Use enum type for discriminator

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

@@ -3526,22 +3526,30 @@ protected CodegenDiscriminator createDiscriminator(String schemaName, Schema sch
             return null;
         }
         CodegenDiscriminator discriminator = new CodegenDiscriminator();
-        String discPropName = sourceDiscriminator.getPropertyName();
-        discriminator.setPropertyName(toVarName(discPropName));
+        String discriminatorPropertyName = sourceDiscriminator.getPropertyName();
+        discriminator.setPropertyName(toVarName(discriminatorPropertyName));
         discriminator.setPropertyBaseName(sourceDiscriminator.getPropertyName());
         discriminator.setPropertyGetter(toGetter(discriminator.getPropertyName()));
 
         if (sourceDiscriminator.getExtensions() != null) {
             discriminator.setVendorExtensions(sourceDiscriminator.getExtensions());
         }
 
-        // FIXME: for now, we assume that the discriminator property is String
-        discriminator.setPropertyType(typeMapping.get("string"));
+        // FIXME: there are other ways to define the type of the discriminator property (inline
+        //  for example). Handling those scenarios is too complicated for me, I'm leaving it for
+        //  the future..
+        String propertyType =
+            Optional.ofNullable(schema.getProperties())
+                .map(p -> (Schema<?>) p.get(discriminatorPropertyName))
+                .map(Schema::get$ref)
+                .map(ModelUtils::getSimpleRef)
+                .orElseGet(() -> typeMapping.get("string"));
+        discriminator.setPropertyType(propertyType);
 
         // check to see if the discriminator property is an enum string
         if (schema.getProperties() != null &&
-                schema.getProperties().get(discPropName) instanceof StringSchema) {
-            StringSchema s = (StringSchema) schema.getProperties().get(discPropName);
+                schema.getProperties().get(discriminatorPropertyName) instanceof StringSchema) {
+            StringSchema s = (StringSchema) schema.getProperties().get(discriminatorPropertyName);
             if (s.getEnum() != null && !s.getEnum().isEmpty()) { // it's an enum string
                 discriminator.setIsEnum(true);
             }
@@ -3586,7 +3594,7 @@ protected CodegenDiscriminator createDiscriminator(String schemaName, Schema sch
         }
         // if there are composed oneOf/anyOf schemas, add them to this discriminator
         if (ModelUtils.isComposedSchema(schema) && !this.getLegacyDiscriminatorBehavior()) {
-            List<MappedModel> otherDescendants = getOneOfAnyOfDescendants(schemaName, discPropName, (ComposedSchema) schema, openAPI);
+            List<MappedModel> otherDescendants = getOneOfAnyOfDescendants(schemaName, discriminatorPropertyName, (ComposedSchema) schema, openAPI);
             for (MappedModel otherDescendant : otherDescendants) {
                 if (!uniqueDescendants.contains(otherDescendant)) {
                     uniqueDescendants.add(otherDescendant);

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

@@ -56,6 +56,7 @@
 import java.util.stream.Collectors;
 
 import static junit.framework.Assert.assertEquals;
+import static org.assertj.core.api.Assertions.assertThat;
 import static org.testng.Assert.*;
 
 public class DefaultCodegenTest {
@@ -1509,6 +1510,12 @@ public void testComposedSchemaOneOfDiscriminatorMap() {
         hs.add(new CodegenDiscriminator.MappedModel(mn, mn));
         Assert.assertEquals(cm.discriminator.getMappedModels(), hs);
 
+        // ref oneOf models with enum property discriminator
+        modelName = "FruitOneOfEnumMappingDisc";
+        sc = openAPI.getComponents().getSchemas().get(modelName);
+        cm = codegen.fromModel(modelName, sc);
+        assertThat(cm.discriminator.getPropertyType()).isEqualTo("FruitTypeEnum");
+
         // ref oneOf models with discriminator in the grandparent schemas of those oneof models
         modelName = "FruitGrandparentDisc";
         sc = openAPI.getComponents().getSchemas().get(modelName);

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

@@ -1538,6 +1538,55 @@ public void testDiscriminatorWithoutMappingIssue14731() throws IOException {
         assertFileContains(Paths.get(outputPath + "/src/main/java/org/openapitools/model/ChildWithoutMappingBDTO.java"), "@JsonTypeName");
     }
 
+    @Test
+    void testOneOfWithEnumDiscriminator() throws IOException {
+        File output = Files.createTempDirectory("test").toFile().getCanonicalFile();
+        output.deleteOnExit();
+        String outputPath = output.getAbsolutePath().replace('\\', '/');
+        OpenAPI openAPI = new OpenAPIParser()
+            .readLocation("src/test/resources/3_0/oneOfDiscriminator.yaml", null, new ParseOptions()).getOpenAPI();
+
+        SpringCodegen codegen = new SpringCodegen();
+        codegen.setOutputDir(output.getAbsolutePath());
+        codegen.additionalProperties().put(CXFServerFeatures.LOAD_TEST_DATA_FROM_FILE, "true");
+        codegen.setUseOneOfInterfaces(true);
+
+        ClientOptInput input = new ClientOptInput();
+        input.openAPI(openAPI);
+        input.config(codegen);
+
+        DefaultGenerator generator = new DefaultGenerator();
+        codegen.setHateoas(true);
+        generator.setGeneratorPropertyDefault(CodegenConstants.MODELS, "true");
+        //generator.setGeneratorPropertyDefault(CodegenConstants.USE_ONEOF_DISCRIMINATOR_LOOKUP, "true");
+        generator.setGeneratorPropertyDefault(CodegenConstants.LEGACY_DISCRIMINATOR_BEHAVIOR, "false");
+
+        codegen.setUseOneOfInterfaces(true);
+        codegen.setLegacyDiscriminatorBehavior(false);
+
+        generator.setGeneratorPropertyDefault(CodegenConstants.MODEL_TESTS, "false");
+        generator.setGeneratorPropertyDefault(CodegenConstants.MODEL_DOCS, "false");
+        generator.setGeneratorPropertyDefault(CodegenConstants.APIS, "true");
+        generator.setGeneratorPropertyDefault(CodegenConstants.SUPPORTING_FILES, "false");
+
+        generator.opts(input).generate();
+
+        assertFileContains(
+            Paths.get(outputPath + "/src/main/java/org/openapitools/model/FruitOneOfEnumMappingDisc.java"),
+            "public FruitTypeEnum getFruitType();"
+        );
+        assertFileContains(
+            Paths.get(outputPath + "/src/main/java/org/openapitools/model/AppleOneOfEnumMappingDisc.java"),
+            "private FruitTypeEnum fruitType;",
+            "public FruitTypeEnum getFruitType() {"
+        );
+        assertFileContains(
+            Paths.get(outputPath + "/src/main/java/org/openapitools/model/BananaOneOfEnumMappingDisc.java"),
+            "private FruitTypeEnum fruitType;",
+            "public FruitTypeEnum getFruitType() {"
+        );
+    }
+
     @Test
     public void testTypeMappings() {
         final SpringCodegen codegen = new SpringCodegen();

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

@@ -170,6 +170,38 @@ components:
           type: integer
       oneOf:
         - $ref: '#/components/schemas/FruitType'
+    FruitTypeEnum:
+      type: string
+      enum: [APPLE, BANANA]
+    FruitOneOfEnumMappingDisc:
+      type: object
+      properties:
+        fruitType:
+          $ref: "#/components/schemas/FruitTypeEnum"
+      required:
+        - fruitType
+      oneOf:
+        - $ref: '#/components/schemas/AppleOneOfEnumMappingDisc'
+        - $ref: '#/components/schemas/BananaOneOfEnumMappingDisc'
+      discriminator:
+        propertyName: fruitType
+        mapping:
+          APPLE: '#/components/schemas/AppleOneOfEnumMappingDisc'
+          BANANA: '#/components/schemas/BananaOneOfEnumMappingDisc'
+    AppleOneOfEnumMappingDisc:
+      type: object
+      required:
+        - seeds
+      properties:
+        seeds:
+          type: integer
+    BananaOneOfEnumMappingDisc:
+      type: object
+      required:
+        - length
+      properties:
+        length:
+          type: integer
     FruitGrandparentDisc:
       oneOf:
         - $ref: '#/components/schemas/AppleGrandparentDisc'

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

@@ -177,6 +177,38 @@ components:
           type: string
       allOf:
         - $ref: '#/components/schemas/Pizza'
+    FruitType:
+      type: string
+      enum: [APPLE, BANANA]
+    Fruit:
+      type: object
+      properties:
+        fruitType:
+          $ref: "#/components/schemas/FruitType"
+      required:
+        - fruitType
+      oneOf:
+        - $ref: '#/components/schemas/Apple'
+        - $ref: '#/components/schemas/Banana'
+      discriminator:
+        propertyName: fruitType
+        mapping:
+          APPLE: '#/components/schemas/Apple'
+          BANANA: '#/components/schemas/Banana'
+    Apple:
+      type: object
+      required:
+        - seeds
+      properties:
+        seeds:
+          type: integer
+    Banana:
+      type: object
+      required:
+        - length
+      properties:
+        length:
+          type: integer
 
   requestBodies:
     Foo:

samples/openapi3/client/petstore/dart-dio/oneof_polymorphism_and_inheritance/.openapi-generator/FILES

@@ -2,6 +2,8 @@
 README.md
 analysis_options.yaml
 doc/Addressable.md
+doc/Apple.md
+doc/Banana.md
 doc/Bar.md
 doc/BarApi.md
 doc/BarCreate.md
@@ -14,6 +16,8 @@ doc/Foo.md
 doc/FooApi.md
 doc/FooRef.md
 doc/FooRefOrValue.md
+doc/Fruit.md
+doc/FruitType.md
 doc/Pasta.md
 doc/Pizza.md
 doc/PizzaSpeziale.md
@@ -29,6 +33,8 @@ lib/src/auth/bearer_auth.dart
 lib/src/auth/oauth.dart
 lib/src/date_serializer.dart
 lib/src/model/addressable.dart
+lib/src/model/apple.dart
+lib/src/model/banana.dart
 lib/src/model/bar.dart
 lib/src/model/bar_create.dart
 lib/src/model/bar_ref.dart
@@ -40,6 +46,8 @@ lib/src/model/extensible.dart
 lib/src/model/foo.dart
 lib/src/model/foo_ref.dart
 lib/src/model/foo_ref_or_value.dart
+lib/src/model/fruit.dart
+lib/src/model/fruit_type.dart
 lib/src/model/pasta.dart
 lib/src/model/pizza.dart
 lib/src/model/pizza_speziale.dart

samples/openapi3/client/petstore/dart-dio/oneof_polymorphism_and_inheritance/README.md

@@ -73,6 +73,8 @@ Class | Method | HTTP request | Description
 ## Documentation For Models
 
  - [Addressable](doc/Addressable.md)
+ - [Apple](doc/Apple.md)
+ - [Banana](doc/Banana.md)
  - [Bar](doc/Bar.md)
  - [BarCreate](doc/BarCreate.md)
  - [BarRef](doc/BarRef.md)
@@ -83,6 +85,8 @@ Class | Method | HTTP request | Description
  - [Foo](doc/Foo.md)
  - [FooRef](doc/FooRef.md)
  - [FooRefOrValue](doc/FooRefOrValue.md)
+ - [Fruit](doc/Fruit.md)
+ - [FruitType](doc/FruitType.md)
  - [Pasta](doc/Pasta.md)
  - [Pizza](doc/Pizza.md)
  - [PizzaSpeziale](doc/PizzaSpeziale.md)

samples/openapi3/client/petstore/dart-dio/oneof_polymorphism_and_inheritance/doc/Apple.md

@@ -0,0 +1,15 @@
+# openapi.model.Apple
+
+## Load the model package
+```dart
+import 'package:openapi/api.dart';
+```
+
+## Properties
+Name | Type | Description | Notes
+------------ | ------------- | ------------- | -------------
+**seeds** | **int** |  | 
+
+[[Back to Model list]](../README.md#documentation-for-models) [[Back to API list]](../README.md#documentation-for-api-endpoints) [[Back to README]](../README.md)
+
+

samples/openapi3/client/petstore/dart-dio/oneof_polymorphism_and_inheritance/doc/Banana.md

@@ -0,0 +1,15 @@
+# openapi.model.Banana
+
+## Load the model package
+```dart
+import 'package:openapi/api.dart';
+```
+
+## Properties
+Name | Type | Description | Notes
+------------ | ------------- | ------------- | -------------
+**length** | **int** |  | 
+
+[[Back to Model list]](../README.md#documentation-for-models) [[Back to API list]](../README.md#documentation-for-api-endpoints) [[Back to README]](../README.md)
+
+

samples/openapi3/client/petstore/dart-dio/oneof_polymorphism_and_inheritance/doc/Fruit.md

@@ -0,0 +1,17 @@
+# openapi.model.Fruit
+
+## Load the model package
+```dart
+import 'package:openapi/api.dart';
+```
+
+## Properties
+Name | Type | Description | Notes
+------------ | ------------- | ------------- | -------------
+**fruitType** | [**FruitType**](FruitType.md) |  | 
+**seeds** | **int** |  | 
+**length** | **int** |  | 
+
+[[Back to Model list]](../README.md#documentation-for-models) [[Back to API list]](../README.md#documentation-for-api-endpoints) [[Back to README]](../README.md)
+
+

samples/openapi3/client/petstore/dart-dio/oneof_polymorphism_and_inheritance/doc/FruitType.md

@@ -0,0 +1,14 @@
+# openapi.model.FruitType
+
+## Load the model package
+```dart
+import 'package:openapi/api.dart';
+```
+
+## Properties
+Name | Type | Description | Notes
+------------ | ------------- | ------------- | -------------
+
+[[Back to Model list]](../README.md#documentation-for-models) [[Back to API list]](../README.md#documentation-for-api-endpoints) [[Back to README]](../README.md)
+
+

samples/openapi3/client/petstore/dart-dio/oneof_polymorphism_and_inheritance/lib/openapi.dart

@@ -13,6 +13,8 @@ export 'package:openapi/src/api/bar_api.dart';
 export 'package:openapi/src/api/foo_api.dart';
 
 export 'package:openapi/src/model/addressable.dart';
+export 'package:openapi/src/model/apple.dart';
+export 'package:openapi/src/model/banana.dart';
 export 'package:openapi/src/model/bar.dart';
 export 'package:openapi/src/model/bar_create.dart';
 export 'package:openapi/src/model/bar_ref.dart';
@@ -23,6 +25,8 @@ export 'package:openapi/src/model/extensible.dart';
 export 'package:openapi/src/model/foo.dart';
 export 'package:openapi/src/model/foo_ref.dart';
 export 'package:openapi/src/model/foo_ref_or_value.dart';
+export 'package:openapi/src/model/fruit.dart';
+export 'package:openapi/src/model/fruit_type.dart';
 export 'package:openapi/src/model/pasta.dart';
 export 'package:openapi/src/model/pizza.dart';
 export 'package:openapi/src/model/pizza_speziale.dart';