fix: Remove stranded commas when generating spec with cookies with Retrofit2 (OpenAPITools#24178)

Author: wgfm

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

@@ -955,6 +955,13 @@ public int compare(CodegenParameter one, CodegenParameter another) {
                                 return 0;
                             }
                         });
+
+                        // Retrofit2 has no annotation for cookie parameters, so they cannot be
+                        // expressed in the interface method signature. Drop them so the generated
+                        // interface (and its Javadoc) only references parameters that are actually
+                        // rendered; otherwise the parameter separator logic would emit a dangling
+                        // comma for the omitted parameter.
+                        operation.allParams.removeIf(param -> param.isCookieParam);
                     }
                 }
             }

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

@@ -337,6 +337,44 @@ public void testImportMappingResult() {
                 .content().contains("import java.time.Instant;");
     }
 
+    @Test
+    public void testRetrofit2CookieParamsOmittedFromSignature() {
+        final Path output = newTempFolder();
+        final CodegenConfigurator configurator = new CodegenConfigurator()
+                .setGeneratorName(JAVA_GENERATOR)
+                .setLibrary(JavaClientCodegen.RETROFIT_2)
+                .setInputSpec("src/test/resources/3_0/java/retrofit2-cookie-params.yaml")
+                .setOutputDir(output.toString().replace("\\", "/"));
+
+        List<File> files = new DefaultGenerator().opts(configurator.toClientOptInput()).generate();
+
+        // Retrofit2 has no annotation for cookie parameters, so they are omitted from the
+        // interface method signature. Previously the cookie param was dropped while its
+        // separator comma was kept, producing an uncompilable signature such as
+        // "cookieLast(@Header(...) String xApiVersion, );". validateJavaSourceFiles parses
+        // every generated file, so a stray leading/trailing comma fails the parse here.
+        validateJavaSourceFiles(files);
+
+        Map<String, File> fileMap = files.stream()
+                .collect(Collectors.toMap(File::getName, Function.identity()));
+
+        JavaFileAssert.assertThat(fileMap.get("DefaultApi.java"))
+                // cookie param is last -> no trailing comma, cookie param omitted
+                .assertMethod("cookieLast", "String")
+                .assertParameter("xApiVersion")
+                .toMethod()
+                .toFileAssert()
+                // cookie param is first -> no leading comma, remaining params kept
+                .assertMethod("cookieFirst", "String", "String")
+                .assertParameter("xApiVersion")
+                .toMethod()
+                .assertParameter("filter")
+                .toMethod()
+                .toFileAssert()
+                // only a cookie param -> empty parameter list
+                .assertMethod("cookieOnly");
+    }
+
     @Test
     public void testSupportedSecuritySchemesJersey() {
         final JavaClientCodegen codegen = new JavaClientCodegen();

modules/openapi-generator/src/test/resources/3_0/java/retrofit2-cookie-params.yaml

@@ -0,0 +1,61 @@
+openapi: 3.0.0
+info:
+  title: Retrofit2 cookie params
+  description: >
+    Retrofit2 has no annotation for cookie parameters, so they are omitted from
+    the generated interface method signature. This spec exercises cookie params
+    in various positions to ensure the parameter separator logic never produces
+    an uncompilable signature (e.g. a trailing or leading comma).
+  version: 1.0.0
+paths:
+  /cookie-last:
+    get:
+      operationId: cookieLast
+      parameters:
+        - name: x-api-version
+          in: header
+          required: true
+          schema:
+            type: string
+        - name: JSESSIONID
+          in: cookie
+          required: true
+          schema:
+            type: string
+      responses:
+        '200':
+          description: OK
+  /cookie-first:
+    get:
+      operationId: cookieFirst
+      parameters:
+        - name: JSESSIONID
+          in: cookie
+          required: true
+          schema:
+            type: string
+        - name: x-api-version
+          in: header
+          required: true
+          schema:
+            type: string
+        - name: filter
+          in: query
+          required: true
+          schema:
+            type: string
+      responses:
+        '200':
+          description: OK
+  /cookie-only:
+    get:
+      operationId: cookieOnly
+      parameters:
+        - name: JSESSIONID
+          in: cookie
+          required: true
+          schema:
+            type: string
+      responses:
+        '200':
+          description: OK