Fix "defaultToEmptyContainer" not properly implemented for non-nullable, required Map

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

@@ -454,4 +454,6 @@ public static enum ENUM_PROPERTY_NAMING_TYPE {camelCase, PascalCase, snake_case,
     public static final String WAIT_TIME_OF_THREAD = "waitTimeMillis";
 
     public static final String USE_DEFAULT_VALUES_FOR_REQUIRED_VARS = "useDefaultValuesForRequiredVars";
+
+    public static final String DEFAULT_TO_EMPTY_CONTAINER = "defaultToEmptyContainer";
 }

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

@@ -88,6 +88,7 @@
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
+import static org.openapitools.codegen.CodegenConstants.DEFAULT_TO_EMPTY_CONTAINER;
 import static org.openapitools.codegen.CodegenConstants.UNSUPPORTED_V310_SPEC_MSG;
 import static org.openapitools.codegen.utils.CamelizeOption.LOWERCASE_FIRST_LETTER;
 import static org.openapitools.codegen.utils.OnceLogger.once;
@@ -338,7 +339,7 @@ apiTemplateFiles are for API outputs only (controllers/handlers).
     @Setter @Getter boolean arrayDefaultToEmpty, arrayNullableDefaultToEmpty, arrayOptionalNullableDefaultToEmpty, arrayOptionalDefaultToEmpty;
     @Setter @Getter boolean mapDefaultToEmpty, mapNullableDefaultToEmpty, mapOptionalNullableDefaultToEmpty, mapOptionalDefaultToEmpty;
     @Setter @Getter protected boolean defaultToEmptyContainer;
-    final String DEFAULT_TO_EMPTY_CONTAINER = "defaultToEmptyContainer";
+
     final List EMPTY_LIST = new ArrayList();
 
     @Override
@@ -4289,7 +4290,7 @@ void updateDefaultToEmptyContainer(CodegenProperty cp, Schema p) {
             } else { // required
                 if (cp.isNullable && mapNullableDefaultToEmpty) { // nullable
                     p.setDefault(EMPTY_LIST);
-                } else if (!cp.isNullable && mapOptionalDefaultToEmpty) { // non-nullable
+                } else if (!cp.isNullable && mapDefaultToEmpty) { // non-nullable
                     p.setDefault(EMPTY_LIST);
                 }
             }

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

@@ -5634,6 +5634,30 @@ public void testCollectionTypesWithDefaults_issue_collection() throws IOExceptio
                 .fileContains("private List<String> stringRequiredList = new ArrayList<>();");
     }
 
+    @Test
+    public void testDefaultForRequiredNonNullableMap() throws IOException {
+        File output = Files.createTempDirectory("test").toFile().getCanonicalFile();
+        output.deleteOnExit();
+
+        OpenAPI openAPI = new OpenAPIParser()
+                .readLocation("src/test/resources/3_0/java/issue_21890.yaml", null, new ParseOptions()).getOpenAPI();
+        SpringCodegen codegen = new SpringCodegen();
+        codegen.setLibrary(SPRING_BOOT);
+        codegen.setOutputDir(output.getAbsolutePath());
+        codegen.additionalProperties().put("defaultToEmptyContainer", "map");
+
+        ClientOptInput input = new ClientOptInput()
+                .openAPI(openAPI)
+                .config(codegen);
+
+        DefaultGenerator generator = new DefaultGenerator();
+        Map<String, File> files = generator.opts(input).generate().stream()
+                .collect(Collectors.toMap(File::getName, Function.identity()));
+
+        JavaFileAssert.assertThat(files.get("Pet.java"))
+                .fileContains("private Map<String, String> requiredNonNullableMap = new HashMap<>();");
+    }
+
     @Test
     public void testGenericReturnTypeWhenUsingResponseEntity_issue1096() throws IOException {
         Map<String, Object> additionalProperties = new HashMap<>();

modules/openapi-generator/src/test/resources/3_0/java/issue_21890.yaml

@@ -0,0 +1,48 @@
+openapi: 3.0.0
+servers:
+  - url: 'http://petstore.swagger.io/v2'
+info:
+  description: >-
+    This is a sample server Petstore server
+  version: 1.0.0
+  title: OpenAPI Petstore
+  license:
+    name: Apache-2.0
+    url: 'https://www.apache.org/licenses/LICENSE-2.0.html'
+paths:
+  '/pet/{petId}':
+    get:
+      tags:
+        - pet
+      summary: Find pet by ID
+      description: Returns a single pet
+      operationId: getPetById
+      parameters:
+        - name: petId
+          in: path
+          description: ID of pet to return
+          required: true
+          schema:
+            type: integer
+            format: int64
+      responses:
+        '200':
+          description: successful operation
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/Pet'
+components:
+  schemas:
+    Pet:
+      title: a Pet
+      description: A pet for sale in the pet store
+      type: object
+      required:
+        - requiredNonNullableMap
+      properties:
+        # Test for issue 21890.
+        # As this map is required and non-nullable, the generated java class should initialise this Map with new HashMap()
+        requiredNonNullableMap:
+          additionalProperties:
+            type: string