better handling of const value

* Autosets the parameters with the only value specified as enum if the parameter is also marked as required

* Autosets the parameters with the only value specified as enum if the parameter is also marked as required

* Autosets the parameters with the only value specified as enum if the parameter is also marked as required for Java default client.

* Autosets the parameters with the only value specified as enum if the parameter is also marked as required for Java default client.

* Autosets the parameters with the only value specified as enum if the parameter is also marked as required for Java default client.

* Autosets the parameters with the only value specified as enum if the parameter is also marked as required for Java default client.

.github/workflows/docker.yaml

@@ -21,7 +21,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Check out code
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
 
       - name: Test run-in-docker.sh
         shell: bash

.github/workflows/gradle-plugin-tests.yaml

@@ -13,7 +13,7 @@ jobs:
     name: Gradle plugin tests
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Set up JDK 11
         uses: actions/setup-java@v3
         with:

.github/workflows/gradle-test.yaml

@@ -30,7 +30,7 @@ jobs:
           - samples/client/petstore/java/okhttp-gson-group-parameter
           - samples/client/petstore/java/webclient-swagger2
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: actions/setup-java@v3
         with:
           distribution: 'temurin'

.github/workflows/linux.yaml

@@ -20,7 +20,7 @@ jobs:
         os: [ubuntu-latest]
     steps:
       - name: Check out code
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
 
       - name: Set up JDK ${{ matrix.java }}
         uses: actions/setup-java@v3
@@ -85,7 +85,7 @@ jobs:
         os: [ubuntu-latest]
     steps:
       - name: Check out code
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
       - name: Setup Maven
         uses: s4u/setup-maven-action@v1.9.0
         with:

.github/workflows/maven-plugin-tests.yaml

@@ -13,7 +13,7 @@ jobs:
     name: Maven plugin tests
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Set up JDK 11
         uses: actions/setup-java@v3
         with:

.github/workflows/misc-test.yaml

@@ -15,7 +15,7 @@ jobs:
     name: Misc tests
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: ruby/setup-ruby@v1
         with:
           ruby-version: '2.6'

.github/workflows/openapi-generator.yaml

@@ -15,7 +15,7 @@ jobs:
     name: Build
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Set up JDK 11
         uses: actions/setup-java@v3
         with:
@@ -53,7 +53,7 @@ jobs:
     needs:
       - build
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Set up JDK 11
         uses: actions/setup-java@v3
         with:
@@ -90,7 +90,7 @@ jobs:
     needs:
       - build
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Set up JDK 11
         uses: actions/setup-java@v3
         with:
@@ -129,7 +129,7 @@ jobs:
       - build
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Set up JDK 11
         uses: actions/setup-java@v3
         with:

.github/workflows/samples-c-libcurl-client.yaml

@@ -13,7 +13,7 @@ jobs:
     name: Build c libcurl client
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Prepare
         run: |
           sudo apt-get update

.github/workflows/samples-cpp-qt-client.yaml

@@ -28,7 +28,7 @@ jobs:
             tools: 'tools_openssl_x64'
     runs-on: ${{ matrix.os }}
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: jurplel/install-qt-action@v3
         with:
           version: ${{ matrix.qt-version }}

.github/workflows/samples-dart.yaml

@@ -17,7 +17,7 @@ jobs:
     name: Tests Dart
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: actions/setup-java@v3
         with:
           distribution: 'temurin'

.github/workflows/samples-dotnet-standard.yaml

@@ -18,7 +18,7 @@ jobs:
           # clients
           - samples/client/petstore/csharp/OpenAPIClient-generichost-netstandard2.0
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: actions/setup-dotnet@v3.2.0
         with:
           dotnet-version: 3.1.*

.github/workflows/samples-dotnet.yaml

@@ -42,7 +42,7 @@ jobs:
           - samples/server/petstore/aspnetcore-6.0-NewtonsoftFalse
           - samples/server/petstore/aspnetcore-6.0-nullableReferenceTypes
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: actions/setup-dotnet@v3.2.0
         with:
           dotnet-version: '7.0.x'

.github/workflows/samples-dotnet6-client-echo-api.yaml

@@ -18,7 +18,7 @@ jobs:
           # clients
           - samples/client/echo_api/csharp-restsharp/
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: actions/setup-dotnet@v3.2.0
         with:
           dotnet-version: '6.0.x'

.github/workflows/samples-dotnet6-client.yaml

@@ -72,7 +72,7 @@ jobs:
           # build C# API client (property, parameter name mappings)
           - samples/client/petstore/csharp-restsharp-name-parameter-mappings
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: actions/setup-dotnet@v3.2.0
         with:
           dotnet-version: '6.0.x'

.github/workflows/samples-dotnet6-server.yaml

@@ -29,7 +29,7 @@ jobs:
           - samples/server/petstore/aspnetcore-6.0-NewtonsoftFalse
           - samples/server/petstore/aspnetcore-6.0-nullableReferenceTypes
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: actions/setup-dotnet@v3.2.0
         with:
           dotnet-version: '6.0.x'

.github/workflows/samples-elm.yaml

@@ -21,7 +21,7 @@ jobs:
           - samples/client/petstore/elm
           - samples/openapi3/client/elm
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: jorelali/setup-elm@v5
         with:
           elm-version: 0.19.1

.github/workflows/samples-erlang.yaml

@@ -26,7 +26,7 @@ jobs:
           - samples/client/petstore/erlang-client/
           - samples/client/petstore/erlang-proper/
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: erlef/setup-beam@v1
         with:
           otp-version: '22.2'

.github/workflows/samples-go.yaml

@@ -24,7 +24,7 @@ jobs:
           - samples/server/petstore/go-api-server/
           - samples/server/petstore/go-chi-server/
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: actions/setup-go@v4
         with:
           go-version: "stable"

.github/workflows/samples-groovy.yaml

@@ -21,7 +21,7 @@ jobs:
         sample:
           - samples/client/petstore/groovy
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: actions/setup-java@v3
         with:
           distribution: 'temurin'

.github/workflows/samples-haskell.yaml

@@ -24,7 +24,7 @@ jobs:
           - samples/server/petstore/haskell-servant/
           - samples/client/petstore/haskell-http-client/
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: haskell/actions/setup@v2
         with:
           # ghc-version: '8.8.4' # Exact version of ghc to use

.github/workflows/samples-java-client-echo-api-jdk11.yaml

@@ -20,7 +20,7 @@ jobs:
           - samples/client/echo_api/java/native
           - samples/client/echo_api/java/feign-gson
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: actions/setup-java@v3
         with:
           distribution: 'temurin'

.github/workflows/samples-java-client-echo-api-jdk8.yaml

@@ -24,7 +24,7 @@ jobs:
           - samples/client/echo_api/java/feign-gson
           - samples/client/echo_api/java/okhttp-gson
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: actions/setup-java@v3
         with:
           distribution: 'temurin'

.github/workflows/samples-java-client-jdk11.yaml

@@ -43,7 +43,6 @@ jobs:
           - samples/client/petstore/java/webclient-swagger2
           - samples/client/petstore/java/vertx
           - samples/client/petstore/java/jersey2-java8-localdatetime
-          - samples/client/petstore/java/resteasy
           - samples/client/petstore/java/google-api-client
           - samples/client/petstore/java/rest-assured
           - samples/client/petstore/java/rest-assured-jackson
@@ -63,7 +62,7 @@ jobs:
           - samples/client/petstore/java/resttemplate-swagger2/
           - samples/openapi3/client/petstore/java/jersey2-java8-swagger2/
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: actions/setup-java@v3
         with:
           distribution: 'temurin'
@@ -78,4 +77,4 @@ jobs:
           key: ${{ runner.os }}-${{ github.job }}-${{ env.cache-name }}-${{ hashFiles('**/pom.xml') }}
       - name: Build
         working-directory: ${{ matrix.sample }}
-        run: mvn clean package
+        run: mvn clean package

.github/workflows/samples-java-client-jdk17.yaml

@@ -21,7 +21,7 @@ jobs:
           - samples/client/petstore/java/resttemplate-jakarta
           - samples/client/petstore/java/webclient-jakarta
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: actions/setup-java@v3
         with:
           distribution: 'temurin'

.github/workflows/samples-java-helidon.yaml

@@ -23,7 +23,7 @@ jobs:
           - samples/server/petstore/java-helidon-server/se
         version: [17]
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: actions/setup-java@v3
         with:
           distribution: 'temurin'

.github/workflows/samples-java-play-framework.yaml

@@ -29,7 +29,7 @@ jobs:
           - samples/server/petstore/java-play-framework-no-swagger-ui
           - samples/server/petstore/java-play-framework-no-wrap-calls
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: actions/setup-java@v3
         with:
           distribution: 'temurin'

.github/workflows/samples-java-server-jdk8.yaml

@@ -31,7 +31,7 @@ jobs:
           - samples/server/petstore/java-pkmst/
           - samples/server/petstore/java-undertow/
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: actions/setup-java@v3
         with:
           distribution: 'temurin'

.github/workflows/samples-jaxrs.yaml

@@ -40,7 +40,7 @@ jobs:
           - samples/server/petstore/jaxrs-cxf-non-spring-app
           - samples/server/petstore/jaxrs-spec-microprofile-openapi-annotations
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: actions/setup-java@v3
         with:
           distribution: 'temurin'

.github/workflows/samples-jdk17.yaml

@@ -45,7 +45,7 @@ jobs:
           - samples/client/petstore/spring-http-interface-reactive
           - samples/client/petstore/spring-http-interface
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: actions/setup-java@v3
         with:
           distribution: 'temurin'

.github/workflows/samples-julia.yaml

@@ -15,7 +15,7 @@ jobs:
     name: Tests Julia
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: julia-actions/setup-julia@v1
         with:
           version: 1.8

.github/workflows/samples-kotlin-client.yaml

@@ -65,7 +65,7 @@ jobs:
           - samples/client/petstore/kotlin-name-parameter-mappings
           - samples/client/others/kotlin-jvm-okhttp-parameter-tests
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: actions/setup-java@v3
         with:
           distribution: 'temurin'

.github/workflows/samples-kotlin-server-jdk17.yaml

@@ -28,7 +28,7 @@ jobs:
           # comment out due to gradle build failure
           # - samples/server/petstore/kotlin-spring-default/
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: actions/setup-java@v3
         with:
           distribution: 'temurin'

.github/workflows/samples-kotlin-server.yaml

@@ -43,7 +43,7 @@ jobs:
           # no build.gradle file
           #- samples/server/petstore/kotlin-vertx-modelMutable
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: actions/setup-java@v3
         with:
           distribution: 'temurin'

.github/workflows/samples-php7.yaml

@@ -18,7 +18,7 @@ jobs:
           # servers
           - samples/server/petstore/php-laravel/lib/
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Setup PHP with tools
         uses: shivammathur/setup-php@v2
         with:

.github/workflows/samples-php8.yaml

@@ -18,7 +18,7 @@ jobs:
           # servers
           - samples/server/petstore/php-symfony/SymfonyBundle-php/
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Setup PHP with tools
         uses: shivammathur/setup-php@v2
         with:

.github/workflows/samples-python-nextgen-client-echo-api.yaml

@@ -18,7 +18,7 @@ jobs:
           # clients
           - samples/client/echo_api/python
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: actions/setup-python@v4
         with:
           python-version: '3.7'

.github/workflows/samples-python-server.yaml

@@ -18,7 +18,7 @@ jobs:
           # servers
           - samples/server/petstore/python-aiohttp/
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: actions/setup-python@v4
         with:
           python-version: '3.7'

.github/workflows/samples-rust.yaml

@@ -25,7 +25,7 @@ jobs:
           - samples/client/petstore/rust/
           - samples/server/petstore/rust-server/
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: actions-rs/toolchain@v1
         with:
           toolchain: stable

.github/workflows/samples-scala.yaml

@@ -31,7 +31,7 @@ jobs:
           - samples/server/petstore/scalatra
           - samples/server/petstore/scala-finch # cannot be tested with jdk11
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: actions/setup-java@v3
         with:
           distribution: 'temurin'

.github/workflows/samples-spring-jdk17.yaml

@@ -18,7 +18,7 @@ jobs:
           # clients
           - samples/openapi3/client/petstore/spring-cloud-3-with-optional
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: actions/setup-java@v3
         with:
           distribution: 'temurin'

.github/workflows/samples-spring.yaml

@@ -3,10 +3,16 @@ name: Samples Java Spring
 on:
   push:
     paths:
+      # clients
+      - 'samples/client/petstore/spring*/**'
+      # servers
       - 'samples/server/petstore/spring*/**'
       - 'samples/openapi3/server/petstore/spring*/**'
   pull_request:
     paths:
+      # clients
+      - 'samples/client/petstore/spring*/**'
+      # servers
       - 'samples/server/petstore/spring*/**'
       - 'samples/openapi3/server/petstore/spring*/**'
 jobs:
@@ -27,6 +33,7 @@ jobs:
           - samples/openapi3/client/petstore/spring-cloud-async
           - samples/openapi3/client/petstore/spring-cloud-spring-pageable
           - samples/client/petstore/spring-cloud-tags
+          - samples/client/petstore/spring-cloud-deprecated
           # servers
           - samples/server/petstore/springboot
           - samples/openapi3/server/petstore/springboot
@@ -49,7 +56,7 @@ jobs:
           - samples/server/petstore/springboot-spring-pageable-without-j8
           - samples/server/petstore/springboot-spring-pageable
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: actions/setup-java@v3
         with:
           distribution: 'temurin'

.github/workflows/samples-swift.yaml

@@ -40,7 +40,7 @@ jobs:
     name: Build Swift samples
     runs-on: ${{ matrix.os }}
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: swift-actions/setup-swift@v1
         if: ${{ matrix.os == 'ubuntu-latest' }}
         with:

.github/workflows/samples-zapier.yaml

@@ -18,7 +18,7 @@ jobs:
         sample:
           - samples/client/petstore/zapier
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - name: Setup node
       uses: actions/setup-node@v3
     - name: Install dependencies

.github/workflows/sonar.yml

@@ -12,7 +12,7 @@ jobs:
     runs-on: ubuntu-latest
     if: ${{ github.repository_owner == 'OpenAPITools' }}
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - name: Set up JDK 11
       uses: actions/setup-java@v3
       with:

.github/workflows/windows.yaml

@@ -18,7 +18,7 @@ jobs:
       matrix:
         java: [11, 17]
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Set up JDK ${{ matrix.java }}
         uses: actions/setup-java@v3
         with:

.gitignore

@@ -89,6 +89,7 @@ samples/client/petstore/cpp-restsdk/cmake_install.cmake
 **/.gradle
 samples/client/petstore/java/hello.txt
 samples/client/petstore/java/okhttp-gson/hello.txt
+samples/client/petstore/java/okhttp-gson-3.1/hello.txt
 samples/client/petstore/java/jersey1/hello.txt
 samples/client/petstore/java/jersey2-java8/hello.txt
 samples/client/petstore/java/jersey2/hello.txt
@@ -211,6 +212,7 @@ samples/server/petstore/kotlin-server/ktor/build
 samples/server/petstore/kotlin-springboot/build
 samples/client/petstore/kotlin*/src/main/kotlin/test/
 samples/client/petstore/kotlin*/build/
+samples/server/others/kotlin-server/jaxrs-spec/build/
 
 # haskell
 .stack-work

.java-version

@@ -1 +1 @@
-1.8
+11

README.md

@@ -1168,7 +1168,7 @@ If you want to join the committee, please kindly apply by sending an email to te
 | Perl                  | @wing328 (2017/07) [:heart:](https://www.patreon.com/wing328) @yue9944882 (2019/06)                                                                                                                                                                   |
 | PHP                   | @jebentier (2017/07), @dkarlovi (2017/07), @mandrean (2017/08), @jfastnacht (2017/09), [@ybelenko](https://github.com/ybelenko) (2018/07), @renepardon (2018/12)                                                                                      |
 | PowerShell            | @wing328 (2020/05)                                                                                                                                                                                                                                    |
-| Python                | @spacether (2019/11) [:heart:][spacether sponsorship] @krjakbrjak (2023/02)                                                                                                                                                                                                 |
+| Python                | @krjakbrjak (2023/02)                                                                                                                                                                                                 |
 | R                     | @Ramanth (2019/07) @saigiridhar21 (2019/07)                                                                                                                                                                                                           |
 | Ruby                  | @cliffano (2017/07) @zlx (2017/09) @autopp (2019/02)                                                                                                                                                                                                  |
 | Rust                  | @frol (2017/07) @farcaller (2017/08) @richardwhiuk (2019/07) @paladinzh (2020/05) @jacob-pro (2022/10)                                                                                                                                                |

bin/configs/csharp-generichost-latest-nrt-useSourceGeneration.yaml

@@ -0,0 +1,12 @@
+# for csharp generichost
+generatorName: csharp
+outputDir: samples/client/petstore/csharp/OpenAPIClient-generichost-net6.0-nrt-useSourceGeneration
+inputSpec: modules/openapi-generator/src/test/resources/3_0/csharp/petstore-with-fake-endpoints-models-for-testing-with-http-signature.yaml
+library: generichost
+templateDir: modules/openapi-generator/src/main/resources/csharp
+additionalProperties:
+  packageGuid: '{321C8C3F-0156-40C1-AE42-D59761FB9B6C}'
+  useCompareNetObjects: true 
+  disallowAdditionalPropertiesIfNotPresent: false
+  useSourceGeneration: true
+  packageName: UseSourceGeneration

bin/configs/go-echo-api.yaml

@@ -0,0 +1,6 @@
+generatorName: go
+outputDir: samples/client/echo_api/go
+inputSpec: modules/openapi-generator/src/test/resources/3_0/echo_api.yaml
+templateDir: modules/openapi-generator/src/main/resources/go
+additionalProperties:
+  hideGenerationTimestamp: "true"

bin/configs/java-okhttp-gson-3.1.yaml

@@ -0,0 +1,16 @@
+generatorName: java
+outputDir: samples/client/petstore/java/okhttp-gson-3.1
+library: okhttp-gson
+inputSpec: modules/openapi-generator/src/test/resources/3_1/java/petstore.yaml
+templateDir: modules/openapi-generator/src/main/resources/Java
+nameMappings:
+  _type: underscoreType
+  type_: typeWithUnderscore
+parameterNameMappings:
+  _type: underscoreType
+  type_: typeWithUnderscore
+additionalProperties:
+  artifactId: petstore-okhttp-gson-31
+  hideGenerationTimestamp: "true"
+  useOneOfDiscriminatorLookup: "true"
+  disallowAdditionalPropertiesIfNotPresent: false

bin/configs/lua.yaml

@@ -4,3 +4,5 @@ inputSpec: modules/openapi-generator/src/test/resources/3_0/petstore.yaml
 templateDir: modules/openapi-generator/src/main/resources/lua
 additionalProperties:
   packageName: petstore
+nameMappings:
+  phone: mobile

bin/configs/perl.yaml

@@ -4,3 +4,7 @@ inputSpec: modules/openapi-generator/src/test/resources/3_0/petstore-with-fake-e
 templateDir: modules/openapi-generator/src/main/resources/perl
 additionalProperties:
   hideGenerationTimestamp: "true"
+nameMappings:
+  NullableMessage: system_message
+modelNameMappings:
+  DeprecatedObject: DeprecatedModel

bin/configs/php-nextgen-echo-api.yaml

@@ -0,0 +1,6 @@
+generatorName: php-nextgen
+outputDir: samples/client/echo_api/php-nextgen
+inputSpec: modules/openapi-generator/src/test/resources/3_0/echo_api.yaml
+templateDir: modules/openapi-generator/src/main/resources/php-nextgen
+additionalProperties:
+  hideGenerationTimestamp: "true"

bin/configs/php-nextgen.yaml

@@ -1,4 +1,4 @@
 generatorName: php-nextgen
 outputDir: samples/client/petstore/php-nextgen/OpenAPIClient-php
-inputSpec: modules/openapi-generator/src/test/resources/3_0/petstore-with-fake-endpoints-models-for-testing.yaml
+inputSpec: modules/openapi-generator/src/test/resources/3_0/php-nextgen/petstore-with-fake-endpoints-models-for-testing.yaml
 templateDir: modules/openapi-generator/src/main/resources/php-nextgen

bin/configs/powershell.yaml

@@ -14,3 +14,7 @@ additionalProperties:
   projectUri: https://github.com/OpenAPITools/openapi-generator
   releaseNotes: 'This is a sample project'
   tags: 'PetStore,powershell,sdk'
+nameMappings:
+  name_mapping: SomethingElse
+modelNameMappings:
+  model-mapping: NewModel

bin/configs/python-flask.yaml

@@ -1,4 +1,4 @@
 generatorName: python-flask
 outputDir: samples/server/petstore/python-flask
-inputSpec: modules/openapi-generator/src/test/resources/2_0/petstore.yaml
+inputSpec: modules/openapi-generator/src/test/resources/2_0/python-flask/petstore.yaml
 templateDir: modules/openapi-generator/src/main/resources/python-flask

bin/configs/spring-cloud-deprecated-oas3.yaml

@@ -0,0 +1,13 @@
+generatorName: spring
+library: spring-cloud
+outputDir: samples/client/petstore/spring-cloud-deprecated
+inputSpec: modules/openapi-generator/src/test/resources/3_0/petstore-with-deprecated-fields.yaml
+templateDir: modules/openapi-generator/src/main/resources/JavaSpring
+additionalProperties:
+  groupId: org.openapitools.openapi3
+  documentationProvider: springdoc
+  artifactId: spring-cloud-deprecated
+  interfaceOnly: "true"
+  singleContentTypes: "true"
+  hideGenerationTimestamp: "true"
+  useTags: "true"

docs/generators/csharp.md

@@ -49,6 +49,7 @@ These options may be applied as additional-properties (cli) or configOptions (pl
 |useCollection|Deserialize array types to Collection<T> instead of List<T>.| |false|
 |useDateTimeOffset|Use DateTimeOffset to model date-time properties| |false|
 |useOneOfDiscriminatorLookup|Use the discriminator's mapping in oneOf to speed up the model lookup. IMPORTANT: Validation (e.g. one and only one match in oneOf's schemas) will be skipped.| |false|
+|useSourceGeneration|Use source generation where available (only `generichost` library supports this option).| |false|
 |validatable|Generates self-validatable models.| |true|
 |zeroBasedEnums|Enumerations with string values will start from 0 when true, 1 when false. If not set, enumerations with string values will start from 0 if the first value is 'unknown', case insensitive.| |null|
 

docs/generators/groovy.md

@@ -25,6 +25,7 @@ These options may be applied as additional-properties (cli) or configOptions (pl
 |apiPackage|package for generated api classes| |org.openapitools.api|
 |artifactId|artifactId in generated pom.xml. This also becomes part of the generated library's filename| |openapi-groovy|
 |artifactVersion|artifact version in generated pom.xml. This also becomes part of the generated library's filename| |1.0.0|
+|autosetConstants|Automatically set Required Params having a Single enum value i.e. Constants in generated code| |false|
 |bigDecimalAsString|Treat BigDecimal values as Strings to avoid precision loss.| |false|
 |booleanGetterPrefix|Set booleanGetterPrefix| |get|
 |camelCaseDollarSign|Fix camelCase when starting with $ sign. when true : $Value when false : $value| |false|

docs/generators/java-camel.md

@@ -30,6 +30,7 @@ These options may be applied as additional-properties (cli) or configOptions (pl
 |artifactUrl|artifact URL in generated pom.xml| |https://github.com/openapitools/openapi-generator|
 |artifactVersion|artifact version in generated pom.xml. This also becomes part of the generated library's filename| |1.0.0|
 |async|use async Callable controllers| |false|
+|autosetConstants|Automatically set Required Params having a Single enum value i.e. Constants in generated code| |false|
 |basePackage|base package (invokerPackage) for generated code| |org.openapitools|
 |bigDecimalAsString|Treat BigDecimal values as Strings to avoid precision loss.| |false|
 |booleanGetterPrefix|Set booleanGetterPrefix| |get|

docs/generators/java-helidon-client.md

@@ -27,6 +27,7 @@ These options may be applied as additional-properties (cli) or configOptions (pl
 |artifactId|artifactId in generated pom.xml. This also becomes part of the generated library's filename| |openapi-java-client|
 |artifactUrl|artifact URL in generated pom.xml| |https://github.com/openapitools/openapi-generator|
 |artifactVersion|artifact version in generated pom.xml. This also becomes part of the generated library's filename| |1.0.0|
+|autosetConstants|Automatically set Required Params having a Single enum value i.e. Constants in generated code| |false|
 |bigDecimalAsString|Treat BigDecimal values as Strings to avoid precision loss.| |false|
 |booleanGetterPrefix|Set booleanGetterPrefix| |get|
 |camelCaseDollarSign|Fix camelCase when starting with $ sign. when true : $Value when false : $value| |false|

docs/generators/java-helidon-server.md

@@ -27,6 +27,7 @@ These options may be applied as additional-properties (cli) or configOptions (pl
 |artifactId|artifactId in generated pom.xml. This also becomes part of the generated library's filename| |openapi-java-server|
 |artifactUrl|artifact URL in generated pom.xml| |https://github.com/openapitools/openapi-generator|
 |artifactVersion|artifact version in generated pom.xml. This also becomes part of the generated library's filename| |1.0.0|
+|autosetConstants|Automatically set Required Params having a Single enum value i.e. Constants in generated code| |false|
 |bigDecimalAsString|Treat BigDecimal values as Strings to avoid precision loss.| |false|
 |booleanGetterPrefix|Set booleanGetterPrefix| |get|
 |camelCaseDollarSign|Fix camelCase when starting with $ sign. when true : $Value when false : $value| |false|

docs/generators/java-inflector.md

@@ -27,6 +27,7 @@ These options may be applied as additional-properties (cli) or configOptions (pl
 |artifactId|artifactId in generated pom.xml. This also becomes part of the generated library's filename| |openapi-inflector-server|
 |artifactUrl|artifact URL in generated pom.xml| |https://github.com/openapitools/openapi-generator|
 |artifactVersion|artifact version in generated pom.xml. This also becomes part of the generated library's filename| |1.0.0|
+|autosetConstants|Automatically set Required Params having a Single enum value i.e. Constants in generated code| |false|
 |bigDecimalAsString|Treat BigDecimal values as Strings to avoid precision loss.| |false|
 |booleanGetterPrefix|Set booleanGetterPrefix| |get|
 |camelCaseDollarSign|Fix camelCase when starting with $ sign. when true : $Value when false : $value| |false|

docs/generators/java-micronaut-client.md

@@ -30,6 +30,7 @@ These options may be applied as additional-properties (cli) or configOptions (pl
 |artifactUrl|artifact URL in generated pom.xml| |https://github.com/openapitools/openapi-generator|
 |artifactVersion|artifact version in generated pom.xml. This also becomes part of the generated library's filename| |1.0.0|
 |authorizationFilterPattern|Configure the authorization filter pattern for the client. Generally defined when generating clients from multiple specification files| |null|
+|autosetConstants|Automatically set Required Params having a Single enum value i.e. Constants in generated code| |false|
 |basePathSeparator|Configure the separator to use between the application name and base path when referencing the property| |-|
 |bigDecimalAsString|Treat BigDecimal values as Strings to avoid precision loss.| |false|
 |booleanGetterPrefix|Set booleanGetterPrefix| |get|

docs/generators/java-micronaut-server.md

@@ -27,6 +27,7 @@ These options may be applied as additional-properties (cli) or configOptions (pl
 |artifactId|artifactId in generated pom.xml. This also becomes part of the generated library's filename| |openapi-micronaut|
 |artifactUrl|artifact URL in generated pom.xml| |https://github.com/openapitools/openapi-generator|
 |artifactVersion|artifact version in generated pom.xml. This also becomes part of the generated library's filename| |1.0.0|
+|autosetConstants|Automatically set Required Params having a Single enum value i.e. Constants in generated code| |false|
 |bigDecimalAsString|Treat BigDecimal values as Strings to avoid precision loss.| |false|
 |booleanGetterPrefix|Set booleanGetterPrefix| |get|
 |build|Specify for which build tool to generate files|<dl><dt>**gradle**</dt><dd>Gradle configuration is generated for the project</dd><dt>**all**</dt><dd>Both Gradle and Maven configurations are generated</dd><dt>**maven**</dt><dd>Maven configuration is generated for the project</dd></dl>|all|

docs/generators/java-msf4j.md

@@ -27,6 +27,7 @@ These options may be applied as additional-properties (cli) or configOptions (pl
 |artifactId|artifactId in generated pom.xml. This also becomes part of the generated library's filename| |openapi-jaxrs-server|
 |artifactUrl|artifact URL in generated pom.xml| |https://github.com/openapitools/openapi-generator|
 |artifactVersion|artifact version in generated pom.xml. This also becomes part of the generated library's filename| |1.0.0|
+|autosetConstants|Automatically set Required Params having a Single enum value i.e. Constants in generated code| |false|
 |bigDecimalAsString|Treat BigDecimal values as Strings to avoid precision loss.| |false|
 |booleanGetterPrefix|Set booleanGetterPrefix| |get|
 |camelCaseDollarSign|Fix camelCase when starting with $ sign. when true : $Value when false : $value| |false|

docs/generators/java-pkmst.md

@@ -27,6 +27,7 @@ These options may be applied as additional-properties (cli) or configOptions (pl
 |artifactId|artifactId in generated pom.xml. This also becomes part of the generated library's filename| |pkmst-microservice|
 |artifactUrl|artifact URL in generated pom.xml| |https://github.com/openapitools/openapi-generator|
 |artifactVersion|artifact version in generated pom.xml. This also becomes part of the generated library's filename| |1.0.0|
+|autosetConstants|Automatically set Required Params having a Single enum value i.e. Constants in generated code| |false|
 |basePackage|base package for java source code| |null|
 |bigDecimalAsString|Treat BigDecimal values as Strings to avoid precision loss.| |false|
 |booleanGetterPrefix|Set booleanGetterPrefix| |get|

docs/generators/java-play-framework.md

@@ -27,6 +27,7 @@ These options may be applied as additional-properties (cli) or configOptions (pl
 |artifactId|artifactId in generated pom.xml. This also becomes part of the generated library's filename| |openapi-java-playframework|
 |artifactUrl|artifact URL in generated pom.xml| |https://github.com/openapitools/openapi-generator|
 |artifactVersion|artifact version in generated pom.xml. This also becomes part of the generated library's filename| |1.0.0|
+|autosetConstants|Automatically set Required Params having a Single enum value i.e. Constants in generated code| |false|
 |basePackage|base package for generated code| |org.openapitools|
 |bigDecimalAsString|Treat BigDecimal values as Strings to avoid precision loss.| |false|
 |booleanGetterPrefix|Set booleanGetterPrefix| |get|

docs/generators/java-undertow-server.md

@@ -27,6 +27,7 @@ These options may be applied as additional-properties (cli) or configOptions (pl
 |artifactId|artifactId in generated pom.xml. This also becomes part of the generated library's filename| |openapi-undertow-server|
 |artifactUrl|artifact URL in generated pom.xml| |https://github.com/openapitools/openapi-generator|
 |artifactVersion|artifact version in generated pom.xml. This also becomes part of the generated library's filename| |1.0.0|
+|autosetConstants|Automatically set Required Params having a Single enum value i.e. Constants in generated code| |false|
 |bigDecimalAsString|Treat BigDecimal values as Strings to avoid precision loss.| |false|
 |booleanGetterPrefix|Set booleanGetterPrefix| |get|
 |camelCaseDollarSign|Fix camelCase when starting with $ sign. when true : $Value when false : $value| |false|

docs/generators/java-vertx-web.md

@@ -27,6 +27,7 @@ These options may be applied as additional-properties (cli) or configOptions (pl
 |artifactId|artifactId in generated pom.xml. This also becomes part of the generated library's filename| |openapi-java-vertx-web-server|
 |artifactUrl|artifact URL in generated pom.xml| |https://github.com/openapitools/openapi-generator|
 |artifactVersion|artifact version in generated pom.xml. This also becomes part of the generated library's filename| |1.0.0-SNAPSHOT|
+|autosetConstants|Automatically set Required Params having a Single enum value i.e. Constants in generated code| |false|
 |bigDecimalAsString|Treat BigDecimal values as Strings to avoid precision loss.| |false|
 |booleanGetterPrefix|Set booleanGetterPrefix| |get|
 |camelCaseDollarSign|Fix camelCase when starting with $ sign. when true : $Value when false : $value| |false|

docs/generators/java-vertx.md

@@ -27,6 +27,7 @@ These options may be applied as additional-properties (cli) or configOptions (pl
 |artifactId|artifactId in generated pom.xml. This also becomes part of the generated library's filename| |openapi-java-vertx-server|
 |artifactUrl|artifact URL in generated pom.xml| |https://github.com/openapitools/openapi-generator|
 |artifactVersion|artifact version in generated pom.xml. This also becomes part of the generated library's filename| |1.0.0-SNAPSHOT|
+|autosetConstants|Automatically set Required Params having a Single enum value i.e. Constants in generated code| |false|
 |bigDecimalAsString|Treat BigDecimal values as Strings to avoid precision loss.| |false|
 |booleanGetterPrefix|Set booleanGetterPrefix| |get|
 |camelCaseDollarSign|Fix camelCase when starting with $ sign. when true : $Value when false : $value| |false|

docs/generators/java.md

@@ -29,6 +29,7 @@ These options may be applied as additional-properties (cli) or configOptions (pl
 |artifactUrl|artifact URL in generated pom.xml| |https://github.com/openapitools/openapi-generator|
 |artifactVersion|artifact version in generated pom.xml. This also becomes part of the generated library's filename| |1.0.0|
 |asyncNative|If true, async handlers will be used, instead of the sync version| |false|
+|autosetConstants|Automatically set Required Params having a Single enum value i.e. Constants in generated code| |false|
 |bigDecimalAsString|Treat BigDecimal values as Strings to avoid precision loss.| |false|
 |booleanGetterPrefix|Set booleanGetterPrefix| |get|
 |camelCaseDollarSign|Fix camelCase when starting with $ sign. when true : $Value when false : $value| |false|

docs/generators/jaxrs-cxf-cdi.md

@@ -27,6 +27,7 @@ These options may be applied as additional-properties (cli) or configOptions (pl
 |artifactId|artifactId in generated pom.xml. This also becomes part of the generated library's filename| |openapi-jaxrs-cxf-cdi-server|
 |artifactUrl|artifact URL in generated pom.xml| |https://github.com/openapitools/openapi-generator|
 |artifactVersion|artifact version in generated pom.xml. This also becomes part of the generated library's filename| |1.0.0|
+|autosetConstants|Automatically set Required Params having a Single enum value i.e. Constants in generated code| |false|
 |bigDecimalAsString|Treat BigDecimal values as Strings to avoid precision loss.| |false|
 |booleanGetterPrefix|Set booleanGetterPrefix| |get|
 |camelCaseDollarSign|Fix camelCase when starting with $ sign. when true : $Value when false : $value| |false|

docs/generators/jaxrs-cxf-client.md

@@ -27,6 +27,7 @@ These options may be applied as additional-properties (cli) or configOptions (pl
 |artifactId|artifactId in generated pom.xml. This also becomes part of the generated library's filename| |openapi-jaxrs-client|
 |artifactUrl|artifact URL in generated pom.xml| |https://github.com/openapitools/openapi-generator|
 |artifactVersion|artifact version in generated pom.xml. This also becomes part of the generated library's filename| |1.0.0|
+|autosetConstants|Automatically set Required Params having a Single enum value i.e. Constants in generated code| |false|
 |bigDecimalAsString|Treat BigDecimal values as Strings to avoid precision loss.| |false|
 |booleanGetterPrefix|Set booleanGetterPrefix| |get|
 |camelCaseDollarSign|Fix camelCase when starting with $ sign. when true : $Value when false : $value| |false|

docs/generators/jaxrs-cxf-extended.md

@@ -28,6 +28,7 @@ These options may be applied as additional-properties (cli) or configOptions (pl
 |artifactId|artifactId in generated pom.xml. This also becomes part of the generated library's filename| |openapi-cxf-server|
 |artifactUrl|artifact URL in generated pom.xml| |https://github.com/openapitools/openapi-generator|
 |artifactVersion|artifact version in generated pom.xml. This also becomes part of the generated library's filename| |1.0.0|
+|autosetConstants|Automatically set Required Params having a Single enum value i.e. Constants in generated code| |false|
 |bigDecimalAsString|Treat BigDecimal values as Strings to avoid precision loss.| |false|
 |booleanGetterPrefix|Set booleanGetterPrefix| |get|
 |camelCaseDollarSign|Fix camelCase when starting with $ sign. when true : $Value when false : $value| |false|

docs/generators/jaxrs-cxf.md

@@ -28,6 +28,7 @@ These options may be applied as additional-properties (cli) or configOptions (pl
 |artifactId|artifactId in generated pom.xml. This also becomes part of the generated library's filename| |openapi-cxf-server|
 |artifactUrl|artifact URL in generated pom.xml| |https://github.com/openapitools/openapi-generator|
 |artifactVersion|artifact version in generated pom.xml. This also becomes part of the generated library's filename| |1.0.0|
+|autosetConstants|Automatically set Required Params having a Single enum value i.e. Constants in generated code| |false|
 |bigDecimalAsString|Treat BigDecimal values as Strings to avoid precision loss.| |false|
 |booleanGetterPrefix|Set booleanGetterPrefix| |get|
 |camelCaseDollarSign|Fix camelCase when starting with $ sign. when true : $Value when false : $value| |false|

docs/generators/jaxrs-jersey.md

@@ -27,6 +27,7 @@ These options may be applied as additional-properties (cli) or configOptions (pl
 |artifactId|artifactId in generated pom.xml. This also becomes part of the generated library's filename| |openapi-jaxrs-server|
 |artifactUrl|artifact URL in generated pom.xml| |https://github.com/openapitools/openapi-generator|
 |artifactVersion|artifact version in generated pom.xml. This also becomes part of the generated library's filename| |1.0.0|
+|autosetConstants|Automatically set Required Params having a Single enum value i.e. Constants in generated code| |false|
 |bigDecimalAsString|Treat BigDecimal values as Strings to avoid precision loss.| |false|
 |booleanGetterPrefix|Set booleanGetterPrefix| |get|
 |camelCaseDollarSign|Fix camelCase when starting with $ sign. when true : $Value when false : $value| |false|

docs/generators/jaxrs-resteasy-eap.md

@@ -27,6 +27,7 @@ These options may be applied as additional-properties (cli) or configOptions (pl
 |artifactId|artifactId in generated pom.xml. This also becomes part of the generated library's filename| |openapi-jaxrs-resteasy-eap-server|
 |artifactUrl|artifact URL in generated pom.xml| |https://github.com/openapitools/openapi-generator|
 |artifactVersion|artifact version in generated pom.xml. This also becomes part of the generated library's filename| |1.0.0|
+|autosetConstants|Automatically set Required Params having a Single enum value i.e. Constants in generated code| |false|
 |bigDecimalAsString|Treat BigDecimal values as Strings to avoid precision loss.| |false|
 |booleanGetterPrefix|Set booleanGetterPrefix| |get|
 |camelCaseDollarSign|Fix camelCase when starting with $ sign. when true : $Value when false : $value| |false|

docs/generators/jaxrs-resteasy.md

@@ -27,6 +27,7 @@ These options may be applied as additional-properties (cli) or configOptions (pl
 |artifactId|artifactId in generated pom.xml. This also becomes part of the generated library's filename| |openapi-jaxrs-resteasy-server|
 |artifactUrl|artifact URL in generated pom.xml| |https://github.com/openapitools/openapi-generator|
 |artifactVersion|artifact version in generated pom.xml. This also becomes part of the generated library's filename| |1.0.0|
+|autosetConstants|Automatically set Required Params having a Single enum value i.e. Constants in generated code| |false|
 |bigDecimalAsString|Treat BigDecimal values as Strings to avoid precision loss.| |false|
 |booleanGetterPrefix|Set booleanGetterPrefix| |get|
 |camelCaseDollarSign|Fix camelCase when starting with $ sign. when true : $Value when false : $value| |false|

docs/generators/jaxrs-spec.md

@@ -27,6 +27,7 @@ These options may be applied as additional-properties (cli) or configOptions (pl
 |artifactId|artifactId in generated pom.xml. This also becomes part of the generated library's filename| |openapi-jaxrs-server|
 |artifactUrl|artifact URL in generated pom.xml| |https://github.com/openapitools/openapi-generator|
 |artifactVersion|artifact version in generated pom.xml. This also becomes part of the generated library's filename| |1.0.0|
+|autosetConstants|Automatically set Required Params having a Single enum value i.e. Constants in generated code| |false|
 |bigDecimalAsString|Treat BigDecimal values as Strings to avoid precision loss.| |false|
 |booleanGetterPrefix|Set booleanGetterPrefix| |get|
 |camelCaseDollarSign|Fix camelCase when starting with $ sign. when true : $Value when false : $value| |false|

docs/generators/kotlin-server.md

@@ -34,6 +34,7 @@ These options may be applied as additional-properties (cli) or configOptions (pl
 |interfaceOnly|Whether to generate only API interface stubs without the server files. This option is currently supported only when using jaxrs-spec library.| |false|
 |library|library template (sub-template)|<dl><dt>**ktor**</dt><dd>ktor framework</dd><dt>**jaxrs-spec**</dt><dd>JAX-RS spec only</dd></dl>|ktor|
 |modelMutable|Create mutable models| |false|
+|omitGradleWrapper|Whether to omit Gradle wrapper for creating a sub project.| |false|
 |packageName|Generated artifact package name.| |org.openapitools.server|
 |parcelizeModels|toggle &quot;@Parcelize&quot; for generated models| |null|
 |returnResponse|Whether generate API interface should return javax.ws.rs.core.Response instead of a deserialized entity. Only useful if interfaceOnly is true. This option is currently supported only when using jaxrs-spec library.| |false|

docs/generators/spring.md

@@ -30,6 +30,7 @@ These options may be applied as additional-properties (cli) or configOptions (pl
 |artifactUrl|artifact URL in generated pom.xml| |https://github.com/openapitools/openapi-generator|
 |artifactVersion|artifact version in generated pom.xml. This also becomes part of the generated library's filename| |1.0.0|
 |async|use async Callable controllers| |false|
+|autosetConstants|Automatically set Required Params having a Single enum value i.e. Constants in generated code| |false|
 |basePackage|base package (invokerPackage) for generated code| |org.openapitools|
 |bigDecimalAsString|Treat BigDecimal values as Strings to avoid precision loss.| |false|
 |booleanGetterPrefix|Set booleanGetterPrefix| |get|

modules/openapi-generator-gradle-plugin/src/main/kotlin/org/openapitools/generator/gradle/plugin/extensions/OpenApiGeneratorValidateExtension.kt

@@ -33,12 +33,5 @@ open class OpenApiGeneratorValidateExtension(project: Project) {
     /**
      * Whether to offer recommendations related to the validated specification document.
      */
-    val recommend = project.objects.property<Boolean?>()
-
-    init {
-        applyDefaults()
-    }
-
-    @Suppress("MemberVisibilityCanBePrivate")
-    fun applyDefaults() = recommend.set(true)
+    val recommend = project.objects.property<Boolean>().convention(true)
 }

modules/openapi-generator-gradle-plugin/src/main/kotlin/org/openapitools/generator/gradle/plugin/tasks/ValidateTask.kt

@@ -58,7 +58,7 @@ open class ValidateTask : DefaultTask() {
 
     @Optional
     @Input
-    val recommend = project.objects.property<Boolean?>()
+    val recommend = project.objects.property<Boolean>().convention(true)
 
     @get:Internal
     @set:Option(option = "input", description = "The input specification.")

modules/openapi-generator-gradle-plugin/src/test/kotlin/ValidateTaskDslTest.kt

@@ -144,4 +144,161 @@ class ValidateTaskDslTest : TestBase() {
             "Expected a failed run, but found ${result.task(":openApiValidate")?.outcome}"
         )
     }
+
+    @Test(dataProvider = "gradle_version_provider")
+    fun `validateGoodSpec as defined task should succeed on valid spec`(gradleVersion: String?) {
+        // Arrange
+        val projectFiles = mapOf(
+            "spec.yaml" to javaClass.classLoader.getResourceAsStream("specs/petstore-v3.0.yaml")
+        )
+
+        withProject(
+            """
+            | plugins {
+            |   id 'org.openapi.generator'
+            | }
+            |
+            | task validateGoodSpec(type: org.openapitools.generator.gradle.plugin.tasks.ValidateTask) {
+            |    inputSpec.set(file("spec.yaml").absolutePath)
+            | }
+        """.trimMargin(), projectFiles
+        )
+
+        // Act
+        val result = getGradleRunner(gradleVersion)
+            .withProjectDir(temp)
+            .withArguments("validateGoodSpec")
+            .withPluginClasspath()
+            .build()
+
+        // Assert
+        assertTrue(
+            result.output.contains("Spec is valid."),
+            "Unexpected/no message presented to the user for a valid spec."
+        )
+        assertEquals(
+            SUCCESS, result.task(":validateGoodSpec")?.outcome,
+            "Expected a successful run, but found ${result.task(":validateGoodSpec")?.outcome}"
+        )
+    }
+
+    @Test(dataProvider = "gradle_version_provider")
+    fun `validateBadSpec as defined task should fail on invalid spec`(gradleVersion: String?) {
+        // Arrange
+        val projectFiles = mapOf(
+            "spec.yaml" to javaClass.classLoader.getResourceAsStream("specs/petstore-v3.0-invalid.yaml")
+        )
+        withProject(
+            """
+            | plugins {
+            |   id 'org.openapi.generator'
+            | }
+            |
+            | task validateBadSpec(type: org.openapitools.generator.gradle.plugin.tasks.ValidateTask) {
+            |    inputSpec.set(file("spec.yaml").absolutePath)
+            | }
+        """.trimMargin(), projectFiles
+        )
+
+        // Act
+        val result = getGradleRunner(gradleVersion)
+            .withProjectDir(temp)
+            .withArguments("validateBadSpec")
+            .withPluginClasspath()
+            .buildAndFail()
+
+        // Assert
+        assertTrue(
+            result.output.contains("Spec is invalid."),
+            "Unexpected/no message presented to the user for an invalid spec."
+        )
+        assertEquals(
+            FAILED, result.task(":validateBadSpec")?.outcome,
+            "Expected a failed run, but found ${result.task(":validateBadSpec")?.outcome}"
+        )
+    }
+
+    @Test(dataProvider = "gradle_version_provider")
+    fun `openApiValidate should succeed with recommendations on valid spec`(gradleVersion: String?) {
+        // Arrange
+        val projectFiles = mapOf(
+            "spec.yaml" to javaClass.classLoader.getResourceAsStream("specs/petstore-v3.0-recommend.yaml")
+        )
+
+        // recommend = true is the default
+        withProject(
+            """
+            | plugins {
+            |   id 'org.openapi.generator'
+            | }
+            |
+            | openApiValidate {
+            |   inputSpec = file("spec.yaml").absolutePath
+            | }
+        """.trimMargin(), projectFiles
+        )
+
+        // Act
+        val result = getGradleRunner(gradleVersion)
+            .withProjectDir(temp)
+            .withArguments("openApiValidate")
+            .withPluginClasspath()
+            .build()
+
+        // Assert
+        assertTrue(
+            result.output.contains("Spec is valid."),
+            "Unexpected/no message presented to the user for a valid spec."
+        )
+        assertTrue(
+            result.output.contains("Spec has issues or recommendations."),
+            "Unexpected/no recommendations message presented to the user for a valid spec."
+        )
+        assertEquals(
+            SUCCESS, result.task(":openApiValidate")?.outcome,
+            "Expected a successful run, but found ${result.task(":openApiValidate")?.outcome}"
+        )
+    }
+
+    @Test(dataProvider = "gradle_version_provider")
+    fun `openApiValidate should succeed without recommendations on valid spec`(gradleVersion: String?) {
+        // Arrange
+        val projectFiles = mapOf(
+            "spec.yaml" to javaClass.classLoader.getResourceAsStream("specs/petstore-v3.0-recommend.yaml")
+        )
+
+        withProject(
+            """
+            | plugins {
+            |   id 'org.openapi.generator'
+            | }
+            |
+            | openApiValidate {
+            |   inputSpec = file("spec.yaml").absolutePath
+            |   recommend = false
+            | }
+        """.trimMargin(), projectFiles
+        )
+
+        // Act
+        val result = getGradleRunner(gradleVersion)
+            .withProjectDir(temp)
+            .withArguments("openApiValidate")
+            .withPluginClasspath()
+            .build()
+
+        // Assert
+        assertTrue(
+            result.output.contains("Spec is valid."),
+            "Unexpected/no message presented to the user for a valid spec."
+        )
+        assertTrue(
+            result.output.contains("Spec has issues or recommendations.").not(),
+            "Unexpected/recommendations message presented to the user for a valid spec"
+        )
+        assertEquals(
+            SUCCESS, result.task(":openApiValidate")?.outcome,
+            "Expected a successful run, but found ${result.task(":openApiValidate")?.outcome}"
+        )
+    }
 }

modules/openapi-generator-gradle-plugin/src/test/resources/specs/petstore-v3.0-recommend.yaml

@@ -0,0 +1,114 @@
+openapi: "3.0.0"
+info:
+  version: 1.0.0
+  title: Swagger Petstore
+  license:
+    name: MIT
+servers:
+  - url: http://petstore.swagger.io/v1
+paths:
+  /pets:
+    get:
+      summary: List all pets
+      operationId: listPets
+      tags:
+        - pets
+      parameters:
+        - name: limit
+          in: query
+          description: How many items to return at one time (max 100)
+          required: false
+          schema:
+            type: integer
+            format: int32
+      requestBody: # warning `API GET/HEAD defined with request body`
+        content:
+          application/json:
+            schema:
+              $ref: "#/components/schemas/Pets"
+      responses:
+        '200':
+          description: A paged array of pets
+          headers:
+            x-next:
+              description: A link to the next page of responses
+              schema:
+                type: string
+          content:
+            application/json:
+              schema:
+                $ref: "#/components/schemas/Pets"
+        default:
+          description: unexpected error
+          content:
+            application/json:
+              schema:
+                $ref: "#/components/schemas/Error"
+    post:
+      summary: Create a pet
+      operationId: createPets
+      tags:
+        - pets
+      responses:
+        '201':
+          description: Null response
+        default:
+          description: unexpected error
+          content:
+            application/json:
+              schema:
+                $ref: "#/components/schemas/Error"
+  /pets/{petId}:
+    get:
+      summary: Info for a specific pet
+      operationId: showPetById
+      tags:
+        - pets
+      parameters:
+        - name: petId
+          in: path
+          required: true
+          description: The id of the pet to retrieve
+          schema:
+            type: string
+      responses:
+        '200':
+          description: Expected response to a valid request
+          content:
+            application/json:
+              schema:
+                $ref: "#/components/schemas/Pets"
+        default:
+          description: unexpected error
+          content:
+            application/json:
+              schema:
+                $ref: "#/components/schemas/Error"
+components:
+  schemas:
+    Pet:
+      required:
+        - id
+        - name
+      properties:
+        id:
+          type: integer
+          format: int64
+        name:
+          type: string
+        tag:
+          type: string
+    Pets:
+      type: array
+      items:
+        $ref: "#/components/schemas/Pet"
+    Error:
+      required:
+        - code
+        - message
+      properties:
+        code:
+          type: integer
+          format: int32
+        message:
+          type: string

modules/openapi-generator-maven-plugin/src/main/java/org/openapitools/codegen/plugin/CodeGenMojo.java

@@ -520,15 +520,6 @@ public class CodeGenMojo extends AbstractMojo {
                             "generated-test-sources/openapi" : "generated-sources/openapi");
         }
 
-        if (cleanupOutput) {
-            try {
-                FileUtils.deleteDirectory(output);
-                LOGGER.info("Previous run output is removed from {}", output);
-            } catch (IOException e) {
-                LOGGER.warn("Failed to clean-up output directory {}", output, e);
-            }
-        }
-
         addCompileSourceRootIfConfigured();
 
         try {
@@ -566,10 +557,19 @@ public class CodeGenMojo extends AbstractMojo {
                 }
             }
 
+            if (cleanupOutput) {
+                try {
+                    FileUtils.deleteDirectory(output);
+                    LOGGER.info("Previous run output is removed from {}", output);
+                } catch (IOException e) {
+                    LOGGER.warn("Failed to clean up output directory {}", output, e);
+                }
+            }
+
             // attempt to read from config file
             CodegenConfigurator configurator = CodegenConfigurator.fromFile(configurationFile);
 
-            // if a config file wasn't specified or we were unable to read it
+            // if a config file wasn't specified, or we were unable to read it
             if (configurator == null) {
                 configurator = new CodegenConfigurator();
             }
@@ -938,8 +938,8 @@ public class CodeGenMojo extends AbstractMojo {
     /**
      * Calculate openapi specification file hash. If specification is hosted on remote resource it is downloaded first
      *
-     * @param inputSpecFile - Openapi specification input file to calculate it's hash.
-     *                        Does not taken into account if input spec is hosted on remote resource
+     * @param inputSpecFile - Openapi specification input file to calculate its hash.
+     *                        Does not take into account if input spec is hosted on remote resource
      * @return openapi specification file hash
      * @throws IOException
      */
@@ -991,8 +991,8 @@ public class CodeGenMojo extends AbstractMojo {
 
     /**
      * Get specification hash file
-     * @param inputSpecFile - Openapi specification input file to calculate it's hash.
-     *                        Does not taken into account if input spec is hosted on remote resource
+     * @param inputSpecFile - Openapi specification input file to calculate its hash.
+     *                        Does not take into account if input spec is hosted on remote resource
      * @return a file with previously calculated hash
      */
     private File getHashFile(File inputSpecFile) {

modules/openapi-generator/src/main/java/org/openapitools/codegen/CodegenOperation.java

@@ -30,7 +30,7 @@ public class CodegenOperation {
             hasVersionHeaders = false, hasVersionQueryParams = false,
             isResponseBinary = false, isResponseFile = false, isResponseOptional = false, hasReference = false, defaultReturnType = false,
             isRestfulIndex, isRestfulShow, isRestfulCreate, isRestfulUpdate, isRestfulDestroy,
-            isRestful, isDeprecated, isCallbackRequest, uniqueItems, hasDefaultResponse = false,
+            isRestful, isDeprecated, isCallbackRequest, uniqueItems, hasDefaultResponse = false, hasConstantParams = false,
             hasErrorResponseObject; // if 4xx, 5xx responses have at least one error object defined
     public CodegenProperty returnProperty;
     public String path, operationId, returnType, returnFormat, httpMethod, returnBaseType,
@@ -45,6 +45,7 @@ public class CodegenOperation {
     public List<CodegenParameter> queryParams = new ArrayList<CodegenParameter>();
     public List<CodegenParameter> headerParams = new ArrayList<CodegenParameter>();
     public List<CodegenParameter> implicitHeadersParams = new ArrayList<CodegenParameter>();
+    public List<CodegenParameter> constantParams = new ArrayList<CodegenParameter>();
     public List<CodegenParameter> formParams = new ArrayList<CodegenParameter>();
     public List<CodegenParameter> cookieParams = new ArrayList<CodegenParameter>();
     public List<CodegenParameter> requiredParams = new ArrayList<CodegenParameter>();
@@ -392,6 +393,7 @@ public class CodegenOperation {
         sb.append(", operationIdLowerCase='").append(operationIdLowerCase).append('\'');
         sb.append(", operationIdCamelCase='").append(operationIdCamelCase).append('\'');
         sb.append(", operationIdSnakeCase='").append(operationIdSnakeCase).append('\'');
+        sb.append(", constantParams='").append(constantParams).append('\'');
         sb.append('}');
         return sb.toString();
     }
@@ -472,7 +474,8 @@ public class CodegenOperation {
                 Objects.equals(operationIdOriginal, that.operationIdOriginal) &&
                 Objects.equals(operationIdLowerCase, that.operationIdLowerCase) &&
                 Objects.equals(operationIdCamelCase, that.operationIdCamelCase) &&
-                Objects.equals(operationIdSnakeCase, that.operationIdSnakeCase);
+                Objects.equals(operationIdSnakeCase, that.operationIdSnakeCase) &&
+                Objects.equals(constantParams, that.constantParams);
     }
 
     @Override
@@ -488,6 +491,6 @@ public class CodegenOperation {
                 pathParams, queryParams, headerParams, formParams, cookieParams, requiredParams, returnProperty, optionalParams,
                 authMethods, tags, responses, callbacks, imports, examples, requestBodyExamples, externalDocs,
                 vendorExtensions, nickname, operationIdOriginal, operationIdLowerCase, operationIdCamelCase,
-                operationIdSnakeCase, hasErrorResponseObject, requiredAndNotNullableParams, notNullableParams);
+                operationIdSnakeCase, hasErrorResponseObject, requiredAndNotNullableParams, notNullableParams, constantParams);
     }
 }

modules/openapi-generator/src/main/java/org/openapitools/codegen/CodegenParameter.java

@@ -112,6 +112,9 @@ public class CodegenParameter implements IJsonSchemaValidationProperties {
      * See http://json-schema.org/latest/json-schema-validation.html#anchor14
      */
     public Number multipleOf;
+
+    public String constant; // for const or enum with a single item
+
     private Integer maxProperties;
     private Integer minProperties;
     public boolean isNull;
@@ -164,6 +167,7 @@ public class CodegenParameter implements IJsonSchemaValidationProperties {
         output.uniqueItems = this.uniqueItems;
         output.setUniqueItemsBoolean(this.uniqueItemsBoolean);
         output.multipleOf = this.multipleOf;
+        output.constant = this.constant;
         output.jsonSchema = this.jsonSchema;
         output.defaultValue = this.defaultValue;
         output.enumDefaultValue = this.enumDefaultValue;
@@ -260,7 +264,20 @@ public class CodegenParameter implements IJsonSchemaValidationProperties {
 
     @Override
     public int hashCode() {
-        return Objects.hash(isFormParam, isQueryParam, isPathParam, isHeaderParam, isCookieParam, isBodyParam, isContainer, isCollectionFormatMulti, isPrimitiveType, isModel, isExplode, baseName, paramName, dataType, datatypeWithEnum, dataFormat, collectionFormat, description, unescapedDescription, baseType, containerType, containerTypeMapped, defaultValue, enumDefaultValue, enumName, style, isDeepObject, isMatrix, isAllowEmptyValue, example, examples, jsonSchema, isString, isNumeric, isInteger, isLong, isNumber, isFloat, isDouble, isDecimal, isByteArray, isBinary, isBoolean, isDate, isDateTime, isUuid, isUri, isEmail, isPassword, isFreeFormObject, isAnyType, isArray, isMap, isFile, isEnum, isEnumRef, _enum, allowableValues, items, mostInnerItems, additionalProperties, vars, requiredVars, vendorExtensions, hasValidation, getMaxProperties(), getMinProperties(), isNullable, isDeprecated, required, getMaximum(), getExclusiveMaximum(), getMinimum(), getExclusiveMinimum(), getMaxLength(), getMinLength(), getPattern(), getMaxItems(), getMinItems(), getUniqueItems(), contentType, multipleOf, isNull, isVoid, additionalPropertiesIsAnyType, hasVars, hasRequired, isShort, isUnboundedInteger, hasDiscriminatorWithNonEmptyMapping, composedSchemas, hasMultipleTypes, schema, content, requiredVarsMap, ref, uniqueItemsBoolean, schemaIsFromAdditionalProperties);
+        return Objects.hash(isFormParam, isQueryParam, isPathParam, isHeaderParam, isCookieParam, isBodyParam,
+                isContainer, isCollectionFormatMulti, isPrimitiveType, isModel, isExplode, baseName, paramName,
+                dataType, datatypeWithEnum, dataFormat, collectionFormat, description, unescapedDescription, baseType,
+                containerType, containerTypeMapped, defaultValue, enumDefaultValue, enumName, style, isDeepObject,
+                isMatrix, isAllowEmptyValue, example, examples, jsonSchema, isString, isNumeric, isInteger, isLong,
+                isNumber, isFloat, isDouble, isDecimal, isByteArray, isBinary, isBoolean, isDate, isDateTime, isUuid,
+                isUri, isEmail, isPassword, isFreeFormObject, isAnyType, isArray, isMap, isFile, isEnum, isEnumRef,
+                _enum, allowableValues, items, mostInnerItems, additionalProperties, vars, requiredVars,
+                vendorExtensions, hasValidation, getMaxProperties(), getMinProperties(), isNullable, isDeprecated,
+                required, getMaximum(), getExclusiveMaximum(), getMinimum(), getExclusiveMinimum(), getMaxLength(),
+                getMinLength(), getPattern(), getMaxItems(), getMinItems(), getUniqueItems(), contentType, multipleOf,
+                isNull, isVoid, additionalPropertiesIsAnyType, hasVars, hasRequired, isShort, isUnboundedInteger,
+                hasDiscriminatorWithNonEmptyMapping, composedSchemas, hasMultipleTypes, schema, content,
+                requiredVarsMap, ref, uniqueItemsBoolean, schemaIsFromAdditionalProperties, constant);
     }
 
     @Override
@@ -365,6 +382,7 @@ public class CodegenParameter implements IJsonSchemaValidationProperties {
                 Objects.equals(getMaxItems(), that.getMaxItems()) &&
                 Objects.equals(getMinItems(), that.getMinItems()) &&
                 Objects.equals(contentType, that.contentType) &&
+                Objects.equals(constant, that.constant) &&
                 Objects.equals(multipleOf, that.multipleOf);
     }
 
@@ -465,6 +483,7 @@ public class CodegenParameter implements IJsonSchemaValidationProperties {
         sb.append(", uniqueItemsBoolean=").append(uniqueItemsBoolean);
         sb.append(", contentType=").append(contentType);
         sb.append(", multipleOf=").append(multipleOf);
+        sb.append(", constant=").append(constant);
         sb.append(", isNull=").append(isNull);
         sb.append(", isVoid=").append(isVoid);
         sb.append(", getAdditionalPropertiesIsAnyType=").append(additionalPropertiesIsAnyType);

modules/openapi-generator/src/main/java/org/openapitools/codegen/CodegenProperty.java

@@ -211,6 +211,9 @@ public class CodegenProperty implements Cloneable, IJsonSchemaValidationProperti
     private LinkedHashMap<String, List<String>> dependentRequired;
     private CodegenProperty contains;
 
+    // JSON Schema keywords
+    private String constant; // for `const`
+
     @Override
     public CodegenProperty getContains() {
         return contains;
@@ -1036,6 +1039,14 @@ public class CodegenProperty implements Cloneable, IJsonSchemaValidationProperti
         return isEnum || isEnumRef;
     }
 
+    public void setConstant(String constant) {
+        this.constant = constant;
+    }
+
+    public String getConstant() {
+        return constant;
+    }
+
     @Override
     public String toString() {
         final StringBuilder sb = new StringBuilder("CodegenProperty{");
@@ -1150,6 +1161,7 @@ public class CodegenProperty implements Cloneable, IJsonSchemaValidationProperti
         sb.append(", format=").append(format);
         sb.append(", dependentRequired=").append(dependentRequired);
         sb.append(", contains=").append(contains);
+        sb.append(", constant=").append(constant);
         sb.append('}');
         return sb.toString();
     }
@@ -1266,7 +1278,8 @@ public class CodegenProperty implements Cloneable, IJsonSchemaValidationProperti
                 Objects.equals(xmlPrefix, that.xmlPrefix) &&
                 Objects.equals(xmlName, that.xmlName) &&
                 Objects.equals(xmlNamespace, that.xmlNamespace) &&
-                Objects.equals(multipleOf, that.multipleOf);
+                Objects.equals(multipleOf, that.multipleOf) &&
+                Objects.equals(constant, that.getConstant());
     }
 
     @Override
@@ -1288,6 +1301,6 @@ public class CodegenProperty implements Cloneable, IJsonSchemaValidationProperti
                 xmlNamespace, isXmlWrapped, isNull, isVoid, additionalPropertiesIsAnyType, hasVars, hasRequired,
                 hasDiscriminatorWithNonEmptyMapping, composedSchemas, hasMultipleTypes, requiredVarsMap,
                 ref, uniqueItemsBoolean, schemaIsFromAdditionalProperties, isBooleanSchemaTrue, isBooleanSchemaFalse,
-                format, dependentRequired, contains);
+                format, dependentRequired, contains, constant);
     }
 }

modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultCodegen.java

@@ -17,6 +17,7 @@
 
 package org.openapitools.codegen;
 
+import com.fasterxml.jackson.annotation.JsonCreator;
 import com.github.benmanes.caffeine.cache.Cache;
 import com.github.benmanes.caffeine.cache.Caffeine;
 import com.github.benmanes.caffeine.cache.Ticker;
@@ -448,6 +449,7 @@ public class DefaultCodegen implements CodegenConfig {
                 .put("pascalcase", new CamelCaseLambda(false).generator(this))
                 .put("forwardslash", new ForwardSlashLambda())
                 .put("backslash", new BackSlashLambda())
+                .put("doublequote", new DoubleQuoteLambda())
                 .put("indented", new IndentedLambda())
                 .put("indented_8", new IndentedLambda(8, " ", false))
                 .put("indented_12", new IndentedLambda(12, " ", false))
@@ -476,6 +478,11 @@ public class DefaultCodegen implements CodegenConfig {
         for (Map.Entry<String, ModelsMap> entry : objs.entrySet()) {
             CodegenModel model = ModelUtils.getModelByName(entry.getKey(), objs);
 
+            if (model == null) {
+                LOGGER.warn("Null model found in postProcessAllModels: {}", entry.getKey());
+                continue;
+            }
+
             // add the model to the discriminator's mapping so templates have access to more than just the string to string mapping
             if (model.discriminator != null && model.discriminator.getMappedModels() != null) {
                 for (CodegenDiscriminator.MappedModel mappedModel : model.discriminator.getMappedModels()) {
@@ -1035,23 +1042,23 @@ public class DefaultCodegen implements CodegenConfig {
                 if (ModelUtils.isComposedSchema(s)) {
                     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);
+                        addOneOfNameExtension(s, nOneOf);
+                        addOneOfInterfaceModel(s, nOneOf);
                     } else {
                         // else this is a component schema, so we will just use that as the oneOf interface model
-                        addOneOfNameExtension((ComposedSchema) s, n);
+                        addOneOfNameExtension(s, n);
                     }
                 } else if (ModelUtils.isArraySchema(s)) {
                     Schema items = ((ArraySchema) s).getItems();
                     if (ModelUtils.isComposedSchema(items)) {
-                        addOneOfNameExtension((ComposedSchema) items, nOneOf);
-                        addOneOfInterfaceModel((ComposedSchema) items, nOneOf);
+                        addOneOfNameExtension(items, nOneOf);
+                        addOneOfInterfaceModel(items, nOneOf);
                     }
                 } else if (ModelUtils.isMapSchema(s)) {
                     Schema addProps = ModelUtils.getAdditionalProperties(s);
                     if (addProps != null && ModelUtils.isComposedSchema(addProps)) {
-                        addOneOfNameExtension((ComposedSchema) addProps, nOneOf);
-                        addOneOfInterfaceModel((ComposedSchema) addProps, nOneOf);
+                        addOneOfNameExtension(addProps, nOneOf);
+                        addOneOfInterfaceModel(addProps, nOneOf);
                     }
                 }
             }
@@ -2273,10 +2280,9 @@ public class DefaultCodegen implements CodegenConfig {
      **/
     @SuppressWarnings("static-method")
     public String getSchemaType(Schema schema) {
-        if (schema instanceof ComposedSchema) { // composed schema
-            ComposedSchema cs = (ComposedSchema) schema;
+        if (ModelUtils.isComposedSchema(schema)) { // composed schema
             // Get the interfaces, i.e. the set of elements under 'allOf', 'anyOf' or 'oneOf'.
-            List<Schema> schemas = ModelUtils.getInterfaces(cs);
+            List<Schema> schemas = ModelUtils.getInterfaces(schema);
 
             List<String> names = new ArrayList<>();
             // Build a list of the schema types under each interface.
@@ -2286,12 +2292,12 @@ public class DefaultCodegen implements CodegenConfig {
                 names.add(getSingleSchemaType(s));
             }
 
-            if (cs.getAllOf() != null) {
-                return toAllOfName(names, cs);
-            } else if (cs.getAnyOf() != null) { // anyOf
-                return toAnyOfName(names, cs);
-            } else if (cs.getOneOf() != null) { // oneOf
-                return toOneOfName(names, cs);
+            if (schema.getAllOf() != null) {
+                return toAllOfName(names, schema);
+            } else if (schema.getAnyOf() != null) { // anyOf
+                return toAnyOfName(names, schema);
+            } else if (schema.getOneOf() != null) { // oneOf
+                return toOneOfName(names, schema);
             }
         }
 
@@ -2327,7 +2333,7 @@ public class DefaultCodegen implements CodegenConfig {
      * @return name of the allOf schema
      */
     @SuppressWarnings("static-method")
-    public String toAllOfName(List<String> names, ComposedSchema composedSchema) {
+    public String toAllOfName(List<String> names, Schema composedSchema) {
         Map<String, Object> exts = composedSchema.getExtensions();
         if (exts != null && exts.containsKey("x-all-of-name")) {
             return (String) exts.get("x-all-of-name");
@@ -2351,7 +2357,7 @@ public class DefaultCodegen implements CodegenConfig {
      * @return name of the anyOf schema
      */
     @SuppressWarnings("static-method")
-    public String toAnyOfName(List<String> names, ComposedSchema composedSchema) {
+    public String toAnyOfName(List<String> names, Schema composedSchema) {
         return "anyOf<" + String.join(",", names) + ">";
     }
 
@@ -2369,7 +2375,7 @@ public class DefaultCodegen implements CodegenConfig {
      * @return name of the oneOf schema
      */
     @SuppressWarnings("static-method")
-    public String toOneOfName(List<String> names, ComposedSchema composedSchema) {
+    public String toOneOfName(List<String> names, Schema composedSchema) {
         Map<String, Object> exts = composedSchema.getExtensions();
         if (exts != null && exts.containsKey("x-one-of-name")) {
             return (String) exts.get("x-one-of-name");
@@ -2674,7 +2680,7 @@ public class DefaultCodegen implements CodegenConfig {
     Map<NamedSchema, CodegenProperty> schemaCodegenPropertyCache = new HashMap<>();
 
     protected void updateModelForComposedSchema(CodegenModel m, Schema schema, Map<String, Schema> allDefinitions) {
-        final ComposedSchema composed = (ComposedSchema) schema;
+        final Schema composed = schema;
         Map<String, Schema> properties = new LinkedHashMap<>();
         List<String> required = new ArrayList<>();
         Map<String, Schema> allProperties = new LinkedHashMap<>();
@@ -2700,17 +2706,17 @@ public class DefaultCodegen implements CodegenConfig {
             if (composed.getAllOf() != null) {
                 int modelImplCnt = 0; // only one inline object allowed in a ComposedModel
                 int modelDiscriminators = 0; // only one discriminator allowed in a ComposedModel
-                for (Schema innerSchema : composed.getAllOf()) { // TODO need to work with anyOf, oneOf as well
-                    if (m.discriminator == null && innerSchema.getDiscriminator() != null) {
+                for (Object innerSchema : composed.getAllOf()) { // TODO need to work with anyOf, oneOf as well
+                    if (m.discriminator == null && ((Schema) innerSchema).getDiscriminator() != null) {
                         LOGGER.debug("discriminator is set to null (not correctly set earlier): {}", m.name);
-                        m.setDiscriminator(createDiscriminator(m.name, innerSchema));
+                        m.setDiscriminator(createDiscriminator(m.name, (Schema) innerSchema));
                         modelDiscriminators++;
                     }
 
-                    if (innerSchema.getXml() != null) {
-                        m.xmlPrefix = innerSchema.getXml().getPrefix();
-                        m.xmlNamespace = innerSchema.getXml().getNamespace();
-                        m.xmlName = innerSchema.getXml().getName();
+                    if (((Schema) innerSchema).getXml() != null) {
+                        m.xmlPrefix = ((Schema) innerSchema).getXml().getPrefix();
+                        m.xmlNamespace = ((Schema) innerSchema).getXml().getNamespace();
+                        m.xmlName = ((Schema) innerSchema).getXml().getName();
                     }
                     if (modelDiscriminators > 1) {
                         LOGGER.error("Allof composed schema is inheriting >1 discriminator. Only use one discriminator: {}", composed);
@@ -2747,14 +2753,14 @@ public class DefaultCodegen implements CodegenConfig {
 
                     if (composed.getAnyOf() != null) {
                         if (m.anyOf.contains(languageType)) {
-                            LOGGER.warn("{} (anyOf schema) already has `{}` defined and therefore it's skipped.", m.name, languageType);
+                            LOGGER.debug("{} (anyOf schema) already has `{}` defined and therefore it's skipped.", m.name, languageType);
                         } else {
                             m.anyOf.add(languageType);
 
                         }
                     } else if (composed.getOneOf() != null) {
                         if (m.oneOf.contains(languageType)) {
-                            LOGGER.warn("{} (oneOf schema) already has `{}` defined and therefore it's skipped.", m.name, languageType);
+                            LOGGER.debug("{} (oneOf schema) already has `{}` defined and therefore it's skipped.", m.name, languageType);
                         } else {
                             m.oneOf.add(languageType);
                         }
@@ -2888,7 +2894,7 @@ public class DefaultCodegen implements CodegenConfig {
     }
 
     protected void updateModelForObject(CodegenModel m, Schema schema) {
-        if (schema.getProperties() != null || schema.getRequired() != null && !(schema instanceof ComposedSchema)) {
+        if (schema.getProperties() != null || schema.getRequired() != null && !(ModelUtils.isComposedSchema(schema))) {
             // passing null to allProperties and allRequired as there's no parent
             addVars(m, unaliasPropertySchema(schema.getProperties()), schema.getRequired(), null, null);
         }
@@ -2917,7 +2923,7 @@ public class DefaultCodegen implements CodegenConfig {
             addAdditionPropertiesToCodeGenModel(m, schema);
             m.isMap = true;
         }
-        if (schema.getProperties() != null || schema.getRequired() != null && !(schema instanceof ComposedSchema)) {
+        if (schema.getProperties() != null || schema.getRequired() != null && !(ModelUtils.isComposedSchema(schema))) {
             // passing null to allProperties and allRequired as there's no parent
             addVars(m, unaliasPropertySchema(schema.getProperties()), schema.getRequired(), null, null);
         }
@@ -3122,7 +3128,7 @@ public class DefaultCodegen implements CodegenConfig {
             m.setRef(schema.get$ref());
         }
 
-        if (schema instanceof ComposedSchema) {
+        if (ModelUtils.isComposedSchema(schema)) {
             updateModelForComposedSchema(m, schema, allDefinitions);
         }
 
@@ -3256,11 +3262,11 @@ public class DefaultCodegen implements CodegenConfig {
             return cp;
         }
         if (ModelUtils.isComposedSchema(refSchema)) {
-            ComposedSchema composedSchema = (ComposedSchema) refSchema;
+            Schema 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, visitedSchemas);
+                for (Object allOf : composedSchema.getAllOf()) {
+                    CodegenProperty cp = discriminatorFound(composedSchemaName, (Schema) allOf, discPropName, visitedSchemas);
                     if (cp != null) {
                         return cp;
                     }
@@ -3269,9 +3275,9 @@ public class DefaultCodegen implements CodegenConfig {
             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$ref());
-                    CodegenProperty thisCp = discriminatorFound(composedSchemaName, oneOf, discPropName, visitedSchemas);
+                for (Object oneOf : composedSchema.getOneOf()) {
+                    String modelName = ModelUtils.getSimpleRef(((Schema) oneOf).get$ref());
+                    CodegenProperty thisCp = discriminatorFound(composedSchemaName, (Schema) oneOf, discPropName, visitedSchemas);
                     if (thisCp == null) {
                         LOGGER.warn(
                                 "'{}' defines discriminator '{}', but the referenced OneOf schema '{}' is missing {}",
@@ -3292,9 +3298,9 @@ public class DefaultCodegen implements CodegenConfig {
             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$ref());
-                    CodegenProperty thisCp = discriminatorFound(composedSchemaName, anyOf, discPropName, visitedSchemas);
+                for (Object anyOf : composedSchema.getAnyOf()) {
+                    String modelName = ModelUtils.getSimpleRef(((Schema) anyOf).get$ref());
+                    CodegenProperty thisCp = discriminatorFound(composedSchemaName, (Schema) anyOf, discPropName, visitedSchemas);
                     if (thisCp == null) {
                         LOGGER.warn(
                                 "'{}' defines discriminator '{}', but the referenced AnyOf schema '{}' is missing {}",
@@ -3343,11 +3349,11 @@ public class DefaultCodegen implements CodegenConfig {
 
         Discriminator disc = new Discriminator();
         if (ModelUtils.isComposedSchema(refSchema)) {
-            ComposedSchema composedSchema = (ComposedSchema) refSchema;
+            Schema 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, visitedSchemas);
+                for (Object allOf : composedSchema.getAllOf()) {
+                    foundDisc = recursiveGetDiscriminator((Schema) allOf, visitedSchemas);
                     if (foundDisc != null) {
                         disc.setPropertyName(foundDisc.getPropertyName());
                         disc.setMapping(foundDisc.getMapping());
@@ -3360,13 +3366,13 @@ public class DefaultCodegen implements CodegenConfig {
                 Integer hasDiscriminatorCnt = 0;
                 Integer hasNullTypeCnt = 0;
                 Set<String> discriminatorsPropNames = new HashSet<>();
-                for (Schema oneOf : composedSchema.getOneOf()) {
-                    if (ModelUtils.isNullType(oneOf)) {
+                for (Object oneOf : composedSchema.getOneOf()) {
+                    if (ModelUtils.isNullType((Schema) oneOf)) {
                         // The null type does not have a discriminator. Skip.
                         hasNullTypeCnt++;
                         continue;
                     }
-                    foundDisc = recursiveGetDiscriminator(oneOf, visitedSchemas);
+                    foundDisc = recursiveGetDiscriminator((Schema) oneOf, visitedSchemas);
                     if (foundDisc != null) {
                         discriminatorsPropNames.add(foundDisc.getPropertyName());
                         hasDiscriminatorCnt++;
@@ -3389,13 +3395,13 @@ public class DefaultCodegen implements CodegenConfig {
                 Integer hasDiscriminatorCnt = 0;
                 Integer hasNullTypeCnt = 0;
                 Set<String> discriminatorsPropNames = new HashSet<>();
-                for (Schema anyOf : composedSchema.getAnyOf()) {
-                    if (ModelUtils.isNullType(anyOf)) {
+                for (Object anyOf : composedSchema.getAnyOf()) {
+                    if (ModelUtils.isNullType((Schema) anyOf)) {
                         // The null type does not have a discriminator. Skip.
                         hasNullTypeCnt++;
                         continue;
                     }
-                    foundDisc = recursiveGetDiscriminator(anyOf, visitedSchemas);
+                    foundDisc = recursiveGetDiscriminator((Schema) anyOf, visitedSchemas);
                     if (foundDisc != null) {
                         discriminatorsPropNames.add(foundDisc.getPropertyName());
                         hasDiscriminatorCnt++;
@@ -3430,7 +3436,7 @@ public class DefaultCodegen implements CodegenConfig {
      * @param c                  The ComposedSchema that contains the discriminator and oneOf/anyOf schemas
      * @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) {
+    protected List<MappedModel> getOneOfAnyOfDescendants(String composedSchemaName, String discPropName, Schema c) {
         ArrayList<List<Schema>> listOLists = new ArrayList<>();
         listOLists.add(c.getOneOf());
         listOLists.add(c.getAnyOf());
@@ -3510,8 +3516,7 @@ public class DefaultCodegen implements CodegenConfig {
                 }
                 Schema child = schemas.get(childName);
                 if (ModelUtils.isComposedSchema(child)) {
-                    ComposedSchema composedChild = (ComposedSchema) child;
-                    List<Schema> parents = composedChild.getAllOf();
+                    List<Schema> parents = child.getAllOf();
                     if (parents != null) {
                         for (Schema parent : parents) {
                             String ref = parent.get$ref();
@@ -3624,7 +3629,7 @@ public class DefaultCodegen implements CodegenConfig {
         }
         // if there are composed oneOf/anyOf schemas, add them to this discriminator
         if (ModelUtils.isComposedSchema(schema) && !this.getLegacyDiscriminatorBehavior()) {
-            List<MappedModel> otherDescendants = getOneOfAnyOfDescendants(schemaName, discriminatorPropertyName, (ComposedSchema) schema);
+            List<MappedModel> otherDescendants = getOneOfAnyOfDescendants(schemaName, discriminatorPropertyName, schema);
             for (MappedModel otherDescendant : otherDescendants) {
                 if (!uniqueDescendants.contains(otherDescendant)) {
                     uniqueDescendants.add(otherDescendant);
@@ -3658,15 +3663,18 @@ public class DefaultCodegen implements CodegenConfig {
      * @param visitedSchemas circuit-breaker - the schemas with which the method was called before for recursive structures
      */
     protected void addProperties(Map<String, Schema> properties, List<String> required, Schema schema, Set<Schema> visitedSchemas) {
+        if (schema == null) {
+            return;
+        }
+
         if (!visitedSchemas.add(schema)) {
             return;
         }
-        if (schema instanceof ComposedSchema) {
-            ComposedSchema composedSchema = (ComposedSchema) schema;
+        if (ModelUtils.isComposedSchema(schema)) {
 
-            if (composedSchema.getAllOf() != null) {
-                for (Schema component : composedSchema.getAllOf()) {
-                    addProperties(properties, required, component, visitedSchemas);
+            if (schema.getAllOf() != null) {
+                for (Object component : schema.getAllOf()) {
+                    addProperties(properties, required, (Schema) component, visitedSchemas);
                 }
             }
 
@@ -3674,15 +3682,15 @@ public class DefaultCodegen implements CodegenConfig {
                 required.addAll(schema.getRequired());
             }
 
-            if (composedSchema.getOneOf() != null) {
-                for (Schema component : composedSchema.getOneOf()) {
-                    addProperties(properties, required, component, visitedSchemas);
+            if (schema.getOneOf() != null) {
+                for (Object component : schema.getOneOf()) {
+                    addProperties(properties, required, (Schema) component, visitedSchemas);
                 }
             }
 
-            if (composedSchema.getAnyOf() != null) {
-                for (Schema component : composedSchema.getAnyOf()) {
-                    addProperties(properties, required, component, visitedSchemas);
+            if (schema.getAnyOf() != null) {
+                for (Object component : schema.getAnyOf()) {
+                    addProperties(properties, required, (Schema) component, visitedSchemas);
                 }
             }
 
@@ -3766,10 +3774,11 @@ public class DefaultCodegen implements CodegenConfig {
         if (Boolean.FALSE.equals(p.getNullable())) {
             LOGGER.warn("Schema '{}' is any type, which includes the 'null' value. 'nullable' cannot be set to 'false'", p.getName());
         }
-        ComposedSchema composedSchema = p instanceof ComposedSchema
-            ? (ComposedSchema) p
-            : null;
-        property.isNullable = property.isNullable || composedSchema == null || composedSchema.getAllOf() == null || composedSchema.getAllOf().size() == 0;
+
+        property.isNullable = property.isNullable ||
+                !(ModelUtils.isComposedSchema(p)) ||
+                p.getAllOf() == null ||
+                p.getAllOf().size() == 0;
         if (languageSpecificPrimitives.contains(property.dataType)) {
             property.isPrimitiveType = true;
         }
@@ -4584,6 +4593,7 @@ public class DefaultCodegen implements CodegenConfig {
         List<CodegenParameter> optionalParams = new ArrayList<>();
         List<CodegenParameter> requiredAndNotNullableParams = new ArrayList<>();
         List<CodegenParameter> notNullableParams = new ArrayList<>();
+        List<CodegenParameter> constantParams = new ArrayList<>();
 
         CodegenParameter bodyParam = null;
         RequestBody requestBody = operation.getRequestBody();
@@ -4647,20 +4657,22 @@ public class DefaultCodegen implements CodegenConfig {
                     }
                 }
 
-                allParams.add(p);
-
-                if (param instanceof QueryParameter || "query".equalsIgnoreCase(param.getIn())) {
-                    queryParams.add(p.copy());
-                } else if (param instanceof PathParameter || "path".equalsIgnoreCase(param.getIn())) {
-                    pathParams.add(p.copy());
-                } else if (param instanceof HeaderParameter || "header".equalsIgnoreCase(param.getIn())) {
-                    headerParams.add(p.copy());
-                } else if (param instanceof CookieParameter || "cookie".equalsIgnoreCase(param.getIn())) {
-                    cookieParams.add(p.copy());
-                } else {
-                    LOGGER.warn("Unknown parameter type {} for {}", p.baseType, p.baseName);
+                if (p.constant != null) { // for constant
+                    constantParams.add(p.copy());
+                } else { // a typical parameter
+                    allParams.add(p);
+                    if (param instanceof QueryParameter || "query".equalsIgnoreCase(param.getIn())) {
+                        queryParams.add(p.copy());
+                    } else if (param instanceof PathParameter || "path".equalsIgnoreCase(param.getIn())) {
+                        pathParams.add(p.copy());
+                    } else if (param instanceof HeaderParameter || "header".equalsIgnoreCase(param.getIn())) {
+                        headerParams.add(p.copy());
+                    } else if (param instanceof CookieParameter || "cookie".equalsIgnoreCase(param.getIn())) {
+                        cookieParams.add(p.copy());
+                    } else {
+                        LOGGER.warn("Unknown parameter type {} for {}", p.baseType, p.baseName);
+                    }
                 }
-
             }
         }
 
@@ -5346,6 +5358,26 @@ public class DefaultCodegen implements CodegenConfig {
         // set default value
         codegenParameter.defaultValue = toDefaultParameterValue(codegenProperty, parameterSchema);
 
+        // set constant
+        if (codegenParameter.getIsEnumOrRef()) { // enum with only 1 item
+            Schema enumSchema = ModelUtils.getReferencedSchema(openAPI, unaliasSchema(parameterSchema));
+            if (enumSchema.getEnum() != null && enumSchema.getEnum().size() == 1) { // only 1 element
+                codegenParameter.constant = toDefaultParameterValue(codegenProperty, enumSchema);
+            }
+        } else if (parameterSchema.getConst() != null) { // JSON Sschema keyword `const`
+            Schema temp = null;
+            Pattern pattern = Pattern.compile("-?\\d+(\\.\\d+)?");
+            String constantValue = String.valueOf(parameterSchema.getConst());
+            if (pattern.matcher(constantValue).matches()) { // numeric constant value
+                temp = new NumberSchema();
+                temp.setDefault(constantValue);
+            } else { // constant value is a string
+                temp = new StringSchema();
+                temp.setDefault(constantValue);
+            }
+            codegenParameter.constant = toDefaultParameterValue(temp);
+        }
+
         finishUpdatingParameter(codegenParameter, parameter);
         return codegenParameter;
     }
@@ -5746,7 +5778,7 @@ public class DefaultCodegen implements CodegenConfig {
      * @param model codegen model
      * @param modelName model name
      */
-    protected void addImport(ComposedSchema composed, Schema childSchema, CodegenModel model, String modelName ) {
+    protected void addImport(Schema composed, Schema childSchema, CodegenModel model, String modelName ) {
         if (composed == null || childSchema == null) {
             return;
         }
@@ -5973,6 +6005,10 @@ public class DefaultCodegen implements CodegenConfig {
     }
 
     private static Boolean isAliasOfSimpleTypes(Schema schema) {
+        if (schema == null) {
+            return false;
+        }
+
         return (!ModelUtils.isObjectSchema(schema)
                 && !ModelUtils.isArraySchema(schema)
                 && !ModelUtils.isMapSchema(schema)
@@ -6925,6 +6961,13 @@ public class DefaultCodegen implements CodegenConfig {
         LOGGER.debug("debugging fromRequestBodyToFormParameters= {}", body);
         Schema schema = ModelUtils.getSchemaFromRequestBody(body);
         schema = ModelUtils.getReferencedSchema(this.openAPI, schema);
+        if(ModelUtils.isMapSchema(schema)) {
+            LOGGER.error("Form parameters with additionalProperties are not supported by OpenAPI Generator. Please report the issue to https://github.com/openapitools/openapi-generator if you need help.");
+        }
+        if(ModelUtils.isArraySchema(schema)) {
+            LOGGER.error("Array form parameters are not supported by OpenAPI Generator. Please report the issue to https://github.com/openapitools/openapi-generator if you need help.");
+        }
+
         List<String> allRequired = new ArrayList<>();
         Map<String, Schema> properties = new LinkedHashMap<>();
         // this traverses a composed schema and extracts all properties in each schema into properties
@@ -6933,6 +6976,8 @@ public class DefaultCodegen implements CodegenConfig {
         // https://github.com/OpenAPITools/openapi-generator/issues/10415
         addProperties(properties, allRequired, schema, new HashSet<>());
 
+        boolean isOneOfOrAnyOf = ModelUtils.isOneOf(schema) || ModelUtils.isAnyOf(schema);
+
         if (!properties.isEmpty()) {
             for (Map.Entry<String, Schema> entry : properties.entrySet()) {
                 CodegenParameter codegenParameter;
@@ -6940,14 +6985,14 @@ public class DefaultCodegen implements CodegenConfig {
                 // value => property schema
                 String propertyName = entry.getKey();
                 Schema propertySchema = entry.getValue();
-                if (ModelUtils.isMapSchema(propertySchema)) {
-                    LOGGER.error("Map of form parameters not supported. Please report the issue to https://github.com/openapitools/openapi-generator if you need help.");
-                    continue;
-                }
                 codegenParameter = fromFormProperty(propertyName, propertySchema, imports);
 
-                // Set 'required' flag defined in the schema element
-                if (!codegenParameter.required && schema.getRequired() != null) {
+                if (isOneOfOrAnyOf) {
+                    // for oneOf/anyOf, mark all the properties collected from the sub-schemas as optional
+                    // so that users can choose which property to include in the form parameters
+                    codegenParameter.required = false;
+                } else if (!codegenParameter.required && schema.getRequired() != null) {
+                    // Set 'required' flag defined in the schema element
                     codegenParameter.required = schema.getRequired().contains(entry.getKey());
                 } else if (!codegenParameter.required) {
                     // Set 'required' flag for properties declared inside the allOf
@@ -7920,12 +7965,12 @@ public class DefaultCodegen implements CodegenConfig {
     /**
      * Add "x-one-of-name" extension to a given oneOf schema (assuming it has at least 1 oneOf elements)
      *
-     * @param s    schema to add the extension to
-     * @param name name of the parent oneOf schema
+     * @param schema schema to add the extension to
+     * @param name   name of the parent oneOf schema
      */
-    public void addOneOfNameExtension(ComposedSchema s, String name) {
-        if (s.getOneOf() != null && s.getOneOf().size() > 0) {
-            s.addExtension("x-one-of-name", name);
+    public void addOneOfNameExtension(Schema schema, String name) {
+        if (schema.getOneOf() != null && schema.getOneOf().size() > 0) {
+            schema.addExtension("x-one-of-name", name);
         }
     }
 
@@ -7935,7 +7980,7 @@ public class DefaultCodegen implements CodegenConfig {
      * @param cs      ComposedSchema object to create as interface model
      * @param type    name to use for the generated interface model
      */
-    public void addOneOfInterfaceModel(ComposedSchema cs, String type) {
+    public void addOneOfInterfaceModel(Schema cs, String type) {
         if (cs.getOneOf() == null) {
             return;
         }
@@ -7944,9 +7989,9 @@ public class DefaultCodegen implements CodegenConfig {
 
         cm.setDiscriminator(createDiscriminator("", cs));
 
-        for (Schema o : Optional.ofNullable(cs.getOneOf()).orElse(Collections.emptyList())) {
-            if (o.get$ref() == null) {
-                if (cm.discriminator != null && o.get$ref() == null) {
+        for (Object o : Optional.ofNullable(cs.getOneOf()).orElse(Collections.emptyList())) {
+            if (((Schema) o).get$ref() == null) {
+                if (cm.discriminator != null && ((Schema) o).get$ref() == null) {
                     // OpenAPI spec states that inline objects should not be considered when discriminator is used
                     // https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.0.2.md#discriminatorObject
                     LOGGER.warn("Ignoring inline object in oneOf definition of {}, since discriminator is used", type);
@@ -7955,7 +8000,7 @@ public class DefaultCodegen implements CodegenConfig {
                 }
                 continue;
             }
-            cm.oneOf.add(toModelName(ModelUtils.getSimpleRef(o.get$ref())));
+            cm.oneOf.add(toModelName(ModelUtils.getSimpleRef(((Schema) o).get$ref())));
         }
         cm.name = type;
         cm.classname = type;
@@ -8126,7 +8171,7 @@ public class DefaultCodegen implements CodegenConfig {
     }
 
     private CodegenComposedSchemas getComposedSchemas(Schema schema) {
-        if (!(schema instanceof ComposedSchema) && schema.getNot() == null) {
+        if (!(ModelUtils.isComposedSchema(schema)) && schema.getNot() == null) {
             return null;
         }
         Schema notSchema = schema.getNot();
@@ -8137,11 +8182,10 @@ public class DefaultCodegen implements CodegenConfig {
         List<CodegenProperty> allOf = new ArrayList<>();
         List<CodegenProperty> oneOf = new ArrayList<>();
         List<CodegenProperty> anyOf = new ArrayList<>();
-        if (schema instanceof ComposedSchema) {
-            ComposedSchema cs = (ComposedSchema) schema;
-            allOf = getComposedProperties(cs.getAllOf(), "all_of");
-            oneOf = getComposedProperties(cs.getOneOf(), "one_of");
-            anyOf = getComposedProperties(cs.getAnyOf(), "any_of");
+        if (ModelUtils.isComposedSchema(schema)) {
+            allOf = getComposedProperties(schema.getAllOf(), "all_of");
+            oneOf = getComposedProperties(schema.getOneOf(), "one_of");
+            anyOf = getComposedProperties(schema.getAnyOf(), "any_of");
         }
         return new CodegenComposedSchemas(
                 allOf,

modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultGenerator.java

@@ -58,6 +58,7 @@ import org.openapitools.codegen.utils.ImplementationVersion;
 import org.openapitools.codegen.utils.ModelUtils;
 import org.openapitools.codegen.utils.ProcessUtils;
 import org.openapitools.codegen.utils.URLPathUtils;
+import org.openapitools.codegen.utils.SemVer;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -262,6 +263,10 @@ public class DefaultGenerator implements Generator {
         // normalize the spec
         try {
             if (config.getUseOpenAPINormalizer()) {
+                SemVer version = new SemVer(openAPI.getOpenapi());
+                if (version.atLeast("3.1.0")) {
+                    config.openapiNormalizer().put("NORMALIZE_31SPEC", "true");
+                }
                 OpenAPINormalizer openapiNormalizer = new OpenAPINormalizer(openAPI, config.openapiNormalizer());
                 openapiNormalizer.normalize();
             }
@@ -1329,8 +1334,10 @@ public class DefaultGenerator implements Generator {
         for (Map.Entry<String, Schema> definitionsEntry : definitions.entrySet()) {
             String key = definitionsEntry.getKey();
             Schema schema = definitionsEntry.getValue();
-            if (schema == null)
-                throw new RuntimeException("schema cannot be null in processModels");
+            if (schema == null) {
+                LOGGER.warn("Schema {} cannot be null in processModels", key);
+                continue;
+            }
             CodegenModel cm = config.fromModel(key, schema);
             ModelMap mo = new ModelMap();
             mo.setModel(cm);

modules/openapi-generator/src/main/java/org/openapitools/codegen/InlineModelResolver.java

@@ -216,32 +216,30 @@ public class InlineModelResolver {
                 return true;
             }
         }
-        if (schema instanceof ComposedSchema) {
+        if (ModelUtils.isComposedSchema(schema)) {
             // allOf, anyOf, oneOf
-            ComposedSchema m = (ComposedSchema) schema;
-
-            boolean isSingleAllOf = m.getAllOf() != null && m.getAllOf().size() == 1;
-            boolean isReadOnly = m.getReadOnly() != null && m.getReadOnly();
-            boolean isNullable = m.getNullable() != null && m.getNullable();
+            boolean isSingleAllOf = schema.getAllOf() != null && schema.getAllOf().size() == 1;
+            boolean isReadOnly = schema.getReadOnly() != null && schema.getReadOnly();
+            boolean isNullable = schema.getNullable() != null && schema.getNullable();
 
             if (isSingleAllOf && (isReadOnly || isNullable)) {
                 // Check if this composed schema only contains an allOf and a readOnly or nullable.
                 ComposedSchema c = new ComposedSchema();
-                c.setAllOf(m.getAllOf());
-                c.setReadOnly(m.getReadOnly());
-                c.setNullable(m.getNullable());
-                if (m.equals(c)) {
-                    return isModelNeeded(m.getAllOf().get(0), visitedSchemas);
+                c.setAllOf(schema.getAllOf());
+                c.setReadOnly(schema.getReadOnly());
+                c.setNullable(schema.getNullable());
+                if (schema.equals(c)) {
+                    return isModelNeeded((Schema) schema.getAllOf().get(0), visitedSchemas);
                 }
-            } else if (isSingleAllOf && StringUtils.isNotEmpty(m.getAllOf().get(0).get$ref())) {
+            } else if (isSingleAllOf && StringUtils.isNotEmpty(((Schema) schema.getAllOf().get(0)).get$ref())) {
                 // single allOf and it's a ref
-                return isModelNeeded(m.getAllOf().get(0), visitedSchemas);
+                return isModelNeeded((Schema) schema.getAllOf().get(0), visitedSchemas);
             }
 
-            if (m.getAllOf() != null && !m.getAllOf().isEmpty()) {
+            if (schema.getAllOf() != null && !schema.getAllOf().isEmpty()) {
                 // check to ensure at least one of the allOf item is model
-                for (Schema inner : m.getAllOf()) {
-                    if (isModelNeeded(ModelUtils.getReferencedSchema(openAPI, inner), visitedSchemas)) {
+                for (Object inner : schema.getAllOf()) {
+                    if (isModelNeeded(ModelUtils.getReferencedSchema(openAPI, (Schema) inner), visitedSchemas)) {
                         return true;
                     }
                 }
@@ -249,10 +247,10 @@ public class InlineModelResolver {
                 return false;
             }
 
-            if (m.getAnyOf() != null && !m.getAnyOf().isEmpty()) {
+            if (schema.getAnyOf() != null && !schema.getAnyOf().isEmpty()) {
                 return true;
             }
-            if (m.getOneOf() != null && !m.getOneOf().isEmpty()) {
+            if (schema.getOneOf() != null && !schema.getOneOf().isEmpty()) {
                 return true;
             }
         }
@@ -273,7 +271,7 @@ public class InlineModelResolver {
             // any to catch OpenAPI violations
             if (isModelNeeded(schema) || "object".equals(schema.getType()) ||
                     schema.getProperties() != null || schema.getAdditionalProperties() != null ||
-                    schema instanceof ComposedSchema) {
+                    ModelUtils.isComposedSchema(schema)) {
                 LOGGER.error("Illegal schema found with $ref combined with other properties," +
                         " no properties should be defined alongside a $ref:\n " + schema.toString());
             }
@@ -288,6 +286,11 @@ public class InlineModelResolver {
             if (props != null) {
                 for (String propName : props.keySet()) {
                     Schema prop = props.get(propName);
+
+                    if (prop == null) {
+                        continue;
+                    }
+
                     String schemaName = resolveModelName(prop.getTitle(), modelPrefix + "_" + propName);
                     // Recurse to create $refs for inner models
                     gatherInlineModels(prop, schemaName);
@@ -295,13 +298,13 @@ public class InlineModelResolver {
                         // If this schema should be split into its own model, do so
                         Schema refSchema = this.makeSchemaInComponents(schemaName, prop);
                         props.put(propName, refSchema);
-                    } else if (prop instanceof ComposedSchema) {
-                        ComposedSchema m = (ComposedSchema) prop;
-                        if (m.getAllOf() != null && m.getAllOf().size() == 1 &&
-                                !(m.getAllOf().get(0).getType() == null || "object".equals(m.getAllOf().get(0).getType()))) {
+                    } else if (ModelUtils.isComposedSchema(prop)) {
+                        if (prop.getAllOf() != null && prop.getAllOf().size() == 1 &&
+                                !(((Schema) prop.getAllOf().get(0)).getType() == null ||
+                                        "object".equals(((Schema) prop.getAllOf().get(0)).getType()))) {
                             // allOf with only 1 type (non-model)
                             LOGGER.info("allOf schema used by the property `{}` replaced by its only item (a type)", propName);
-                            props.put(propName, m.getAllOf().get(0));
+                            props.put(propName, (Schema) prop.getAllOf().get(0));
                         }
                     }
                 }
@@ -310,13 +313,15 @@ public class InlineModelResolver {
             if (schema.getAdditionalProperties() != null) {
                 if (schema.getAdditionalProperties() instanceof Schema) {
                     Schema inner = (Schema) schema.getAdditionalProperties();
-                    String schemaName = resolveModelName(schema.getTitle(), modelPrefix + this.inlineSchemaOptions.get("MAP_ITEM_SUFFIX"));
-                    // Recurse to create $refs for inner models
-                    gatherInlineModels(inner, schemaName);
-                    if (isModelNeeded(inner)) {
-                        // If this schema should be split into its own model, do so
-                        Schema refSchema = this.makeSchemaInComponents(schemaName, inner);
-                        schema.setAdditionalProperties(refSchema);
+                    if (inner != null) {
+                        String schemaName = resolveModelName(schema.getTitle(), modelPrefix + this.inlineSchemaOptions.get("MAP_ITEM_SUFFIX"));
+                        // Recurse to create $refs for inner models
+                        gatherInlineModels(inner, schemaName);
+                        if (isModelNeeded(inner)) {
+                            // If this schema should be split into its own model, do so
+                            Schema refSchema = this.makeSchemaInComponents(schemaName, inner);
+                            schema.setAdditionalProperties(refSchema);
+                        }
                     }
                 }
             }
@@ -336,10 +341,6 @@ public class InlineModelResolver {
         if (schema instanceof ArraySchema) {
             ArraySchema array = (ArraySchema) schema;
             Schema items = array.getItems();
-            /*if (items.getTitle() != null) {
-                LOGGER.info("schema title {}", items);
-                throw new RuntimeException("getTitle for array item is not null");
-            }*/
             if (items == null) {
                 LOGGER.error("Illegal schema found with array type but no items," +
                         " items must be defined for array schemas:\n " + schema.toString());
@@ -357,82 +358,91 @@ public class InlineModelResolver {
             }
         }
         // Check allOf, anyOf, oneOf for inline models
-        if (schema instanceof ComposedSchema) {
-            ComposedSchema m = (ComposedSchema) schema;
-            if (m.getAllOf() != null) {
+        if (ModelUtils.isComposedSchema(schema)) {
+            if (schema.getAllOf() != null) {
                 List<Schema> newAllOf = new ArrayList<Schema>();
                 boolean atLeastOneModel = false;
-                for (Schema inner : m.getAllOf()) {
-                    String schemaName = resolveModelName(inner.getTitle(), modelPrefix + "_allOf");
+                for (Object inner : schema.getAllOf()) {
+                    if (inner == null) {
+                        continue;
+                    }
+                    String schemaName = resolveModelName(((Schema) inner).getTitle(), modelPrefix + "_allOf");
                     // Recurse to create $refs for inner models
-                    gatherInlineModels(inner, schemaName);
-                    if (isModelNeeded(inner)) {
+                    gatherInlineModels((Schema) inner, schemaName);
+                    if (isModelNeeded((Schema) inner)) {
                         if (Boolean.TRUE.equals(this.refactorAllOfInlineSchemas)) {
-                            Schema refSchema = this.makeSchemaInComponents(schemaName, inner);
+                            Schema refSchema = this.makeSchemaInComponents(schemaName, (Schema) inner);
                             newAllOf.add(refSchema); // replace with ref
                             atLeastOneModel = true;
                         } else { // do not refactor allOf inline schemas
-                            newAllOf.add(inner);
+                            newAllOf.add((Schema) inner);
                             atLeastOneModel = true;
                         }
                     } else {
-                        newAllOf.add(inner);
+                        newAllOf.add((Schema) inner);
                     }
                 }
                 if (atLeastOneModel) {
-                    m.setAllOf(newAllOf);
+                    schema.setAllOf(newAllOf);
                 } else {
                     // allOf is just one or more types only so do not generate the inline allOf model
-                    if (m.getAllOf().size() == 1) {
+                    if (schema.getAllOf().size() == 1) {
                         // handle earlier in this function when looping through properties
-                    } else if (m.getAllOf().size() > 1) {
+                    } else if (schema.getAllOf().size() > 1) {
                         LOGGER.warn("allOf schema `{}` containing multiple types (not model) is not supported at the moment.", schema.getName());
                     } else {
                         LOGGER.error("allOf schema `{}` contains no items.", schema.getName());
                     }
                 }
             }
-            if (m.getAnyOf() != null) {
+            if (schema.getAnyOf() != null) {
                 List<Schema> newAnyOf = new ArrayList<Schema>();
-                for (Schema inner : m.getAnyOf()) {
-                    String schemaName = resolveModelName(inner.getTitle(), modelPrefix + "_anyOf");
+                for (Object inner : schema.getAnyOf()) {
+                    if (inner == null) {
+                        continue;
+                    }
+                    String schemaName = resolveModelName(((Schema) inner).getTitle(), modelPrefix + "_anyOf");
                     // Recurse to create $refs for inner models
-                    gatherInlineModels(inner, schemaName);
-                    if (isModelNeeded(inner)) {
-                        Schema refSchema = this.makeSchemaInComponents(schemaName, inner);
+                    gatherInlineModels((Schema) inner, schemaName);
+                    if (isModelNeeded((Schema) inner)) {
+                        Schema refSchema = this.makeSchemaInComponents(schemaName, (Schema) inner);
                         newAnyOf.add(refSchema); // replace with ref
                     } else {
-                        newAnyOf.add(inner);
+                        newAnyOf.add((Schema) inner);
                     }
                 }
-                m.setAnyOf(newAnyOf);
-
+                schema.setAnyOf(newAnyOf);
             }
-            if (m.getOneOf() != null) {
+            if (schema.getOneOf() != null) {
                 List<Schema> newOneOf = new ArrayList<Schema>();
-                for (Schema inner : m.getOneOf()) {
-                    String schemaName = resolveModelName(inner.getTitle(), modelPrefix + "_oneOf");
+                for (Object inner : schema.getOneOf()) {
+                    if (inner == null) {
+                        continue;
+                    }
+                    String schemaName = resolveModelName(((Schema) inner).getTitle(), modelPrefix + "_oneOf");
                     // Recurse to create $refs for inner models
-                    gatherInlineModels(inner, schemaName);
-                    if (isModelNeeded(inner)) {
-                        Schema refSchema = this.makeSchemaInComponents(schemaName, inner);
+                    gatherInlineModels((Schema) inner, schemaName);
+                    if (isModelNeeded((Schema) inner)) {
+                        Schema refSchema = this.makeSchemaInComponents(schemaName, (Schema) inner);
                         newOneOf.add(refSchema); // replace with ref
                     } else {
-                        newOneOf.add(inner);
+                        newOneOf.add((Schema) inner);
                     }
                 }
-                m.setOneOf(newOneOf);
+                schema.setOneOf(newOneOf);
             }
         }
         // Check not schema
         if (schema.getNot() != null) {
             Schema not = schema.getNot();
-            String schemaName = resolveModelName(schema.getTitle(), modelPrefix + "_not");
-            // Recurse to create $refs for inner models
-            gatherInlineModels(not, schemaName);
-            if (isModelNeeded(not)) {
-                Schema refSchema = this.makeSchemaInComponents(schemaName, not);
-                schema.setNot(refSchema);
+            if (not != null) {
+                String schemaName = resolveModelName(schema.getTitle(), modelPrefix + "_not");
+                // Recurse to create $refs for inner models
+                gatherInlineModels(not, schemaName);
+                if (isModelNeeded(not)) {
+                    Schema refSchema = this.makeSchemaInComponents(schemaName, not);
+                    schema.setNot(refSchema);
+                }
             }
         }
     }
@@ -633,16 +643,18 @@ public class InlineModelResolver {
         List<String> modelNames = new ArrayList<String>(models.keySet());
         for (String modelName : modelNames) {
             Schema model = models.get(modelName);
+            if (model == null) {
+                continue;
+            }
             if (ModelUtils.isAnyOf(model)) { // contains anyOf only
                 gatherInlineModels(model, modelName);
             } else if (ModelUtils.isOneOf(model)) { // contains oneOf only
                 gatherInlineModels(model, modelName);
             } else if (ModelUtils.isComposedSchema(model)) {
-                ComposedSchema m = (ComposedSchema) model;
                 // inline child schemas
-                flattenComposedChildren(modelName + "_allOf", m.getAllOf(), !Boolean.TRUE.equals(this.refactorAllOfInlineSchemas));
-                flattenComposedChildren(modelName + "_anyOf", m.getAnyOf(), false);
-                flattenComposedChildren(modelName + "_oneOf", m.getOneOf(), false);
+                flattenComposedChildren(modelName + "_allOf", model.getAllOf(), !Boolean.TRUE.equals(this.refactorAllOfInlineSchemas));
+                flattenComposedChildren(modelName + "_anyOf", model.getAnyOf(), false);
+                flattenComposedChildren(modelName + "_oneOf", model.getOneOf(), false);
             } else {
                 gatherInlineModels(model, modelName);
             }

modules/openapi-generator/src/main/java/org/openapitools/codegen/OpenAPINormalizer.java

@@ -19,6 +19,7 @@ package org.openapitools.codegen;
 
 import io.swagger.v3.oas.models.*;
 import io.swagger.v3.oas.models.callbacks.Callback;
+import io.swagger.v3.oas.models.headers.Header;
 import io.swagger.v3.oas.models.media.*;
 import io.swagger.v3.oas.models.parameters.Parameter;
 import io.swagger.v3.oas.models.parameters.RequestBody;
@@ -87,6 +88,9 @@ public class OpenAPINormalizer {
     // the allOf contains a new schema containing the properties in the top level
     final String REFACTOR_ALLOF_WITH_PROPERTIES_ONLY = "REFACTOR_ALLOF_WITH_PROPERTIES_ONLY";
 
+    // when set to true, normalize OpenAPI 3.1 spec to make it work with the generator
+    final String NORMALIZE_31SPEC = "NORMALIZE_31SPEC";
+
     // ============= end of rules =============
 
     /**
@@ -115,6 +119,7 @@ public class OpenAPINormalizer {
         ruleNames.add(SET_TAGS_FOR_ALL_OPERATIONS);
         ruleNames.add(ADD_UNSIGNED_TO_INTEGER_WITH_INVALID_MAX_VALUE);
         ruleNames.add(REFACTOR_ALLOF_WITH_PROPERTIES_ONLY);
+        ruleNames.add(NORMALIZE_31SPEC);
 
         // rules that are default to true
         rules.put(SIMPLIFY_ONEOF_ANYOF, true);
@@ -148,7 +153,7 @@ public class OpenAPINormalizer {
 
         // loop through all the rules
         for (Map.Entry<String, String> rule : inputRules.entrySet()) {
-            LOGGER.info("processing rule {} => {}", rule.getKey(), rule.getValue());
+            LOGGER.debug("processing rule {} => {}", rule.getKey(), rule.getValue());
             if (!ruleNames.contains(rule.getKey())) { // invalid rule name
                 LOGGER.warn("Invalid openapi-normalizer rule name: ", rule.getKey());
             } else if (enableAll) {
@@ -247,11 +252,13 @@ public class OpenAPINormalizer {
             } else if (mediaType.getSchema() == null) {
                 continue;
             } else {
-                normalizeSchema(mediaType.getSchema(), new HashSet<>());
+                Schema newSchema = normalizeSchema(mediaType.getSchema(), new HashSet<>());
+                mediaType.setSchema(newSchema);
             }
         }
     }
 
+
     /**
      * Normalizes schemas in RequestBody
      *
@@ -291,7 +298,8 @@ public class OpenAPINormalizer {
             if (parameter.getSchema() == null) {
                 continue;
             } else {
-                normalizeSchema(parameter.getSchema(), new HashSet<>());
+                Schema newSchema = normalizeSchema(parameter.getSchema(), new HashSet<>());
+                parameter.setSchema(newSchema);
             }
         }
     }
@@ -312,10 +320,29 @@ public class OpenAPINormalizer {
                 continue;
             } else {
                 normalizeContent(responsesEntry.getValue().getContent());
+                normalizeHeaders(responsesEntry.getValue().getHeaders());
+
             }
         }
     }
 
+    /**
+     * Normalizes schemas in headers
+     *
+     * @param headers a map of headers
+     */
+    private void normalizeHeaders(Map<String, Header> headers) {
+        if (headers == null || headers.isEmpty()) {
+            return;
+        }
+
+        for (String headerKey : headers.keySet()) {
+            Header h = headers.get(headerKey);
+            Schema updatedHeader = normalizeSchema(h.getSchema(), new HashSet<>());
+            h.setSchema(updatedHeader);
+        }
+    }
+
     /**
      * Normalizes schemas in components
      */
@@ -408,7 +435,7 @@ public class OpenAPINormalizer {
         } else if (schema instanceof IntegerSchema) {
             normalizeIntegerSchema(schema, visitedSchemas);
         } else if (schema instanceof Schema) {
-            normalizeSchemaWithOnlyProperties(schema, visitedSchemas);
+            return normalizeSimpleSchema(schema, visitedSchemas);
         } else {
             throw new RuntimeException("Unknown schema type found in normalizer: " + schema);
         }
@@ -416,6 +443,10 @@ public class OpenAPINormalizer {
         return schema;
     }
 
+    private Schema normalizeSimpleSchema(Schema schema, Set<Schema> visitedSchemas) {
+        return processNormalize31Spec(schema, visitedSchemas);
+    }
+
     private void normalizeBooleanSchema(Schema schema, Set<Schema> visitedSchemas) {
         processSimplifyBooleanEnum(schema);
     }
@@ -424,10 +455,6 @@ public class OpenAPINormalizer {
         processAddUnsignedToIntegerWithInvalidMaxValue(schema);
     }
 
-    private void normalizeSchemaWithOnlyProperties(Schema schema, Set<Schema> visitedSchemas) {
-        // normalize non-composed schema (e.g. schema with only properties)
-    }
-
     private void normalizeProperties(Map<String, Schema> properties, Set<Schema> visitedSchemas) {
         if (properties == null) {
             return;
@@ -670,9 +697,9 @@ public class OpenAPINormalizer {
 
     /**
      * Check if the schema is of type 'null'
-     * 
+     * <p>
      * Return true if the schema's type is 'null' or not specified
-     * 
+     *
      * @param schema Schema
      */
     private boolean isNullTypeSchema(Schema schema) {
@@ -803,7 +830,7 @@ public class OpenAPINormalizer {
         }
     }
 
-    /*
+    /**
      * When set to true, refactor schema with allOf and properties in the same level to a schema with allOf only and
      * the allOf contains a new schema containing the properties in the top level.
      *
@@ -844,5 +871,75 @@ public class OpenAPINormalizer {
         return schema;
     }
 
+    /**
+     * When set to true, normalize schema so that it works well with the generator.
+     *
+     * @param schema         Schema
+     * @param visitedSchemas a set of visited schemas
+     * @return Schema
+     */
+    private Schema processNormalize31Spec(Schema schema, Set<Schema> visitedSchemas) {
+        if (!getRule(NORMALIZE_31SPEC)) {
+            return schema;
+        }
+
+        if (schema == null || schema.getTypes() == null) {
+            return null;
+        }
+
+        // process null
+        if (schema.getTypes().contains("null")) {
+            schema.setNullable(true);
+            schema.getTypes().remove("null");
+        }
+
+        // only one item (type) left
+        if (schema.getTypes().size() == 1) {
+            String type = String.valueOf(schema.getTypes().iterator().next());
+            if ("array".equals(type)) {
+                ArraySchema as = new ArraySchema();
+                as.setXml(schema.getXml());
+                // `items` is also a json schema
+                if (StringUtils.isNotEmpty(schema.getItems().get$ref())) {
+                    Schema ref = new Schema();
+                    ref.set$ref(schema.getItems().get$ref());
+                    as.setItems(ref);
+                } else { // inline schema (e.g. model, string, etc)
+                    Schema updatedItems = normalizeSchema(schema.getItems(), visitedSchemas);
+                    as.setItems(updatedItems);
+                }
+
+                return as;
+            } else { // other primitive type such as string
+                // set type (3.0 spec) directly
+                schema.setType(type);
+            }
+        } else { // more than 1 item
+            // convert to anyOf and keep all other attributes (e.g. nullable, description)
+            // the same. No need to handle null as it should have been removed at this point.
+            for (Object type : schema.getTypes()) {
+                switch (String.valueOf(type)) {
+                    case "string":
+                        schema.addAnyOfItem(new StringSchema());
+                        break;
+                    case "integer":
+                        schema.addAnyOfItem(new IntegerSchema());
+                        break;
+                    case "number":
+                        schema.addAnyOfItem(new NumberSchema());
+                        break;
+                    case "boolean":
+                        schema.addAnyOfItem(new BooleanSchema());
+                        break;
+                    default:
+                        LOGGER.error("Type {} not yet supported in openapi-normalizer to process OpenAPI 3.1 spec with multiple types.");
+                        LOGGER.error("Please report the issue via https://github.com/OpenAPITools/openapi-generator/issues/new/.");
+                }
+            }
+        }
+
+        return schema;
+    }
+
     // ===================== end of rules =====================
 }

modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractCSharpCodegen.java

@@ -59,6 +59,7 @@ public abstract class AbstractCSharpCodegen extends DefaultCodegen implements Co
     protected boolean returnICollection = false;
     protected boolean netCoreProjectFileFlag = false;
     protected boolean nullReferenceTypesFlag = false;
+    protected boolean useSourceGeneration = false;
 
     protected String modelPropertyNaming = CodegenConstants.MODEL_PROPERTY_NAMING_TYPE.PascalCase.name();
 
@@ -416,12 +417,15 @@ public abstract class AbstractCSharpCodegen extends DefaultCodegen implements Co
                 .put("required", new RequiredParameterLambda())
                 .put("optional", new OptionalParameterLambda().generator(this))
                 .put("joinWithComma", new JoinWithCommaLambda())
+                .put("joinLinesWithComma", new JoinWithCommaLambda(false, "\n", ",\n"))
                 .put("trimLineBreaks", new TrimLineBreaksLambda())
                 .put("trimTrailingWithNewLine", new TrimTrailingWhiteSpaceLambda(true))
+                .put("trimTrailing", new TrimTrailingWhiteSpaceLambda(false))
                 .put("first", new FirstLambda("  "))
                 .put("firstDot", new FirstLambda("\\."))
                 .put("indent3", new IndentedLambda(12, " ", false))
-                .put("indent4", new IndentedLambda(16, " ", false));
+                .put("indent4", new IndentedLambda(16, " ", false))
+                .put("uniqueLinesWithNewLine", new UniqueLambda("\n", true));
     }
 
     @Override
@@ -523,7 +527,7 @@ public abstract class AbstractCSharpCodegen extends DefaultCodegen implements Co
             // GrandparentAnimal has a discriminator, but no oneOf nor anyOf
             // modules\openapi-generator\src\test\resources\3_0\csharp\petstore-with-fake-endpoints-models-for-testing-with-http-signature.yaml
             model.setHasDiscriminatorWithNonEmptyMapping(
-                    ((model.anyOf != null && model.anyOf.size() > 0) || (model.anyOf != null && model.oneOf.size() > 0)) &&
+                    ((model.anyOf != null && model.anyOf.size() > 0) || (model.oneOf != null && model.oneOf.size() > 0)) &&
                             model.discriminator != null &&
                             model.discriminator.getMappedModels() != null &&
                             model.discriminator.getMappedModels().size() > 0);
@@ -1350,6 +1354,14 @@ public abstract class AbstractCSharpCodegen extends DefaultCodegen implements Co
         return this.nullReferenceTypesFlag;
     }
 
+    public void setUseSourceGeneration(final Boolean useSourceGeneration) {
+        this.useSourceGeneration = useSourceGeneration;
+    }
+
+    public boolean getUseSourceGeneration() {
+        return this.useSourceGeneration;
+    }
+
     public void setInterfacePrefix(final String interfacePrefix) {
         this.interfacePrefix = interfacePrefix;
     }

modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractJavaCodegen.java

@@ -83,6 +83,7 @@ public abstract class AbstractJavaCodegen extends DefaultCodegen implements Code
     public static final String TEST_OUTPUT = "testOutput";
     public static final String IMPLICIT_HEADERS = "implicitHeaders";
     public static final String IMPLICIT_HEADERS_REGEX = "implicitHeadersRegex";
+    public static final String AUTOSET_CONSTANTS = "autosetConstants";
     public static final String JAVAX_PACKAGE = "javaxPackage";
     public static final String USE_JAKARTA_EE = "useJakartaEe";
     public static final String CONTAINER_DEFAULT_TO_NULL = "containerDefaultToNull";
@@ -137,6 +138,7 @@ public abstract class AbstractJavaCodegen extends DefaultCodegen implements Code
     protected AnnotationLibrary annotationLibrary;
     protected boolean implicitHeaders = false;
     protected String implicitHeadersRegex = null;
+    protected boolean autosetConstants = false;
     protected boolean camelCaseDollarSign = false;
     protected boolean useJakartaEe = false;
     protected boolean containerDefaultToNull = false;
@@ -277,6 +279,7 @@ public abstract class AbstractJavaCodegen extends DefaultCodegen implements Code
         cliOptions.add(CliOption.newBoolean(OPENAPI_NULLABLE, "Enable OpenAPI Jackson Nullable library", this.openApiNullable));
         cliOptions.add(CliOption.newBoolean(IMPLICIT_HEADERS, "Skip header parameters in the generated API methods using @ApiImplicitParams annotation.", implicitHeaders));
         cliOptions.add(CliOption.newString(IMPLICIT_HEADERS_REGEX, "Skip header parameters that matches given regex in the generated API methods using @ApiImplicitParams annotation. Note: this parameter is ignored when implicitHeaders=true"));
+        cliOptions.add(CliOption.newBoolean(AUTOSET_CONSTANTS, "Automatically set Required Params having a Single enum value i.e. Constants in generated code", autosetConstants));
         cliOptions.add(CliOption.newBoolean(CAMEL_CASE_DOLLAR_SIGN, "Fix camelCase when starting with $ sign. when true : $Value when false : $value"));
         cliOptions.add(CliOption.newBoolean(USE_JAKARTA_EE, "whether to use Jakarta EE namespace instead of javax"));
         cliOptions.add(CliOption.newBoolean(CONTAINER_DEFAULT_TO_NULL, "Set containers (array, set, map) default to null"));
@@ -563,6 +566,10 @@ public abstract class AbstractJavaCodegen extends DefaultCodegen implements Code
             this.setImplicitHeadersRegex(additionalProperties.get(IMPLICIT_HEADERS_REGEX).toString());
         }
 
+        if (additionalProperties.containsKey(AUTOSET_CONSTANTS)) {
+            this.setAutosetConstants(Boolean.parseBoolean(additionalProperties.get(AUTOSET_CONSTANTS).toString()));
+        }
+
         if (additionalProperties.containsKey(CAMEL_CASE_DOLLAR_SIGN)) {
             this.setCamelCaseDollarSign(Boolean.parseBoolean(additionalProperties.get(CAMEL_CASE_DOLLAR_SIGN).toString()));
         }
@@ -1062,7 +1069,7 @@ public abstract class AbstractJavaCodegen extends DefaultCodegen implements Code
             } else { // has default value
                 return toArrayDefaultValue(cp, schema);
             }
-        } else if (ModelUtils.isMapSchema(schema) && !(schema instanceof ComposedSchema)) {
+        } else if (ModelUtils.isMapSchema(schema) && !(ModelUtils.isComposedSchema(schema))) {
             if (schema.getProperties() != null && schema.getProperties().size() > 0) {
                 // object is complex object with free-form additional properties
                 if (schema.getDefault() != null) {
@@ -1349,8 +1356,7 @@ public abstract class AbstractJavaCodegen extends DefaultCodegen implements Code
         if (example == null) {
             example = "null";
         } else if (Boolean.TRUE.equals(p.isArray)) {
-
-            if (p.items.defaultValue != null) {
+            if (p.items != null && p.items.defaultValue != null) {
                 String innerExample;
                 if ("String".equals(p.items.dataType)) {
                     innerExample = "\"" + p.items.defaultValue + "\"";
@@ -1579,6 +1585,7 @@ public abstract class AbstractJavaCodegen extends DefaultCodegen implements Code
             op.vendorExtensions.put("x-java-import", operationImports);
 
             handleImplicitHeaders(op);
+            handleConstantParams(op);
         }
 
         return objs;
@@ -1646,11 +1653,11 @@ public abstract class AbstractJavaCodegen extends DefaultCodegen implements Code
                                     .map(Schema::getProperties))
                     .forEach(schemas -> schemas.replaceAll(
                             (name, s) -> Stream.of(s)
-                                    .filter(schema -> schema instanceof ComposedSchema)
-                                    .map(schema -> (ComposedSchema) schema)
-                                    .filter(schema -> Objects.nonNull(schema.getAnyOf()))
-                                    .flatMap(schema -> schema.getAnyOf().stream())
-                                    .filter(schema -> Objects.nonNull(schema.getEnum()))
+                                    .filter(schema -> ModelUtils.isComposedSchema((Schema) schema))
+                                    //.map(schema -> (ComposedSchema) schema)
+                                    .filter(schema -> Objects.nonNull(((Schema) schema).getAnyOf()))
+                                    .flatMap(schema -> ((Schema) schema).getAnyOf().stream())
+                                    .filter(schema -> Objects.nonNull(((Schema) schema).getEnum()))
                                     .findFirst()
                                     .orElse((Schema) s)));
         }
@@ -2053,6 +2060,10 @@ public abstract class AbstractJavaCodegen extends DefaultCodegen implements Code
         this.implicitHeadersRegex = implicitHeadersRegex;
     }
 
+    public void setAutosetConstants(boolean autosetConstants) {
+        this.autosetConstants = autosetConstants;
+    }
+
     public void setCamelCaseDollarSign(boolean camelCaseDollarSign) {
         this.camelCaseDollarSign = camelCaseDollarSign;
     }
@@ -2295,6 +2306,45 @@ public abstract class AbstractJavaCodegen extends DefaultCodegen implements Code
         operation.hasParams = !operation.allParams.isEmpty();
     }
 
+    /**
+     * This method removes all constant Query, Header and Cookie Params from allParams and sets them as constantParams in the CodegenOperation.
+     * The definition of constant is single valued required enum params.
+     * The constantParams in the the generated code should be hardcoded to the constantValue if autosetConstants feature is enabled.
+     *
+     * @param operation - operation to be processed
+     */
+    protected void handleConstantParams(CodegenOperation operation) {
+        if (!autosetConstants || operation.allParams.isEmpty()) {            
+            return;
+        }
+        final ArrayList<CodegenParameter> copy = new ArrayList<>(operation.allParams);
+        // Remove all params from Params, Non constant params will be added back later.
+        operation.allParams.clear();
+
+        // Finds all constant params, removes them from allParams and adds them to constant params.
+        // Also, adds back non constant params to allParams.
+        for (CodegenParameter p : copy) {
+            if (p.isEnum && p.required && p._enum != null && p._enum.size() == 1) {
+                // Add to constantParams for use in the code generation templates. 
+                operation.constantParams.add(p);
+                if(p.isQueryParam) {
+                    operation.queryParams.removeIf(param -> param.baseName.equals(p.baseName));
+                }
+                if(p.isHeaderParam) {
+                    operation.headerParams.removeIf(param -> param.baseName.equals(p.baseName));
+                }
+                if(p.isCookieParam) {
+                    operation.cookieParams.removeIf(param -> param.baseName.equals(p.baseName));
+                }
+                LOGGER.info("Update operation [{}]. Remove parameter [{}] because it can only have a fixed value of [{}]", operation.operationId, p.baseName, p._enum.get(0));
+            } else {
+                // Add back to allParams as the param is not a constant.
+                operation.allParams.add(p);
+            }
+        }
+        operation.hasParams = !operation.allParams.isEmpty();
+    }
+
     private boolean shouldBeImplicitHeader(CodegenParameter parameter) {
         return StringUtils.isNotBlank(implicitHeadersRegex) && parameter.baseName.matches(implicitHeadersRegex);
     }

modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractKotlinCodegen.java

@@ -1143,7 +1143,7 @@ public abstract class AbstractKotlinCodegen extends DefaultCodegen implements Co
          * ModelUtils.isMapSchema
          * In other generators, isMap is true for all type object schemas
          */
-        if (schema.getProperties() != null || schema.getRequired() != null && !(schema instanceof ComposedSchema)) {
+        if (schema.getProperties() != null || schema.getRequired() != null && !(ModelUtils.isComposedSchema(schema))) {
             // passing null to allProperties and allRequired as there's no parent
             addVars(m, unaliasPropertySchema(schema.getProperties()), schema.getRequired(), null, null);
         }

modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractPythonCodegen.java

@@ -529,7 +529,7 @@ public abstract class AbstractPythonCodegen extends DefaultCodegen implements Co
             }
             example += ")";
         } else {
-            LOGGER.warn("Type {} not handled properly in toExampleValue", schema.getType());
+            LOGGER.debug("Type {} not handled properly in toExampleValue", schema.getType());
         }
 
         if (ModelUtils.isStringSchema(schema)) {
@@ -591,7 +591,7 @@ public abstract class AbstractPythonCodegen extends DefaultCodegen implements Co
             // type is a model class, e.g. User
             example = this.packageName + "." + type + "()";
         } else {
-            LOGGER.warn("Type {} not handled properly in setParameterExampleValue", type);
+            LOGGER.debug("Type {} not handled properly in setParameterExampleValue", type);
         }
 
         if (example == null) {
@@ -1747,6 +1747,7 @@ public abstract class AbstractPythonCodegen extends DefaultCodegen implements Co
     @Override
     public OperationsMap postProcessOperationsWithModels(OperationsMap objs, List<ModelMap> allModels) {
         hasModelsToImport = false;
+        boolean importAnnotated = false;
         TreeSet<String> typingImports = new TreeSet<>();
         TreeSet<String> pydanticImports = new TreeSet<>();
         TreeSet<String> datetimeImports = new TreeSet<>();
@@ -1807,6 +1808,7 @@ public abstract class AbstractPythonCodegen extends DefaultCodegen implements Co
                     param.vendorExtensions.put("x-py-typing", typing);
                 } else {
                     param.vendorExtensions.put("x-py-typing", String.format(Locale.ROOT, "Annotated[%s, %s]", typing, fieldCustomization));
+                    importAnnotated = true;
                 }
             }
 
@@ -1838,6 +1840,12 @@ public abstract class AbstractPythonCodegen extends DefaultCodegen implements Co
 
         List<Map<String, String>> newImports = new ArrayList<>();
 
+        if (importAnnotated) {
+            Map<String, String> item = new HashMap<>();
+            item.put("import", String.format(Locale.ROOT, String.format(Locale.ROOT, "from typing_extensions import Annotated")));
+            newImports.add(item);
+        }
+
         // need datetime import
         if (!datetimeImports.isEmpty()) {
             Map<String, String> item = new HashMap<>();
@@ -1973,4 +1981,17 @@ public abstract class AbstractPythonCodegen extends DefaultCodegen implements Co
     public String toEnumDefaultValue(String value, String datatype) {
         return value;
     }
+
+    /**
+     * checks if the data should be classified as "string" in enum
+     * e.g. double in C# needs to be double-quoted (e.g. "2.8") by treating it as a string
+     * In the future, we may rename this function to "isEnumString"
+     *
+     * @param dataType data type
+     * @return true if it's a enum string
+     */
+    @Override
+    public boolean isDataTypeString(String dataType) {
+        return "str".equals(dataType);
+    }
 }

modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractPythonConnexionServerCodegen.java

@@ -16,17 +16,9 @@
 
 package org.openapitools.codegen.languages;
 
-import static org.openapitools.codegen.utils.StringUtils.camelize;
-
 import java.io.File;
 import java.io.IOException;
-import java.util.ArrayList;
-import java.util.Collection;
-import java.util.Collections;
-import java.util.HashMap;
-import java.util.List;
-import java.util.Map;
-import java.util.Set;
+import java.util.*;
 
 import org.apache.commons.lang3.StringUtils;
 import org.openapitools.codegen.CliOption;
@@ -69,6 +61,8 @@ import io.swagger.v3.oas.models.parameters.Parameter;
 import io.swagger.v3.oas.models.parameters.RequestBody;
 import io.swagger.v3.oas.models.security.SecurityScheme;
 
+import static org.openapitools.codegen.utils.StringUtils.*;
+
 public abstract class AbstractPythonConnexionServerCodegen extends AbstractPythonCodegen implements CodegenConfig {
     private static class PythonBooleanSerializer extends JsonSerializer<Boolean> {
         @Override
@@ -178,7 +172,7 @@ public abstract class AbstractPythonConnexionServerCodegen extends AbstractPytho
         cliOptions.add(new CliOption(USE_PYTHON_SRC_ROOT_IN_IMPORTS, "include pythonSrcRoot in import namespaces.").
                 defaultValue("false"));
         cliOptions.add(new CliOption(MOVE_TESTS_UNDER_PYTHON_SRC_ROOT, "generates test under the pythonSrcRoot folder.")
-            .defaultValue("false"));
+                .defaultValue("false"));
     }
 
     protected void addSupportingFiles() {
@@ -333,7 +327,6 @@ public abstract class AbstractPythonConnexionServerCodegen extends AbstractPytho
     }
 
 
-
     @Override
     public String toApiTestFilename(String name) {
         return "test_" + toApiFilename(name);
@@ -636,12 +629,6 @@ public abstract class AbstractPythonConnexionServerCodegen extends AbstractPytho
         postProcessPattern(property.pattern, property.vendorExtensions);
     }
 
-    @Override
-    public ModelsMap postProcessModels(ModelsMap objs) {
-        // process enum in models
-        return postProcessModelsEnum(objs);
-    }
-
     @Override
     public Map<String, ModelsMap> postProcessAllModels(Map<String, ModelsMap> objs) {
         Map<String, ModelsMap> result = super.postProcessAllModels(objs);