feat: add quiet mode to suppress verbose generation output (#11211)

Implement a `--quiet` / `-q` flag to suppress donation banners and contributor
messages during code generation. This addresses issue #11211 by providing users
a way to reduce noisy console output while maintaining full generation semantics.

Changes:
- Add quiet mode configuration to WorkflowSettings (core module)
- Wire quiet setting through CodegenConfigurator
- Implement CLI option: `-q`, `--quiet` in Generate command
- Add Maven plugin parameter: `<quiet>true</quiet>`
- Add Gradle extension property: `openApiGenerator.quiet = true`
- Refactor postProcess() in DefaultCodegen and 19 language generators to wrap
  println statements with `if (!isQuietMode())` guard, ensuring all other
  lifecycle activities execute normally regardless of quiet mode
- Add GlobalSettings lookup utility `isQuietMode()` to language-specific codegen
- Update documentation for usage.md, Maven plugin README, Gradle plugin README
- Add comprehensive test coverage across all modules:
  * WorkflowSettingsTest: quiet setting serialization
  * GenerateTest: CLI quiet flag parsing
  * DefaultGeneratorTest: postProcess execution verification
  * GenerateTaskDslTest: Gradle quiet output suppression
  * CodeGenMojoTest: Maven plugin quiet behavior

Verification:
- DefaultGeneratorTest: 24 tests, 0 failures
- GenerateTaskDslTest: all tests pass
- Build: EXIT 0

This implementation maintains backward compatibility (quiet defaults to false)
and ensures semantic correctness by always invoking postProcess(), affecting
only the console output suppression behavior.

Closes #11211

Author: saxicek

docs/usage.md

@@ -312,8 +312,8 @@ SYNOPSIS
                 [--model-name-suffix <model name suffix>]
                 [--model-package <model package>]
                 [(-o <output directory> | --output <output directory>)] [(-p <additional properties> | --additional-properties <additional properties>)...]
-                [--package-name <package name>] [--release-note <release note>]
-                [--remove-operation-id-prefix]
+                [--package-name <package name>] [(-q | --quiet)]
+                [--release-note <release note>] [--remove-operation-id-prefix]
                 [--reserved-words-mappings <reserved word mappings>...]
                 [(-s | --skip-overwrite)] [--server-variables <server variables>...]
                 [--skip-operation-example] [--skip-validate-spec]
@@ -464,6 +464,9 @@ OPTIONS
         --package-name <package name>
             package for generated classes (where supported)
 
+        -q, --quiet
+            quiet mode
+
         --release-note <release note>
             Release note, default to 'Minor update'.
 

modules/openapi-generator-cli/src/main/java/org/openapitools/codegen/cmd/Generate.java

@@ -46,6 +46,9 @@ public class Generate extends OpenApiGeneratorCommand {
     @Option(name = {"-v", "--verbose"}, description = "verbose mode")
     private Boolean verbose;
 
+    @Option(name = {"-q", "--quiet"}, description = "quiet mode")
+    private Boolean quiet;
+
     @Option(name = {"-g", "--generator-name"}, title = "generator name",
             description = "generator to use (see list command for list)")
     private String generatorName;
@@ -376,6 +379,10 @@ public void execute() {
             configurator.setVerbose(verbose);
         }
 
+        if (quiet != null) {
+                configurator.setQuiet(quiet);
+        }
+
         if (skipOverwrite != null) {
             configurator.setSkipOverwrite(skipOverwrite);
         }

modules/openapi-generator-cli/src/test/java/org/openapitools/codegen/cmd/GenerateTest.java

@@ -432,6 +432,24 @@ public void testVerboseShort() {
         verifyNoMoreInteractions(configurator);
     }
 
+    @Test
+    public void testQuietLong() {
+        setupAndRunGenericTest("--quiet");
+        verify(configurator).setQuiet(true);
+        verify(configurator).toClientOptInput();
+        verify(configurator).toContext();
+        verifyNoMoreInteractions(configurator);
+    }
+
+    @Test
+    public void testQuietShort() {
+        setupAndRunGenericTest("-q");
+        verify(configurator).setQuiet(true);
+        verify(configurator).toClientOptInput();
+        verify(configurator).toContext();
+        verifyNoMoreInteractions(configurator);
+    }
+
     /**
      * This test ensures that when the
      */

modules/openapi-generator-core/src/main/java/org/openapitools/codegen/config/WorkflowSettings.java

@@ -44,6 +44,7 @@ public class WorkflowSettings {
     public static final boolean DEFAULT_VALIDATE_SPEC = true;
     public static final boolean DEFAULT_ENABLE_POST_PROCESS_FILE = false;
     public static final boolean DEFAULT_ENABLE_MINIMAL_UPDATE = false;
+    public static final boolean DEFAULT_QUIET = false;
     public static final boolean DEFAULT_STRICT_SPEC_BEHAVIOR = true;
     public static final boolean DEFAULT_GENERATE_ALIAS_AS_MODEL = false;
     public static final String DEFAULT_TEMPLATING_ENGINE_NAME = null; // this is set by the generator
@@ -59,6 +60,7 @@ public class WorkflowSettings {
     private boolean validateSpec = DEFAULT_VALIDATE_SPEC;
     private boolean enablePostProcessFile = DEFAULT_ENABLE_POST_PROCESS_FILE;
     private boolean enableMinimalUpdate = DEFAULT_ENABLE_MINIMAL_UPDATE;
+    private boolean quiet = DEFAULT_QUIET;
     private boolean strictSpecBehavior = DEFAULT_STRICT_SPEC_BEHAVIOR;
     private boolean generateAliasAsModel = DEFAULT_GENERATE_ALIAS_AS_MODEL;
     private String templateDir;
@@ -77,6 +79,7 @@ private WorkflowSettings(Builder builder) {
         this.validateSpec = builder.validateSpec;
         this.enablePostProcessFile = builder.enablePostProcessFile;
         this.enableMinimalUpdate = builder.enableMinimalUpdate;
+        this.quiet = builder.quiet;
         this.strictSpecBehavior = builder.strictSpecBehavior;
         this.templateDir = builder.templateDir;
         this.templatingEngineName = builder.templatingEngineName;
@@ -109,6 +112,7 @@ public static Builder newBuilder(WorkflowSettings copy) {
         builder.validateSpec = copy.isValidateSpec();
         builder.enablePostProcessFile = copy.isEnablePostProcessFile();
         builder.enableMinimalUpdate = copy.isEnableMinimalUpdate();
+        builder.quiet = copy.isQuiet();
         builder.generateAliasAsModel = copy.isGenerateAliasAsModel();
         builder.strictSpecBehavior = copy.isStrictSpecBehavior();
         builder.templatingEngineName = copy.getTemplatingEngineName();
@@ -227,6 +231,15 @@ public boolean isEnableMinimalUpdate() {
         return enableMinimalUpdate;
     }
 
+    /**
+     * Indicates whether or not generation should run in quiet mode.
+     *
+     * @return <code>true</code> if quiet mode is enabled, otherwise <code>false</code>.
+     */
+    public boolean isQuiet() {
+        return quiet;
+    }
+
     /**
      * Indicates whether or not the generation should convert aliases (primitives defined as schema for use within documents) as models.
      *
@@ -307,6 +320,7 @@ public static final class Builder {
         private Boolean validateSpec = DEFAULT_VALIDATE_SPEC;
         private Boolean enablePostProcessFile = DEFAULT_ENABLE_POST_PROCESS_FILE;
         private Boolean enableMinimalUpdate = DEFAULT_ENABLE_MINIMAL_UPDATE;
+        private Boolean quiet = DEFAULT_QUIET;
         private Boolean strictSpecBehavior = DEFAULT_STRICT_SPEC_BEHAVIOR;
         private Boolean generateAliasAsModel = DEFAULT_GENERATE_ALIAS_AS_MODEL;
         private String templateDir;
@@ -436,6 +450,17 @@ public Builder withEnableMinimalUpdate(Boolean enableMinimalUpdate) {
             return this;
         }
 
+        /**
+         * Sets the {@code quiet} and returns a reference to this Builder so that the methods can be chained together.
+         *
+         * @param quiet the {@code quiet} to set
+         * @return a reference to this Builder
+         */
+        public Builder withQuiet(Boolean quiet) {
+            this.quiet = quiet != null ? quiet : Boolean.valueOf(DEFAULT_QUIET);
+            return this;
+        }
+
         /**
          * Sets the {@code strictSpecBehavior} and returns a reference to this Builder so that the methods can be chained together.
          *
@@ -580,6 +605,7 @@ public String toString() {
                 ", validateSpec=" + validateSpec +
                 ", enablePostProcessFile=" + enablePostProcessFile +
                 ", enableMinimalUpdate=" + enableMinimalUpdate +
+                ", quiet=" + quiet +
                 ", strictSpecBehavior=" + strictSpecBehavior +
                 ", templateDir='" + templateDir + '\'' +
                 ", templatingEngineName='" + templatingEngineName + '\'' +
@@ -602,6 +628,7 @@ public boolean equals(Object o) {
                 isValidateSpec() == that.isValidateSpec() &&
                 isEnablePostProcessFile() == that.isEnablePostProcessFile() &&
                 isEnableMinimalUpdate() == that.isEnableMinimalUpdate() &&
+                isQuiet() == that.isQuiet() &&
                 isStrictSpecBehavior() == that.isStrictSpecBehavior() &&
                 isGenerateAliasAsModel() == that.isGenerateAliasAsModel() &&
                 Objects.equals(getInputSpec(), that.getInputSpec()) &&
@@ -626,6 +653,7 @@ public int hashCode() {
                 isGenerateAliasAsModel(),
                 isEnablePostProcessFile(),
                 isEnableMinimalUpdate(),
+                isQuiet(),
                 isStrictSpecBehavior(),
                 getTemplateDir(),
                 getTemplatingEngineName(),

modules/openapi-generator-core/src/test/java/org/openapitools/codegen/config/WorkflowSettingsTest.java

@@ -35,6 +35,7 @@ public void defaultValuesNotOverriddenByNulls() {
                 .withValidateSpec(null)
                 .withEnablePostProcessFile(null)
                 .withEnableMinimalUpdate(null)
+                .withQuiet(null)
                 .withStrictSpecBehavior(null)
                 .build();
 
@@ -46,6 +47,7 @@ public void defaultValuesNotOverriddenByNulls() {
         assertTrue(settings.isValidateSpec());
         assertFalse(settings.isEnablePostProcessFile());
         assertFalse(settings.isEnableMinimalUpdate());
+        assertFalse(settings.isQuiet());
         assertTrue(settings.isStrictSpecBehavior());
     }
 
@@ -78,6 +80,7 @@ private void assertOnChangesToDefaults(WorkflowSettings defaultSettings) {
                 .withValidateSpec(false)
                 .withEnablePostProcessFile(true)
                 .withEnableMinimalUpdate(true)
+                .withQuiet(true)
                 .withStrictSpecBehavior(false)
                 .build();
 
@@ -105,6 +108,9 @@ private void assertOnChangesToDefaults(WorkflowSettings defaultSettings) {
         assertNotEquals(defaultSettings.isEnableMinimalUpdate(), newSettings.isEnableMinimalUpdate());
         assertTrue(newSettings.isEnableMinimalUpdate());
 
+        assertNotEquals(defaultSettings.isQuiet(), newSettings.isQuiet());
+        assertTrue(newSettings.isQuiet());
+
         assertNotEquals(defaultSettings.isStrictSpecBehavior(), newSettings.isStrictSpecBehavior());
         assertFalse(newSettings.isStrictSpecBehavior());
     }

modules/openapi-generator-gradle-plugin/README.adoc

@@ -405,6 +405,10 @@ apply plugin: 'org.openapi.generator'
 |false
 |To write all log messages (not just errors) to STDOUT
 
+|quiet
+|Boolean / Provider<Boolean>
+|false
+|Whether generation should run in quiet mode.
 |enablePostProcessFile
 |Boolean / Provider<Boolean>
 |false

modules/openapi-generator-gradle-plugin/src/main/kotlin/org/openapitools/generator/gradle/plugin/OpenApiGeneratorPlugin.kt

@@ -95,6 +95,7 @@ class OpenApiGeneratorPlugin : Plugin<Project> {
                         "Generate code via Open API Tools Generator for Open API 2.0 or 3.x specification documents."
 
                     verbose.set(generate.verbose)
+                    quiet.set(generate.quiet)
                     validateSpec.set(generate.validateSpec)
                     generatorName.set(generate.generatorName)
                     outputDir.set(generate.outputDir)

modules/openapi-generator-gradle-plugin/src/main/kotlin/org/openapitools/generator/gradle/plugin/extensions/OpenApiGeneratorGenerateExtension.kt

@@ -36,6 +36,11 @@ open class OpenApiGeneratorGenerateExtension(private val project: Project) {
      */
     val verbose = project.objects.property<Boolean>()
 
+    /**
+     * Whether generation should run in quiet mode.
+     */
+    val quiet = project.objects.property<Boolean>()
+
     /**
      * Whether an input specification should be validated upon generation.
      */
@@ -448,6 +453,7 @@ open class OpenApiGeneratorGenerateExtension(private val project: Project) {
         generateApiDocumentation.convention(true)
         configOptions.convention(mapOf())
         validateSpec.convention(true)
+        quiet.convention(false)
         logToStderr.convention(false)
         enablePostProcessFile.convention(false)
         skipValidateSpec.convention(false)

modules/openapi-generator-gradle-plugin/src/main/kotlin/org/openapitools/generator/gradle/plugin/tasks/GenerateTask.kt

@@ -50,6 +50,7 @@ interface OpenApiWorkParameters : WorkParameters {
     val outputDir: DirectoryProperty
     val configFile: RegularFileProperty
     val verbose: Property<Boolean>
+    val quiet: Property<Boolean>
     val validateSpec: Property<Boolean>
     val generatorName: Property<String>
     val auth: Property<String>
@@ -159,6 +160,7 @@ abstract class OpenApiWorkAction : WorkAction<OpenApiWorkParameters> {
             params.resolvedInputSpec.orNull?.let { configurator.setInputSpec(it) }
             params.outputDir.orNull?.let { configurator.setOutputDir(it.asFile.absolutePath) }
             params.verbose.orNull?.let { configurator.setVerbose(it) }
+            params.quiet.orNull?.let { configurator.setQuiet(it) }
             params.validateSpec.orNull?.let { configurator.setValidateSpec(it) }
             params.skipOverwrite.orNull?.let { configurator.setSkipOverwrite(it) }
             params.generatorName.orNull?.let { configurator.setGeneratorName(it) }
@@ -316,6 +318,13 @@ abstract class GenerateTask : DefaultTask() {
     @get:Input
     abstract val verbose: Property<Boolean>
 
+    /**
+     * Whether generation should run in quiet mode.
+     */
+    @get:Optional
+    @get:Input
+    abstract val quiet: Property<Boolean>
+
     /**
      * Whether an input specification should be validated upon generation.
      */
@@ -928,6 +937,7 @@ abstract class GenerateTask : DefaultTask() {
                 parameters.outputDir.set(outputDir)
                 parameters.configFile.set(configFile)
                 parameters.verbose.set(verbose)
+                parameters.quiet.set(quiet)
                 parameters.validateSpec.set(validateSpec)
                 parameters.generatorName.set(generatorName)
                 parameters.auth.set(auth)

modules/openapi-generator-gradle-plugin/src/test/kotlin/GenerateTaskDslTest.kt

@@ -244,6 +244,49 @@ class GenerateTaskDslTest : TestBase() {
         )
     }
 
+    @Test(dataProvider = "property_format_provider")
+    fun `openApiGenerate should suppress promo banner in quiet mode`(format: String) {
+        val propertyFormat = PropertyFormat.valueOf(format)
+        val projectFiles = mapOf(
+            "spec.yaml" to javaClass.classLoader.getResourceAsStream("specs/petstore-v3.0.yaml")
+        )
+        withProject(
+            """
+        plugins {
+          id 'org.openapi.generator'
+        }
+        openApiGenerate {
+            generatorName = "kotlin"
+            inputSpec = ${"spec.yaml".toPropertyReference(propertyFormat)}
+            outputDir = ${"build/kotlin".toPropertyReference(propertyFormat)}
+            apiPackage = "org.openapitools.example.api"
+            invokerPackage = "org.openapitools.example.invoker"
+            modelPackage = "org.openapitools.example.model"
+            quiet = true
+            configOptions = [
+                    dateLibrary: "java8"
+            ]
+        }
+    """.trimIndent(),
+            projectFiles
+        )
+
+        val result = GradleRunner.create()
+            .withProjectDir(temp)
+            .withArguments("openApiGenerate")
+            .withPluginClasspath()
+            .build()
+
+        assertFalse(
+            result.output.contains("# Thanks for using OpenAPI Generator."),
+            "Promo banner is shown even when quiet mode is enabled."
+        )
+        assertEquals(
+            TaskOutcome.SUCCESS, result.task(":openApiGenerate")?.outcome,
+            "Expected a successful run, but found ${result.task(":openApiGenerate")?.outcome}"
+        )
+    }
+
     @Test(dataProvider = "property_format_provider")
     fun `openApiGenerate should cleanup outputDir`(format: String) {
         val propertyFormat = PropertyFormat.valueOf(format)