[kotlin-spring] Add clientRegistrationId option for declarative HTTP interface (#25013)

Mirror the Java spring generator's clientRegistrationId option (#22726) for
kotlin-spring with library=spring-declarative-http-interface. When set, the
generated interfaces are annotated with @ClientRegistrationId and the
spring-boot-starter-oauth2-client dependency is added to the Spring Boot 4
build files even if the spec declares no security schemes.

The option requires useSpringBoot4=true and is rejected for other libraries,
matching the Java generator. Output is unchanged when it is not set.

Fixes #24936

Author: kdelay

docs/generators/kotlin-spring.md

@@ -27,6 +27,7 @@ These options may be applied as additional-properties (cli) or configOptions (pl
 |autoXSpringPaginated|Automatically add x-spring-paginated to operations that have the given set of pagination query parameters. 'page-size-sort' requires 'page', 'size', and 'sort'; 'page-size' requires only 'page' and 'size' (sort may be absent). Operations with x-spring-paginated explicitly set to false will not be auto-detected. The legacy values 'true' (alias for 'page-size-sort') and 'false' (alias for 'none') are deprecated and will be removed in a future release.|<dl><dt>**none**</dt><dd>Disable auto-detection.</dd><dt>**page-size-sort**</dt><dd>Require 'page', 'size', and 'sort' query parameters.</dd><dt>**page-size**</dt><dd>Require only 'page' and 'size' query parameters.</dd><dt>**true**</dt><dd>(deprecated) alias for 'page-size-sort'.</dd><dt>**false**</dt><dd>(deprecated) alias for 'none'.</dd></dl>|none|
 |basePackage|base package (invokerPackage) for generated code| |org.openapitools|
 |beanQualifiers|Whether to add fully-qualifier class names as bean qualifiers in @Component and @RestController annotations. May be used to prevent bean names clash if multiple generated libraries (contexts) added to single project.| |false|
+|clientRegistrationId|Client registration ID for OAuth2 in Spring HTTP Interface (@ClientRegistrationId annotation). Requires library=spring-declarative-http-interface and useSpringBoot4=true (Spring Security 7).| |null|
 |companionObject|Whether to generate companion objects in data classes, enabling companion extensions.| |false|
 |configPackage|configuration package for generated code| |org.openapitools.configuration|
 |declarativeInterfaceReactiveMode|What type of reactive style to use in Spring Http declarative interface|<dl><dt>**coroutines**</dt><dd>Use kotlin-idiomatic 'suspend' functions</dd><dt>**reactor**</dt><dd>Use reactor return wrappers 'Mono' and 'Flux'</dd></dl>|coroutines|

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

@@ -101,6 +101,7 @@ public class KotlinSpringServerCodegen extends AbstractKotlinCodegen
     public static final String BEAN_QUALIFIERS = "beanQualifiers";
     public static final String USE_RESPONSE_ENTITY = "useResponseEntity";
     public static final String DECLARATIVE_INTERFACE_REACTIVE_MODE = "declarativeInterfaceReactiveMode";
+    public static final String CLIENT_REGISTRATION_ID = "clientRegistrationId";
 
     public static final String USE_SPRING_BOOT3 = "useSpringBoot3";
     public static final String USE_SPRING_BOOT4 = "useSpringBoot4";
@@ -223,6 +224,8 @@ public void setAutoXSpringPaginated(boolean autoXSpringPaginated) {
     protected boolean useSpringBoot4 = false;
     @Getter @Setter
     protected boolean useSpringBuiltInValidation = false;
+    @Getter @Setter
+    protected String clientRegistrationId = null;
     @Setter
     @Getter
     protected RequestMappingMode requestMappingMode = RequestMappingMode.controller;
@@ -426,6 +429,8 @@ public KotlinSpringServerCodegen() {
         }
         cliOptions.add(declarativeInterfaceReactiveModeOpt);
 
+        cliOptions.add(CliOption.newString(CLIENT_REGISTRATION_ID, "Client registration ID for OAuth2 in Spring HTTP Interface (@ClientRegistrationId annotation). Requires library=" + SPRING_DECLARATIVE_HTTP_INTERFACE_LIBRARY + " and useSpringBoot4=true (Spring Security 7)."));
+
         if (null != defaultDocumentationProvider()) {
             CliOption documentationProviderCliOption = new CliOption(DOCUMENTATION_PROVIDER,
                     "Select the OpenAPI documentation provider.")
@@ -601,6 +606,9 @@ public void processOpts() {
         if (additionalProperties.containsKey(USE_SPRING_BOOT4)) {
             this.setUseSpringBoot4(convertPropertyToBoolean(USE_SPRING_BOOT4));
         }
+        if (additionalProperties.containsKey(CLIENT_REGISTRATION_ID)) {
+            this.setClientRegistrationId(additionalProperties.get(CLIENT_REGISTRATION_ID).toString());
+        }
         if (additionalProperties.containsKey(USE_SPRING_BUILT_IN_VALIDATION)) {
             this.setUseSpringBuiltInValidation(convertPropertyToBoolean(USE_SPRING_BUILT_IN_VALIDATION));
             writePropertyBack(USE_SPRING_BUILT_IN_VALIDATION, useSpringBuiltInValidation);
@@ -805,6 +813,17 @@ public void processOpts() {
             writePropertyBack(USE_FEIGN_CLIENT, useFeignClient);
             writePropertyBack(SKIP_DEFAULT_INTERFACE, skipDefaultInterface);
         }
+        if (clientRegistrationId != null && !clientRegistrationId.isEmpty()) {
+            if (!SPRING_DECLARATIVE_HTTP_INTERFACE_LIBRARY.equals(library)) {
+                throw new IllegalArgumentException(CLIENT_REGISTRATION_ID + " is only supported with the " + SPRING_DECLARATIVE_HTTP_INTERFACE_LIBRARY + " library");
+            }
+            if (!isUseSpringBoot4()) {
+                throw new IllegalArgumentException(CLIENT_REGISTRATION_ID + " requires " + USE_SPRING_BOOT4 + "=true because @ClientRegistrationId is provided by Spring Security 7");
+            }
+            additionalProperties.put(CLIENT_REGISTRATION_ID, clientRegistrationId);
+        } else {
+            additionalProperties.remove(CLIENT_REGISTRATION_ID);
+        }
         writePropertyBack(REACTIVE, reactive);
         writePropertyBack(REACTIVE_MULTIPART, reactive && SPRING_BOOT.equals(library));
         writePropertyBack(EXCEPTION_HANDLER, exceptionHandler);

modules/openapi-generator/src/main/resources/kotlin-spring/libraries/spring-declarative-http-interface/apiInterface.mustache

@@ -29,6 +29,9 @@ import io.swagger.annotations.AuthorizationScope
 
 import org.springframework.web.service.annotation.*
 import org.springframework.web.bind.annotation.*
+{{#clientRegistrationId}}
+import org.springframework.security.oauth2.client.annotation.ClientRegistrationId
+{{/clientRegistrationId}}
 {{^useResponseEntity}}
 import org.springframework.http.HttpStatus
 {{/useResponseEntity}}
@@ -55,6 +58,9 @@ import kotlin.collections.Map
 {{#useBeanValidation}}
 @Validated
 {{/useBeanValidation}}
+{{#clientRegistrationId}}
+@ClientRegistrationId("{{{clientRegistrationId}}}")
+{{/clientRegistrationId}}
 {{#operations}}
 interface {{classname}} {
 

modules/openapi-generator/src/main/resources/kotlin-spring/libraries/spring-declarative-http-interface/buildGradle-sb4-Kts.mustache

@@ -67,7 +67,8 @@ dependencies {
 {{/useJackson3}}
 
 {{#hasAuthMethods}}
-    implementation("org.springframework.boot:spring-boot-starter-oauth2-client"){{/hasAuthMethods}}
+    implementation("org.springframework.boot:spring-boot-starter-oauth2-client"){{/hasAuthMethods}}{{^hasAuthMethods}}{{#clientRegistrationId}}
+    implementation("org.springframework.boot:spring-boot-starter-oauth2-client"){{/clientRegistrationId}}{{/hasAuthMethods}}
 
 {{#useBeanValidation}}
     implementation("jakarta.validation:jakarta.validation-api"){{/useBeanValidation}}

modules/openapi-generator/src/main/resources/kotlin-spring/libraries/spring-declarative-http-interface/pom-sb4.mustache

@@ -180,6 +180,14 @@
             <artifactId>spring-boot-starter-oauth2-client</artifactId>
         </dependency>
         {{/hasAuthMethods}}
+        {{^hasAuthMethods}}
+        {{#clientRegistrationId}}
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-oauth2-client</artifactId>
+        </dependency>
+        {{/clientRegistrationId}}
+        {{/hasAuthMethods}}
 {{#useJackson3}}
         <dependency>
             <groupId>{{jacksonPackage}}.dataformat</groupId>

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

@@ -1510,6 +1510,67 @@ public void generateHttpInterfaceRendersOperationExtraAnnotation() throws Except
         );
     }
 
+    @Test
+    public void generateHttpInterfaceWithClientRegistrationId() throws Exception {
+        Map<String, Object> props = new HashMap<>();
+        props.put(USE_SPRING_BOOT4, "true");
+        props.put(CLIENT_REGISTRATION_ID, "my-oauth-client");
+
+        Map<String, File> files = generateFromContract("src/test/resources/3_0/kotlin/petstore.yaml", props, new HashMap<>(),
+                configurator -> configurator.setLibrary(SPRING_DECLARATIVE_HTTP_INTERFACE_LIBRARY));
+
+        Path petApi = files.get("PetApi.kt").toPath();
+        assertFileContains(petApi,
+                "import org.springframework.security.oauth2.client.annotation.ClientRegistrationId",
+                "@ClientRegistrationId(\"my-oauth-client\")\ninterface PetApi {");
+    }
+
+    @Test
+    public void generateHttpInterfaceWithClientRegistrationIdAddsOAuth2ClientDependencyWithoutAuthMethods() throws Exception {
+        Map<String, Object> props = new HashMap<>();
+        props.put(USE_SPRING_BOOT4, "true");
+        props.put(CLIENT_REGISTRATION_ID, "my-oauth-client");
+
+        Map<String, File> files = generateFromContract("src/test/resources/3_0/kotlin/bean-qualifiers.yaml", props, new HashMap<>(),
+                configurator -> configurator.setLibrary(SPRING_DECLARATIVE_HTTP_INTERFACE_LIBRARY));
+
+        assertFileContains(files.get("build.gradle.kts").toPath(),
+                "implementation(\"org.springframework.boot:spring-boot-starter-oauth2-client\")");
+    }
+
+    @Test
+    public void generateHttpInterfaceWithoutClientRegistrationId() throws Exception {
+        Map<String, Object> props = new HashMap<>();
+        props.put(USE_SPRING_BOOT4, "true");
+
+        Map<String, File> files = generateFromContract("src/test/resources/3_0/kotlin/petstore.yaml", props, new HashMap<>(),
+                configurator -> configurator.setLibrary(SPRING_DECLARATIVE_HTTP_INTERFACE_LIBRARY));
+
+        assertFileNotContains(files.get("PetApi.kt").toPath(), "ClientRegistrationId");
+    }
+
+    @Test
+    public void shouldRefuseClientRegistrationIdWithoutSpringBoot4() {
+        Map<String, Object> props = new HashMap<>();
+        props.put(CLIENT_REGISTRATION_ID, "my-oauth-client");
+
+        Assertions.assertThatExceptionOfType(IllegalArgumentException.class)
+                .isThrownBy(() -> generateFromContract("src/test/resources/3_0/kotlin/petstore.yaml", props, new HashMap<>(),
+                        configurator -> configurator.setLibrary(SPRING_DECLARATIVE_HTTP_INTERFACE_LIBRARY)))
+                .withMessageContaining(USE_SPRING_BOOT4);
+    }
+
+    @Test
+    public void shouldRefuseClientRegistrationIdOutsideDeclarativeHttpInterface() {
+        Map<String, Object> props = new HashMap<>();
+        props.put(USE_SPRING_BOOT4, "true");
+        props.put(CLIENT_REGISTRATION_ID, "my-oauth-client");
+
+        Assertions.assertThatExceptionOfType(IllegalArgumentException.class)
+                .isThrownBy(() -> generateFromContract("src/test/resources/3_0/kotlin/petstore.yaml", props))
+                .withMessageContaining(SPRING_DECLARATIVE_HTTP_INTERFACE_LIBRARY);
+    }
+
     @Test
     public void generateHttpInterfaceReactiveWithCoroutinesResponseEntity() throws Exception {
         File output = Files.createTempDirectory("test").toFile().getCanonicalFile();