[csharp][java] Fix enum discriminator default value (#19614)

* Fix enum discriminator default value

* Remove system out call

* Add case when discriminator type is ref

* Use correct schema

* Handle different use cases of mappings

* Add missing enum type Lizzy

* Make it more robust

* Add missing test for Sedan

* Refactor some code to make it cleaner

* Initialize discriminator enum field

* Don't override existing default value

* Fix issue with finding discriminators

* Move setIsEnum back to its original location

* Be smarter about figuring out the model name

* Fix final warnings

* Add javadocs to introduced methods

Author: david-marconis

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

@@ -3098,6 +3098,7 @@ public CodegenModel fromModel(String name, Schema schema) {
             listOLists.add(m.requiredVars);
             listOLists.add(m.vars);
             listOLists.add(m.allVars);
+            listOLists.add(m.readWriteVars);
             for (List<CodegenProperty> theseVars : listOLists) {
                 for (CodegenProperty requiredVar : theseVars) {
                     if (discPropName.equals(requiredVar.baseName)) {
@@ -3131,6 +3132,63 @@ public CodegenModel fromModel(String name, Schema schema) {
         return m;
     }
 
+    /**
+     * Sets the default value for an enum discriminator property in the provided {@link CodegenModel}.
+     * <p>
+     * If the model's discriminator is defined, this method identifies the discriminator properties among the model's
+     * variables and assigns the default value to reflect the corresponding enum value for the model type.
+     * </p>
+     * <p>
+     * Example: If the discriminator is for type `Animal`, and the model is `Cat`, the default value
+     * will be set to `Animal.Cat` for the properties that have the same name as the discriminator.
+     * </p>
+     *
+     * @param model the {@link CodegenModel} whose discriminator property default value is to be set
+     */
+    protected static void setEnumDiscriminatorDefaultValue(CodegenModel model) {
+        if (model.discriminator == null) {
+            return;
+        }
+        String discPropName = model.discriminator.getPropertyBaseName();
+        Stream.of(model.requiredVars, model.vars, model.allVars, model.readWriteVars)
+                .flatMap(List::stream)
+                .filter(v -> discPropName.equals(v.baseName))
+                .forEach(v -> v.defaultValue = getEnumValueForProperty(model.schemaName, model.discriminator, v));
+    }
+
+    /**
+     * Retrieves the appropriate default value for an enum discriminator property based on the model name.
+     * <p>
+     * If the discriminator has a mapping defined, it attempts to find a mapping for the model name.
+     * Otherwise, it defaults to one of the allowable enum value associated with the property.
+     * If no suitable value is found, the original default value of the property is returned.
+     * </p>
+     *
+     * @param modelName     the name of the model to determine the default value for
+     * @param discriminator the {@link CodegenDiscriminator} containing the mapping and enum details
+     * @param var           the {@link CodegenProperty} representing the discriminator property
+     * @return the default value for the enum discriminator property, or its original default value if none is found
+     */
+    protected static String getEnumValueForProperty(
+            String modelName, CodegenDiscriminator discriminator, CodegenProperty var) {
+        if (!discriminator.getIsEnum() && !var.isEnum) {
+            return var.defaultValue;
+        }
+        Map<String, String> mapping = Optional.ofNullable(discriminator.getMapping()).orElseGet(Collections::emptyMap);
+        for (Map.Entry<String, String> e : mapping.entrySet()) {
+            String schemaName = e.getValue().indexOf('/') < 0 ? e.getValue() : ModelUtils.getSimpleRef(e.getValue());
+            if (modelName.equals(schemaName)) {
+                return e.getKey();
+            }
+        }
+        Object values = var.allowableValues.get("values");
+        if (!(values instanceof List<?>)) {
+            return var.defaultValue;
+        }
+        List<?> valueList = (List<?>) values;
+        return valueList.stream().filter(o -> o.equals(modelName)).map(o -> (String) o).findAny().orElse(var.defaultValue);
+    }
+
     protected void SortModelPropertiesByRequiredFlag(CodegenModel model) {
         Comparator<CodegenProperty> comparator = new Comparator<CodegenProperty>() {
             @Override
@@ -3201,15 +3259,19 @@ protected void setAddProps(Schema schema, IJsonSchemaValidationProperties proper
      * @param visitedSchemas     A set of visited schema names
      */
     private CodegenProperty discriminatorFound(String composedSchemaName, Schema sc, String discPropName, Set<String> visitedSchemas) {
-        if (visitedSchemas.contains(composedSchemaName)) { // recursive schema definition found
+        Schema refSchema = ModelUtils.getReferencedSchema(openAPI, sc);
+        String schemaName = Optional.ofNullable(composedSchemaName)
+                .or(() -> Optional.ofNullable(refSchema.getName()))
+                .or(() -> Optional.ofNullable(sc.get$ref()).map(ModelUtils::getSimpleRef))
+                .orElseGet(sc::toString);
+        if (visitedSchemas.contains(schemaName)) { // recursive schema definition found
             return null;
         } else {
-            visitedSchemas.add(composedSchemaName);
+            visitedSchemas.add(schemaName);
         }
 
-        Schema refSchema = ModelUtils.getReferencedSchema(openAPI, sc);
         if (refSchema.getProperties() != null && refSchema.getProperties().get(discPropName) != null) {
-            Schema discSchema = (Schema) refSchema.getProperties().get(discPropName);
+            Schema discSchema = ModelUtils.getReferencedSchema(openAPI, (Schema)refSchema.getProperties().get(discPropName));
             CodegenProperty cp = new CodegenProperty();
             if (ModelUtils.isStringSchema(discSchema)) {
                 cp.isString = true;
@@ -3218,14 +3280,16 @@ private CodegenProperty discriminatorFound(String composedSchemaName, Schema sc,
             if (refSchema.getRequired() != null && refSchema.getRequired().contains(discPropName)) {
                 cp.setRequired(true);
             }
+            cp.setIsEnum(discSchema.getEnum() != null && !discSchema.getEnum().isEmpty());
             return cp;
         }
         if (ModelUtils.isComposedSchema(refSchema)) {
             Schema composedSchema = refSchema;
             if (composedSchema.getAllOf() != null) {
                 // If our discriminator is in one of the allOf schemas break when we find it
                 for (Object allOf : composedSchema.getAllOf()) {
-                    CodegenProperty cp = discriminatorFound(composedSchemaName, (Schema) allOf, discPropName, visitedSchemas);
+                    Schema allOfSchema = (Schema) allOf;
+                    CodegenProperty cp = discriminatorFound(allOfSchema.getName(), allOfSchema, discPropName, visitedSchemas);
                     if (cp != null) {
                         return cp;
                     }
@@ -3235,8 +3299,11 @@ private CodegenProperty discriminatorFound(String composedSchemaName, Schema sc,
                 // All oneOf definitions must contain the discriminator
                 CodegenProperty cp = new CodegenProperty();
                 for (Object oneOf : composedSchema.getOneOf()) {
-                    String modelName = ModelUtils.getSimpleRef(((Schema) oneOf).get$ref());
-                    CodegenProperty thisCp = discriminatorFound(composedSchemaName, (Schema) oneOf, discPropName, visitedSchemas);
+                    Schema oneOfSchema = (Schema) oneOf;
+                    String modelName = ModelUtils.getSimpleRef((oneOfSchema).get$ref());
+                    // Must use a copied set as the oneOf schemas can point to the same discriminator.
+                    Set<String> visitedSchemasCopy = new TreeSet<>(visitedSchemas);
+                    CodegenProperty thisCp = discriminatorFound(oneOfSchema.getName(), oneOfSchema, discPropName, visitedSchemasCopy);
                     if (thisCp == null) {
                         once(LOGGER).warn(
                                 "'{}' defines discriminator '{}', but the referenced OneOf schema '{}' is missing {}",
@@ -3258,8 +3325,11 @@ private CodegenProperty discriminatorFound(String composedSchemaName, Schema sc,
                 // All anyOf definitions must contain the discriminator because a min of one must be selected
                 CodegenProperty cp = new CodegenProperty();
                 for (Object anyOf : composedSchema.getAnyOf()) {
-                    String modelName = ModelUtils.getSimpleRef(((Schema) anyOf).get$ref());
-                    CodegenProperty thisCp = discriminatorFound(composedSchemaName, (Schema) anyOf, discPropName, visitedSchemas);
+                    Schema anyOfSchema = (Schema) anyOf;
+                    String modelName = ModelUtils.getSimpleRef(anyOfSchema.get$ref());
+                    // Must use a copied set as the anyOf schemas can point to the same discriminator.
+                    Set<String> visitedSchemasCopy = new TreeSet<>(visitedSchemas);
+                    CodegenProperty thisCp = discriminatorFound(anyOfSchema.getName(), anyOfSchema, discPropName, visitedSchemasCopy);
                     if (thisCp == null) {
                         once(LOGGER).warn(
                                 "'{}' defines discriminator '{}', but the referenced AnyOf schema '{}' is missing {}",
@@ -3542,13 +3612,11 @@ protected CodegenDiscriminator createDiscriminator(String schemaName, Schema sch
         discriminator.setPropertyType(propertyType);
 
         // check to see if the discriminator property is an enum string
-        if (schema.getProperties() != null &&
-                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);
-            }
-        }
+        boolean isEnum = Optional
+                .ofNullable(discriminatorFound(schemaName, schema, discriminatorPropertyName, new TreeSet<>()))
+                .map(CodegenProperty::getIsEnum)
+                .orElse(false);
+        discriminator.setIsEnum(isEnum);
 
         discriminator.setMapping(sourceDiscriminator.getMapping());
         List<MappedModel> uniqueDescendants = new ArrayList<>();

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

@@ -1713,6 +1713,7 @@ public CodegenModel fromModel(String name, Schema model) {
 
         // additional import for different cases
         addAdditionalImports(codegenModel, codegenModel.getComposedSchemas());
+        setEnumDiscriminatorDefaultValue(codegenModel);
         return codegenModel;
     }
 

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

@@ -432,6 +432,7 @@ public String apiTestFileFolder() {
     public CodegenModel fromModel(String name, Schema model) {
         Map<String, Schema> allDefinitions = ModelUtils.getSchemas(this.openAPI);
         CodegenModel codegenModel = super.fromModel(name, model);
+        setEnumDiscriminatorDefaultValue(codegenModel);
         if (allDefinitions != null && codegenModel != null && codegenModel.parent != null) {
             final Schema<?> parentModel = allDefinitions.get(toModelName(codegenModel.parent));
             if (parentModel != null) {

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

@@ -1611,6 +1611,12 @@ public static String getParentName(Schema composedSchema, Map<String, Schema> al
      * @return the name of the parent model
      */
     public static List<String> getAllParentsName(Schema composedSchema, Map<String, Schema> allSchemas, boolean includeAncestors) {
+        return getAllParentsName(composedSchema, allSchemas, includeAncestors, new HashSet<>());
+    }
+
+    // Use a set of seen names to avoid infinite recursion
+    private static List<String> getAllParentsName(
+            Schema composedSchema, Map<String, Schema> allSchemas, boolean includeAncestors, Set<String> seenNames) {
         List<Schema> interfaces = getInterfaces(composedSchema);
         List<String> names = new ArrayList<String>();
 
@@ -1619,6 +1625,10 @@ public static List<String> getAllParentsName(Schema composedSchema, Map<String,
                 // get the actual schema
                 if (StringUtils.isNotEmpty(schema.get$ref())) {
                     String parentName = getSimpleRef(schema.get$ref());
+                    if (seenNames.contains(parentName)) {
+                        continue;
+                    }
+                    seenNames.add(parentName);
                     Schema s = allSchemas.get(parentName);
                     if (s == null) {
                         LOGGER.error("Failed to obtain schema from {}", parentName);
@@ -1627,7 +1637,7 @@ public static List<String> getAllParentsName(Schema composedSchema, Map<String,
                         // discriminator.propertyName is used or x-parent is used
                         names.add(parentName);
                         if (includeAncestors && isComposedSchema(s)) {
-                            names.addAll(getAllParentsName(s, allSchemas, true));
+                            names.addAll(getAllParentsName(s, allSchemas, true, seenNames));
                         }
                     } else {
                         // not a parent since discriminator.propertyName is not set

modules/openapi-generator/src/main/resources/Java/libraries/okhttp-gson/pojo.mustache

@@ -81,6 +81,11 @@ public class {{classname}} {{#parent}}extends {{{.}}} {{/parent}}{{#vendorExtens
     {{/parcelableModel}}
     {{/parent}}
     {{#discriminator}}
+    {{#discriminator.isEnum}}
+{{#readWriteVars}}{{#isDiscriminator}}{{#defaultValue}}
+    this.{{name}} = {{defaultValue}};
+{{/defaultValue}}{{/isDiscriminator}}{{/readWriteVars}}
+    {{/discriminator.isEnum}}
     {{^discriminator.isEnum}}
     this.{{{discriminatorName}}} = this.getClass().getSimpleName();
     {{/discriminator.isEnum}}

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

@@ -140,4 +140,46 @@ public void test31specAdditionalPropertiesOfOneOf() throws IOException {
         assertFileContains(modelFile.toPath(),
                 " Dictionary<string, ResponseResultsValue> results = default(Dictionary<string, ResponseResultsValue>");
     }
+
+    @Test
+    public void testEnumDiscriminatorDefaultValueIsNotString() throws IOException {
+        File output = Files.createTempDirectory("test").toFile().getCanonicalFile();
+        output.deleteOnExit();
+        final OpenAPI openAPI = TestUtils.parseFlattenSpec(
+                "src/test/resources/3_0/enum_discriminator_inheritance.yaml");
+        final DefaultGenerator defaultGenerator = new DefaultGenerator();
+        final ClientOptInput clientOptInput = new ClientOptInput();
+        clientOptInput.openAPI(openAPI);
+        CSharpClientCodegen cSharpClientCodegen = new CSharpClientCodegen();
+        cSharpClientCodegen.setOutputDir(output.getAbsolutePath());
+        cSharpClientCodegen.setAutosetConstants(true);
+        clientOptInput.config(cSharpClientCodegen);
+        defaultGenerator.opts(clientOptInput);
+
+        Map<String, File> files = defaultGenerator.generate().stream()
+                .collect(Collectors.toMap(File::getPath, Function.identity()));
+
+        Map<String, String> expectedContents = Map.of(
+                "Cat", "PetTypeEnum petType = PetTypeEnum.Catty",
+                "Dog", "PetTypeEnum petType = PetTypeEnum.Dog",
+                "Gecko", "PetTypeEnum petType = PetTypeEnum.Gecko",
+                "Chameleon", "PetTypeEnum petType = PetTypeEnum.Camo",
+                "MiniVan", "CarType carType = CarType.MiniVan",
+                "CargoVan", "CarType carType = CarType.CargoVan",
+                "SUV", "CarType carType = CarType.SUV",
+                "Truck", "CarType carType = CarType.Truck",
+                "Sedan", "CarType carType = CarType.Sedan"
+
+        );
+        for (Map.Entry<String, String> e : expectedContents.entrySet()) {
+            String modelName = e.getKey();
+            String expectedContent = e.getValue();
+            File file = files.get(Paths
+                    .get(output.getAbsolutePath(), "src", "Org.OpenAPITools", "Model", modelName + ".cs")
+                    .toString()
+            );
+            assertNotNull(file, "Could not find file for model: " + modelName);
+            assertFileContains(file.toPath(), expectedContent);
+        }
+    }
 }

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

@@ -2408,6 +2408,39 @@ public void testOpenapiGeneratorIgnoreListOption() {
         assertNull(files.get("pom.xml"));
     }
 
+    @Test
+    public void testEnumDiscriminatorDefaultValueIsNotString() {
+        final Path output = newTempFolder();
+        final OpenAPI openAPI = TestUtils.parseFlattenSpec(
+                "src/test/resources/3_0/enum_discriminator_inheritance.yaml");
+        JavaClientCodegen codegen = new JavaClientCodegen();
+        codegen.setOutputDir(output.toString());
+
+        Map<String, File> files = new DefaultGenerator().opts(new ClientOptInput().openAPI(openAPI).config(codegen))
+                .generate().stream().collect(Collectors.toMap(File::getName, Function.identity()));
+
+        Map<String, String> expectedContents = Map.of(
+                "Cat", "this.petType = PetTypeEnum.CATTY",
+                "Dog", "this.petType = PetTypeEnum.DOG",
+                "Gecko", "this.petType = PetTypeEnum.GECKO",
+                "Chameleon", "this.petType = PetTypeEnum.CAMO",
+                "MiniVan", "this.carType = CarType.MINI_VAN",
+                "CargoVan", "this.carType = CarType.CARGO_VAN",
+                "SUV", "this.carType = CarType.SUV",
+                "Truck", "this.carType = CarType.TRUCK",
+                "Sedan", "this.carType = CarType.SEDAN"
+
+        );
+        for (Map.Entry<String, String> e : expectedContents.entrySet()) {
+            String modelName = e.getKey();
+            String expectedContent = e.getValue();
+            File entityFile = files.get(modelName + ".java");
+            assertNotNull(entityFile);
+            assertThat(entityFile).content().doesNotContain("Type = this.getClass().getSimpleName();");
+            assertThat(entityFile).content().contains(expectedContent);
+        }
+    }
+
     @Test
     public void testRestTemplateHandleURIEnum() {
         String[] expectedInnerEnumLines = new String[]{