[Java] ensure JsonTypeName not generated for class implementing oneOf with discriminator (#24024)

* fix 23997: ensure that no JsonTypeName is created when the parent interface has a discriminator mapping

* add test for @JsonTypeInfo

* Fix Cubic findings

Author: jpfinne

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

@@ -577,6 +577,14 @@ public Map<String, ModelsMap> postProcessAllModels(Map<String, ModelsMap> objs)
                         }
                         // if this is oneOf interface, make sure we include the necessary imports for it
                         addImportsToOneOfInterface(modelsImports);
+                        //
+                        // ensure that no JsonTypeName is created when the parent interface has a discriminator mapping
+                        if (cm.discriminator != null && cm.discriminator.getMappedModels() != null && !cm.discriminator.getMappedModels().isEmpty()) {
+                            cm.discriminator.getMappedModels().stream()
+                                    .map(MappedModel::getModel)
+                                    .filter(Objects::nonNull)
+                                    .forEach(model -> model.setHasDiscriminatorWithNonEmptyMapping(true));
+                        }
                     }
                 }
             }

modules/openapi-generator/src/test/java/org/openapitools/codegen/java/spring/SpringCodegenTest.java

@@ -8145,4 +8145,21 @@ void schemaMappingWithNullableAllOfRendersNullableJavaProperty() throws IOExcept
         JavaFileAssert.assertThat(files.get("MyObject.java"))
                 .assertProperty("optionalRef").withType("JsonNullable<com.example.ExternalModel>");
     }
+
+    @Test
+    void issue24003() throws IOException {
+        Map<String, File> files = generateFromContract(
+                "src/test/resources/3_0/spring/issue_24003.yaml", SPRING_BOOT,
+                Map.of(USE_SPRING_BOOT4, true, MODEL_NAME_SUFFIX, "DTO", INTERFACE_ONLY, "true"));
+        JavaFileAssert.assertThat(files.get("BrLockDTO.java")).isInterface()
+                .assertTypeAnnotations()
+                .containsWithNameAndAttributes("JsonTypeInfo", Map.of("use", "JsonTypeInfo.Id.NAME", "include", "JsonTypeInfo.As.PROPERTY", "property", "\"lockType\"", "visible", "true"))
+                .containsWithName("JsonSubTypes")
+                .recursivelyContainsWithNameAndAttributes("JsonSubTypes.Type", Map.of("value", "ComponentBrLockDTO.class", "name", "\"COMPONENT\""))
+                .recursivelyContainsWithNameAndAttributes("JsonSubTypes.Type", Map.of("value", "UserBrLockDTO.class", "name", "\"USER\""));
+        JavaFileAssert.assertThat(files.get("ComponentBrLockDTO.java")).implementsInterfaces("BrLockDTO")
+                .fileDoesNotContain("@JsonTypeName");
+        JavaFileAssert.assertThat(files.get("UserBrLockDTO.java")).implementsInterfaces("BrLockDTO")
+                .fileDoesNotContain("@JsonTypeName");
+    }
 }

modules/openapi-generator/src/test/resources/3_0/spring/issue_24003.yaml

@@ -0,0 +1,68 @@
+openapi: 3.0.1
+info:
+  title: x-discriminator-value JsonTypeName bug
+  version: 1.0.0
+paths:
+  /locks:
+    get:
+      operationId: getLocks
+      responses:
+        '200':
+          description: list of locks
+          content:
+            application/json:
+              schema:
+                type: array
+                items:
+                  $ref: '#/components/schemas/BrLock'
+components:
+  schemas:
+    LockType:
+      type: string
+      enum:
+        - USER
+        - COMPONENT
+
+    BrLock:
+      type: object
+      required:
+        - lockType
+      properties:
+        lockType:
+          $ref: '#/components/schemas/LockType'
+      oneOf:
+        - $ref: '#/components/schemas/UserBrLock'
+        - $ref: '#/components/schemas/ComponentBrLock'
+      discriminator:
+        propertyName: lockType
+        mapping:
+          USER: '#/components/schemas/UserBrLock'
+          COMPONENT: '#/components/schemas/ComponentBrLock'
+
+    BaseBrLock:
+      type: object
+      required:
+        - lockType
+      properties:
+        lockType:
+          $ref: '#/components/schemas/LockType'
+
+    UserBrLock:
+      allOf:
+        - $ref: '#/components/schemas/BaseBrLock'
+        - type: object
+          required:
+            - userId
+          properties:
+            userId:
+              type: string
+
+    ComponentBrLock:
+      allOf:
+        - $ref: '#/components/schemas/BaseBrLock'
+        - type: object
+          required:
+            - componentId
+          properties:
+            componentId:
+              type: string