mark oneOf form parameters as optional (#16512)

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

@@ -6943,6 +6943,8 @@ 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;
@@ -6952,8 +6954,12 @@ public class DefaultCodegen implements CodegenConfig {
                 Schema propertySchema = entry.getValue();
                 codegenParameter = fromFormProperty(propertyName, propertySchema, imports);
 
+                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
-                if (!codegenParameter.required && schema.getRequired() != null) {
                     codegenParameter.required = schema.getRequired().contains(entry.getKey());
                 } else if (!codegenParameter.required) {
                     // Set 'required' flag for properties declared inside the allOf

modules/openapi-generator/src/test/java/org/openapitools/codegen/swift5/Swift5ClientCodegenTest.java

@@ -292,4 +292,32 @@ public class Swift5ClientCodegenTest {
         }
     }
 
+    @Test(description = "optional form parameters when using oneOf schema", enabled = true)
+    public void oneOfFormParameterTest() {
+        final OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_0/issue_15511.yaml");
+        final DefaultCodegen codegen = new Swift5ClientCodegen();
+        codegen.setOpenAPI(openAPI);
+        codegen.processOpts();
+        final String path = "/as/token.oauth2";
+        final Operation p = openAPI.getPaths().get(path).getPost();
+        final CodegenOperation op = codegen.fromOperation(path, "post", p, null);
+
+        Assert.assertEquals(op.formParams.size(), 6);
+
+        Assert.assertEquals(op.formParams.get(0).baseName, "client_id");
+        Assert.assertEquals(op.formParams.get(1).baseName, "grant_type");
+        Assert.assertEquals(op.formParams.get(2).baseName, "password");
+        Assert.assertEquals(op.formParams.get(3).baseName, "scope");
+        Assert.assertEquals(op.formParams.get(4).baseName, "username");
+        Assert.assertEquals(op.formParams.get(5).baseName, "refresh_token");
+
+        Assert.assertEquals(op.formParams.get(0).required, false);
+        Assert.assertEquals(op.formParams.get(1).required, false);
+        Assert.assertEquals(op.formParams.get(2).required, false);
+        Assert.assertEquals(op.formParams.get(3).required, false);
+        Assert.assertEquals(op.formParams.get(4).required, false);
+        Assert.assertEquals(op.formParams.get(5).required, false);
+
+    }
+
 }

modules/openapi-generator/src/test/resources/3_0/issue_15511.yaml

@@ -0,0 +1,129 @@
+
+openapi: 3.0.3
+info:
+  title: Auth Server Client API
+  description: |-
+    foobarbaz
+  version: 1.0.0
+tags:
+  - name: auth
+    description: Auth Server Client APIs for obtaining, refreshing and revoking a token
+paths:
+  /as/token.oauth2:
+    post:
+      tags:
+        - auth
+      summary: Obtains a new token from Auth server
+      requestBody:
+        content:
+          application/x-www-form-urlencoded; charset=utf-8:
+            schema:
+              oneOf:
+                - $ref: '#/components/schemas/LoginRequestModel'
+                - $ref: '#/components/schemas/TokenRefreshRequestModel'
+        required: true
+      responses:
+        '200':
+          description: Successful operation
+          content:
+            application/json:
+              schema:
+                oneOf:
+                  - $ref: '#/components/schemas/LoginResponseModel'
+                  - $ref: '#/components/schemas/TokenRefreshResponseModel'
+        default:
+          description: An error occured
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/AuthResponseError'
+components:
+  schemas:
+    LoginResponseModel:
+      type: object
+      properties:
+        expires_in:
+          type: integer
+          format: int32
+        access_token:
+          type: string
+        refresh_token:
+          type: string
+        token_type:
+          type: string
+      required:
+        [expires_in, access_token, refresh_token]
+    TokenRefreshResponseModel:
+      type: object
+      description: Be aware, that we may either receive a new refresh token in the response or not. In case where we do not receive a new refresh token we must use the refresh token from the old token for subsequent token refreshs.
+      properties:
+        expires_in:
+          type: integer
+          format: int32
+        access_token:
+          type: string
+        refresh_token:
+          type: string
+        token_type:
+          type: string
+      required:
+        [expires_in, access_token]
+    LoginRequestModel:
+      type: object
+      properties:
+        client_id:
+          type: string
+        grant_type:
+          type: string
+          enum: ["refresh_token", "password"]
+        password:
+          type: string
+        scope:
+          type: string
+        username:
+          type: string
+      required:
+        [client_id, grant_type, password, scope, username]
+    TokenRefreshRequestModel:
+      type: object
+      properties:
+        grant_type:
+          type: string
+          enum: ["refresh_token", "password"]
+        refresh_token:
+          type: string
+      required:
+        [grant_type, refresh_token]
+    AuthResponseError:
+      type: object
+      properties:
+        error_description:
+          type: string
+        error:
+          type: string
+          enum: ["invalid_request", "invalid_client", "invalid_grant", "invalid_scope", "unauthorized_client", "unsupported_grant_type"]
+          x-enum-descriptions:
+            - 'Request is missing a parameter or contains an unsupported parameter of repeats parameters.'
+            - 'Client authentication fails due to an invalid client id or secret.'
+            - 'Authorization code or password is invalid or expired.'
+            - 'Invalid scope for the given access token.'
+            - 'Client is not authorized for requested grant type.'
+            - 'Given grant type is unsupported.'
+          x-enum-varnames:
+            - INVALID_REQUEST
+            - INVALID_CLIENT
+            - INVALID_GRANT
+            - INVALID_SCOPE
+            - UNAUTHORIZED_CLIENT
+            - UNSUPPORTED_GRANT_TYPE
+        errors:
+          type: array
+          items:
+            $ref: "#/components/schemas/AuthErrorDescription"
+      required:
+        [error_description, error]
+    AuthErrorDescription:
+      type: object
+      properties:
+        description:
+          type: string