fix: [JAVA/SPRING] [#12692] fixed optional config property legacyDisc… (#12713)

* fix: [JAVA/SPRING] [#12692] fixed optional config property legacyDiscriminatorBehavior always being overwritten to false in spring codegen

* feat: [JAVA/SPRING] [#12692] spaces instead of tabs

* feat: [JAVA/SPRING] [#12692] spaces instead of tabs in test

* fix: [JAVA/SPRING] [#12692] added comment

* fix: [JAVA/SPRING] [#12692] spaces instead of tabs

* fix: [JAVA/SPRING] [#12692] spaces instead of tabs in test

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

@@ -297,10 +297,12 @@ public class SpringCodegen extends AbstractJavaCodegen
             LOGGER.info("Set base package to invoker package ({})", basePackage);
         }
 
-        super.processOpts();
         useOneOfInterfaces = true;
         legacyDiscriminatorBehavior = false;
 
+        // Please refrain from updating values of Config Options after super.ProcessOpts() is called
+        super.processOpts();
+
         if (DocumentationProvider.SPRINGFOX.equals(getDocumentationProvider())) {
             LOGGER.warn("The springfox documentation provider is deprecated for removal. Use the springdoc provider instead.");
         }

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

@@ -1473,4 +1473,30 @@ public class SpringCodegenTest {
                 "consumes", "{ \"application/octet-stream\", \"application/*\" }"
             ));
     }
+
+    @Test
+    public void shouldGenerateDiscriminatorFromAllOfWhenUsingLegacyDiscriminatorBehaviour_issue12692() throws IOException {
+        File output = Files.createTempDirectory("test").toFile().getCanonicalFile();
+        output.deleteOnExit();
+
+        OpenAPI openAPI = new OpenAPIParser()
+                .readLocation("src/test/resources/bugs/issue_12692.yml", null, new ParseOptions()).getOpenAPI();
+        SpringCodegen codegen = new SpringCodegen();
+        codegen.setLibrary(SPRING_BOOT);
+        codegen.setOutputDir(output.getAbsolutePath());
+        codegen.additionalProperties().put(CodegenConstants.LEGACY_DISCRIMINATOR_BEHAVIOR, "true");
+
+        ClientOptInput input = new ClientOptInput()
+                .openAPI(openAPI)
+                .config(codegen);
+
+        DefaultGenerator generator = new DefaultGenerator();
+        generator.opts(input).generate();
+
+        String jsonTypeInfo = "@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, property = \"type\", visible = true)";
+        String jsonSubType = "@JsonSubTypes({\n" +
+                             "  @JsonSubTypes.Type(value = Cat.class, name = \"cat\")" +
+                             "})";
+        assertFileContains(Paths.get(output.getAbsolutePath() + "/src/main/java/org/openapitools/model/Pet.java"), jsonTypeInfo, jsonSubType);
+    }
 }

modules/openapi-generator/src/test/resources/bugs/issue_12692.yml

@@ -0,0 +1,45 @@
+openapi: 3.0.1
+info:
+  version: 1.0.0
+  title: Swagger Petstore
+  license:
+    name: MIT
+paths:
+  "/pets":
+    get:
+      operationId: listPets
+      responses:
+        '200':
+          description: description
+          content:
+            application/json:
+              schema:
+                type: array
+                items:
+                  "$ref": "#/components/schemas/Pet"
+components:
+  schemas:
+    Pet:
+      type: object
+      required:
+        - type
+      properties:
+        type:
+          type: string
+      discriminator:
+        propertyName: type
+        mapping:
+          cat: "#/components/schemas/Cat"
+    Cat:
+      allOf:
+        - "$ref": "#/components/schemas/Pet"
+        - type: object
+          required:
+            - type
+          properties:
+            type:
+              type: string
+          discriminator:
+            propertyName: type
+            mapping:
+              cat: "#/components/schemas/Cat"