended to all enum names. A special 'v4-compat' value enables the backward-compatible behavior (as pre v4.2.3)| |v4-compat|
 |enumPropertyNaming|Naming convention for enum properties: 'camelCase', 'PascalCase', 'snake_case', 'UPPERCASE', and 'original'| |PascalCase|
 |jqueryAlreadyImported|When using this in legacy app using mix of typescript and javascript, this will only declare jquery and not import it| |false|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelPropertyNaming|Naming convention for the property: 'camelCase', 'PascalCase', 'snake_case' and 'original', which keeps the original name. Only change it if you provide your own run-time code for (de-)serialization of models| |original|
 |npmName|The name under which you want to publish generated npm package. Required to generate a full package| |null|
 |npmRepository|Use this property to set an url your private npmRepo in the package.json| |null|
diff --git a/docs/generators/typescript-node.md b/docs/generators/typescript-node.md
index d4bdee29bcc..06a4853986a 100644
--- a/docs/generators/typescript-node.md
+++ b/docs/generators/typescript-node.md
@@ -9,6 +9,16 @@ sidebar_label: typescript-node
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |enumNameSuffix|Suffix that will be appended to all enum names. A special 'v4-compat' value enables the backward-compatible behavior (as pre v4.2.3)| |v4-compat|
 |enumPropertyNaming|Naming convention for enum properties: 'camelCase', 'PascalCase', 'snake_case', 'UPPERCASE', and 'original'| |PascalCase|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelPropertyNaming|Naming convention for the property: 'camelCase', 'PascalCase', 'snake_case' and 'original', which keeps the original name| |camelCase|
 |npmName|The name under which you want to publish generated npm package. Required to generate a full package| |null|
 |npmRepository|Use this property to set an url your private npmRepo in the package.json| |null|
diff --git a/docs/generators/typescript-redux-query.md b/docs/generators/typescript-redux-query.md
index e5674a4c302..14fbe4c8543 100644
--- a/docs/generators/typescript-redux-query.md
+++ b/docs/generators/typescript-redux-query.md
@@ -9,6 +9,16 @@ sidebar_label: typescript-redux-query
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |enumNameSuffix|Suffix that will be appended to all enum names. A special 'v4-compat' value enables the backward-compatible behavior (as pre v4.2.3)| |v4-compat|
 |enumPropertyNaming|Naming convention for enum properties: 'camelCase', 'PascalCase', 'snake_case', 'UPPERCASE', and 'original'| |PascalCase|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelPropertyNaming|Naming convention for the property: 'camelCase', 'PascalCase', 'snake_case' and 'original', which keeps the original name| |camelCase|
 |npmName|The name under which you want to publish generated npm package. Required to generate a full package| |null|
 |npmRepository|Use this property to set an url your private npmRepo in the package.json| |null|
diff --git a/docs/generators/typescript-rxjs.md b/docs/generators/typescript-rxjs.md
index 9a210f4934b..e9638e2fbdd 100644
--- a/docs/generators/typescript-rxjs.md
+++ b/docs/generators/typescript-rxjs.md
@@ -9,6 +9,16 @@ sidebar_label: typescript-rxjs
 |ensureUniqueParams|Whether to ensure parameter names are unique in an operation (rename parameters that are not).| |true|
 |enumNameSuffix|Suffix that will be appended to all enum names. A special 'v4-compat' value enables the backward-compatible behavior (as pre v4.2.3)| |v4-compat|
 |enumPropertyNaming|Naming convention for enum properties: 'camelCase', 'PascalCase', 'snake_case', 'UPPERCASE', and 'original'| |PascalCase|
+|legacyDiscriminatorBehavior|This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.
+
+When this flag is set to false:
+
+- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.
+- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.
+When this flag is set to true:
+
+- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.
+Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.| |true|
 |modelPropertyNaming|Naming convention for the property: 'camelCase', 'PascalCase', 'snake_case' and 'original', which keeps the original name. Only change it if you provide your own run-time code for (de-)serialization of models| |original|
 |npmName|The name under which you want to publish generated npm package. Required to generate a full package| |null|
 |npmRepository|Use this property to set an url your private npmRepo in the package.json| |null|
diff --git a/modules/openapi-generator-cli/src/main/java/org/openapitools/codegen/cmd/Generate.java b/modules/openapi-generator-cli/src/main/java/org/openapitools/codegen/cmd/Generate.java
index e40f3c624ac..084026f5552 100644
--- a/modules/openapi-generator-cli/src/main/java/org/openapitools/codegen/cmd/Generate.java
+++ b/modules/openapi-generator-cli/src/main/java/org/openapitools/codegen/cmd/Generate.java
@@ -240,6 +240,9 @@ public class Generate extends OpenApiGeneratorCommand {
     @Option(name = {"--generate-alias-as-model"}, title = "generate alias (array, map) as model", description = CodegenConstants.GENERATE_ALIAS_AS_MODEL_DESC)
     private Boolean generateAliasAsModel;
 
+    @Option(name = {"--legacy-discriminator-behavior"}, title = "Support legacy logic for evaluating discriminators", description = CodegenConstants.LEGACY_DISCRIMINATOR_BEHAVIOR_DESC)
+    private Boolean legacyDiscriminatorBehavior;
+
     @Option(name = {"--minimal-update"},
         title = "Minimal update",
         description = "Only write output files that have changed.")
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/CodegenConstants.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/CodegenConstants.java
index 14e1fe5fce3..5b2cc91645b 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/CodegenConstants.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/CodegenConstants.java
@@ -351,4 +351,17 @@ public class CodegenConstants {
 
     public static final String REMOVE_ENUM_VALUE_PREFIX = "removeEnumValuePrefix";
     public static final String REMOVE_ENUM_VALUE_PREFIX_DESC = "Remove the common prefix of enum values";
+
+    public static final String LEGACY_DISCRIMINATOR_BEHAVIOR = "legacyDiscriminatorBehavior";
+    public static final String LEGACY_DISCRIMINATOR_BEHAVIOR_DESC = "This flag is used by OpenAPITools codegen to influence the processing of the discriminator attribute in OpenAPI documents. This flag has no impact if the OAS document does not use the discriminator attribute. The default value of this flag is set in each language-specific code generator (e.g. Python, Java, go...)using the method toModelName.\n" +
+            "\n" +
+            "When this flag is set to false:\n" +
+            "\n" +
+            "- The mapping in the discriminator includes any descendent schemas that allOf inherit from self, any oneOf schemas, any anyOf schemas, any x-discriminator-values, and the discriminator mapping schemas in the OAS document.\n" +
+            "- Codegen validates that oneOf and anyOf schemas contain the required discriminator and throws an error if the discriminator is missing.\n" +
+            "When this flag is set to true:\n" +
+            "\n" +
+            "- The mapping in the discriminator includes descendent schemas that allOf inherit from self and the discriminator mapping schemas in the OAS document.\n" +
+            "Note to developers supporting a language generator in OpenAPITools: to fully support the discriminator attribute as defined in the OAS specification 3.x, language generators should set this flag to true by default; however this requires updating the mustache templates to generate a language-specific discriminator lookup function that iterates over {{#mappedModels}} and does not iterate over {{children}}, {{#anyOf}}, or {{#oneOf}}.";
+
 }
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/CodegenDiscriminator.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/CodegenDiscriminator.java
index 73d85052e70..4e30df0c9ea 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/CodegenDiscriminator.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/CodegenDiscriminator.java
@@ -7,12 +7,39 @@ import java.util.Map;
 import java.util.Objects;
 import java.util.Set;
 
+/**
+ * This class encapsulates the OpenAPI discriminator construct, as specified at
+ * https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.0.3.md#discriminatorObject.
+ *
+ * When request bodies or response payloads may be one of a number of different schemas,
+ * a discriminator object can be used to aid in serialization, deserialization, and validation.
+ * The discriminator is a specific object in a schema which is used to inform the consumer of
+ * the specification of an alternative schema based on the value associated with it.
+ */
 public class CodegenDiscriminator {
+    // The name of the property in the payload that will hold the discriminator value.
+    // This is the propertyName as specified in the OpenAPI discriminator object.
     private String propertyName;
     private String propertyBaseName;
     private String propertyGetter;
     private String propertyType;
     private Map<String, String> mapping;
+
+    // mappedModels is populated differently if discriminatorExplicitMappingVerbose is
+    // True or False. When:
+    //
+    // discriminatorExplicitMappingVerbose == False, this contains:
+    // - the name to schema map info in the discriminator mapping entry in your openapi spec OR
+    // - child schemas that allOf inherit self schema
+    //
+    // discriminatorExplicitMappingVerbose == True, this contains:
+    // - the name to schema map info in the discriminMappedModelator mapping entry in your openapi spec AND
+    // - x-discriminator-value mappings in child oneOf + anyOf schemas + descendant schemas that allOf inherit self schema AND
+    // - descendant schemas that allOf inherit self schema AND
+    // - child oneOf + anyOf schemas
+    //
+    // see the method createDiscriminator in DefaultCodegen.java
+
     private Set<MappedModel> mappedModels = new LinkedHashSet<>();
 
     public String getPropertyName() {
@@ -63,8 +90,21 @@ public class CodegenDiscriminator {
         this.mappedModels = mappedModels;
     }
 
-    public static class MappedModel {
+    /**
+     * An object to hold discriminator mappings between payload values and schema names or
+     * references.
+     *
+     * In the OpenAPI document, the discriminator "mapping" attribute is optional.
+     * In scenarios where the value of the discriminator field does not match the schema name
+     * or implicit mapping is not possible, an optional mapping definition MAY be used.
+     * In OpenAPITools codegen, the MappedModel is the union of all the discriminator mappings,
+     * both explicitly defined in the OpenAPI document and inherited from oneOf/allOf/anyOf.
+     */
+    public static class MappedModel implements Comparable<MappedModel>{
+        // The value of the discriminator property in the payload.
         private String mappingName;
+        // The OAS schema name. It is obtained from the OAS document, and the string value
+        // is converted to a sanitized, internal representation within codegen.
         private String modelName;
 
         public MappedModel(String mappingName, String modelName) {
@@ -72,6 +112,18 @@ public class CodegenDiscriminator {
             this.modelName = modelName;
         }
 
+        @Override
+        public int compareTo(MappedModel other) {
+            if (getMappingName() == null && other.getMappingName() == null) {
+                return 0;
+            } else if (getMappingName() == null) {
+                return 1;
+            } else if (other.getMappingName() == null) {
+                return -1;
+            }
+            return getMappingName().compareTo(other.getMappingName());
+        }
+
         public String getMappingName() {
             return mappingName;
         }
@@ -130,4 +182,4 @@ public class CodegenDiscriminator {
         sb.append('}');
         return sb.toString();
     }
-}
+}
\ No newline at end of file
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/CodegenModel.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/CodegenModel.java
index 16a296f84e1..e9d25fd5ca7 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/CodegenModel.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/CodegenModel.java
@@ -696,6 +696,17 @@ public class CodegenModel implements IJsonSchemaValidationProperties {
         return sb.toString();
     }
 
+    public void addDiscriminatorMappedModelsImports(){
+        if (discriminator == null || discriminator.getMappedModels() == null) {
+            return;
+        }
+        for (CodegenDiscriminator.MappedModel mm : discriminator.getMappedModels()) {
+            if (!"".equals(mm.getModelName())) {
+                imports.add(mm.getModelName());
+            }
+        }
+    }
+
     public boolean isEmptyVars() {
         return emptyVars;
     }
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/CodegenProperty.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/CodegenProperty.java
index b6255e1fe02..bc1101c015e 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/CodegenProperty.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/CodegenProperty.java
@@ -150,6 +150,7 @@ public class CodegenProperty implements Cloneable, IJsonSchemaValidationProperti
     public boolean isNullable;
     public boolean isSelfReference;
     public boolean isCircularReference;
+    public boolean isDiscriminator;
     public List<String> _enum;
     public Map<String, Object> allowableValues;
     public CodegenProperty items;
@@ -651,6 +652,7 @@ public class CodegenProperty implements Cloneable, IJsonSchemaValidationProperti
         sb.append(", isNullable=").append(isNullable);
         sb.append(", isSelfReference=").append(isSelfReference);
         sb.append(", isCircularReference=").append(isCircularReference);
+        sb.append(", isDiscriminator=").append(isDiscriminator);
         sb.append(", _enum=").append(_enum);
         sb.append(", allowableValues=").append(allowableValues);
         sb.append(", items=").append(items);
@@ -717,6 +719,7 @@ public class CodegenProperty implements Cloneable, IJsonSchemaValidationProperti
                 isNullable == that.isNullable &&
                 isSelfReference == that.isSelfReference &&
                 isCircularReference == that.isCircularReference &&
+                isDiscriminator == that.isDiscriminator &&
                 hasValidation == that.hasValidation &&
                 isInherited == that.isInherited &&
                 isXmlAttribute == that.isXmlAttribute &&
@@ -775,7 +778,7 @@ public class CodegenProperty implements Cloneable, IJsonSchemaValidationProperti
                 isInteger, isLong, isNumber, isFloat, isDouble, isByteArray, isBinary, isFile,
                 isBoolean, isDate, isDateTime, isUuid, isUri, isEmail, isFreeFormObject,
                 isListContainer, isMapContainer, isEnum, isReadOnly, isWriteOnly, isNullable,
-                isSelfReference, isCircularReference, _enum, allowableValues, items, mostInnerItems,
+                isSelfReference, isCircularReference, isDiscriminator, _enum, allowableValues, items, mostInnerItems,
                 vendorExtensions, hasValidation, isInherited, discriminatorValue, nameInCamelCase,
                 nameInSnakeCase, enumName, maxItems, minItems, isXmlAttribute, xmlPrefix, xmlName,
                 xmlNamespace, isXmlWrapped);
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultCodegen.java
index 6f5990074ce..91edad3cd51 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultCodegen.java
@@ -215,6 +215,9 @@ public class DefaultCodegen implements CodegenConfig {
     // flag to indicate whether enum value prefixes are removed
     protected boolean removeEnumValuePrefix = true;
 
+    // Support legacy logic for evaluating discriminators
+    protected boolean legacyDiscriminatorBehavior = true;
+
     // make openapi available to all methods
     protected OpenAPI openAPI;
 
@@ -306,6 +309,11 @@ public class DefaultCodegen implements CodegenConfig {
             this.setRemoveEnumValuePrefix(Boolean.valueOf(additionalProperties
                     .get(CodegenConstants.REMOVE_ENUM_VALUE_PREFIX).toString()));
         }
+
+        if (additionalProperties.containsKey(CodegenConstants.LEGACY_DISCRIMINATOR_BEHAVIOR)) {
+            this.setLegacyDiscriminatorBehavior(Boolean.valueOf(additionalProperties
+                    .get(CodegenConstants.LEGACY_DISCRIMINATOR_BEHAVIOR).toString()));
+        }
     }
 
     /***
@@ -468,7 +476,8 @@ public class DefaultCodegen implements CodegenConfig {
                 }
                 parent.getChildren().add(cm);
                 parent.hasChildren = true;
-                if (parent.getDiscriminator() == null) {
+                Schema parentSchema = this.openAPI.getComponents().getSchemas().get(parent.name);
+                if (parentSchema.getDiscriminator() == null) {
                     parent = allModels.get(parent.getParent());
                 } else {
                     parent = null;
@@ -765,7 +774,7 @@ public class DefaultCodegen implements CodegenConfig {
                     if (e.getKey().contains("/")) {
                         // if this is property schema, we also need to generate the oneOf interface model
                         addOneOfNameExtension((ComposedSchema) s, nOneOf);
-                        addOneOfInterfaceModel((ComposedSchema) s, nOneOf);
+                        addOneOfInterfaceModel((ComposedSchema) s, nOneOf, openAPI);
                     } else {
                         // else this is a component schema, so we will just use that as the oneOf interface model
                         addOneOfNameExtension((ComposedSchema) s, n);
@@ -774,13 +783,13 @@ public class DefaultCodegen implements CodegenConfig {
                     Schema items = ((ArraySchema) s).getItems();
                     if (ModelUtils.isComposedSchema(items)) {
                         addOneOfNameExtension((ComposedSchema) items, nOneOf);
-                        addOneOfInterfaceModel((ComposedSchema) items, nOneOf);
+                        addOneOfInterfaceModel((ComposedSchema) items, nOneOf, openAPI);
                     }
                 } else if (ModelUtils.isMapSchema(s)) {
                     Schema addProps = ModelUtils.getAdditionalProperties(s);
                     if (addProps != null && ModelUtils.isComposedSchema(addProps)) {
                         addOneOfNameExtension((ComposedSchema) addProps, nOneOf);
-                        addOneOfInterfaceModel((ComposedSchema) addProps, nOneOf);
+                        addOneOfInterfaceModel((ComposedSchema) addProps, nOneOf, openAPI);
                     }
                 }
             }
@@ -1109,6 +1118,14 @@ public class DefaultCodegen implements CodegenConfig {
         this.ensureUniqueParams = ensureUniqueParams;
     }
 
+    public Boolean getLegacyDiscriminatorBehavior() {
+        return legacyDiscriminatorBehavior;
+    }
+
+    public void setLegacyDiscriminatorBehavior(boolean val){
+        this.legacyDiscriminatorBehavior = val;
+    }
+
     public Boolean getAllowUnicodeIdentifiers() {
         return allowUnicodeIdentifiers;
     }
@@ -1423,6 +1440,9 @@ public class DefaultCodegen implements CodegenConfig {
         // option to change the order of form/body parameter
         cliOptions.add(CliOption.newBoolean(CodegenConstants.PREPEND_FORM_OR_BODY_PARAMETERS,
                 CodegenConstants.PREPEND_FORM_OR_BODY_PARAMETERS_DESC).defaultValue(Boolean.FALSE.toString()));
+        cliOptions.add(CliOption.newBoolean(CodegenConstants.LEGACY_DISCRIMINATOR_BEHAVIOR,
+                CodegenConstants.LEGACY_DISCRIMINATOR_BEHAVIOR_DESC).defaultValue(Boolean.TRUE.toString()));
+
 
         // initialize special character mapping
         initalizeSpecialCharacterMapping();
@@ -2115,7 +2135,10 @@ public class DefaultCodegen implements CodegenConfig {
         }
         m.isAlias = (typeAliases.containsKey(name)
                 || isAliasOfSimpleTypes(schema)); // check if the unaliased schema is an alias of simple OAS types
-        m.discriminator = createDiscriminator(name, schema);
+        m.discriminator = createDiscriminator(name, schema, this.openAPI);
+        if (!this.getLegacyDiscriminatorBehavior()) {
+            m.addDiscriminatorMappedModelsImports();
+        }
 
         if (schema.getDeprecated() != null) {
             m.isDeprecated = schema.getDeprecated();
@@ -2161,7 +2184,10 @@ public class DefaultCodegen implements CodegenConfig {
                     for (Schema innerSchema : composed.getAllOf()) { // TODO need to work with anyOf, oneOf as well
                         if (m.discriminator == null && innerSchema.getDiscriminator() != null) {
                             LOGGER.debug("discriminator is set to null (not correctly set earlier): {}", name);
-                            m.discriminator = createDiscriminator(name, innerSchema);
+                            m.discriminator = createDiscriminator(name, innerSchema, this.openAPI);
+                            if (!this.getLegacyDiscriminatorBehavior()) {
+                                m.addDiscriminatorMappedModelsImports();
+                            }
                             modelDiscriminators++;
                         }
 
@@ -2285,6 +2311,7 @@ public class DefaultCodegen implements CodegenConfig {
                 required.addAll(composed.getRequired());
                 allRequired.addAll(composed.getRequired());
             }
+
             addVars(m, unaliasPropertySchema(properties), required, unaliasPropertySchema(allProperties), allRequired);
 
             // end of code block for composed schema
@@ -2353,6 +2380,22 @@ public class DefaultCodegen implements CodegenConfig {
             }
         }
 
+        // set isDiscriminator on the discriminator property
+        if (m.discriminator != null) {
+            String discPropName = m.discriminator.getPropertyBaseName();
+            List<List<CodegenProperty>> listOLists = new ArrayList<List<CodegenProperty>>();
+            listOLists.add(m.requiredVars);
+            listOLists.add(m.vars);
+            listOLists.add(m.allVars);
+            for (List<CodegenProperty> theseVars: listOLists) {
+                for (CodegenProperty requiredVar: theseVars) {
+                    if (discPropName.equals(requiredVar.baseName)) {
+                        requiredVar.isDiscriminator = true;
+                    }
+                }
+            }
+        }
+
         if (sortModelPropertiesByRequiredFlag) {
             Comparator<CodegenProperty> comparator = new Comparator<CodegenProperty>() {
                 @Override
@@ -2369,36 +2412,316 @@ public class DefaultCodegen implements CodegenConfig {
         return m;
     }
 
-    protected CodegenDiscriminator createDiscriminator(String schemaName, Schema schema) {
-        if (schema.getDiscriminator() == null) {
+    /**
+     * Recursively look in Schema sc for the discriminator discPropName
+     * and return a CodegenProperty with the dataType and required params set
+     * the returned CodegenProperty may not be required and it may not be of type string
+     * @param composedSchemaName The name of the sc Schema
+     * @param sc The Schema that may contain the discriminator
+     * @param discPropName The String that is the discriminator propertyName in the schema
+     */
+    private CodegenProperty discriminatorFound(String composedSchemaName, Schema sc, String discPropName, OpenAPI openAPI) {
+        Schema refSchema = ModelUtils.getReferencedSchema(openAPI, sc);
+        if (refSchema.getProperties() != null && refSchema.getProperties().get(discPropName) != null) {
+            Schema discSchema = (Schema) refSchema.getProperties().get(discPropName);
+            CodegenProperty cp = new CodegenProperty();
+            if (ModelUtils.isStringSchema(discSchema)) {
+                cp.isString = true;
+            }
+            cp.setRequired(false);
+            if (refSchema.getRequired() != null && refSchema.getRequired().contains(discPropName)) {
+                cp.setRequired(true);
+            }
+            return cp;
+        }
+        if (ModelUtils.isComposedSchema(refSchema)) {
+            ComposedSchema composedSchema = (ComposedSchema) refSchema;
+            if (composedSchema.getAllOf() != null) {
+                // If our discriminator is in one of the allOf schemas break when we find it
+                for  (Schema allOf: composedSchema.getAllOf()) {
+                    CodegenProperty cp = discriminatorFound(composedSchemaName, allOf, discPropName, openAPI);
+                    if (cp != null) {
+                        return cp;
+                    }
+                }
+            }
+            if (composedSchema.getOneOf() != null && composedSchema.getOneOf().size() != 0) {
+                // All oneOf definitions must contain the discriminator
+                CodegenProperty cp = new CodegenProperty();
+                for  (Schema oneOf: composedSchema.getOneOf()) {
+                    String modelName = ModelUtils.getSimpleRef(oneOf.get$ref());
+                    CodegenProperty thisCp = discriminatorFound(composedSchemaName, oneOf, discPropName, openAPI);
+                    if (thisCp == null) {
+                        throw new RuntimeException("'" + composedSchemaName + "' defines discriminator '" + discPropName + "', but the referenced OneOf schema '" + modelName + "' is missing "+discPropName);
+                    }
+                    if (cp.dataType == null) {
+                        cp = thisCp;
+                        continue;
+                    }
+                    if (cp != thisCp) {
+                        throw new RuntimeException("'" + composedSchemaName + "' defines discriminator '" + discPropName + "', but the OneOf schema '" + modelName + "' has a different "+discPropName+" definition than the prior OneOf schema's. Make sure the "+discPropName+" type and required values are the same");
+                    }
+                }
+                return cp;
+            }
+            if (composedSchema.getAnyOf() != null && composedSchema.getAnyOf().size() != 0) {
+                // All anyOf definitions must contain the discriminator because a min of one must be selected
+                CodegenProperty cp = new CodegenProperty();
+                for  (Schema anyOf: composedSchema.getAnyOf()) {
+                    String modelName = ModelUtils.getSimpleRef(anyOf.get$ref());
+                    CodegenProperty thisCp = discriminatorFound(composedSchemaName, anyOf, discPropName, openAPI);
+                    if (thisCp == null) {
+                        throw new RuntimeException("'" + composedSchemaName + "' defines discriminator '" + discPropName + "', but the referenced AnyOf schema '" + modelName + "' is missing "+discPropName);
+                    }
+                    if (cp.dataType == null) {
+                        cp = thisCp;
+                        continue;
+                    }
+                    if (cp != thisCp) {
+                        throw new RuntimeException("'" + composedSchemaName + "' defines discriminator '" + discPropName + "', but the AnyOf schema '" + modelName + "' has a different "+discPropName+" definition than the prior AnyOf schema's. Make sure the "+discPropName+" type and required values are the same");
+                    }
+                }
+                return cp;
+
+            }
+        }
+        return null;
+    }
+
+    /**
+     * Recursively look in Schema sc for the discriminator and return it
+     * Schema sc location
+     * OpenAPI openAPI the spec where we are searching for the discriminator
+     * @param sc The Schema that may contain the discriminator
+     */
+    private Discriminator recursiveGetDiscriminator(Schema sc, OpenAPI openAPI) {
+        Schema refSchema = ModelUtils.getReferencedSchema(openAPI, sc);
+        Discriminator foundDisc = refSchema.getDiscriminator();
+        if (foundDisc != null) {
+            return foundDisc;
+        }
+        if (!!this.getLegacyDiscriminatorBehavior()) {
+            return null;
+        }
+        Discriminator disc = new Discriminator();
+        if (ModelUtils.isComposedSchema(refSchema)) {
+            ComposedSchema composedSchema = (ComposedSchema) refSchema;
+            if (composedSchema.getAllOf() != null) {
+                // If our discriminator is in one of the allOf schemas break when we find it
+                for  (Schema allOf: composedSchema.getAllOf()) {
+                    foundDisc = recursiveGetDiscriminator(allOf, openAPI);
+                    if (foundDisc != null) {
+                        disc.setPropertyName(foundDisc.getPropertyName());
+                        disc.setMapping(foundDisc.getMapping());
+                        return disc;
+                    }
+                }
+            }
+            if (composedSchema.getOneOf() != null && composedSchema.getOneOf().size() != 0) {
+                // All oneOf definitions must contain the discriminator
+                Integer hasDiscriminatorCnt = 0;
+                Set<String> discriminatorsPropNames = new HashSet<>();
+                for  (Schema oneOf: composedSchema.getOneOf()) {
+                    foundDisc = recursiveGetDiscriminator(oneOf, openAPI);
+                    if (foundDisc != null) {
+                        discriminatorsPropNames.add(foundDisc.getPropertyName());
+                        hasDiscriminatorCnt++;
+                    }
+                }
+                if (hasDiscriminatorCnt == composedSchema.getOneOf().size() && discriminatorsPropNames.size() == 1) {
+                    disc.setPropertyName(foundDisc.getPropertyName());
+                    disc.setMapping(foundDisc.getMapping());
+                    return disc;
+                }
+            }
+            if (composedSchema.getAnyOf() != null && composedSchema.getAnyOf().size() != 0) {
+                // All anyOf definitions must contain the discriminator because a min of one must be selected
+                Integer hasDiscriminatorCnt = 0;
+                Set<String> discriminatorsPropNames = new HashSet<>();
+                for  (Schema anyOf: composedSchema.getAnyOf()) {
+                    foundDisc = recursiveGetDiscriminator(anyOf, openAPI);
+                    if (foundDisc != null) {
+                        discriminatorsPropNames.add(foundDisc.getPropertyName());
+                        hasDiscriminatorCnt++;
+                    }
+                }
+                if (hasDiscriminatorCnt == composedSchema.getAnyOf().size() && discriminatorsPropNames.size() == 1) {
+                    disc.setPropertyName(foundDisc.getPropertyName());
+                    disc.setMapping(foundDisc.getMapping());
+                    return disc;
+                }
+            }
+        }
+        return null;
+    }
+
+    /**
+     * This function is only used for composed schemas which have a discriminator
+     * Process oneOf and anyOf models in a composed schema and adds them into
+     * a list if the oneOf and anyOf models contain
+     * the required discriminator. If they don't contain the required
+     * discriminator or the discriminator is the wrong type then an error is
+     * thrown
+     * @param composedSchemaName The String model name of the composed schema where we are setting the discriminator map
+     * @param discPropName The String that is the discriminator propertyName in the schema
+     * @param c The ComposedSchema that contains the discriminator and oneOf/anyOf schemas
+     * @param openAPI The OpenAPI spec that we are using
+     * @return the list of oneOf and anyOf MappedModel that need to be added to the discriminator map
+     */
+    protected List<MappedModel> getOneOfAnyOfDescendants(String composedSchemaName, String discPropName, ComposedSchema c, OpenAPI openAPI) {
+        ArrayList<List<Schema>> listOLists = new ArrayList<List<Schema>>();
+        listOLists.add(c.getOneOf());
+        listOLists.add(c.getAnyOf());
+        List<MappedModel> descendentSchemas = new ArrayList();
+        for (List<Schema> schemaList: listOLists) {
+            if (schemaList == null) {
+                continue;
+            }
+            for  (Schema sc: schemaList) {
+                String ref = sc.get$ref();
+                if (ref == null) {
+                    // for schemas with no ref, it is not possible to build the discriminator map
+                    // because ref is how we get the model name
+                    // we only hit this use case for a schema with inline composed schemas, and one of those
+                    // schemas also has inline composed schemas
+                    // Note: if it is only inline one level, then the inline model resolver will move it into its own
+                    // schema and make it a $ref schema in the oneOf/anyOf location
+                    throw new RuntimeException("Invalid inline schema defined in oneOf/anyOf in '" + composedSchemaName + "'. Per the OpenApi spec, for this case when a composed schema defines a discriminator, the oneOf/anyOf schemas must use $ref. Change this inline definition to a $ref definition");
+                }
+                CodegenProperty df = discriminatorFound(composedSchemaName, sc, discPropName, openAPI);
+                String modelName = ModelUtils.getSimpleRef(ref);
+                if (df == null || !df.isString || df.required != true) {
+                    String msgSuffix = "";
+                    if (df == null) {
+                        msgSuffix += discPropName+" is missing from the schema, define it as required and type string";
+                    } else {
+                        if (!df.isString) {
+                            msgSuffix += "invalid type for "+discPropName+", set it to string";
+                        }
+                        if (df.required != true) {
+                            String spacer = "";
+                            if (msgSuffix.length() != 0) {
+                                spacer = ". ";
+                            }
+                            msgSuffix += spacer+"invalid optional definition of "+discPropName+", include it in required";
+                        }
+                    }
+                    throw new RuntimeException("'" + composedSchemaName + "' defines discriminator '" + discPropName + "', but the referenced schema '" + modelName + "' is incorrect. "+msgSuffix);
+                }
+                MappedModel mm = new MappedModel(modelName, toModelName(modelName));
+                descendentSchemas.add(mm);
+                Schema cs = ModelUtils.getSchema(openAPI, modelName);
+                Map<String, Object> vendorExtensions = cs.getExtensions();
+                if (vendorExtensions != null && !vendorExtensions.isEmpty() && vendorExtensions.containsKey("x-discriminator-value")) {
+                    String xDiscriminatorValue = (String) vendorExtensions.get("x-discriminator-value");
+                    mm = new MappedModel(xDiscriminatorValue, toModelName(modelName));
+                    descendentSchemas.add(mm);
+                }
+
+            }
+        }
+        return descendentSchemas;
+    }
+
+    protected List<MappedModel> getAllOfDescendants(String thisSchemaName, OpenAPI openAPI) {
+        ArrayList<String> queue = new ArrayList();;
+        List<MappedModel> descendentSchemas = new ArrayList();
+        Map<String, Schema> schemas = ModelUtils.getSchemas(openAPI);
+        String currentSchemaName = thisSchemaName;
+        while (true) {
+            for (String childName : schemas.keySet()) {
+                if (childName == thisSchemaName) {
+                    continue;
+                }
+                Schema child = schemas.get(childName);
+                if (ModelUtils.isComposedSchema(child)) {
+                    ComposedSchema composedChild = (ComposedSchema) child;
+                    List<Schema> parents = composedChild.getAllOf();
+                    if (parents != null) {
+                        for  (Schema parent: parents) {
+                            String ref = parent.get$ref();
+                            if (ref == null) {
+                                // for schemas with no ref, it is not possible to build the discriminator map
+                                // because ref is how we get the model name
+                                // we only hit this use case for a schema with inline composed schemas, and one of those
+                                // schemas also has inline composed schemas
+                                throw new RuntimeException("Invalid inline schema defined in allOf in '" + childName + "'. Per the OpenApi spec, for this case when a composed schema defines a discriminator, the allOf schemas must use $ref. Change this inline definition to a $ref definition");
+                            }
+                            String parentName = ModelUtils.getSimpleRef(ref);
+                            if (parentName.equals(currentSchemaName)) {
+                                if (queue.contains(childName) || descendentSchemas.contains(childName)) {
+                                    throw new RuntimeException("Stack overflow hit when looking for "+thisSchemaName+" an infinite loop starting and ending at "+childName+" was seen");
+                                }
+                                queue.add(childName);
+                                break;
+                            }
+                        }
+                    }
+                }
+            }
+            if (queue.size() == 0) {
+                break;
+            }
+            currentSchemaName = queue.remove(0);
+            MappedModel mm = new MappedModel(currentSchemaName, toModelName(currentSchemaName));
+            descendentSchemas.add(mm);
+            Schema cs = schemas.get(currentSchemaName);
+            Map<String, Object> vendorExtensions = cs.getExtensions();
+            if (vendorExtensions != null && !vendorExtensions.isEmpty() && vendorExtensions.containsKey("x-discriminator-value")) {
+                String xDiscriminatorValue = (String) vendorExtensions.get("x-discriminator-value");
+                mm = new MappedModel(xDiscriminatorValue, toModelName(currentSchemaName));
+                descendentSchemas.add(mm);
+            }
+        }
+        return descendentSchemas;
+    }
+
+    protected CodegenDiscriminator createDiscriminator(String schemaName, Schema schema, OpenAPI openAPI) {
+        Discriminator sourceDiscriminator = recursiveGetDiscriminator(schema, openAPI);
+        if (sourceDiscriminator == null) {
             return null;
         }
         CodegenDiscriminator discriminator = new CodegenDiscriminator();
-        discriminator.setPropertyName(toVarName(schema.getDiscriminator().getPropertyName()));
-        discriminator.setPropertyBaseName(schema.getDiscriminator().getPropertyName());
+        String discPropName = sourceDiscriminator.getPropertyName();
+        discriminator.setPropertyName(toVarName(discPropName));
+        discriminator.setPropertyBaseName(sourceDiscriminator.getPropertyName());
         discriminator.setPropertyGetter(toGetter(discriminator.getPropertyName()));
         // FIXME: for now, we assume that the discriminator property is String
         discriminator.setPropertyType(typeMapping.get("string"));
-        discriminator.setMapping(schema.getDiscriminator().getMapping());
-        if (schema.getDiscriminator().getMapping() != null && !schema.getDiscriminator().getMapping().isEmpty()) {
-            for (Entry<String, String> e : schema.getDiscriminator().getMapping().entrySet()) {
+        discriminator.setMapping(sourceDiscriminator.getMapping());
+        List<MappedModel> uniqueDescendants = new ArrayList();
+        if (sourceDiscriminator.getMapping() != null && !sourceDiscriminator.getMapping().isEmpty()) {
+            for (Entry<String, String> e : sourceDiscriminator.getMapping().entrySet()) {
                 String nameOrRef = e.getValue();
                 String name = nameOrRef.indexOf('/') >= 0 ? ModelUtils.getSimpleRef(nameOrRef) : nameOrRef;
                 String modelName = toModelName(name);
-                discriminator.getMappedModels().add(new MappedModel(e.getKey(), modelName));
+                uniqueDescendants.add(new MappedModel(e.getKey(), modelName));
             }
-        } else {
-            Map<String, Schema> allDefinitions = ModelUtils.getSchemas(this.openAPI);
-            allDefinitions.forEach((childName, child) -> {
-                if (child instanceof ComposedSchema && ((ComposedSchema) child).getAllOf() != null) {
-
-                    final List<String> parentSchemas = ModelUtils.getAllParentsName((ComposedSchema) child, allDefinitions, true);
-                    if (parentSchemas.contains(schemaName)) {
-                        discriminator.getMappedModels().add(new MappedModel(childName, toModelName(childName)));
-                    }
-                }
-            });
         }
+
+        boolean legacyUseCase = (this.getLegacyDiscriminatorBehavior() && uniqueDescendants.isEmpty());
+        if (!this.getLegacyDiscriminatorBehavior() || legacyUseCase) {
+            // for schemas that allOf inherit from this schema, add those descendants to this discriminator map
+            List<MappedModel> otherDescendants = getAllOfDescendants(schemaName, openAPI);
+            for (MappedModel otherDescendant: otherDescendants) {
+                if (!uniqueDescendants.contains(otherDescendant)) {
+                    uniqueDescendants.add(otherDescendant);
+                }
+            }
+        }
+        // if there are composed oneOf/anyOf schemas, add them to this discriminator
+        if (ModelUtils.isComposedSchema(schema) && !this.getLegacyDiscriminatorBehavior()) {
+            List<MappedModel> otherDescendants = getOneOfAnyOfDescendants(schemaName, discPropName, (ComposedSchema) schema, openAPI);
+            for (MappedModel otherDescendant: otherDescendants) {
+                if (!uniqueDescendants.contains(otherDescendant)) {
+                    uniqueDescendants.add(otherDescendant);
+                }
+            }
+        }
+        if (!this.getLegacyDiscriminatorBehavior()) {
+            Collections.sort(uniqueDescendants);
+        }
+        discriminator.getMappedModels().addAll(uniqueDescendants);
         return discriminator;
     }
 
@@ -2428,11 +2751,15 @@ public class DefaultCodegen implements CodegenConfig {
             }
 
             if (composedSchema.getOneOf() != null) {
-                throw new RuntimeException("Please report the issue: Cannot process oneOf (Composed Scheme) in addProperties: " + schema);
+                for (Schema component : composedSchema.getOneOf()) {
+                    addProperties(properties, required, component);
+                }
             }
 
             if (composedSchema.getAnyOf() != null) {
-                throw new RuntimeException("Please report the issue: Cannot process anyOf (Composed Schema) in addProperties: " + schema);
+                for (Schema component : composedSchema.getAnyOf()) {
+                    addProperties(properties, required, component);
+                }
             }
 
             return;
@@ -5830,15 +6157,19 @@ public class DefaultCodegen implements CodegenConfig {
      *
      * @param cs   ComposedSchema object to create as interface model
      * @param type name to use for the generated interface model
+     * @param openAPI OpenAPI spec that we are using
      */
-    public void addOneOfInterfaceModel(ComposedSchema cs, String type) {
+    public void addOneOfInterfaceModel(ComposedSchema cs, String type, OpenAPI openAPI) {
         if (cs.getOneOf() == null) {
             return;
         }
+
         CodegenModel cm = new CodegenModel();
 
-        cm.discriminator = createDiscriminator("", (Schema) cs);
-
+        cm.discriminator = createDiscriminator("", (Schema) cs, openAPI);
+        if (!this.getLegacyDiscriminatorBehavior()) {
+            cm.addDiscriminatorMappedModelsImports();
+        }
         for (Schema o : Optional.ofNullable(cs.getOneOf()).orElse(Collections.emptyList())) {
             if (o.get$ref() == null) {
                 if (cm.discriminator != null && o.get$ref() == null) {
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultGenerator.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultGenerator.java
index e8dab26d05f..1681434c442 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultGenerator.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultGenerator.java
@@ -156,7 +156,7 @@ public class DefaultGenerator extends AbstractGenerator implements Generator {
         return defaultValue;
     }
 
-    private void configureGeneratorProperties() {
+    void configureGeneratorProperties() {
         // allows generating only models by specifying a CSV of models to generate, or empty for all
         // NOTE: Boolean.TRUE is required below rather than `true` because of JVM boxing constraints and type inference.
         generateApis = GlobalSettings.getProperty(CodegenConstants.APIS) != null ? Boolean.TRUE : getGeneratorPropertyDefaultSwitch(CodegenConstants.APIS, null);
@@ -394,7 +394,7 @@ public class DefaultGenerator extends AbstractGenerator implements Generator {
     }
 
     @SuppressWarnings("unchecked")
-    private void generateModels(List<File> files, List<Object> allModels, List<String> unusedModels) {
+    void generateModels(List<File> files, List<Object> allModels, List<String> unusedModels) {
         if (!generateModels) {
             // TODO: Process these anyway and add to dryRun info
             LOGGER.info("Skipping generation of models.");
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/GoClientExperimentalCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/GoClientExperimentalCodegen.java
index 56c63ec0c63..89e189c8c38 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/GoClientExperimentalCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/GoClientExperimentalCodegen.java
@@ -77,6 +77,7 @@ public class GoClientExperimentalCodegen extends GoClientCodegen {
 
     @Override
     public void processOpts() {
+        this.setLegacyDiscriminatorBehavior(false);
         super.processOpts();
         supportingFiles.add(new SupportingFile("utils.mustache", "", "utils.go"));
 
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PythonClientExperimentalCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PythonClientExperimentalCodegen.java
index 8d2544c6af7..6aa9c08250c 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PythonClientExperimentalCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PythonClientExperimentalCodegen.java
@@ -111,6 +111,8 @@ public class PythonClientExperimentalCodegen extends PythonClientCodegen {
 
     @Override
     public void processOpts() {
+        this.setLegacyDiscriminatorBehavior(false);
+
         super.processOpts();
 
         supportingFiles.remove(new SupportingFile("api_client.mustache", packagePath(), "api_client.py"));
diff --git a/modules/openapi-generator/src/main/resources/Java/pojo.mustache b/modules/openapi-generator/src/main/resources/Java/pojo.mustache
index c438cd43eb7..653f44062d1 100644
--- a/modules/openapi-generator/src/main/resources/Java/pojo.mustache
+++ b/modules/openapi-generator/src/main/resources/Java/pojo.mustache
@@ -69,7 +69,7 @@ public class {{classname}} {{#parent}}extends {{{parent}}} {{/parent}}{{#vendorE
   private {{{datatypeWithEnum}}} {{name}}{{#required}}{{#defaultValue}} = {{{.}}}{{/defaultValue}}{{/required}}{{^required}} = null{{/required}};
   {{/isContainer}}
   {{^isContainer}}
-  private {{{datatypeWithEnum}}} {{name}}{{#defaultValue}} = {{{.}}}{{/defaultValue}};
+  {{#isDiscriminator}}protected{{/isDiscriminator}}{{^isDiscriminator}}private{{/isDiscriminator}} {{{datatypeWithEnum}}} {{name}}{{#defaultValue}} = {{{.}}}{{/defaultValue}};
   {{/isContainer}}
   {{/vendorExtensions.x-is-jackson-optional-nullable}}
 
diff --git a/modules/openapi-generator/src/main/resources/python/api_client.mustache b/modules/openapi-generator/src/main/resources/python/api_client.mustache
index c69e7d5945e..de25b7cf975 100644
--- a/modules/openapi-generator/src/main/resources/python/api_client.mustache
+++ b/modules/openapi-generator/src/main/resources/python/api_client.mustache
@@ -643,9 +643,12 @@ class ApiClient(object):
         :param klass: class literal.
         :return: model object.
         """
+        has_discriminator = False
+        if (hasattr(klass, 'get_real_child_model')
+                and klass.discriminator_value_class_map):
+            has_discriminator = True
 
-        if not klass.openapi_types and not hasattr(klass,
-                                                   'get_real_child_model'):
+        if not klass.openapi_types and has_discriminator is False:
             return data
 
         kwargs = {}
@@ -659,7 +662,7 @@ class ApiClient(object):
 
         instance = klass(**kwargs)
 
-        if hasattr(instance, 'get_real_child_model'):
+        if has_discriminator:
             klass_name = instance.get_real_child_model(data)
             if klass_name:
                 instance = self.__deserialize(data, klass_name)
diff --git a/modules/openapi-generator/src/main/resources/python/model.mustache b/modules/openapi-generator/src/main/resources/python/model.mustache
index 70f6e7489a7..112246604dc 100644
--- a/modules/openapi-generator/src/main/resources/python/model.mustache
+++ b/modules/openapi-generator/src/main/resources/python/model.mustache
@@ -52,8 +52,9 @@ class {{classname}}(object):
 {{#discriminator}}
 
     discriminator_value_class_map = {
-        {{#children}}'{{^vendorExtensions.x-discriminator-value}}{{name}}{{/vendorExtensions.x-discriminator-value}}{{#vendorExtensions.x-discriminator-value}}{{{vendorExtensions.x-discriminator-value}}}{{/vendorExtensions.x-discriminator-value}}': '{{{classname}}}'{{^-last}},
-        {{/-last}}{{/children}}
+{{#children}}
+        '{{^vendorExtensions.x-discriminator-value}}{{name}}{{/vendorExtensions.x-discriminator-value}}{{#vendorExtensions.x-discriminator-value}}{{{vendorExtensions.x-discriminator-value}}}{{/vendorExtensions.x-discriminator-value}}': '{{{classname}}}'{{^-last}},{{/-last}}
+{{/children}}
     }
 {{/discriminator}}
 
diff --git a/modules/openapi-generator/src/main/resources/python/python-experimental/model_templates/classvars.mustache b/modules/openapi-generator/src/main/resources/python/python-experimental/model_templates/classvars.mustache
index 60fff484ef4..8b49e58edbf 100644
--- a/modules/openapi-generator/src/main/resources/python/python-experimental/model_templates/classvars.mustache
+++ b/modules/openapi-generator/src/main/resources/python/python-experimental/model_templates/classvars.mustache
@@ -115,15 +115,11 @@
 
     @staticmethod
     def discriminator():
-        return {{^discriminator}}None{{/discriminator}}{{#discriminator}}{
-            '{{{discriminatorName}}}': {
-{{#children}}
-                '{{^vendorExtensions.x-discriminator-value}}{{name}}{{/vendorExtensions.x-discriminator-value}}{{#vendorExtensions.x-discriminator-value}}{{{vendorExtensions.x-discriminator-value}}}{{/vendorExtensions.x-discriminator-value}}': {{{classname}}},
-{{/children}}
-{{^children}}
+        {{^discriminator}}return None{{/discriminator}}{{#discriminator}}val = {
 {{#mappedModels}}
-                '{{mappingName}}': {{{modelName}}},
+            '{{mappingName}}': {{{modelName}}},
 {{/mappedModels}}
-{{/children}}
-            },
-        }{{/discriminator}}
\ No newline at end of file
+        }
+        if not val:
+            return None
+        return {'{{{discriminatorName}}}': val}{{/discriminator}}
\ No newline at end of file
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/DefaultCodegenTest.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/DefaultCodegenTest.java
index 28fff725bb8..bebe90010f7 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/DefaultCodegenTest.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/DefaultCodegenTest.java
@@ -33,6 +33,7 @@ import io.swagger.v3.oas.models.responses.ApiResponse;
 import io.swagger.v3.oas.models.responses.ApiResponses;
 import io.swagger.v3.parser.core.models.ParseOptions;
 
+import org.openapitools.codegen.languages.JavaClientCodegen;
 import org.openapitools.codegen.templating.mustache.CamelCaseLambda;
 import org.openapitools.codegen.templating.mustache.IndentedLambda;
 import org.openapitools.codegen.templating.mustache.LowercaseLambda;
@@ -42,6 +43,7 @@ import org.openapitools.codegen.utils.ModelUtils;
 import org.testng.Assert;
 import org.testng.annotations.Test;
 
+import java.io.File;
 import java.util.*;
 import java.util.stream.Collectors;
 
@@ -569,6 +571,7 @@ public class DefaultCodegenTest {
     public void testDiscriminatorWithCustomMapping() {
         final OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_0/allOf.yaml");
         DefaultCodegen codegen = new DefaultCodegen();
+        codegen.setLegacyDiscriminatorBehavior(false);
         codegen.setOpenAPI(openAPI);
 
         String path = "/person/display/{personId}";
@@ -643,6 +646,570 @@ public class DefaultCodegenTest {
         Assert.assertEquals(adultModel.allParents, Collections.singletonList("Person"));
     }
 
+    @Test
+    public void testComposedSchemaAllOfDiscriminatorMap() {
+        final OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_0/allOf_composition_discriminator.yaml");
+        DefaultCodegen codegen = new DefaultCodegen();
+        codegen.setOpenAPI(openAPI);
+        codegen.setLegacyDiscriminatorBehavior(false);
+        Schema sc;
+        String modelName;
+
+        String propertyName = "petType";
+        String propertyBaseName = propertyName;
+        CodegenDiscriminator emptyMapDisc = new CodegenDiscriminator();
+        emptyMapDisc.setPropertyName(propertyName);
+        emptyMapDisc.setPropertyBaseName(propertyBaseName);
+
+        // all leaf Schemas have discriminators with PropertyName/BaseName + empty discriminator maps
+        List<String> leafModelNames = Arrays.asList("Cat", "Dog", "Lizard", "Snake");
+        for (String leafModelName: leafModelNames) {
+            Schema leafSc = openAPI.getComponents().getSchemas().get(leafModelName);
+            CodegenModel leafCm = codegen.fromModel(leafModelName, leafSc);
+            Assert.assertEquals(leafCm.discriminator, emptyMapDisc);
+        }
+
+        // the Pet discriminator map contains all animals + Reptile (children + grandchildren)
+        CodegenDiscriminator petDisc = new CodegenDiscriminator();
+        petDisc.setPropertyName(propertyName);
+        petDisc.setPropertyBaseName(propertyBaseName);
+        java.util.LinkedHashSet hs = new LinkedHashSet<>();
+        for (String leafModelName: leafModelNames) {
+            hs.add(new CodegenDiscriminator.MappedModel(leafModelName, codegen.toModelName(leafModelName)));
+        }
+        hs.add(new CodegenDiscriminator.MappedModel("Reptile", codegen.toModelName("Reptile")));
+        petDisc.setMappedModels(hs);
+        modelName = "Pet";
+        sc = openAPI.getComponents().getSchemas().get(modelName);
+        CodegenModel pet = codegen.fromModel(modelName, sc);
+        Assert.assertEquals(pet.discriminator, petDisc);
+
+        // the Reptile discriminator contains both reptiles
+        List<String> reptileModelNames = Arrays.asList("Lizard", "Snake");
+        CodegenDiscriminator reptileDisc = new CodegenDiscriminator();
+        reptileDisc.setPropertyName(propertyName);
+        reptileDisc.setPropertyBaseName(propertyBaseName);
+        hs.clear();
+        for (String reptileModelName: reptileModelNames) {
+            hs.add(new CodegenDiscriminator.MappedModel(reptileModelName, codegen.toModelName(reptileModelName)));
+        }
+        reptileDisc.setMappedModels(hs);
+        modelName = "Reptile";
+        sc = openAPI.getComponents().getSchemas().get(modelName);
+        CodegenModel reptile = codegen.fromModel(modelName, sc);
+        Assert.assertEquals(reptile.discriminator, reptileDisc);
+
+        // the MyPets discriminator contains Cat and Lizard
+        List<String> myPetNames = Arrays.asList("Cat", "Lizard");
+        CodegenDiscriminator myPetDisc = new CodegenDiscriminator();
+        myPetDisc.setPropertyName(propertyName);
+        myPetDisc.setPropertyBaseName(propertyBaseName);
+        hs.clear();
+        for (String myPetName: myPetNames) {
+            hs.add(new CodegenDiscriminator.MappedModel(myPetName, codegen.toModelName(myPetName)));
+        }
+        myPetDisc.setMappedModels(hs);
+        modelName = "MyPets";
+        sc = openAPI.getComponents().getSchemas().get(modelName);
+        CodegenModel myPets = codegen.fromModel(modelName, sc);
+        Assert.assertEquals(myPets.discriminator, myPetDisc);
+
+        // the MyPetsNoDisc discriminator is created because all oneOf classes have the same discriminator
+        modelName = "MyPetsNoDisc";
+        sc = openAPI.getComponents().getSchemas().get(modelName);
+        CodegenModel myPetsNoDisc = codegen.fromModel(modelName, sc);
+        Assert.assertEquals(myPetsNoDisc.discriminator, myPetDisc);
+
+        CodegenModel cm;
+
+        // the mapping in b is in A
+        modelName = "A";
+        sc = openAPI.getComponents().getSchemas().get(modelName);
+        cm = codegen.fromModel(modelName, sc);
+        hs.clear();
+        hs.add(new CodegenDiscriminator.MappedModel("b", codegen.toModelName("B")));
+        hs.add(new CodegenDiscriminator.MappedModel("B", codegen.toModelName("B")));
+        hs.add(new CodegenDiscriminator.MappedModel("C", codegen.toModelName("C")));
+        Assert.assertEquals(cm.discriminator.getMappedModels(), hs);
+
+        // the mapping in b is in B
+        modelName = "B";
+        sc = openAPI.getComponents().getSchemas().get(modelName);
+        cm = codegen.fromModel(modelName, sc);
+        hs.clear();
+        hs.add(new CodegenDiscriminator.MappedModel("b", codegen.toModelName("B")));
+        hs.add(new CodegenDiscriminator.MappedModel("C", codegen.toModelName("C")));
+
+        Assert.assertEquals(cm.discriminator.getMappedModels(), hs);
+
+        // the mapping in b is in C
+        modelName = "C";
+        sc = openAPI.getComponents().getSchemas().get(modelName);
+        cm = codegen.fromModel(modelName, sc);
+        hs.clear();
+        hs.add(new CodegenDiscriminator.MappedModel("b", codegen.toModelName("B")));
+        Assert.assertEquals(cm.discriminator.getMappedModels(), hs);
+    }
+
+    @Test
+    public void testComposedSchemaAllOfDiscriminatorMapLegacy() {
+        final OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_0/allOf_composition_discriminator.yaml");
+        DefaultCodegen codegen = new DefaultCodegen();
+        // codegen.discriminatorExplicitMappingVerbose remains false in the legacy use case
+        codegen.setOpenAPI(openAPI);
+        Schema sc;
+        String modelName;
+
+        String propertyName = "petType";
+        String propertyBaseName = propertyName;
+        CodegenDiscriminator emptyMapDisc = new CodegenDiscriminator();
+        emptyMapDisc.setPropertyName(propertyName);
+        emptyMapDisc.setPropertyBaseName(propertyBaseName);
+
+        // all leaf Schemas have discriminators with PropertyName/BaseName + empty discriminator maps
+        List<String> leafModelNames = Arrays.asList("Cat", "Dog", "Lizard", "Snake");
+        for (String leafModelName: leafModelNames) {
+            Schema leafSc = openAPI.getComponents().getSchemas().get(leafModelName);
+            CodegenModel leafCm = codegen.fromModel(leafModelName, leafSc);
+            Assert.assertEquals(leafCm.discriminator, null);
+        }
+
+        // the Pet discriminator map contains all animals + Reptile (children + grandchildren)
+        CodegenDiscriminator petDisc = new CodegenDiscriminator();
+        petDisc.setPropertyName(propertyName);
+        petDisc.setPropertyBaseName(propertyBaseName);
+        java.util.LinkedHashSet hs = new LinkedHashSet<>();
+        for (String leafModelName: leafModelNames) {
+            hs.add(new CodegenDiscriminator.MappedModel(leafModelName, codegen.toModelName(leafModelName)));
+        }
+        hs.add(new CodegenDiscriminator.MappedModel("Reptile", codegen.toModelName("Reptile")));
+        petDisc.setMappedModels(hs);
+        modelName = "Pet";
+        sc = openAPI.getComponents().getSchemas().get(modelName);
+        CodegenModel pet = codegen.fromModel(modelName, sc);
+        Assert.assertEquals(pet.discriminator, petDisc);
+
+        // the Reptile discriminator contains both reptiles
+        List<String> reptileModelNames = Arrays.asList("Lizard", "Snake");
+        CodegenDiscriminator reptileDisc = new CodegenDiscriminator();
+        reptileDisc.setPropertyName(propertyName);
+        reptileDisc.setPropertyBaseName(propertyBaseName);
+        hs.clear();
+        for (String reptileModelName: reptileModelNames) {
+            hs.add(new CodegenDiscriminator.MappedModel(reptileModelName, codegen.toModelName(reptileModelName)));
+        }
+        reptileDisc.setMappedModels(hs);
+        modelName = "Reptile";
+        sc = openAPI.getComponents().getSchemas().get(modelName);
+        CodegenModel reptile = codegen.fromModel(modelName, sc);
+        Assert.assertEquals(reptile.discriminator, null);
+
+        // the MyPets discriminator contains Cat and Lizard
+        CodegenDiscriminator myPetDisc = new CodegenDiscriminator();
+        myPetDisc.setPropertyName(propertyName);
+        myPetDisc.setPropertyBaseName(propertyBaseName);
+        hs.clear();
+        modelName = "MyPets";
+        sc = openAPI.getComponents().getSchemas().get(modelName);
+        CodegenModel myPets = codegen.fromModel(modelName, sc);
+        Assert.assertEquals(myPets.discriminator, myPetDisc);
+
+        // the MyPetsNoDisc discriminator is created because all oneOf classes have the same discriminator
+        modelName = "MyPetsNoDisc";
+        sc = openAPI.getComponents().getSchemas().get(modelName);
+        CodegenModel myPetsNoDisc = codegen.fromModel(modelName, sc);
+        Assert.assertEquals(myPetsNoDisc.discriminator, null);
+
+        CodegenModel cm;
+
+        // the mapping in b is in A
+        modelName = "A";
+        sc = openAPI.getComponents().getSchemas().get(modelName);
+        cm = codegen.fromModel(modelName, sc);
+        hs.clear();
+        hs.add(new CodegenDiscriminator.MappedModel("b", codegen.toModelName("B")));
+        Assert.assertEquals(cm.discriminator.getMappedModels(), hs);
+
+        // the mapping in b is in B
+        modelName = "B";
+        sc = openAPI.getComponents().getSchemas().get(modelName);
+        cm = codegen.fromModel(modelName, sc);
+        Assert.assertEquals(cm.discriminator, null);
+
+        // the mapping in b is in C
+        modelName = "C";
+        sc = openAPI.getComponents().getSchemas().get(modelName);
+        cm = codegen.fromModel(modelName, sc);
+        Assert.assertEquals(cm.discriminator, null);
+    }
+
+    @Test
+    public void testComposedSchemaOneOfDiscriminatorsInvalid() {
+        final OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_0/oneOfDiscriminator.yaml");
+        DefaultCodegen codegen = new DefaultCodegen();
+        codegen.setLegacyDiscriminatorBehavior(false);
+        codegen.setOpenAPI(openAPI);
+
+        HashMap<String, String> hm = new HashMap<>();
+        hm.put("ComposedDiscMissingNoProperties", "'ComposedDiscMissingNoProperties' defines discriminator 'fruitType', but the referenced schema 'DiscMissingNoProperties' is incorrect. fruitType is missing from the schema, define it as required and type string");
+        hm.put("ComposedDiscMissingFromProperties", "'ComposedDiscMissingFromProperties' defines discriminator 'fruitType', but the referenced schema 'DiscMissingFromProperties' is incorrect. fruitType is missing from the schema, define it as required and type string");
+        hm.put("ComposedDiscOptionalTypeCorrect", "'ComposedDiscOptionalTypeCorrect' defines discriminator 'fruitType', but the referenced schema 'DiscOptionalTypeCorrect' is incorrect. invalid optional definition of fruitType, include it in required");
+        hm.put("ComposedDiscOptionalTypeIncorrect", "'ComposedDiscOptionalTypeIncorrect' defines discriminator 'fruitType', but the referenced schema 'DiscOptionalTypeIncorrect' is incorrect. invalid type for fruitType, set it to string. invalid optional definition of fruitType, include it in required");
+        hm.put("ComposedDiscOptionalTypeInconsistent", "'ComposedDiscOptionalTypeInconsistent' defines discriminator 'fruitType', but the referenced schema 'DiscOptionalTypeIncorrect' is incorrect. invalid type for fruitType, set it to string. invalid optional definition of fruitType, include it in required");
+        hm.put("ComposedDiscTypeIncorrect", "'ComposedDiscTypeIncorrect' defines discriminator 'fruitType', but the referenced schema 'DiscTypeIncorrect' is incorrect. invalid type for fruitType, set it to string");
+        hm.put("ComposedDiscTypeInconsistent", "'ComposedDiscTypeInconsistent' defines discriminator 'fruitType', but the referenced schema 'DiscTypeIncorrect' is incorrect. invalid type for fruitType, set it to string");
+        hm.put("ComposedDiscRequiredInconsistent", "'ComposedDiscRequiredInconsistent' defines discriminator 'fruitType', but the referenced schema 'DiscOptionalTypeCorrect' is incorrect. invalid optional definition of fruitType, include it in required");
+
+        for(Map.Entry<String, String> entry : hm.entrySet()) {
+            String modelName = entry.getKey();
+            String errorMessageExpected = entry.getValue();
+
+            Schema sc = openAPI.getComponents().getSchemas().get(modelName);
+
+            try {
+                codegen.fromModel(modelName, sc);
+                Assert.assertTrue(false, "A RuntimeException should have been thrown when processing "+modelName+ " but it was not");
+            } catch (RuntimeException re) {
+                Assert.assertEquals(re.getMessage(), errorMessageExpected);
+            }
+        }
+    }
+
+    @Test
+    public void testComposedSchemaAnyOfDiscriminatorsInvalid() {
+        final OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_0/anyOfDiscriminator.yaml");
+        DefaultCodegen codegen = new DefaultCodegen();
+        codegen.setLegacyDiscriminatorBehavior(false);
+        codegen.setOpenAPI(openAPI);
+
+        HashMap<String, String> hm = new HashMap<>();
+        hm.put("ComposedDiscMissingNoProperties", "'ComposedDiscMissingNoProperties' defines discriminator 'fruitType', but the referenced schema 'DiscMissingNoProperties' is incorrect. fruitType is missing from the schema, define it as required and type string");
+        hm.put("ComposedDiscMissingFromProperties", "'ComposedDiscMissingFromProperties' defines discriminator 'fruitType', but the referenced schema 'DiscMissingFromProperties' is incorrect. fruitType is missing from the schema, define it as required and type string");
+        hm.put("ComposedDiscOptionalTypeCorrect", "'ComposedDiscOptionalTypeCorrect' defines discriminator 'fruitType', but the referenced schema 'DiscOptionalTypeCorrect' is incorrect. invalid optional definition of fruitType, include it in required");
+        hm.put("ComposedDiscOptionalTypeIncorrect", "'ComposedDiscOptionalTypeIncorrect' defines discriminator 'fruitType', but the referenced schema 'DiscOptionalTypeIncorrect' is incorrect. invalid type for fruitType, set it to string. invalid optional definition of fruitType, include it in required");
+        hm.put("ComposedDiscOptionalTypeInconsistent", "'ComposedDiscOptionalTypeInconsistent' defines discriminator 'fruitType', but the referenced schema 'DiscOptionalTypeIncorrect' is incorrect. invalid type for fruitType, set it to string. invalid optional definition of fruitType, include it in required");
+        hm.put("ComposedDiscTypeIncorrect", "'ComposedDiscTypeIncorrect' defines discriminator 'fruitType', but the referenced schema 'DiscTypeIncorrect' is incorrect. invalid type for fruitType, set it to string");
+        hm.put("ComposedDiscTypeInconsistent", "'ComposedDiscTypeInconsistent' defines discriminator 'fruitType', but the referenced schema 'DiscTypeIncorrect' is incorrect. invalid type for fruitType, set it to string");
+        hm.put("ComposedDiscRequiredInconsistent", "'ComposedDiscRequiredInconsistent' defines discriminator 'fruitType', but the referenced schema 'DiscOptionalTypeCorrect' is incorrect. invalid optional definition of fruitType, include it in required");
+
+        for(Map.Entry<String, String> entry : hm.entrySet()) {
+            String modelName = entry.getKey();
+            String errorMessageExpected = entry.getValue();
+
+            Schema sc = openAPI.getComponents().getSchemas().get(modelName);
+
+            try {
+                codegen.fromModel(modelName, sc);
+                Assert.assertTrue(false, "A RuntimeException should have been thrown when processing "+modelName+ " but it was not");
+            } catch (RuntimeException re) {
+                Assert.assertEquals(re.getMessage(), errorMessageExpected);
+            }
+        }
+    }
+
+    @Test
+    public void testComposedSchemaAnyOfDiscriminatorMap() {
+        final OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_0/anyOfDiscriminator.yaml");
+        DefaultCodegen codegen = new DefaultCodegen();
+        codegen.setLegacyDiscriminatorBehavior(false);
+        codegen.setOpenAPI(openAPI);
+
+        String modelName;
+        Schema sc;
+        CodegenModel cm;
+        java.util.LinkedHashSet hs;
+        String mn;
+
+        // inline anyOf models work because the inline schemas are turned into $refs
+        modelName = "FruitInlineDisc";
+        sc = openAPI.getComponents().getSchemas().get(modelName);
+        cm = codegen.fromModel(modelName, sc);
+        hs = new java.util.LinkedHashSet();
+        mn = "FruitInlineDisc_anyOf";
+        hs.add(new CodegenDiscriminator.MappedModel(mn, codegen.toModelName(mn)));
+        mn = "FruitInlineDisc_anyOf_1";
+        hs.add(new CodegenDiscriminator.MappedModel(mn, codegen.toModelName(mn)));
+        Assert.assertEquals(cm.discriminator.getMappedModels(), hs);
+
+        // inline anyOf with inline anyOf model doesn't work because we have null $refs and we throw an exception
+        final String fmodelName = "FruitInlineInlineDisc";
+        final Schema fsc = openAPI.getComponents().getSchemas().get(fmodelName);
+        Assert.assertThrows(() -> codegen.fromModel(fmodelName, fsc));
+
+        // ref anyOf models with discriminator in properties in those models
+        modelName = "FruitReqDisc";
+        sc = openAPI.getComponents().getSchemas().get(modelName);
+        cm = codegen.fromModel(modelName, sc);
+        hs = new java.util.LinkedHashSet();
+        mn = "AppleReqDisc";
+        hs.add(new CodegenDiscriminator.MappedModel(mn, mn));
+        mn = "BananaReqDisc";
+        hs.add(new CodegenDiscriminator.MappedModel(mn, mn));
+        Assert.assertEquals(cm.discriminator.getMappedModels(), hs);
+
+        // ref oneOf models with discriminator in allOf in those models
+        modelName = "FruitAllOfDisc";
+        sc = openAPI.getComponents().getSchemas().get(modelName);
+        cm = codegen.fromModel(modelName, sc);
+        hs = new java.util.LinkedHashSet();
+        mn = "AppleAllOfDisc";
+        hs.add(new CodegenDiscriminator.MappedModel(mn, mn));
+        mn = "BananaAllOfDisc";
+        hs.add(new CodegenDiscriminator.MappedModel(mn, mn));
+        Assert.assertEquals(cm.discriminator.getMappedModels(), hs);
+
+        // ref oneOf models with discriminator in anyOf in those models
+        modelName = "FruitAnyOfDisc";
+        sc = openAPI.getComponents().getSchemas().get(modelName);
+        cm = codegen.fromModel(modelName, sc);
+        hs = new java.util.LinkedHashSet();
+        mn = "AppleAnyOfDisc";
+        hs.add(new CodegenDiscriminator.MappedModel(mn, mn));
+        mn = "BananaAnyOfDisc";
+        hs.add(new CodegenDiscriminator.MappedModel(mn, mn));
+        Assert.assertEquals(cm.discriminator.getMappedModels(), hs);
+
+        // ref oneOf models with discriminator in anyOf in those models
+        modelName = "FruitAnyOfDisc";
+        sc = openAPI.getComponents().getSchemas().get(modelName);
+        cm = codegen.fromModel(modelName, sc);
+        hs = new java.util.LinkedHashSet();
+        mn = "AppleAnyOfDisc";
+        hs.add(new CodegenDiscriminator.MappedModel(mn, mn));
+        mn = "BananaAnyOfDisc";
+        hs.add(new CodegenDiscriminator.MappedModel(mn, mn));
+        Assert.assertEquals(cm.discriminator.getMappedModels(), hs);
+
+        // ref oneOf models with discriminator in the grandparent schemas of those anyof models
+        modelName = "FruitGrandparentDisc";
+        sc = openAPI.getComponents().getSchemas().get(modelName);
+        cm = codegen.fromModel(modelName, sc);
+        hs = new java.util.LinkedHashSet();
+        mn = "AppleGrandparentDisc";
+        hs.add(new CodegenDiscriminator.MappedModel(mn, mn));
+        mn = "BananaGrandparentDisc";
+        hs.add(new CodegenDiscriminator.MappedModel(mn, mn));
+        Assert.assertEquals(cm.discriminator.getMappedModels(), hs);
+    }
+
+    @Test
+    public void testComposedSchemaOneOfDiscriminatorMap() {
+        final OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_0/oneOfDiscriminator.yaml");
+        DefaultCodegen codegen = new DefaultCodegen();
+        codegen.setLegacyDiscriminatorBehavior(false);
+        codegen.setOpenAPI(openAPI);
+
+        String modelName;
+        Schema sc;
+        CodegenModel cm;
+        java.util.LinkedHashSet hs;
+        String mn;
+
+        // inline oneOf models work because the inline schemas are turned into $refs
+        modelName = "FruitInlineDisc";
+        sc = openAPI.getComponents().getSchemas().get(modelName);
+        cm = codegen.fromModel(modelName, sc);
+        hs = new java.util.LinkedHashSet();
+        mn = "FruitInlineDisc_oneOf";
+        hs.add(new CodegenDiscriminator.MappedModel(mn, codegen.toModelName(mn)));
+        mn = "FruitInlineDisc_oneOf_1";
+        hs.add(new CodegenDiscriminator.MappedModel(mn, codegen.toModelName(mn)));
+        Assert.assertEquals(cm.discriminator.getMappedModels(), hs);
+
+        // inline oneOf with inline oneOf model doesn't work because we have null $refs and we throw an exception
+        final String fmodelName = "FruitInlineInlineDisc";
+        final Schema fsc = openAPI.getComponents().getSchemas().get(fmodelName);
+        Assert.assertThrows(() -> codegen.fromModel(fmodelName, fsc));
+
+        // ref oneOf models with discriminator in properties in those models
+        modelName = "FruitReqDisc";
+        sc = openAPI.getComponents().getSchemas().get(modelName);
+        cm = codegen.fromModel(modelName, sc);
+        hs = new java.util.LinkedHashSet();
+        mn = "AppleReqDisc";
+        hs.add(new CodegenDiscriminator.MappedModel(mn, mn));
+        mn = "BananaReqDisc";
+        hs.add(new CodegenDiscriminator.MappedModel(mn, mn));
+        Assert.assertEquals(cm.discriminator.getMappedModels(), hs);
+
+        // ref oneOf models with discriminator in allOf in those models
+        modelName = "FruitAllOfDisc";
+        sc = openAPI.getComponents().getSchemas().get(modelName);
+        cm = codegen.fromModel(modelName, sc);
+        hs = new java.util.LinkedHashSet();
+        mn = "AppleAllOfDisc";
+        hs.add(new CodegenDiscriminator.MappedModel(mn, mn));
+        mn = "BananaAllOfDisc";
+        hs.add(new CodegenDiscriminator.MappedModel(mn, mn));
+        Assert.assertEquals(cm.discriminator.getMappedModels(), hs);
+
+        // ref oneOf models with discriminator in anyOf in those models
+        modelName = "FruitAnyOfDisc";
+        sc = openAPI.getComponents().getSchemas().get(modelName);
+        cm = codegen.fromModel(modelName, sc);
+        hs = new java.util.LinkedHashSet();
+        mn = "AppleAnyOfDisc";
+        hs.add(new CodegenDiscriminator.MappedModel(mn, mn));
+        mn = "BananaAnyOfDisc";
+        hs.add(new CodegenDiscriminator.MappedModel(mn, mn));
+        Assert.assertEquals(cm.discriminator.getMappedModels(), hs);
+
+        // ref oneOf models with discriminator in oneOf in those models
+        modelName = "FruitOneOfDisc";
+        sc = openAPI.getComponents().getSchemas().get(modelName);
+        cm = codegen.fromModel(modelName, sc);
+        hs = new java.util.LinkedHashSet();
+        mn = "AppleOneOfDisc";
+        hs.add(new CodegenDiscriminator.MappedModel(mn, mn));
+        mn = "BananaOneOfDisc";
+        hs.add(new CodegenDiscriminator.MappedModel(mn, mn));
+        Assert.assertEquals(cm.discriminator.getMappedModels(), hs);
+
+        // ref oneOf models with discriminator in the grandparent schemas of those oneof models
+        modelName = "FruitGrandparentDisc";
+        sc = openAPI.getComponents().getSchemas().get(modelName);
+        cm = codegen.fromModel(modelName, sc);
+        hs = new java.util.LinkedHashSet();
+        mn = "AppleGrandparentDisc";
+        hs.add(new CodegenDiscriminator.MappedModel(mn, mn));
+        mn = "BananaGrandparentDisc";
+        hs.add(new CodegenDiscriminator.MappedModel(mn, mn));
+        Assert.assertEquals(cm.discriminator.getMappedModels(), hs);
+    }
+
+    @Test
+    public void testComposedSchemaMyPetsOneOfDiscriminatorMap() {
+        final OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_0/allOf_composition_discriminator.yaml");
+
+        DefaultCodegen codegen = new DefaultCodegen();
+        codegen.setLegacyDiscriminatorBehavior(false);
+        codegen.setOpenAPI(openAPI);
+
+        String path = "/mypets";
+
+        Operation operation = openAPI.getPaths().get(path).getGet();
+        CodegenOperation codegenOperation = codegen.fromOperation(path, "GET", operation, null);
+        verifyMyPetsDiscriminator(codegenOperation.discriminator);
+
+        Schema pet = openAPI.getComponents().getSchemas().get("MyPets");
+        CodegenModel petModel = codegen.fromModel("MyPets", pet);
+        verifyMyPetsDiscriminator(petModel.discriminator);
+    }
+
+    @Test
+    public void testComposedSchemaAllOfHierarchy(){
+        final OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_0/allOf_composition_discriminator.yaml");
+
+        DefaultCodegen codegen = new DefaultCodegen();
+        codegen.setLegacyDiscriminatorBehavior(false);
+        codegen.setOpenAPI(openAPI);
+
+        Schema pet = openAPI.getComponents().getSchemas().get("Lizard");
+        CodegenModel petModel = codegen.fromModel("Lizard", pet);
+        verifyLizardDiscriminator(petModel.discriminator);
+
+        pet = openAPI.getComponents().getSchemas().get("Reptile");
+        petModel = codegen.fromModel("Reptile", pet);
+        verifyReptileDiscriminator(petModel.discriminator);
+    }
+
+    private void verifyLizardDiscriminator(CodegenDiscriminator discriminator) {
+        CodegenDiscriminator test = new CodegenDiscriminator();
+        String prop = "petType";
+        test.setPropertyName(prop);
+        test.setPropertyBaseName(prop);
+        test.setMapping(null);
+        test.setMappedModels(new HashSet<>());
+        assertEquals(discriminator, test);
+    }
+
+    private void verifyReptileDiscriminator(CodegenDiscriminator discriminator) {
+        CodegenDiscriminator test = new CodegenDiscriminator();
+        String prop = "petType";
+        test.setPropertyName(prop);
+        test.setPropertyBaseName(prop);
+        test.setMapping(null);
+        test.setMappedModels(new HashSet<CodegenDiscriminator.MappedModel>(){{
+            add(new CodegenDiscriminator.MappedModel("Snake", "Snake"));
+            add(new CodegenDiscriminator.MappedModel("Lizard", "Lizard"));
+        }});
+        assertEquals(discriminator, test);
+    }
+
+    private void verifyMyPetsDiscriminator(CodegenDiscriminator discriminator) {
+        CodegenDiscriminator test = new CodegenDiscriminator();
+        String prop = "petType";
+        test.setPropertyName(prop);
+        test.setPropertyBaseName(prop);
+        test.setMapping(null);
+        test.setMappedModels(new HashSet<CodegenDiscriminator.MappedModel>(){{
+            add(new CodegenDiscriminator.MappedModel("Cat", "Cat"));
+            add(new CodegenDiscriminator.MappedModel("Lizard", "Lizard"));
+        }});
+        assertEquals(discriminator, test);
+    }
+
+    public CodegenModel getModel(List<Object> allModels, String modelName) {
+        for (Object obj: allModels) {
+            HashMap<String, Object> hm = (HashMap<String, Object>) obj;
+            CodegenModel cm = (CodegenModel) hm.get("model");
+            if (modelName.equals(cm.name)) {
+                return cm;
+            }
+        }
+        return null;
+    }
+
+    @Test
+    public void verifyXDiscriminatorValue() {
+        final OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/2_0/x-discriminator-value.yaml");
+        final DefaultCodegen config = new DefaultCodegen();
+        config.setOpenAPI(openAPI);
+
+        String modelName;
+        CodegenDiscriminator discriminator;
+        Schema sc;
+        CodegenModel cm;
+
+        Boolean dryRun = Boolean.TRUE;
+        final DefaultGenerator generator = new DefaultGenerator(dryRun);
+        generator.openAPI = openAPI;
+        generator.config = config;
+        generator.configureGeneratorProperties();
+
+        // for us to check a model's children we need to run generator.generateModels
+        // because children are assigned in config.updateAllModels which is invoked in generator.generateModels
+        List<File> files = new ArrayList<>();
+        List<String> filteredSchemas = ModelUtils.getSchemasUsedOnlyInFormParam(openAPI);
+        List<Object> allModels = new ArrayList<>();
+        generator.generateModels(files, allModels, filteredSchemas);
+
+        // check that the model's children contain the x-discriminator-values
+        modelName = "BaseObj";
+        cm = getModel(allModels, modelName);
+        List<String> excpectedDiscriminatorValues = new ArrayList<>(Arrays.asList("daily", "sub-obj"));
+        ArrayList<String> xDiscriminatorValues = new ArrayList<>();
+        for (CodegenModel child: cm.children) {
+            xDiscriminatorValues.add((String) child.vendorExtensions.get("x-discriminator-value"));
+        }
+        assertEquals(xDiscriminatorValues, excpectedDiscriminatorValues);
+
+        // check that the discriminator's MappedModels also contains the x-discriminator-values
+        discriminator = new CodegenDiscriminator();
+        String prop = "object_type";
+        discriminator.setPropertyName(config.toVarName(prop));
+        discriminator.setPropertyBaseName(prop);
+        discriminator.setMapping(null);
+        discriminator.setMappedModels(new HashSet<CodegenDiscriminator.MappedModel>(){{
+            add(new CodegenDiscriminator.MappedModel("DailySubObj", "DailySubObj"));
+            add(new CodegenDiscriminator.MappedModel("SubObj", "SubObj"));
+            add(new CodegenDiscriminator.MappedModel("daily", "DailySubObj"));
+            add(new CodegenDiscriminator.MappedModel("sub-obj", "SubObj"));
+        }});
+        assertEquals(cm.discriminator, discriminator);
+    }
+
+
     @Test
     public void testAllOfSingleRefNoOwnProps() {
         final OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/2_0/composed-allof.yaml");
@@ -1033,6 +1600,8 @@ public class DefaultCodegenTest {
         test.getMapping().put("c", "Child");
         test.getMappedModels().add(new CodegenDiscriminator.MappedModel("a", "Adult"));
         test.getMappedModels().add(new CodegenDiscriminator.MappedModel("c", "Child"));
+        test.getMappedModels().add(new CodegenDiscriminator.MappedModel("Adult", "Adult"));
+        test.getMappedModels().add(new CodegenDiscriminator.MappedModel("Child", "Child"));
         Assert.assertEquals(discriminator, test);
     }
 
@@ -1139,8 +1708,7 @@ public class DefaultCodegenTest {
         DefaultCodegen codegen = new DefaultCodegen();
         codegen.supportsInheritance = true;
 
-        OpenAPI openAPI = new OpenAPIParser()
-                .readLocation("src/test/resources/3_0/generic.yaml", null, new ParseOptions()).getOpenAPI();
+        final OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_0/generic.yaml");
         codegen.setOpenAPI(openAPI);
 
         CodegenModel codegenModel = codegen.fromModel("Dog", openAPI.getComponents().getSchemas().get("Dog"));
@@ -1169,8 +1737,7 @@ public class DefaultCodegenTest {
         codegen.supportsInheritance = true;
         codegen.setModelNamePrefix("prefix");
 
-        OpenAPI openAPI = new OpenAPIParser()
-                .readLocation("src/test/resources/3_0/generic.yaml", null, new ParseOptions()).getOpenAPI();
+        final OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_0/generic.yaml");
         codegen.setOpenAPI(openAPI);
 
         CodegenModel codegenModel = codegen.fromModel("Dog", openAPI.getComponents().getSchemas().get("Dog"));
@@ -1184,8 +1751,7 @@ public class DefaultCodegenTest {
         codegen.supportsInheritance = true;
         codegen.setModelNameSuffix("suffix");
 
-        OpenAPI openAPI = new OpenAPIParser()
-                .readLocation("src/test/resources/3_0/generic.yaml", null, new ParseOptions()).getOpenAPI();
+        final OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_0/generic.yaml");
         codegen.setOpenAPI(openAPI);
 
         CodegenModel codegenModel = codegen.fromModel("Dog", openAPI.getComponents().getSchemas().get("Dog"));
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/BashClientOptionsProvider.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/BashClientOptionsProvider.java
index 17fddc4cfb6..45b03efccce 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/BashClientOptionsProvider.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/BashClientOptionsProvider.java
@@ -70,6 +70,7 @@ public class BashClientOptionsProvider implements OptionsProvider {
                 .put(CodegenConstants.ENSURE_UNIQUE_PARAMS, "false")
                 .put(CodegenConstants.ALLOW_UNICODE_IDENTIFIERS, ALLOW_UNICODE_IDENTIFIERS_VALUE)
                 .put(CodegenConstants.PREPEND_FORM_OR_BODY_PARAMETERS, PREPEND_FORM_OR_BODY_PARAMETERS_VALUE)
+                .put(CodegenConstants.LEGACY_DISCRIMINATOR_BEHAVIOR, "true")
                 .build();
     
     }
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/DartClientOptionsProvider.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/DartClientOptionsProvider.java
index 226389505b0..79cf084234f 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/DartClientOptionsProvider.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/DartClientOptionsProvider.java
@@ -62,6 +62,7 @@ public class DartClientOptionsProvider implements OptionsProvider {
                 .put(CodegenConstants.ALLOW_UNICODE_IDENTIFIERS, ALLOW_UNICODE_IDENTIFIERS_VALUE)
                 .put(CodegenConstants.PREPEND_FORM_OR_BODY_PARAMETERS, PREPEND_FORM_OR_BODY_PARAMETERS_VALUE)
                 .put(DartClientCodegen.SUPPORT_DART2, "false")
+                .put(CodegenConstants.LEGACY_DISCRIMINATOR_BEHAVIOR, "true")
                 .build();
     }
 
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/DartDioClientOptionsProvider.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/DartDioClientOptionsProvider.java
index da24d2e195a..9e54e028f7f 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/DartDioClientOptionsProvider.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/DartDioClientOptionsProvider.java
@@ -67,6 +67,7 @@ public class DartDioClientOptionsProvider implements OptionsProvider {
                 .put(DartDioClientCodegen.SUPPORT_DART2, "false")
                 .put(DartDioClientCodegen.DATE_LIBRARY, DATE_LIBRARY)
                 .put(DartDioClientCodegen.NULLABLE_FIELDS, NULLABLE_FIELDS)
+                .put(CodegenConstants.LEGACY_DISCRIMINATOR_BEHAVIOR, "true")
                 .build();
     }
 
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/ElixirClientOptionsProvider.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/ElixirClientOptionsProvider.java
index 0a0f86e4eeb..f6efa94aa51 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/ElixirClientOptionsProvider.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/ElixirClientOptionsProvider.java
@@ -43,6 +43,7 @@ public class ElixirClientOptionsProvider implements OptionsProvider {
                 .put("licenseHeader", "# Copyright 2017 Me\n#\n# Licensed under the Apache License")
                 .put(CodegenConstants.PACKAGE_NAME, "yay_pets")
                 .put(CodegenConstants.PREPEND_FORM_OR_BODY_PARAMETERS, PREPEND_FORM_OR_BODY_PARAMETERS_VALUE)
+                .put(CodegenConstants.LEGACY_DISCRIMINATOR_BEHAVIOR, "true")
                 .build();
     }
 
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/HaskellServantOptionsProvider.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/HaskellServantOptionsProvider.java
index 15a46665096..f883ebbed19 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/HaskellServantOptionsProvider.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/HaskellServantOptionsProvider.java
@@ -48,6 +48,7 @@ public class HaskellServantOptionsProvider implements OptionsProvider {
                 .put(CodegenConstants.ALLOW_UNICODE_IDENTIFIERS, ALLOW_UNICODE_IDENTIFIERS_VALUE)
                 .put(CodegenConstants.PREPEND_FORM_OR_BODY_PARAMETERS, PREPEND_FORM_OR_BODY_PARAMETERS_VALUE)
                 .put(HaskellServantCodegen.PROP_SERVE_STATIC, HaskellServantCodegen.PROP_SERVE_STATIC_DEFAULT.toString())
+                .put(CodegenConstants.LEGACY_DISCRIMINATOR_BEHAVIOR, "true")
                 .build();
     }
 
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/PhpClientOptionsProvider.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/PhpClientOptionsProvider.java
index b1aed3e446e..245957be407 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/PhpClientOptionsProvider.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/PhpClientOptionsProvider.java
@@ -58,6 +58,7 @@ public class PhpClientOptionsProvider implements OptionsProvider {
                 .put(CodegenConstants.HIDE_GENERATION_TIMESTAMP, "true")
                 .put(CodegenConstants.ALLOW_UNICODE_IDENTIFIERS, ALLOW_UNICODE_IDENTIFIERS_VALUE)
                 .put(CodegenConstants.PREPEND_FORM_OR_BODY_PARAMETERS, PREPEND_FORM_OR_BODY_PARAMETERS_VALUE)
+                .put(CodegenConstants.LEGACY_DISCRIMINATOR_BEHAVIOR, "true")
                 .build();
     }
 
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/PhpLumenServerOptionsProvider.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/PhpLumenServerOptionsProvider.java
index 8f2c1d574ff..97ad8132ce4 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/PhpLumenServerOptionsProvider.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/PhpLumenServerOptionsProvider.java
@@ -57,6 +57,7 @@ public class PhpLumenServerOptionsProvider implements OptionsProvider {
                 .put(CodegenConstants.ARTIFACT_VERSION, ARTIFACT_VERSION_VALUE)
                 .put(CodegenConstants.ALLOW_UNICODE_IDENTIFIERS, ALLOW_UNICODE_IDENTIFIERS_VALUE)
                 .put(CodegenConstants.PREPEND_FORM_OR_BODY_PARAMETERS, PREPEND_FORM_OR_BODY_PARAMETERS_VALUE)
+                .put(CodegenConstants.LEGACY_DISCRIMINATOR_BEHAVIOR, "true")
                 .build();
     }
 
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/PhpSilexServerOptionsProvider.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/PhpSilexServerOptionsProvider.java
index faf3992c99d..a3f32f9b4a0 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/PhpSilexServerOptionsProvider.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/PhpSilexServerOptionsProvider.java
@@ -42,6 +42,7 @@ public class PhpSilexServerOptionsProvider implements OptionsProvider {
                 .put(CodegenConstants.ENSURE_UNIQUE_PARAMS, ENSURE_UNIQUE_PARAMS_VALUE)
                 .put(CodegenConstants.ALLOW_UNICODE_IDENTIFIERS, ALLOW_UNICODE_IDENTIFIERS_VALUE)
                 .put(CodegenConstants.PREPEND_FORM_OR_BODY_PARAMETERS, PREPEND_FORM_OR_BODY_PARAMETERS_VALUE)
+                .put(CodegenConstants.LEGACY_DISCRIMINATOR_BEHAVIOR, "true")
                 .build();
     }
 
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/PhpSlim4ServerOptionsProvider.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/PhpSlim4ServerOptionsProvider.java
index 98c1ded49d2..4bf91932a3f 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/PhpSlim4ServerOptionsProvider.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/PhpSlim4ServerOptionsProvider.java
@@ -60,6 +60,7 @@ public class PhpSlim4ServerOptionsProvider implements OptionsProvider {
                 .put(CodegenConstants.ALLOW_UNICODE_IDENTIFIERS, ALLOW_UNICODE_IDENTIFIERS_VALUE)
                 .put(CodegenConstants.PREPEND_FORM_OR_BODY_PARAMETERS, PREPEND_FORM_OR_BODY_PARAMETERS_VALUE)
                 .put(PhpSlim4ServerCodegen.PSR7_IMPLEMENTATION, PSR7_IMPLEMENTATION_VALUE)
+                .put(CodegenConstants.LEGACY_DISCRIMINATOR_BEHAVIOR, "true")
                 .build();
     }
 
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/PhpSlimServerOptionsProvider.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/PhpSlimServerOptionsProvider.java
index 70eed81c9e2..537b7b10c66 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/PhpSlimServerOptionsProvider.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/PhpSlimServerOptionsProvider.java
@@ -57,6 +57,7 @@ public class PhpSlimServerOptionsProvider implements OptionsProvider {
                 .put(CodegenConstants.ENSURE_UNIQUE_PARAMS, ENSURE_UNIQUE_PARAMS_VALUE)
                 .put(CodegenConstants.ALLOW_UNICODE_IDENTIFIERS, ALLOW_UNICODE_IDENTIFIERS_VALUE)
                 .put(CodegenConstants.PREPEND_FORM_OR_BODY_PARAMETERS, PREPEND_FORM_OR_BODY_PARAMETERS_VALUE)
+                .put(CodegenConstants.LEGACY_DISCRIMINATOR_BEHAVIOR, "true")
                 .build();
     }
 
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/RubyClientOptionsProvider.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/RubyClientOptionsProvider.java
index dce16e7245d..09bd0dceabc 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/RubyClientOptionsProvider.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/RubyClientOptionsProvider.java
@@ -66,6 +66,7 @@ public class RubyClientOptionsProvider implements OptionsProvider {
                 .put(CodegenConstants.ALLOW_UNICODE_IDENTIFIERS, ALLOW_UNICODE_IDENTIFIERS_VALUE)
                 .put(CodegenConstants.PREPEND_FORM_OR_BODY_PARAMETERS, PREPEND_FORM_OR_BODY_PARAMETERS_VALUE)
                 .put(CodegenConstants.LIBRARY, LIBRARY)
+                .put(CodegenConstants.LEGACY_DISCRIMINATOR_BEHAVIOR, "true")
                 .build();
     }
 
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/ScalaAkkaClientOptionsProvider.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/ScalaAkkaClientOptionsProvider.java
index f9ac4d5ee3b..4b982932b98 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/ScalaAkkaClientOptionsProvider.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/ScalaAkkaClientOptionsProvider.java
@@ -55,6 +55,7 @@ public class ScalaAkkaClientOptionsProvider implements OptionsProvider {
                 .put("mainPackage", MAIN_PACKAGE_VALUE)
                 .put(CodegenConstants.MODEL_PROPERTY_NAMING, MODEL_PROPERTY_NAMING)
                 .put("dateLibrary", DATE_LIBRARY)
+                .put(CodegenConstants.LEGACY_DISCRIMINATOR_BEHAVIOR, "true")
                 .build();
     }
 
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/ScalaHttpClientOptionsProvider.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/ScalaHttpClientOptionsProvider.java
index c128ea1bba7..11825e2ec12 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/ScalaHttpClientOptionsProvider.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/ScalaHttpClientOptionsProvider.java
@@ -52,6 +52,7 @@ public class ScalaHttpClientOptionsProvider implements OptionsProvider {
                 .put(CodegenConstants.ALLOW_UNICODE_IDENTIFIERS, ALLOW_UNICODE_IDENTIFIERS_VALUE)
                 .put(CodegenConstants.PREPEND_FORM_OR_BODY_PARAMETERS, PREPEND_FORM_OR_BODY_PARAMETERS_VALUE)
                 .put("dateLibrary", DATE_LIBRARY)
+                .put(CodegenConstants.LEGACY_DISCRIMINATOR_BEHAVIOR, "true")
                 .build();
     }
 
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/Swift3OptionsProvider.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/Swift3OptionsProvider.java
index 6e496e915af..d83863cd739 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/Swift3OptionsProvider.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/Swift3OptionsProvider.java
@@ -79,6 +79,7 @@ public class Swift3OptionsProvider implements OptionsProvider {
                 .put(CodegenConstants.HIDE_GENERATION_TIMESTAMP, "true")
                 .put(CodegenConstants.ALLOW_UNICODE_IDENTIFIERS, ALLOW_UNICODE_IDENTIFIERS_VALUE)
                 .put(CodegenConstants.PREPEND_FORM_OR_BODY_PARAMETERS, PREPEND_FORM_OR_BODY_PARAMETERS_VALUE)
+                .put(CodegenConstants.LEGACY_DISCRIMINATOR_BEHAVIOR, "true")
                 .build();
     }
 
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/Swift4OptionsProvider.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/Swift4OptionsProvider.java
index 87c2ecbebd3..aa2d61f2829 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/Swift4OptionsProvider.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/Swift4OptionsProvider.java
@@ -81,6 +81,7 @@ public class Swift4OptionsProvider implements OptionsProvider {
                 .put(CodegenConstants.HIDE_GENERATION_TIMESTAMP, "true")
                 .put(CodegenConstants.ALLOW_UNICODE_IDENTIFIERS, ALLOW_UNICODE_IDENTIFIERS_VALUE)
                 .put(CodegenConstants.PREPEND_FORM_OR_BODY_PARAMETERS, PREPEND_FORM_OR_BODY_PARAMETERS_VALUE)
+                .put(CodegenConstants.LEGACY_DISCRIMINATOR_BEHAVIOR, "true")
                 .build();
     }
 
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/Swift5OptionsProvider.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/Swift5OptionsProvider.java
index 3f85681caa6..d5cd8cbe38e 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/Swift5OptionsProvider.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/Swift5OptionsProvider.java
@@ -80,6 +80,7 @@ public class Swift5OptionsProvider implements OptionsProvider {
                 .put(CodegenConstants.PREPEND_FORM_OR_BODY_PARAMETERS, PREPEND_FORM_OR_BODY_PARAMETERS_VALUE)
                 .put(CodegenConstants.API_NAME_PREFIX, "")
                 .put(CodegenConstants.LIBRARY, LIBRARY_VALUE)
+                .put(CodegenConstants.LEGACY_DISCRIMINATOR_BEHAVIOR, "true")
                 .build();
     }
 
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/TypeScriptAngularClientOptionsProvider.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/TypeScriptAngularClientOptionsProvider.java
index 5635465a632..51b62748e3c 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/TypeScriptAngularClientOptionsProvider.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/TypeScriptAngularClientOptionsProvider.java
@@ -81,6 +81,7 @@ public class TypeScriptAngularClientOptionsProvider implements OptionsProvider {
                 .put(CodegenConstants.ALLOW_UNICODE_IDENTIFIERS, ALLOW_UNICODE_IDENTIFIERS_VALUE)
                 .put(CodegenConstants.PREPEND_FORM_OR_BODY_PARAMETERS, PREPEND_FORM_OR_BODY_PARAMETERS_VALUE)
                 .put(TypeScriptAngularClientCodegen.FILE_NAMING, FILE_NAMING_VALUE)
+                .put(CodegenConstants.LEGACY_DISCRIMINATOR_BEHAVIOR, "true")
                 .build();
     }
 
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/TypeScriptAngularJsClientOptionsProvider.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/TypeScriptAngularJsClientOptionsProvider.java
index 2ab399a12bb..1e008de1ed1 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/TypeScriptAngularJsClientOptionsProvider.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/TypeScriptAngularJsClientOptionsProvider.java
@@ -53,6 +53,7 @@ public class TypeScriptAngularJsClientOptionsProvider implements OptionsProvider
                 .put(CodegenConstants.MODEL_PROPERTY_NAMING, MODEL_PROPERTY_NAMING_VALUE)
                 .put(CodegenConstants.ALLOW_UNICODE_IDENTIFIERS, ALLOW_UNICODE_IDENTIFIERS_VALUE)
                 .put(CodegenConstants.PREPEND_FORM_OR_BODY_PARAMETERS, PREPEND_FORM_OR_BODY_PARAMETERS_VALUE)
+                .put(CodegenConstants.LEGACY_DISCRIMINATOR_BEHAVIOR, "true")
                 .build();
     }
 
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/TypeScriptAureliaClientOptionsProvider.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/TypeScriptAureliaClientOptionsProvider.java
index 9c72ca44ab9..58b5aa61826 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/TypeScriptAureliaClientOptionsProvider.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/TypeScriptAureliaClientOptionsProvider.java
@@ -59,6 +59,7 @@ public class TypeScriptAureliaClientOptionsProvider implements OptionsProvider {
                 .put(TypeScriptAureliaClientCodegen.SNAPSHOT, Boolean.FALSE.toString())
                 .put(CodegenConstants.ALLOW_UNICODE_IDENTIFIERS, ALLOW_UNICODE_IDENTIFIERS_VALUE)
                 .put(CodegenConstants.PREPEND_FORM_OR_BODY_PARAMETERS, PREPEND_FORM_OR_BODY_PARAMETERS_VALUE)
+                .put(CodegenConstants.LEGACY_DISCRIMINATOR_BEHAVIOR, "true")
                 .build();
     }
 
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/TypeScriptFetchClientOptionsProvider.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/TypeScriptFetchClientOptionsProvider.java
index 196e220fb32..7bec81c9ae3 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/TypeScriptFetchClientOptionsProvider.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/TypeScriptFetchClientOptionsProvider.java
@@ -66,6 +66,7 @@ public class TypeScriptFetchClientOptionsProvider implements OptionsProvider {
                 .put(TypeScriptFetchClientCodegen.TYPESCRIPT_THREE_PLUS, TYPESCRIPT_THREE_PLUS)
                 .put(CodegenConstants.ALLOW_UNICODE_IDENTIFIERS, ALLOW_UNICODE_IDENTIFIERS_VALUE)
                 .put(CodegenConstants.PREPEND_FORM_OR_BODY_PARAMETERS, PREPEND_FORM_OR_BODY_PARAMETERS_VALUE)
+                .put(CodegenConstants.LEGACY_DISCRIMINATOR_BEHAVIOR, "true")
                 .build();
     }
 
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/TypeScriptNodeClientOptionsProvider.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/TypeScriptNodeClientOptionsProvider.java
index 23da17ea1c4..a2dc76d63f4 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/TypeScriptNodeClientOptionsProvider.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/options/TypeScriptNodeClientOptionsProvider.java
@@ -63,6 +63,7 @@ public class TypeScriptNodeClientOptionsProvider implements OptionsProvider {
                 .put(TypeScriptAngularClientCodegen.NPM_REPOSITORY, NPM_REPOSITORY)
                 .put(CodegenConstants.ALLOW_UNICODE_IDENTIFIERS, ALLOW_UNICODE_IDENTIFIERS_VALUE)
                 .put(CodegenConstants.PREPEND_FORM_OR_BODY_PARAMETERS, PREPEND_FORM_OR_BODY_PARAMETERS_VALUE)
+                .put(CodegenConstants.LEGACY_DISCRIMINATOR_BEHAVIOR, "true")
                 .build();
     }
 
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/ruby/RubyClientCodegenTest.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/ruby/RubyClientCodegenTest.java
index 7191f6e5ee0..cdde6ddc8f3 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/ruby/RubyClientCodegenTest.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/ruby/RubyClientCodegenTest.java
@@ -363,6 +363,7 @@ public class RubyClientCodegenTest {
     public void allOfTest() {
         final OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_0/allOf.yaml");
         final RubyClientCodegen codegen = new RubyClientCodegen();
+        codegen.setLegacyDiscriminatorBehavior(false);
         codegen.setModuleName("OnlinePetstore");
 
         final Schema schema = openAPI.getComponents().getSchemas().get("Person");
@@ -372,10 +373,29 @@ public class RubyClientCodegenTest {
 
         CodegenDiscriminator codegenDiscriminator = person.getDiscriminator();
         Set<CodegenDiscriminator.MappedModel> mappedModels = new LinkedHashSet<CodegenDiscriminator.MappedModel>();
-        CodegenDiscriminator.MappedModel adult = new CodegenDiscriminator.MappedModel("a", "Adult");
-        mappedModels.add(adult);
-        CodegenDiscriminator.MappedModel child = new CodegenDiscriminator.MappedModel("c", "Child");
-        mappedModels.add(child);
+        mappedModels.add(new CodegenDiscriminator.MappedModel("a", "Adult"));
+        mappedModels.add(new CodegenDiscriminator.MappedModel("c", "Child"));
+        mappedModels.add(new CodegenDiscriminator.MappedModel("Adult", "Adult"));
+        mappedModels.add(new CodegenDiscriminator.MappedModel("Child", "Child"));
+        Assert.assertEquals(codegenDiscriminator.getMappedModels(), mappedModels);
+    }
+
+    @Test(description = "test allOf (OAS3)")
+    public void allOfTestLegacy() {
+        final OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_0/allOf.yaml");
+        final RubyClientCodegen codegen = new RubyClientCodegen();
+        // codegen.discriminatorExplicitMappingVerbose == false by default
+        codegen.setModuleName("OnlinePetstore");
+
+        final Schema schema = openAPI.getComponents().getSchemas().get("Person");
+        codegen.setOpenAPI(openAPI);
+        CodegenModel person = codegen.fromModel("Person", schema);
+        Assert.assertNotNull(person);
+
+        CodegenDiscriminator codegenDiscriminator = person.getDiscriminator();
+        Set<CodegenDiscriminator.MappedModel> mappedModels = new LinkedHashSet<CodegenDiscriminator.MappedModel>();
+        mappedModels.add(new CodegenDiscriminator.MappedModel("a", "Adult"));
+        mappedModels.add(new CodegenDiscriminator.MappedModel("c", "Child"));
         Assert.assertEquals(codegenDiscriminator.getMappedModels(), mappedModels);
     }
 
diff --git a/modules/openapi-generator/src/test/resources/2_0/python-client-experimental/petstore-with-fake-endpoints-models-for-testing.yaml b/modules/openapi-generator/src/test/resources/2_0/python-client-experimental/petstore-with-fake-endpoints-models-for-testing.yaml
index 7397e6c5d5f..ba8906a1a2d 100644
--- a/modules/openapi-generator/src/test/resources/2_0/python-client-experimental/petstore-with-fake-endpoints-models-for-testing.yaml
+++ b/modules/openapi-generator/src/test/resources/2_0/python-client-experimental/petstore-with-fake-endpoints-models-for-testing.yaml
@@ -2077,12 +2077,11 @@ definitions:
     properties:
       pet_type:
         type: string
+    discriminator: pet_type
   ParentPet:
     type: object
     allOf:
     - $ref: '#/definitions/GrandparentAnimal'
-    - type: object
-      discriminator: pet_type
   ChildCat:
     allOf:
     - $ref: '#/definitions/ParentPet'
diff --git a/modules/openapi-generator/src/test/resources/2_0/x-discriminator-value.yaml b/modules/openapi-generator/src/test/resources/2_0/x-discriminator-value.yaml
new file mode 100644
index 00000000000..9dc4dea3e29
--- /dev/null
+++ b/modules/openapi-generator/src/test/resources/2_0/x-discriminator-value.yaml
@@ -0,0 +1,66 @@
+swagger: '2.0'
+info:
+  description: 'blah'
+  version: 1.0.0
+  title: sample spec
+host: fake.site.com
+tags: []
+schemes:
+  - https
+paths:
+  /numberdata:
+    post:
+      operationId: getNumberHolder
+      consumes:
+        - application/json
+      produces:
+        - application/json
+      parameters: []
+      responses:
+        '200':
+          description: successful operation
+          schema:
+            $ref: '#/definitions/BaseObj'
+securityDefinitions: {}
+definitions:
+  BaseObj:
+    type: object
+    discriminator: object_type
+    required:
+      - id
+      - object_type
+    properties:
+      id:
+        type: integer
+        format: int64
+      object_type:
+        type: string
+  SubObjType:
+    type: string
+    enum:
+      - daily
+      - monthly
+      - quarterly
+      - yearly
+  SubObj:
+    x-discriminator-value: sub-obj
+    allOf:
+      - $ref: '#/definitions/BaseObj'
+      - type: object
+        discriminator: sub_obj_type
+        required:
+          - sub_obj_type
+        properties:
+          sub_obj_type:
+            $ref: '#/definitions/SubObjType'
+          name:
+            type: string
+  DailySubObj:
+    x-discriminator-value: daily
+    allOf:
+      - $ref: '#/definitions/SubObj'
+      - type: object
+        properties:
+          day_of_month:
+            type: integer
+            format: int32
\ No newline at end of file
diff --git a/modules/openapi-generator/src/test/resources/3_0/allOf_composition_discriminator.yaml b/modules/openapi-generator/src/test/resources/3_0/allOf_composition_discriminator.yaml
new file mode 100644
index 00000000000..efeaa5fd02e
--- /dev/null
+++ b/modules/openapi-generator/src/test/resources/3_0/allOf_composition_discriminator.yaml
@@ -0,0 +1,103 @@
+openapi: 3.0.2
+info:
+  title: OAI Specification example for Polymorphism
+  version: 1.0.0
+paths:
+  /pet:
+    get:
+      responses:
+        '200':
+          description: desc
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/Pet'
+  /reptile:
+    get:
+      responses:
+        '200':
+          description: desc
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/Reptile'
+  /mypets:
+    get:
+      responses:
+        '200':
+          description: desc
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/MyPets'
+components:
+  schemas:
+    Pet:
+      type: object
+      required:
+        - petType
+      properties:
+        petType:
+          type: string
+      discriminator:
+        propertyName: petType
+    Cat:
+      allOf:
+        - $ref: '#/components/schemas/Pet'
+        - type: object
+          properties:
+            name:
+              type: string
+    Reptile:
+      allOf:
+        - $ref: '#/components/schemas/Pet'
+    Dog:
+      allOf:
+        - $ref: '#/components/schemas/Pet'
+        - type: object
+          properties:
+            bark:
+              type: string
+    Lizard:
+      allOf:
+        - $ref: '#/components/schemas/Reptile'
+        - type: object
+          properties:
+            lovesRocks:
+              type: boolean
+    Snake:
+      allOf:
+        - $ref: '#/components/schemas/Reptile'
+        - type: object
+          properties:
+            hasLegs:
+              type: boolean
+    MyPets:
+      oneOf:
+        - $ref: '#/components/schemas/Cat'
+        - $ref: '#/components/schemas/Lizard'
+      discriminator:
+        propertyName: petType
+        # per https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.0.2.md#discriminatorObject
+        # this discriminator must be included to use it as a hint to pick a schema
+    MyPetsNoDisc:
+      oneOf:
+        - $ref: '#/components/schemas/Cat'
+        - $ref: '#/components/schemas/Lizard'
+    A:
+      type: object
+      required:
+        - petType
+      properties:
+        petType:
+          type: string
+      discriminator:
+        propertyName: petType
+        mapping:
+          b: '#/components/schemas/B'
+    B:
+      allOf:
+        - $ref: '#/components/schemas/A'
+    C:
+      allOf:
+        - $ref: '#/components/schemas/B'
diff --git a/modules/openapi-generator/src/test/resources/3_0/anyOfDiscriminator.yaml b/modules/openapi-generator/src/test/resources/3_0/anyOfDiscriminator.yaml
new file mode 100644
index 00000000000..72fa6abbb7d
--- /dev/null
+++ b/modules/openapi-generator/src/test/resources/3_0/anyOfDiscriminator.yaml
@@ -0,0 +1,244 @@
+openapi: 3.0.1
+info:
+   title: fruity
+   version: 0.0.1
+paths:
+   /:
+      get:
+         responses:
+            '200':
+               description: desc
+               content:
+                  application/json:
+                     schema:
+                        $ref: '#/components/schemas/FruitAllOfDisc'
+components:
+   schemas:
+    FruitType:
+      properties:
+        fruitType:
+          type: string
+      required:
+      - fruitType
+    FruitInlineDisc:
+      anyOf:
+        - type: object
+          required:
+            - seeds
+            - fruitType
+          properties:
+            seeds:
+              type: integer
+            fruitType:
+              type: string
+        - type: object
+          required:
+            - length
+            - fruitType
+          properties:
+            length:
+              type: integer
+            fruitType:
+              type: string
+      discriminator:
+        propertyName: fruitType
+    FruitInlineInlineDisc:
+      anyOf:
+        - type: object
+          required:
+            - seeds
+          properties:
+            seeds:
+              type: integer
+          anyOf:
+            - type: object
+              properties:
+                fruitType:
+                  type: string
+              required:
+              - fruitType
+        - type: object
+          required:
+            - length
+          properties:
+            length:
+              type: integer
+          anyOf:
+            - type: object
+              properties:
+                fruitType:
+                  type: string
+              required:
+              - fruitType
+      discriminator:
+        propertyName: fruitType
+    FruitReqDisc:
+      anyOf:
+        - $ref: '#/components/schemas/AppleReqDisc'
+        - $ref: '#/components/schemas/BananaReqDisc'
+      discriminator:
+        propertyName: fruitType
+    AppleReqDisc:
+      type: object
+      required:
+        - seeds
+        - fruitType
+      properties:
+        seeds:
+          type: integer
+        fruitType:
+          type: string
+    BananaReqDisc:
+      type: object
+      required:
+        - length
+        - fruitType
+      properties:
+        length:
+          type: integer
+        fruitType:
+          type: string
+    FruitAllOfDisc:
+      anyOf:
+        - $ref: '#/components/schemas/AppleAllOfDisc'
+        - $ref: '#/components/schemas/BananaAllOfDisc'
+      discriminator:
+        propertyName: fruitType
+    AppleAllOfDisc:
+      type: object
+      required:
+        - seeds
+      properties:
+        seeds:
+          type: integer
+      allOf:
+        - $ref: '#/components/schemas/FruitType'
+    BananaAllOfDisc:
+      type: object
+      required:
+        - length
+      properties:
+        length:
+          type: integer
+      allOf:
+        - $ref: '#/components/schemas/FruitType'
+    FruitAnyOfDisc:
+      anyOf:
+        - $ref: '#/components/schemas/AppleAnyOfDisc'
+        - $ref: '#/components/schemas/BananaAnyOfDisc'
+      discriminator:
+        propertyName: fruitType
+    AppleAnyOfDisc:
+      type: object
+      required:
+        - seeds
+      properties:
+        seeds:
+          type: integer
+      anyOf:
+        - $ref: '#/components/schemas/FruitType'
+    BananaAnyOfDisc:
+      type: object
+      required:
+        - length
+      properties:
+        length:
+          type: integer
+      anyOf:
+        - $ref: '#/components/schemas/FruitType'
+    FruitGrandparentDisc:
+      anyOf:
+        - $ref: '#/components/schemas/AppleGrandparentDisc'
+        - $ref: '#/components/schemas/BananaGrandparentDisc'
+      discriminator:
+        propertyName: fruitType
+    Parent:
+      type: object
+      allOf:
+        # the FruitType schema is a grandparent of AppleGrandparentDisc + BananaGrandparentDisc
+        - $ref: '#/components/schemas/FruitType'
+    AppleGrandparentDisc:
+      type: object
+      required:
+        - seeds
+      properties:
+        seeds:
+          type: integer
+      allOf:
+        - $ref: '#/components/schemas/Parent'
+    BananaGrandparentDisc:
+      type: object
+      required:
+        - length
+      properties:
+        length:
+          type: integer
+      allOf:
+        - $ref: '#/components/schemas/Parent'
+    ComposedDiscMissingNoProperties:
+      anyOf:
+        - $ref: '#/components/schemas/DiscMissingNoProperties'
+      discriminator:
+        propertyName: fruitType
+    DiscMissingNoProperties:
+      type: object
+    ComposedDiscMissingFromProperties:
+      anyOf:
+        - $ref: '#/components/schemas/DiscMissingFromProperties'
+      discriminator:
+        propertyName: fruitType
+    DiscMissingFromProperties:
+      type: object
+      properties:
+        length:
+          type: integer
+    ComposedDiscOptionalTypeCorrect:
+      anyOf:
+        - $ref: '#/components/schemas/DiscOptionalTypeCorrect'
+      discriminator:
+        propertyName: fruitType
+    DiscOptionalTypeCorrect:
+      type: object
+      properties:
+        fruitType:
+          type: string
+    ComposedDiscOptionalTypeIncorrect:
+      anyOf:
+        - $ref: '#/components/schemas/DiscOptionalTypeIncorrect'
+      discriminator:
+        propertyName: fruitType
+    DiscOptionalTypeIncorrect:
+      type: object
+      properties:
+        fruitType:
+          type: integer
+    ComposedDiscOptionalTypeInconsistent:
+      anyOf:
+        - $ref: '#/components/schemas/DiscOptionalTypeIncorrect'
+        - $ref: '#/components/schemas/DiscOptionalTypeCorrect'
+      discriminator:
+        propertyName: fruitType
+    ComposedDiscTypeIncorrect:
+      anyOf:
+        - $ref: '#/components/schemas/DiscTypeIncorrect'
+      discriminator:
+        propertyName: fruitType
+    DiscTypeIncorrect:
+      type: object
+      properties:
+        fruitType:
+          type: integer
+      required:
+        - fruitType
+    ComposedDiscTypeInconsistent:
+      anyOf:
+        - $ref: '#/components/schemas/DiscTypeIncorrect'
+        - $ref: '#/components/schemas/FruitType'
+      discriminator:
+        propertyName: fruitType
+    ComposedDiscRequiredInconsistent:
+      anyOf:
+        - $ref: '#/components/schemas/DiscOptionalTypeCorrect'
+        - $ref: '#/components/schemas/FruitType'
+      discriminator:
+        propertyName: fruitType
\ No newline at end of file
diff --git a/modules/openapi-generator/src/test/resources/3_0/oneOfDiscriminator.yaml b/modules/openapi-generator/src/test/resources/3_0/oneOfDiscriminator.yaml
new file mode 100644
index 00000000000..e9a34298074
--- /dev/null
+++ b/modules/openapi-generator/src/test/resources/3_0/oneOfDiscriminator.yaml
@@ -0,0 +1,268 @@
+openapi: 3.0.1
+info:
+   title: fruity
+   version: 0.0.1
+paths:
+   /:
+      get:
+         responses:
+            '200':
+               description: desc
+               content:
+                  application/json:
+                     schema:
+                        $ref: '#/components/schemas/FruitAllOfDisc'
+components:
+   schemas:
+    FruitType:
+      properties:
+        fruitType:
+          type: string
+      required:
+      - fruitType
+    FruitInlineDisc:
+      oneOf:
+        - type: object
+          required:
+            - seeds
+            - fruitType
+          properties:
+            seeds:
+              type: integer
+            fruitType:
+              type: string
+        - type: object
+          required:
+            - length
+            - fruitType
+          properties:
+            length:
+              type: integer
+            fruitType:
+              type: string
+      discriminator:
+        propertyName: fruitType
+    FruitInlineInlineDisc:
+      oneOf:
+        - type: object
+          required:
+            - seeds
+          properties:
+            seeds:
+              type: integer
+          oneOf:
+            - type: object
+              properties:
+                fruitType:
+                  type: string
+              required:
+              - fruitType
+        - type: object
+          required:
+            - length
+          properties:
+            length:
+              type: integer
+          oneOf:
+            - type: object
+              properties:
+                fruitType:
+                  type: string
+              required:
+              - fruitType
+      discriminator:
+        propertyName: fruitType
+    FruitReqDisc:
+      oneOf:
+        - $ref: '#/components/schemas/AppleReqDisc'
+        - $ref: '#/components/schemas/BananaReqDisc'
+      discriminator:
+        propertyName: fruitType
+    AppleReqDisc:
+      type: object
+      required:
+        - seeds
+        - fruitType
+      properties:
+        seeds:
+          type: integer
+        fruitType:
+          type: string
+    BananaReqDisc:
+      type: object
+      required:
+        - length
+        - fruitType
+      properties:
+        length:
+          type: integer
+        fruitType:
+          type: string
+    FruitAllOfDisc:
+      oneOf:
+        - $ref: '#/components/schemas/AppleAllOfDisc'
+        - $ref: '#/components/schemas/BananaAllOfDisc'
+      discriminator:
+        propertyName: fruitType
+    AppleAllOfDisc:
+      type: object
+      required:
+        - seeds
+      properties:
+        seeds:
+          type: integer
+      allOf:
+        - $ref: '#/components/schemas/FruitType'
+    BananaAllOfDisc:
+      type: object
+      required:
+        - length
+      properties:
+        length:
+          type: integer
+      allOf:
+        - $ref: '#/components/schemas/FruitType'
+    FruitAnyOfDisc:
+      oneOf:
+        - $ref: '#/components/schemas/AppleAnyOfDisc'
+        - $ref: '#/components/schemas/BananaAnyOfDisc'
+      discriminator:
+        propertyName: fruitType
+    AppleAnyOfDisc:
+      type: object
+      required:
+        - seeds
+      properties:
+        seeds:
+          type: integer
+      anyOf:
+        - $ref: '#/components/schemas/FruitType'
+    BananaAnyOfDisc:
+      type: object
+      required:
+        - length
+      properties:
+        length:
+          type: integer
+      anyOf:
+        - $ref: '#/components/schemas/FruitType'
+    FruitOneOfDisc:
+      oneOf:
+        - $ref: '#/components/schemas/AppleOneOfDisc'
+        - $ref: '#/components/schemas/BananaOneOfDisc'
+      discriminator:
+        propertyName: fruitType
+    AppleOneOfDisc:
+      type: object
+      required:
+        - seeds
+      properties:
+        seeds:
+          type: integer
+      oneOf:
+        - $ref: '#/components/schemas/FruitType'
+    BananaOneOfDisc:
+      type: object
+      required:
+        - length
+      properties:
+        length:
+          type: integer
+      oneOf:
+        - $ref: '#/components/schemas/FruitType'
+    FruitGrandparentDisc:
+      oneOf:
+        - $ref: '#/components/schemas/AppleGrandparentDisc'
+        - $ref: '#/components/schemas/BananaGrandparentDisc'
+      discriminator:
+        propertyName: fruitType
+    Parent:
+      type: object
+      allOf:
+        # the FruitType schema is a grandparent of AppleGrandparentDisc + BananaGrandparentDisc
+        - $ref: '#/components/schemas/FruitType'
+    AppleGrandparentDisc:
+      type: object
+      required:
+        - seeds
+      properties:
+        seeds:
+          type: integer
+      allOf:
+        - $ref: '#/components/schemas/Parent'
+    BananaGrandparentDisc:
+      type: object
+      required:
+        - length
+      properties:
+        length:
+          type: integer
+      allOf:
+        - $ref: '#/components/schemas/Parent'
+    ComposedDiscMissingNoProperties:
+      oneOf:
+        - $ref: '#/components/schemas/DiscMissingNoProperties'
+      discriminator:
+        propertyName: fruitType
+    DiscMissingNoProperties:
+      type: object
+    ComposedDiscMissingFromProperties:
+      oneOf:
+        - $ref: '#/components/schemas/DiscMissingFromProperties'
+      discriminator:
+        propertyName: fruitType
+    DiscMissingFromProperties:
+      type: object
+      properties:
+        length:
+          type: integer
+    ComposedDiscOptionalTypeCorrect:
+      oneOf:
+        - $ref: '#/components/schemas/DiscOptionalTypeCorrect'
+      discriminator:
+        propertyName: fruitType
+    DiscOptionalTypeCorrect:
+      type: object
+      properties:
+        fruitType:
+          type: string
+    ComposedDiscOptionalTypeIncorrect:
+      oneOf:
+        - $ref: '#/components/schemas/DiscOptionalTypeIncorrect'
+      discriminator:
+        propertyName: fruitType
+    DiscOptionalTypeIncorrect:
+      type: object
+      properties:
+        fruitType:
+          type: integer
+    ComposedDiscOptionalTypeInconsistent:
+      oneOf:
+        - $ref: '#/components/schemas/DiscOptionalTypeIncorrect'
+        - $ref: '#/components/schemas/DiscOptionalTypeCorrect'
+      discriminator:
+        propertyName: fruitType
+    ComposedDiscTypeIncorrect:
+      oneOf:
+        - $ref: '#/components/schemas/DiscTypeIncorrect'
+      discriminator:
+        propertyName: fruitType
+    DiscTypeIncorrect:
+      type: object
+      properties:
+        fruitType:
+          type: integer
+      required:
+        - fruitType
+    ComposedDiscTypeInconsistent:
+      oneOf:
+        - $ref: '#/components/schemas/DiscTypeIncorrect'
+        - $ref: '#/components/schemas/FruitType'
+      discriminator:
+        propertyName: fruitType
+    ComposedDiscRequiredInconsistent:
+      oneOf:
+        - $ref: '#/components/schemas/DiscOptionalTypeCorrect'
+        - $ref: '#/components/schemas/FruitType'
+      discriminator:
+        propertyName: fruitType
diff --git a/samples/client/petstore/java/feign/src/main/java/org/openapitools/client/model/Animal.java b/samples/client/petstore/java/feign/src/main/java/org/openapitools/client/model/Animal.java
index 00db7a1b7b6..ff1964caa4b 100644
--- a/samples/client/petstore/java/feign/src/main/java/org/openapitools/client/model/Animal.java
+++ b/samples/client/petstore/java/feign/src/main/java/org/openapitools/client/model/Animal.java
@@ -43,7 +43,7 @@ import com.fasterxml.jackson.annotation.JsonPropertyOrder;
 
 public class Animal {
   public static final String JSON_PROPERTY_CLASS_NAME = "className";
-  private String className;
+  protected String className;
 
   public static final String JSON_PROPERTY_COLOR = "color";
   private String color = "red";
diff --git a/samples/client/petstore/java/feign10x/src/main/java/org/openapitools/client/model/Animal.java b/samples/client/petstore/java/feign10x/src/main/java/org/openapitools/client/model/Animal.java
index e0ae875483b..bbadf265ba6 100644
--- a/samples/client/petstore/java/feign10x/src/main/java/org/openapitools/client/model/Animal.java
+++ b/samples/client/petstore/java/feign10x/src/main/java/org/openapitools/client/model/Animal.java
@@ -42,7 +42,7 @@ import com.fasterxml.jackson.annotation.JsonPropertyOrder;
 
 public class Animal {
   public static final String JSON_PROPERTY_CLASS_NAME = "className";
-  private String className;
+  protected String className;
 
   public static final String JSON_PROPERTY_COLOR = "color";
   private String color = "red";
diff --git a/samples/client/petstore/java/google-api-client/src/main/java/org/openapitools/client/model/Animal.java b/samples/client/petstore/java/google-api-client/src/main/java/org/openapitools/client/model/Animal.java
index e0ae875483b..bbadf265ba6 100644
--- a/samples/client/petstore/java/google-api-client/src/main/java/org/openapitools/client/model/Animal.java
+++ b/samples/client/petstore/java/google-api-client/src/main/java/org/openapitools/client/model/Animal.java
@@ -42,7 +42,7 @@ import com.fasterxml.jackson.annotation.JsonPropertyOrder;
 
 public class Animal {
   public static final String JSON_PROPERTY_CLASS_NAME = "className";
-  private String className;
+  protected String className;
 
   public static final String JSON_PROPERTY_COLOR = "color";
   private String color = "red";
diff --git a/samples/client/petstore/java/jersey1/src/main/java/org/openapitools/client/model/Animal.java b/samples/client/petstore/java/jersey1/src/main/java/org/openapitools/client/model/Animal.java
index e0ae875483b..bbadf265ba6 100644
--- a/samples/client/petstore/java/jersey1/src/main/java/org/openapitools/client/model/Animal.java
+++ b/samples/client/petstore/java/jersey1/src/main/java/org/openapitools/client/model/Animal.java
@@ -42,7 +42,7 @@ import com.fasterxml.jackson.annotation.JsonPropertyOrder;
 
 public class Animal {
   public static final String JSON_PROPERTY_CLASS_NAME = "className";
-  private String className;
+  protected String className;
 
   public static final String JSON_PROPERTY_COLOR = "color";
   private String color = "red";
diff --git a/samples/client/petstore/java/jersey2-java6/src/main/java/org/openapitools/client/model/Animal.java b/samples/client/petstore/java/jersey2-java6/src/main/java/org/openapitools/client/model/Animal.java
index b5b4f315c16..345d7734631 100644
--- a/samples/client/petstore/java/jersey2-java6/src/main/java/org/openapitools/client/model/Animal.java
+++ b/samples/client/petstore/java/jersey2-java6/src/main/java/org/openapitools/client/model/Animal.java
@@ -41,7 +41,7 @@ import com.fasterxml.jackson.annotation.JsonPropertyOrder;
 
 public class Animal {
   public static final String JSON_PROPERTY_CLASS_NAME = "className";
-  private String className;
+  protected String className;
 
   public static final String JSON_PROPERTY_COLOR = "color";
   private String color = "red";
diff --git a/samples/client/petstore/java/jersey2-java8/src/main/java/org/openapitools/client/model/Animal.java b/samples/client/petstore/java/jersey2-java8/src/main/java/org/openapitools/client/model/Animal.java
index e0ae875483b..bbadf265ba6 100644
--- a/samples/client/petstore/java/jersey2-java8/src/main/java/org/openapitools/client/model/Animal.java
+++ b/samples/client/petstore/java/jersey2-java8/src/main/java/org/openapitools/client/model/Animal.java
@@ -42,7 +42,7 @@ import com.fasterxml.jackson.annotation.JsonPropertyOrder;
 
 public class Animal {
   public static final String JSON_PROPERTY_CLASS_NAME = "className";
-  private String className;
+  protected String className;
 
   public static final String JSON_PROPERTY_COLOR = "color";
   private String color = "red";
diff --git a/samples/client/petstore/java/jersey2/src/main/java/org/openapitools/client/model/Animal.java b/samples/client/petstore/java/jersey2/src/main/java/org/openapitools/client/model/Animal.java
index e0ae875483b..bbadf265ba6 100644
--- a/samples/client/petstore/java/jersey2/src/main/java/org/openapitools/client/model/Animal.java
+++ b/samples/client/petstore/java/jersey2/src/main/java/org/openapitools/client/model/Animal.java
@@ -42,7 +42,7 @@ import com.fasterxml.jackson.annotation.JsonPropertyOrder;
 
 public class Animal {
   public static final String JSON_PROPERTY_CLASS_NAME = "className";
-  private String className;
+  protected String className;
 
   public static final String JSON_PROPERTY_COLOR = "color";
   private String color = "red";
diff --git a/samples/client/petstore/java/native/src/main/java/org/openapitools/client/model/Animal.java b/samples/client/petstore/java/native/src/main/java/org/openapitools/client/model/Animal.java
index e0ae875483b..bbadf265ba6 100644
--- a/samples/client/petstore/java/native/src/main/java/org/openapitools/client/model/Animal.java
+++ b/samples/client/petstore/java/native/src/main/java/org/openapitools/client/model/Animal.java
@@ -42,7 +42,7 @@ import com.fasterxml.jackson.annotation.JsonPropertyOrder;
 
 public class Animal {
   public static final String JSON_PROPERTY_CLASS_NAME = "className";
-  private String className;
+  protected String className;
 
   public static final String JSON_PROPERTY_COLOR = "color";
   private String color = "red";
diff --git a/samples/client/petstore/java/okhttp-gson-parcelableModel/src/main/java/org/openapitools/client/model/Animal.java b/samples/client/petstore/java/okhttp-gson-parcelableModel/src/main/java/org/openapitools/client/model/Animal.java
index 1367d6dd788..4b6c177d34a 100644
--- a/samples/client/petstore/java/okhttp-gson-parcelableModel/src/main/java/org/openapitools/client/model/Animal.java
+++ b/samples/client/petstore/java/okhttp-gson-parcelableModel/src/main/java/org/openapitools/client/model/Animal.java
@@ -34,7 +34,7 @@ import android.os.Parcel;
 public class Animal implements Parcelable {
   public static final String SERIALIZED_NAME_CLASS_NAME = "className";
   @SerializedName(SERIALIZED_NAME_CLASS_NAME)
-  private String className;
+  protected String className;
 
   public static final String SERIALIZED_NAME_COLOR = "color";
   @SerializedName(SERIALIZED_NAME_COLOR)
diff --git a/samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/Animal.java b/samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/Animal.java
index af469dda3f4..cea2ff5988d 100644
--- a/samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/Animal.java
+++ b/samples/client/petstore/java/okhttp-gson/src/main/java/org/openapitools/client/model/Animal.java
@@ -32,7 +32,7 @@ import java.io.IOException;
 public class Animal {
   public static final String SERIALIZED_NAME_CLASS_NAME = "className";
   @SerializedName(SERIALIZED_NAME_CLASS_NAME)
-  private String className;
+  protected String className;
 
   public static final String SERIALIZED_NAME_COLOR = "color";
   @SerializedName(SERIALIZED_NAME_COLOR)
diff --git a/samples/client/petstore/java/rest-assured-jackson/src/main/java/org/openapitools/client/model/Animal.java b/samples/client/petstore/java/rest-assured-jackson/src/main/java/org/openapitools/client/model/Animal.java
index 57dad620ef0..0390cab3e8c 100644
--- a/samples/client/petstore/java/rest-assured-jackson/src/main/java/org/openapitools/client/model/Animal.java
+++ b/samples/client/petstore/java/rest-assured-jackson/src/main/java/org/openapitools/client/model/Animal.java
@@ -45,7 +45,7 @@ import org.hibernate.validator.constraints.*;
 
 public class Animal {
   public static final String JSON_PROPERTY_CLASS_NAME = "className";
-  private String className;
+  protected String className;
 
   public static final String JSON_PROPERTY_COLOR = "color";
   private String color = "red";
diff --git a/samples/client/petstore/java/rest-assured/src/main/java/org/openapitools/client/model/Animal.java b/samples/client/petstore/java/rest-assured/src/main/java/org/openapitools/client/model/Animal.java
index bb64354ab52..4cbc678b532 100644
--- a/samples/client/petstore/java/rest-assured/src/main/java/org/openapitools/client/model/Animal.java
+++ b/samples/client/petstore/java/rest-assured/src/main/java/org/openapitools/client/model/Animal.java
@@ -35,7 +35,7 @@ import org.hibernate.validator.constraints.*;
 public class Animal {
   public static final String SERIALIZED_NAME_CLASS_NAME = "className";
   @SerializedName(SERIALIZED_NAME_CLASS_NAME)
-  private String className;
+  protected String className;
 
   public static final String SERIALIZED_NAME_COLOR = "color";
   @SerializedName(SERIALIZED_NAME_COLOR)
diff --git a/samples/client/petstore/java/resteasy/src/main/java/org/openapitools/client/model/Animal.java b/samples/client/petstore/java/resteasy/src/main/java/org/openapitools/client/model/Animal.java
index e0ae875483b..bbadf265ba6 100644
--- a/samples/client/petstore/java/resteasy/src/main/java/org/openapitools/client/model/Animal.java
+++ b/samples/client/petstore/java/resteasy/src/main/java/org/openapitools/client/model/Animal.java
@@ -42,7 +42,7 @@ import com.fasterxml.jackson.annotation.JsonPropertyOrder;
 
 public class Animal {
   public static final String JSON_PROPERTY_CLASS_NAME = "className";
-  private String className;
+  protected String className;
 
   public static final String JSON_PROPERTY_COLOR = "color";
   private String color = "red";
diff --git a/samples/client/petstore/java/resttemplate-withXml/src/main/java/org/openapitools/client/model/Animal.java b/samples/client/petstore/java/resttemplate-withXml/src/main/java/org/openapitools/client/model/Animal.java
index af9c0df7038..87a9c706f4a 100644
--- a/samples/client/petstore/java/resttemplate-withXml/src/main/java/org/openapitools/client/model/Animal.java
+++ b/samples/client/petstore/java/resttemplate-withXml/src/main/java/org/openapitools/client/model/Animal.java
@@ -48,7 +48,7 @@ import javax.xml.bind.annotation.*;
 public class Animal {
   public static final String JSON_PROPERTY_CLASS_NAME = "className";
   @XmlElement(name = "className")
-  private String className;
+  protected String className;
 
   public static final String JSON_PROPERTY_COLOR = "color";
   @XmlElement(name = "color")
diff --git a/samples/client/petstore/java/resttemplate/src/main/java/org/openapitools/client/model/Animal.java b/samples/client/petstore/java/resttemplate/src/main/java/org/openapitools/client/model/Animal.java
index e0ae875483b..bbadf265ba6 100644
--- a/samples/client/petstore/java/resttemplate/src/main/java/org/openapitools/client/model/Animal.java
+++ b/samples/client/petstore/java/resttemplate/src/main/java/org/openapitools/client/model/Animal.java
@@ -42,7 +42,7 @@ import com.fasterxml.jackson.annotation.JsonPropertyOrder;
 
 public class Animal {
   public static final String JSON_PROPERTY_CLASS_NAME = "className";
-  private String className;
+  protected String className;
 
   public static final String JSON_PROPERTY_COLOR = "color";
   private String color = "red";
diff --git a/samples/client/petstore/java/retrofit/src/main/java/org/openapitools/client/model/Animal.java b/samples/client/petstore/java/retrofit/src/main/java/org/openapitools/client/model/Animal.java
index af469dda3f4..cea2ff5988d 100644
--- a/samples/client/petstore/java/retrofit/src/main/java/org/openapitools/client/model/Animal.java
+++ b/samples/client/petstore/java/retrofit/src/main/java/org/openapitools/client/model/Animal.java
@@ -32,7 +32,7 @@ import java.io.IOException;
 public class Animal {
   public static final String SERIALIZED_NAME_CLASS_NAME = "className";
   @SerializedName(SERIALIZED_NAME_CLASS_NAME)
-  private String className;
+  protected String className;
 
   public static final String SERIALIZED_NAME_COLOR = "color";
   @SerializedName(SERIALIZED_NAME_COLOR)
diff --git a/samples/client/petstore/java/retrofit2-play24/src/main/java/org/openapitools/client/model/Animal.java b/samples/client/petstore/java/retrofit2-play24/src/main/java/org/openapitools/client/model/Animal.java
index 38b0a1b2f15..e93cac2705d 100644
--- a/samples/client/petstore/java/retrofit2-play24/src/main/java/org/openapitools/client/model/Animal.java
+++ b/samples/client/petstore/java/retrofit2-play24/src/main/java/org/openapitools/client/model/Animal.java
@@ -44,7 +44,7 @@ import javax.validation.Valid;
 
 public class Animal {
   public static final String JSON_PROPERTY_CLASS_NAME = "className";
-  private String className;
+  protected String className;
 
   public static final String JSON_PROPERTY_COLOR = "color";
   private String color = "red";
diff --git a/samples/client/petstore/java/retrofit2-play25/src/main/java/org/openapitools/client/model/Animal.java b/samples/client/petstore/java/retrofit2-play25/src/main/java/org/openapitools/client/model/Animal.java
index 38b0a1b2f15..e93cac2705d 100644
--- a/samples/client/petstore/java/retrofit2-play25/src/main/java/org/openapitools/client/model/Animal.java
+++ b/samples/client/petstore/java/retrofit2-play25/src/main/java/org/openapitools/client/model/Animal.java
@@ -44,7 +44,7 @@ import javax.validation.Valid;
 
 public class Animal {
   public static final String JSON_PROPERTY_CLASS_NAME = "className";
-  private String className;
+  protected String className;
 
   public static final String JSON_PROPERTY_COLOR = "color";
   private String color = "red";
diff --git a/samples/client/petstore/java/retrofit2-play26/src/main/java/org/openapitools/client/model/Animal.java b/samples/client/petstore/java/retrofit2-play26/src/main/java/org/openapitools/client/model/Animal.java
index 38b0a1b2f15..e93cac2705d 100644
--- a/samples/client/petstore/java/retrofit2-play26/src/main/java/org/openapitools/client/model/Animal.java
+++ b/samples/client/petstore/java/retrofit2-play26/src/main/java/org/openapitools/client/model/Animal.java
@@ -44,7 +44,7 @@ import javax.validation.Valid;
 
 public class Animal {
   public static final String JSON_PROPERTY_CLASS_NAME = "className";
-  private String className;
+  protected String className;
 
   public static final String JSON_PROPERTY_COLOR = "color";
   private String color = "red";
diff --git a/samples/client/petstore/java/retrofit2/src/main/java/org/openapitools/client/model/Animal.java b/samples/client/petstore/java/retrofit2/src/main/java/org/openapitools/client/model/Animal.java
index af469dda3f4..cea2ff5988d 100644
--- a/samples/client/petstore/java/retrofit2/src/main/java/org/openapitools/client/model/Animal.java
+++ b/samples/client/petstore/java/retrofit2/src/main/java/org/openapitools/client/model/Animal.java
@@ -32,7 +32,7 @@ import java.io.IOException;
 public class Animal {
   public static final String SERIALIZED_NAME_CLASS_NAME = "className";
   @SerializedName(SERIALIZED_NAME_CLASS_NAME)
-  private String className;
+  protected String className;
 
   public static final String SERIALIZED_NAME_COLOR = "color";
   @SerializedName(SERIALIZED_NAME_COLOR)
diff --git a/samples/client/petstore/java/retrofit2rx/src/main/java/org/openapitools/client/model/Animal.java b/samples/client/petstore/java/retrofit2rx/src/main/java/org/openapitools/client/model/Animal.java
index af469dda3f4..cea2ff5988d 100644
--- a/samples/client/petstore/java/retrofit2rx/src/main/java/org/openapitools/client/model/Animal.java
+++ b/samples/client/petstore/java/retrofit2rx/src/main/java/org/openapitools/client/model/Animal.java
@@ -32,7 +32,7 @@ import java.io.IOException;
 public class Animal {
   public static final String SERIALIZED_NAME_CLASS_NAME = "className";
   @SerializedName(SERIALIZED_NAME_CLASS_NAME)
-  private String className;
+  protected String className;
 
   public static final String SERIALIZED_NAME_COLOR = "color";
   @SerializedName(SERIALIZED_NAME_COLOR)
diff --git a/samples/client/petstore/java/retrofit2rx2/src/main/java/org/openapitools/client/model/Animal.java b/samples/client/petstore/java/retrofit2rx2/src/main/java/org/openapitools/client/model/Animal.java
index af469dda3f4..cea2ff5988d 100644
--- a/samples/client/petstore/java/retrofit2rx2/src/main/java/org/openapitools/client/model/Animal.java
+++ b/samples/client/petstore/java/retrofit2rx2/src/main/java/org/openapitools/client/model/Animal.java
@@ -32,7 +32,7 @@ import java.io.IOException;
 public class Animal {
   public static final String SERIALIZED_NAME_CLASS_NAME = "className";
   @SerializedName(SERIALIZED_NAME_CLASS_NAME)
-  private String className;
+  protected String className;
 
   public static final String SERIALIZED_NAME_COLOR = "color";
   @SerializedName(SERIALIZED_NAME_COLOR)
diff --git a/samples/client/petstore/java/vertx/src/main/java/org/openapitools/client/model/Animal.java b/samples/client/petstore/java/vertx/src/main/java/org/openapitools/client/model/Animal.java
index e0ae875483b..bbadf265ba6 100644
--- a/samples/client/petstore/java/vertx/src/main/java/org/openapitools/client/model/Animal.java
+++ b/samples/client/petstore/java/vertx/src/main/java/org/openapitools/client/model/Animal.java
@@ -42,7 +42,7 @@ import com.fasterxml.jackson.annotation.JsonPropertyOrder;
 
 public class Animal {
   public static final String JSON_PROPERTY_CLASS_NAME = "className";
-  private String className;
+  protected String className;
 
   public static final String JSON_PROPERTY_COLOR = "color";
   private String color = "red";
diff --git a/samples/client/petstore/java/webclient/src/main/java/org/openapitools/client/model/Animal.java b/samples/client/petstore/java/webclient/src/main/java/org/openapitools/client/model/Animal.java
index e0ae875483b..bbadf265ba6 100644
--- a/samples/client/petstore/java/webclient/src/main/java/org/openapitools/client/model/Animal.java
+++ b/samples/client/petstore/java/webclient/src/main/java/org/openapitools/client/model/Animal.java
@@ -42,7 +42,7 @@ import com.fasterxml.jackson.annotation.JsonPropertyOrder;
 
 public class Animal {
   public static final String JSON_PROPERTY_CLASS_NAME = "className";
-  private String className;
+  protected String className;
 
   public static final String JSON_PROPERTY_COLOR = "color";
   private String color = "red";
diff --git a/samples/client/petstore/python-asyncio/petstore_api/api_client.py b/samples/client/petstore/python-asyncio/petstore_api/api_client.py
index bed70584efb..8aae783bfc3 100644
--- a/samples/client/petstore/python-asyncio/petstore_api/api_client.py
+++ b/samples/client/petstore/python-asyncio/petstore_api/api_client.py
@@ -625,9 +625,12 @@ class ApiClient(object):
         :param klass: class literal.
         :return: model object.
         """
+        has_discriminator = False
+        if (hasattr(klass, 'get_real_child_model')
+                and klass.discriminator_value_class_map):
+            has_discriminator = True
 
-        if not klass.openapi_types and not hasattr(klass,
-                                                   'get_real_child_model'):
+        if not klass.openapi_types and has_discriminator is False:
             return data
 
         kwargs = {}
@@ -641,7 +644,7 @@ class ApiClient(object):
 
         instance = klass(**kwargs)
 
-        if hasattr(instance, 'get_real_child_model'):
+        if has_discriminator:
             klass_name = instance.get_real_child_model(data)
             if klass_name:
                 instance = self.__deserialize(data, klass_name)
diff --git a/samples/client/petstore/python-experimental/petstore_api/models/animal.py b/samples/client/petstore/python-experimental/petstore_api/models/animal.py
index 45058ec7612..39dd9789ff8 100644
--- a/samples/client/petstore/python-experimental/petstore_api/models/animal.py
+++ b/samples/client/petstore/python-experimental/petstore_api/models/animal.py
@@ -90,12 +90,13 @@ class Animal(ModelNormal):
 
     @staticmethod
     def discriminator():
-        return {
-            'class_name': {
-                'Cat': cat.Cat,
-                'Dog': dog.Dog,
-            },
+        val = {
+            'Cat': cat.Cat,
+            'Dog': dog.Dog,
         }
+        if not val:
+            return None
+        return {'class_name': val}
 
     attribute_map = {
         'class_name': 'className',  # noqa: E501
diff --git a/samples/client/petstore/python-experimental/petstore_api/models/cat.py b/samples/client/petstore/python-experimental/petstore_api/models/cat.py
index d40464eaf0e..3f3c2384ec2 100644
--- a/samples/client/petstore/python-experimental/petstore_api/models/cat.py
+++ b/samples/client/petstore/python-experimental/petstore_api/models/cat.py
@@ -91,7 +91,11 @@ class Cat(ModelComposed):
 
     @staticmethod
     def discriminator():
-        return None
+        val = {
+        }
+        if not val:
+            return None
+        return {'class_name': val}
 
     attribute_map = {
         'class_name': 'className',  # noqa: E501
@@ -194,3 +198,16 @@ class Cat(ModelComposed):
           'oneOf': [
           ],
         }
+
+    @classmethod
+    def get_discriminator_class(cls, from_server, data):
+        """Returns the child class specified by the discriminator"""
+        discriminator = cls.discriminator()
+        discr_propertyname_py = list(discriminator.keys())[0]
+        discr_propertyname_js = cls.attribute_map[discr_propertyname_py]
+        if from_server:
+            class_name = data[discr_propertyname_js]
+        else:
+            class_name = data[discr_propertyname_py]
+        class_name_to_discr_class = discriminator[discr_propertyname_py]
+        return class_name_to_discr_class.get(class_name)
diff --git a/samples/client/petstore/python-experimental/petstore_api/models/child_cat.py b/samples/client/petstore/python-experimental/petstore_api/models/child_cat.py
index b83986bd68a..e7894c9c7af 100644
--- a/samples/client/petstore/python-experimental/petstore_api/models/child_cat.py
+++ b/samples/client/petstore/python-experimental/petstore_api/models/child_cat.py
@@ -90,7 +90,11 @@ class ChildCat(ModelComposed):
 
     @staticmethod
     def discriminator():
-        return None
+        val = {
+        }
+        if not val:
+            return None
+        return {'pet_type': val}
 
     attribute_map = {
         'pet_type': 'pet_type',  # noqa: E501
@@ -191,3 +195,16 @@ class ChildCat(ModelComposed):
           'oneOf': [
           ],
         }
+
+    @classmethod
+    def get_discriminator_class(cls, from_server, data):
+        """Returns the child class specified by the discriminator"""
+        discriminator = cls.discriminator()
+        discr_propertyname_py = list(discriminator.keys())[0]
+        discr_propertyname_js = cls.attribute_map[discr_propertyname_py]
+        if from_server:
+            class_name = data[discr_propertyname_js]
+        else:
+            class_name = data[discr_propertyname_py]
+        class_name_to_discr_class = discriminator[discr_propertyname_py]
+        return class_name_to_discr_class.get(class_name)
diff --git a/samples/client/petstore/python-experimental/petstore_api/models/child_dog.py b/samples/client/petstore/python-experimental/petstore_api/models/child_dog.py
index da568bd7d27..8544773e884 100644
--- a/samples/client/petstore/python-experimental/petstore_api/models/child_dog.py
+++ b/samples/client/petstore/python-experimental/petstore_api/models/child_dog.py
@@ -90,7 +90,11 @@ class ChildDog(ModelComposed):
 
     @staticmethod
     def discriminator():
-        return None
+        val = {
+        }
+        if not val:
+            return None
+        return {'pet_type': val}
 
     attribute_map = {
         'pet_type': 'pet_type',  # noqa: E501
@@ -191,3 +195,16 @@ class ChildDog(ModelComposed):
           'oneOf': [
           ],
         }
+
+    @classmethod
+    def get_discriminator_class(cls, from_server, data):
+        """Returns the child class specified by the discriminator"""
+        discriminator = cls.discriminator()
+        discr_propertyname_py = list(discriminator.keys())[0]
+        discr_propertyname_js = cls.attribute_map[discr_propertyname_py]
+        if from_server:
+            class_name = data[discr_propertyname_js]
+        else:
+            class_name = data[discr_propertyname_py]
+        class_name_to_discr_class = discriminator[discr_propertyname_py]
+        return class_name_to_discr_class.get(class_name)
diff --git a/samples/client/petstore/python-experimental/petstore_api/models/child_lizard.py b/samples/client/petstore/python-experimental/petstore_api/models/child_lizard.py
index 62fa11f26e8..681e99ae666 100644
--- a/samples/client/petstore/python-experimental/petstore_api/models/child_lizard.py
+++ b/samples/client/petstore/python-experimental/petstore_api/models/child_lizard.py
@@ -90,7 +90,11 @@ class ChildLizard(ModelComposed):
 
     @staticmethod
     def discriminator():
-        return None
+        val = {
+        }
+        if not val:
+            return None
+        return {'pet_type': val}
 
     attribute_map = {
         'pet_type': 'pet_type',  # noqa: E501
@@ -191,3 +195,16 @@ class ChildLizard(ModelComposed):
           'oneOf': [
           ],
         }
+
+    @classmethod
+    def get_discriminator_class(cls, from_server, data):
+        """Returns the child class specified by the discriminator"""
+        discriminator = cls.discriminator()
+        discr_propertyname_py = list(discriminator.keys())[0]
+        discr_propertyname_js = cls.attribute_map[discr_propertyname_py]
+        if from_server:
+            class_name = data[discr_propertyname_js]
+        else:
+            class_name = data[discr_propertyname_py]
+        class_name_to_discr_class = discriminator[discr_propertyname_py]
+        return class_name_to_discr_class.get(class_name)
diff --git a/samples/client/petstore/python-experimental/petstore_api/models/dog.py b/samples/client/petstore/python-experimental/petstore_api/models/dog.py
index 69af821b27e..5d5712d428e 100644
--- a/samples/client/petstore/python-experimental/petstore_api/models/dog.py
+++ b/samples/client/petstore/python-experimental/petstore_api/models/dog.py
@@ -91,7 +91,11 @@ class Dog(ModelComposed):
 
     @staticmethod
     def discriminator():
-        return None
+        val = {
+        }
+        if not val:
+            return None
+        return {'class_name': val}
 
     attribute_map = {
         'class_name': 'className',  # noqa: E501
@@ -194,3 +198,16 @@ class Dog(ModelComposed):
           'oneOf': [
           ],
         }
+
+    @classmethod
+    def get_discriminator_class(cls, from_server, data):
+        """Returns the child class specified by the discriminator"""
+        discriminator = cls.discriminator()
+        discr_propertyname_py = list(discriminator.keys())[0]
+        discr_propertyname_js = cls.attribute_map[discr_propertyname_py]
+        if from_server:
+            class_name = data[discr_propertyname_js]
+        else:
+            class_name = data[discr_propertyname_py]
+        class_name_to_discr_class = discriminator[discr_propertyname_py]
+        return class_name_to_discr_class.get(class_name)
diff --git a/samples/client/petstore/python-experimental/petstore_api/models/grandparent_animal.py b/samples/client/petstore/python-experimental/petstore_api/models/grandparent_animal.py
index af25951ed73..db7e6f33887 100644
--- a/samples/client/petstore/python-experimental/petstore_api/models/grandparent_animal.py
+++ b/samples/client/petstore/python-experimental/petstore_api/models/grandparent_animal.py
@@ -29,6 +29,26 @@ from petstore_api.model_utils import (  # noqa: F401
     str,
     validate_get_composed_info,
 )
+try:
+    from petstore_api.models import child_cat
+except ImportError:
+    child_cat = sys.modules[
+        'petstore_api.models.child_cat']
+try:
+    from petstore_api.models import child_dog
+except ImportError:
+    child_dog = sys.modules[
+        'petstore_api.models.child_dog']
+try:
+    from petstore_api.models import child_lizard
+except ImportError:
+    child_lizard = sys.modules[
+        'petstore_api.models.child_lizard']
+try:
+    from petstore_api.models import parent_pet
+except ImportError:
+    parent_pet = sys.modules[
+        'petstore_api.models.parent_pet']
 
 
 class GrandparentAnimal(ModelNormal):
@@ -79,7 +99,15 @@ class GrandparentAnimal(ModelNormal):
 
     @staticmethod
     def discriminator():
-        return None
+        val = {
+            'ChildCat': child_cat.ChildCat,
+            'ChildDog': child_dog.ChildDog,
+            'ChildLizard': child_lizard.ChildLizard,
+            'ParentPet': parent_pet.ParentPet,
+        }
+        if not val:
+            return None
+        return {'pet_type': val}
 
     attribute_map = {
         'pet_type': 'pet_type',  # noqa: E501
@@ -134,3 +162,16 @@ class GrandparentAnimal(ModelNormal):
                 # discard variable.
                 continue
             setattr(self, var_name, var_value)
+
+    @classmethod
+    def get_discriminator_class(cls, from_server, data):
+        """Returns the child class specified by the discriminator"""
+        discriminator = cls.discriminator()
+        discr_propertyname_py = list(discriminator.keys())[0]
+        discr_propertyname_js = cls.attribute_map[discr_propertyname_py]
+        if from_server:
+            class_name = data[discr_propertyname_js]
+        else:
+            class_name = data[discr_propertyname_py]
+        class_name_to_discr_class = discriminator[discr_propertyname_py]
+        return class_name_to_discr_class.get(class_name)
diff --git a/samples/client/petstore/python-experimental/petstore_api/models/parent_pet.py b/samples/client/petstore/python-experimental/petstore_api/models/parent_pet.py
index cdb96676c55..e7f2a6fb63f 100644
--- a/samples/client/petstore/python-experimental/petstore_api/models/parent_pet.py
+++ b/samples/client/petstore/python-experimental/petstore_api/models/parent_pet.py
@@ -99,13 +99,14 @@ class ParentPet(ModelComposed):
 
     @staticmethod
     def discriminator():
-        return {
-            'pet_type': {
-                'ChildCat': child_cat.ChildCat,
-                'ChildDog': child_dog.ChildDog,
-                'ChildLizard': child_lizard.ChildLizard,
-            },
+        val = {
+            'ChildCat': child_cat.ChildCat,
+            'ChildDog': child_dog.ChildDog,
+            'ChildLizard': child_lizard.ChildLizard,
         }
+        if not val:
+            return None
+        return {'pet_type': val}
 
     attribute_map = {
         'pet_type': 'pet_type',  # noqa: E501
diff --git a/samples/client/petstore/python-tornado/petstore_api/api_client.py b/samples/client/petstore/python-tornado/petstore_api/api_client.py
index 6b9c738128f..328c1a70e10 100644
--- a/samples/client/petstore/python-tornado/petstore_api/api_client.py
+++ b/samples/client/petstore/python-tornado/petstore_api/api_client.py
@@ -626,9 +626,12 @@ class ApiClient(object):
         :param klass: class literal.
         :return: model object.
         """
+        has_discriminator = False
+        if (hasattr(klass, 'get_real_child_model')
+                and klass.discriminator_value_class_map):
+            has_discriminator = True
 
-        if not klass.openapi_types and not hasattr(klass,
-                                                   'get_real_child_model'):
+        if not klass.openapi_types and has_discriminator is False:
             return data
 
         kwargs = {}
@@ -642,7 +645,7 @@ class ApiClient(object):
 
         instance = klass(**kwargs)
 
-        if hasattr(instance, 'get_real_child_model'):
+        if has_discriminator:
             klass_name = instance.get_real_child_model(data)
             if klass_name:
                 instance = self.__deserialize(data, klass_name)
diff --git a/samples/client/petstore/python/petstore_api/api_client.py b/samples/client/petstore/python/petstore_api/api_client.py
index c0564c598f1..a80084e04b0 100644
--- a/samples/client/petstore/python/petstore_api/api_client.py
+++ b/samples/client/petstore/python/petstore_api/api_client.py
@@ -624,9 +624,12 @@ class ApiClient(object):
         :param klass: class literal.
         :return: model object.
         """
+        has_discriminator = False
+        if (hasattr(klass, 'get_real_child_model')
+                and klass.discriminator_value_class_map):
+            has_discriminator = True
 
-        if not klass.openapi_types and not hasattr(klass,
-                                                   'get_real_child_model'):
+        if not klass.openapi_types and has_discriminator is False:
             return data
 
         kwargs = {}
@@ -640,7 +643,7 @@ class ApiClient(object):
 
         instance = klass(**kwargs)
 
-        if hasattr(instance, 'get_real_child_model'):
+        if has_discriminator:
             klass_name = instance.get_real_child_model(data)
             if klass_name:
                 instance = self.__deserialize(data, klass_name)
diff --git a/samples/openapi3/client/petstore/python-experimental/petstore_api/models/animal.py b/samples/openapi3/client/petstore/python-experimental/petstore_api/models/animal.py
index 45058ec7612..39dd9789ff8 100644
--- a/samples/openapi3/client/petstore/python-experimental/petstore_api/models/animal.py
+++ b/samples/openapi3/client/petstore/python-experimental/petstore_api/models/animal.py
@@ -90,12 +90,13 @@ class Animal(ModelNormal):
 
     @staticmethod
     def discriminator():
-        return {
-            'class_name': {
-                'Cat': cat.Cat,
-                'Dog': dog.Dog,
-            },
+        val = {
+            'Cat': cat.Cat,
+            'Dog': dog.Dog,
         }
+        if not val:
+            return None
+        return {'class_name': val}
 
     attribute_map = {
         'class_name': 'className',  # noqa: E501
diff --git a/samples/openapi3/client/petstore/python-experimental/petstore_api/models/cat.py b/samples/openapi3/client/petstore/python-experimental/petstore_api/models/cat.py
index 92076d35c06..c3641a6862b 100644
--- a/samples/openapi3/client/petstore/python-experimental/petstore_api/models/cat.py
+++ b/samples/openapi3/client/petstore/python-experimental/petstore_api/models/cat.py
@@ -96,7 +96,11 @@ class Cat(ModelComposed):
 
     @staticmethod
     def discriminator():
-        return None
+        val = {
+        }
+        if not val:
+            return None
+        return {'class_name': val}
 
     attribute_map = {
         'class_name': 'className',  # noqa: E501
@@ -200,3 +204,16 @@ class Cat(ModelComposed):
           'oneOf': [
           ],
         }
+
+    @classmethod
+    def get_discriminator_class(cls, from_server, data):
+        """Returns the child class specified by the discriminator"""
+        discriminator = cls.discriminator()
+        discr_propertyname_py = list(discriminator.keys())[0]
+        discr_propertyname_js = cls.attribute_map[discr_propertyname_py]
+        if from_server:
+            class_name = data[discr_propertyname_js]
+        else:
+            class_name = data[discr_propertyname_py]
+        class_name_to_discr_class = discriminator[discr_propertyname_py]
+        return class_name_to_discr_class.get(class_name)
diff --git a/samples/openapi3/client/petstore/python-experimental/petstore_api/models/dog.py b/samples/openapi3/client/petstore/python-experimental/petstore_api/models/dog.py
index 69af821b27e..5d5712d428e 100644
--- a/samples/openapi3/client/petstore/python-experimental/petstore_api/models/dog.py
+++ b/samples/openapi3/client/petstore/python-experimental/petstore_api/models/dog.py
@@ -91,7 +91,11 @@ class Dog(ModelComposed):
 
     @staticmethod
     def discriminator():
-        return None
+        val = {
+        }
+        if not val:
+            return None
+        return {'class_name': val}
 
     attribute_map = {
         'class_name': 'className',  # noqa: E501
@@ -194,3 +198,16 @@ class Dog(ModelComposed):
           'oneOf': [
           ],
         }
+
+    @classmethod
+    def get_discriminator_class(cls, from_server, data):
+        """Returns the child class specified by the discriminator"""
+        discriminator = cls.discriminator()
+        discr_propertyname_py = list(discriminator.keys())[0]
+        discr_propertyname_js = cls.attribute_map[discr_propertyname_py]
+        if from_server:
+            class_name = data[discr_propertyname_js]
+        else:
+            class_name = data[discr_propertyname_py]
+        class_name_to_discr_class = discriminator[discr_propertyname_py]
+        return class_name_to_discr_class.get(class_name)
diff --git a/samples/openapi3/client/petstore/python-experimental/petstore_api/models/mammal.py b/samples/openapi3/client/petstore/python-experimental/petstore_api/models/mammal.py
index 303838fd7d4..d5ee114fe25 100644
--- a/samples/openapi3/client/petstore/python-experimental/petstore_api/models/mammal.py
+++ b/samples/openapi3/client/petstore/python-experimental/petstore_api/models/mammal.py
@@ -97,12 +97,13 @@ class Mammal(ModelComposed):
 
     @staticmethod
     def discriminator():
-        return {
-            'class_name': {
-                'whale': whale.Whale,
-                'zebra': zebra.Zebra,
-            },
+        val = {
+            'whale': whale.Whale,
+            'zebra': zebra.Zebra,
         }
+        if not val:
+            return None
+        return {'class_name': val}
 
     attribute_map = {
         'class_name': 'className',  # noqa: E501
diff --git a/samples/openapi3/client/petstore/python/petstore_api/api_client.py b/samples/openapi3/client/petstore/python/petstore_api/api_client.py
index c0564c598f1..a80084e04b0 100644
--- a/samples/openapi3/client/petstore/python/petstore_api/api_client.py
+++ b/samples/openapi3/client/petstore/python/petstore_api/api_client.py
@@ -624,9 +624,12 @@ class ApiClient(object):
         :param klass: class literal.
         :return: model object.
         """
+        has_discriminator = False
+        if (hasattr(klass, 'get_real_child_model')
+                and klass.discriminator_value_class_map):
+            has_discriminator = True
 
-        if not klass.openapi_types and not hasattr(klass,
-                                                   'get_real_child_model'):
+        if not klass.openapi_types and has_discriminator is False:
             return data
 
         kwargs = {}
@@ -640,7 +643,7 @@ class ApiClient(object):
 
         instance = klass(**kwargs)
 
-        if hasattr(instance, 'get_real_child_model'):
+        if has_discriminator:
             klass_name = instance.get_real_child_model(data)
             if klass_name:
                 instance = self.__deserialize(data, klass_name)