[kotlin-spring] Implement skipDefaultValues in mustache templates

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

@@ -77,6 +77,7 @@ public class KotlinSpringServerCodegen extends AbstractKotlinCodegen
     public static final String GRADLE_BUILD_FILE = "gradleBuildFile";
     public static final String SERVICE_INTERFACE = "serviceInterface";
     public static final String SERVICE_IMPLEMENTATION = "serviceImplementation";
+    public static final String OMIT_DEFAULT_NULL_VALUES = "omitDefaultNullValues";
     public static final String SKIP_DEFAULT_INTERFACE = "skipDefaultInterface";
     public static final String SKIP_DEFAULT_API_INTERFACE = "skipDefaultApiInterface";
     public static final String SKIP_DEFAULT_DELEGATE_INTERFACE = "skipDefaultDelegateInterface";
@@ -141,6 +142,7 @@ public String getDescription() {
     private String title = "OpenAPI Kotlin Spring";
     private boolean useBeanValidation = true;
     @Setter private boolean skipDefaultInterface = false;
+    @Setter private boolean omitDefaultNullValues = false;
     @Setter private boolean skipDefaultApiInterface = false;
     @Setter private boolean skipDefaultDelegateInterface = false;
     @Setter private boolean exceptionHandler = true;
@@ -243,6 +245,7 @@ public KotlinSpringServerCodegen() {
                 "interfaces. If this is set to true service interfaces will also be generated", serviceImplementation);
         addSwitch(USE_BEANVALIDATION, "Use BeanValidation API annotations to validate data types", useBeanValidation);
         addSwitch(SKIP_DEFAULT_INTERFACE, "Whether to skip generation of default implementations for interfaces (Api interfaces or Delegate interfaces depending on the delegatePattern option)", skipDefaultInterface);
+        addSwitch(OMIT_DEFAULT_NULL_VALUES, "Whether to skip default values for data classes", omitDefaultNullValues);
         addSwitch(REACTIVE, "use coroutines for reactive behavior", reactive);
         addSwitch(INTERFACE_ONLY, "Whether to generate only API interface stubs without the server files.", interfaceOnly);
         addSwitch(USE_FEIGN_CLIENT_URL, "Whether to generate Feign client with url parameter.", useFeignClientUrl);
@@ -586,6 +589,11 @@ public void processOpts() {
         }
         writePropertyBack(SKIP_DEFAULT_INTERFACE, skipDefaultInterface);
 
+        if (additionalProperties.containsKey(OMIT_DEFAULT_NULL_VALUES)) {
+            this.setOmitDefaultNullValues(convertPropertyToBoolean(OMIT_DEFAULT_NULL_VALUES));
+        }
+        writePropertyBack(OMIT_DEFAULT_NULL_VALUES, omitDefaultNullValues);
+
         if (additionalProperties.containsKey(REACTIVE)) {
             if (SPRING_CLOUD_LIBRARY.equals(library)) {
                 throw new IllegalArgumentException("Currently, reactive option doesn't supported by Spring Cloud");

modules/openapi-generator/src/main/resources/kotlin-spring/dataClassOptVar.mustache

@@ -3,4 +3,4 @@
     @ApiModelProperty({{#example}}example = "{{#lambdaRemoveLineBreak}}{{#lambdaEscapeInNormalString}}{{{.}}}{{/lambdaEscapeInNormalString}}{{/lambdaRemoveLineBreak}}", {{/example}}{{#isReadOnly}}readOnly = {{{isReadOnly}}}, {{/isReadOnly}}value = "{{{description}}}"){{/swagger1AnnotationLibrary}}{{#deprecated}}
     @Deprecated(message = ""){{/deprecated}}{{#vendorExtensions.x-field-extra-annotation}}
     {{{.}}}{{/vendorExtensions.x-field-extra-annotation}}
-    @get:JsonProperty("{{{baseName}}}"){{#isInherited}} override{{/isInherited}} {{>modelMutable}} {{{name}}}: {{#isEnum}}{{#isArray}}{{baseType}}<{{/isArray}}{{classname}}.{{{nameInPascalCase}}}{{#isArray}}>{{/isArray}}{{/isEnum}}{{^isEnum}}{{{dataType}}}{{/isEnum}}? = {{^defaultValue}}null{{/defaultValue}}{{#defaultValue}}{{^isNumber}}{{{defaultValue}}}{{/isNumber}}{{#isNumber}}{{{dataType}}}("{{{defaultValue}}}"){{/isNumber}}{{/defaultValue}}
+    @get:JsonProperty("{{{baseName}}}"){{#isInherited}} override{{/isInherited}} {{>modelMutable}} {{{name}}}: {{#isEnum}}{{#isArray}}{{baseType}}<{{/isArray}}{{classname}}.{{{nameInPascalCase}}}{{#isArray}}>{{/isArray}}{{/isEnum}}{{^isEnum}}{{{dataType}}}{{/isEnum}}?{{^defaultValue}}{{^omitDefaultNullValues}} = null{{/omitDefaultNullValues}}{{/defaultValue}}{{#defaultValue}} = {{^isNumber}}{{{defaultValue}}}{{/isNumber}}{{#isNumber}}{{{dataType}}}("{{{defaultValue}}}"){{/isNumber}}{{/defaultValue}}

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

@@ -4663,6 +4663,25 @@ public void testSealedResponseInterfacesVoidResponse() throws IOException {
         Assert.assertTrue(petContent.contains(") : CreatePetResponse {") || petContent.contains(") : CreatePetResponse"),
                 "Pet should implement CreatePetResponse");
     }
-}
 
+    @Test
+    public void testOmitDefaultNullValues() throws IOException {
+        File output = Files.createTempDirectory("test").toFile().getCanonicalFile();
+        output.deleteOnExit();
+
+        final KotlinSpringServerCodegen codegen = new KotlinSpringServerCodegen();
+        codegen.setOutputDir(output.getAbsolutePath());
+        codegen.additionalProperties().put(OMIT_DEFAULT_NULL_VALUES, true);
 
+        new DefaultGenerator().opts(new ClientOptInput()
+                        .openAPI(TestUtils.parseFlattenSpec("src/test/resources/3_0/petstore.yaml"))
+                        .config(codegen))
+                .generate();
+
+        // Pet model has optional properties that would normally get "= null" defaults
+        assertFileNotContains(
+                Paths.get(output + "/src/main/kotlin/org/openapitools/model/Pet.kt"),
+                "= null"
+        );
+    }
+}