Generate configuration parameters overview

build.gradle.kts

@@ -18,6 +18,8 @@ extra["license"] = License(
 val mavenizedProjects = listOf(
 	projects.junitStart,
 	projects.junitPlatformCommons,
+	projects.junitPlatformConfigurationApi,
+	projects.junitPlatformConfigurationProcessor,
 	projects.junitPlatformConsole,
 	projects.junitPlatformConsoleStandalone,
 	projects.junitPlatformEngine,

junit-jupiter-api/junit-jupiter-api.gradle.kts

@@ -9,6 +9,8 @@ plugins {
 description = "JUnit Jupiter API"
 
 dependencies {
+	annotationProcessor(projects.junitPlatformConfigurationProcessor)
+
 	api(platform(projects.junitBom))
 	api(libs.opentest4j)
 	api(projects.junitPlatformCommons)
@@ -17,6 +19,7 @@ dependencies {
 	compileOnlyApi(libs.jspecify)
 
 	compileOnly(kotlin("stdlib"))
+	compileOnly(projects.junitPlatformConfigurationApi)
 
 	testFixturesImplementation(libs.assertj)
 	testFixturesImplementation(testFixtures(projects.junitPlatformCommons))
@@ -35,7 +38,7 @@ eclipseConventions {
 
 tasks {
 	compileJava {
-		options.compilerArgs.add("-Xlint:-module") // due to qualified exports
+		options.compilerArgs.add("-Xlint:-module,-processing") // -module: due to qualified exports, -processing: not all annotations need to be processed
 	}
 	jar {
 		bundle {

junit-jupiter-api/src/main/java/module-info.java

@@ -21,6 +21,7 @@
 	requires transitive org.junit.platform.commons;
 	requires transitive org.opentest4j;
 
+	requires static org.junit.platform.configuration.api;
 	requires static kotlin.stdlib;
 
 	exports org.junit.jupiter.api;

junit-jupiter-api/src/main/java/org/junit/jupiter/api/Constants.java

@@ -20,6 +20,7 @@
 import org.junit.jupiter.api.io.CleanupMode;
 import org.junit.jupiter.api.io.TempDir;
 import org.junit.jupiter.api.parallel.Execution;
+import org.junit.platform.configuration.api.ConfigurationProperty;
 
 /**
  * Collection of configuration constants for the Jupiter test engine.
@@ -64,6 +65,7 @@ public final class Constants {
 	 *
 	 * <p>Note: A class that matches both an inclusion and exclusion pattern will be excluded.
 	 */
+	@ConfigurationProperty
 	public static final String EXTENSIONS_AUTODETECTION_INCLUDE_PROPERTY_NAME = "junit.jupiter.extensions.autodetection.include";
 
 	/**

junit-platform-configuration-api/junit-platform-configuration-api.gradle.kts

@@ -0,0 +1,17 @@
+plugins {
+	id("junitbuild.java-library-conventions")
+}
+
+description = "JUnit Platform Configuration API"
+
+dependencies {
+	api(platform(projects.junitBom))
+	api(projects.junitPlatformCommons)
+
+	compileOnlyApi(libs.apiguardian)
+	compileOnlyApi(libs.jspecify)
+}
+
+backwardCompatibilityChecks {
+	enabled = false // not yet released
+}

junit-platform-configuration-api/src/main/java/module-info.java

@@ -0,0 +1,16 @@
+/*
+ * Copyright 2015-2026 the original author or authors.
+ *
+ * All rights reserved. This program and the accompanying materials are
+ * made available under the terms of the Eclipse Public License v2.0 which
+ * accompanies this distribution and is available at
+ *
+ * https://www.eclipse.org/legal/epl-v20.html
+ */
+
+module org.junit.platform.configuration.api {
+	requires static transitive org.jspecify;
+	requires static transitive org.apiguardian.api;
+
+	exports org.junit.platform.configuration.api;
+}

junit-platform-configuration-api/src/main/java/org/junit/platform/configuration/api/ConfigurationProperty.java

@@ -0,0 +1,24 @@
+/*
+ * Copyright 2026 the original author or authors.
+ *
+ * All rights reserved. This program and the accompanying materials are
+ * made available under the terms of the Eclipse Public License v2.0 which
+ * accompanies this distribution and is available at
+ *
+ * https://www.eclipse.org/legal/epl-v20.html
+ */
+
+package org.junit.platform.configuration.api;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+import org.apiguardian.api.API;
+
+@API(status = API.Status.EXPERIMENTAL)
+@Retention(RetentionPolicy.SOURCE)
+@Target(ElementType.FIELD)
+public @interface ConfigurationProperty {
+}

junit-platform-configuration-api/src/main/java/org/junit/platform/configuration/api/package-info.java

@@ -0,0 +1,14 @@
+/*
+ * Copyright 2012 the original author or authors.
+ *
+ * All rights reserved. This program and the accompanying materials are
+ * made available under the terms of the Eclipse Public License v2.0 which
+ * accompanies this distribution and is available at
+ *
+ * https://www.eclipse.org/legal/epl-v20.html
+ */
+
+@NullMarked
+package org.junit.platform.configuration.api;
+
+import org.jspecify.annotations.NullMarked;

junit-platform-configuration-processor/junit-platform-configuration-processor.gradle.kts

@@ -0,0 +1,18 @@
+plugins {
+	id("junitbuild.java-library-conventions")
+}
+
+description = "JUnit Platform Configuration Processor"
+
+dependencies {
+	api(platform(projects.junitBom))
+	api(projects.junitPlatformConfigurationApi)
+	api(projects.junitPlatformCommons)
+
+	compileOnlyApi(libs.apiguardian)
+	compileOnlyApi(libs.jspecify)
+}
+
+backwardCompatibilityChecks {
+	enabled = false // not yet released
+}

junit-platform-configuration-processor/src/main/java/module-info.java

@@ -0,0 +1,19 @@
+/*
+ * Copyright 2015-2026 the original author or authors.
+ *
+ * All rights reserved. This program and the accompanying materials are
+ * made available under the terms of the Eclipse Public License v2.0 which
+ * accompanies this distribution and is available at
+ *
+ * https://www.eclipse.org/legal/epl-v20.html
+ */
+
+module org.junit.platform.configuration.processor {
+	requires static transitive org.jspecify;
+	requires static transitive org.apiguardian.api;
+
+	requires java.compiler;
+	requires org.junit.platform.configuration.api;
+
+	provides javax.annotation.processing.Processor with org.junit.platform.configuration.processor.ConfigurationMetadataAnnotationProcessor;
+}

junit-platform-configuration-processor/src/main/java/org/junit/platform/configuration/processor/ConfigurationMetadataAnnotationProcessor.java

@@ -0,0 +1,59 @@
+/*
+ * Copyright 2026 the original author or authors.
+ *
+ * All rights reserved. This program and the accompanying materials are
+ * made available under the terms of the Eclipse Public License v2.0 which
+ * accompanies this distribution and is available at
+ *
+ * https://www.eclipse.org/legal/epl-v20.html
+ */
+
+package org.junit.platform.configuration.processor;
+
+import static java.util.Objects.requireNonNull;
+
+import java.nio.charset.StandardCharsets;
+import java.util.Set;
+
+import javax.annotation.processing.AbstractProcessor;
+import javax.annotation.processing.ProcessingEnvironment;
+import javax.annotation.processing.RoundEnvironment;
+import javax.annotation.processing.SupportedAnnotationTypes;
+import javax.annotation.processing.SupportedSourceVersion;
+import javax.lang.model.SourceVersion;
+import javax.lang.model.element.TypeElement;
+import javax.tools.StandardLocation;
+
+import org.apiguardian.api.API;
+import org.jspecify.annotations.Nullable;
+
+@API(status = API.Status.EXPERIMENTAL)
+@SupportedSourceVersion(SourceVersion.RELEASE_17)
+@SupportedAnnotationTypes("org.junit.platform.configuration.api.ConfigurationProperty")
+public class ConfigurationMetadataAnnotationProcessor extends AbstractProcessor {
+	private static final String METADATA_PATH = "META-INF/junit-platform-configuration-metadata.json";
+	private @Nullable ProcessingEnvironment environment;
+
+	@Override
+	public synchronized void init(ProcessingEnvironment environment) {
+		super.init(environment);
+		this.environment = environment;
+	}
+
+	@Override
+	public boolean process(Set<? extends TypeElement> annotations, RoundEnvironment roundEnv) {
+		if (roundEnv.processingOver()) {
+			try {
+				var resource = requireNonNull(environment).getFiler().createResource(StandardLocation.CLASS_OUTPUT, "",
+					METADATA_PATH);
+				try (var out = resource.openOutputStream()) {
+					out.write("{}".getBytes(StandardCharsets.UTF_8));
+				}
+			}
+			catch (Exception ex) {
+				throw new IllegalStateException("Failed to write metadata", ex);
+			}
+		}
+		return false;
+	}
+}

junit-platform-configuration-processor/src/main/java/org/junit/platform/configuration/processor/package-info.java

@@ -0,0 +1,14 @@
+/*
+ * Copyright 2012 the original author or authors.
+ *
+ * All rights reserved. This program and the accompanying materials are
+ * made available under the terms of the Eclipse Public License v2.0 which
+ * accompanies this distribution and is available at
+ *
+ * https://www.eclipse.org/legal/epl-v20.html
+ */
+
+@NullMarked
+package org.junit.platform.configuration.processor;
+
+import org.jspecify.annotations.NullMarked;

junit-platform-configuration-processor/src/main/resources/META-INF/gradle/incremental.annotation.processors

@@ -0,0 +1 @@
+org.junit.platform.configuration.processor.ConfigurationMetadataAnnotationProcessor,aggregating

junit-platform-configuration-processor/src/main/resources/META-INF/services/javax.annotation.processing.Processor

@@ -0,0 +1 @@
+org.junit.platform.configuration.processor.ConfigurationMetadataAnnotationProcessor

junit-platform-console-standalone/junit-platform-console-standalone.gradle.kts

@@ -58,6 +58,8 @@ tasks {
 		// https://github.com/junit-team/junit-framework/issues/2557
 		// exclude compiled module declarations from any source (e.g. /*, /META-INF/versions/N/*)
 		exclude("**/module-info.class")
+		// TODO: merge meta data files?
+		exclude("META-INF/junit-platform-configuration-metadata.json")
 		// https://github.com/junit-team/junit-framework/issues/761
 		// prevent duplicates, add 3rd-party licenses explicitly
 		exclude("**/COPYRIGHT*")

junit-platform-launcher/junit-platform-launcher.gradle.kts

@@ -6,12 +6,16 @@ plugins {
 description = "JUnit Platform Launcher"
 
 dependencies {
+	annotationProcessor(projects.junitPlatformConfigurationProcessor)
+
 	api(platform(projects.junitBom))
 	api(projects.junitPlatformEngine)
 
 	compileOnlyApi(libs.apiguardian)
 	compileOnlyApi(libs.jspecify)
 
+	compileOnly(projects.junitPlatformConfigurationApi)
+
 	osgiVerification(projects.junitJupiterEngine)
 }
 
@@ -20,6 +24,9 @@ javadocConventions {
 }
 
 tasks {
+	compileJava {
+		options.compilerArgs.add("-Xlint:-processing") // -processing: not all annotations need to be processed
+	}
 	jar {
 		bundle {
 			bnd("""

junit-platform-launcher/src/main/java/module-info.java

@@ -25,6 +25,8 @@
 
 	requires static transitive org.apiguardian.api;
 	requires static transitive org.jspecify;
+
+	requires static org.junit.platform.configuration.api;
 	requires static jdk.jfr;
 
 	requires transitive java.logging;

junit-platform-launcher/src/main/java/org/junit/platform/launcher/LauncherConstants.java

@@ -16,6 +16,7 @@
 
 import org.apiguardian.api.API;
 import org.junit.platform.commons.util.ClassNamePatternFilterUtils;
+import org.junit.platform.configuration.api.ConfigurationProperty;
 import org.junit.platform.engine.EngineDiscoveryRequest;
 import org.junit.platform.engine.TestDescriptor;
 import org.junit.platform.engine.reporting.ReportEntry;
@@ -44,6 +45,7 @@ public class LauncherConstants {
 	 * @see ReportEntry
 	 * @see TestExecutionListener#reportingEntryPublished(TestIdentifier, ReportEntry)
 	 */
+	@ConfigurationProperty
 	public static final String CAPTURE_STDOUT_PROPERTY_NAME = "junit.platform.output.capture.stdout";
 
 	/**

junit-platform-launcher/src/main/java/org/junit/platform/launcher/core/ClasspathAlignmentChecker.java

@@ -37,6 +37,8 @@ class ClasspathAlignmentChecker {
 		"org.junit.jupiter.params", //
 		"org.junit.platform.commons", //
 		"org.junit.platform.console", //
+		"org.junit.platform.configuration.api", //
+		"org.junit.platform.configuration.processor", //
 		"org.junit.platform.engine", //
 		"org.junit.platform.launcher", //
 		"org.junit.platform.reporting", //

junit-vintage-engine/junit-vintage-engine.gradle.kts

@@ -9,13 +9,17 @@ plugins {
 description = "JUnit Vintage Engine"
 
 dependencies {
+	annotationProcessor(projects.junitPlatformConfigurationProcessor)
+
 	api(platform(projects.junitBom))
 	api(projects.junitPlatformEngine)
 	api(libs.junit4)
 
 	compileOnlyApi(libs.apiguardian)
 	compileOnlyApi(libs.jspecify)
 
+	compileOnly(projects.junitPlatformConfigurationApi)
+
 	testFixturesApi(platform(libs.groovy2.bom))
 	testFixturesApi(libs.spock1)
 	testFixturesImplementation(projects.junitPlatformSuiteApi)
@@ -33,7 +37,7 @@ dependencies {
 
 tasks {
 	compileJava {
-		options.compilerArgs.add("-Xlint:-requires-automatic") // JUnit 4
+		options.compilerArgs.add("-Xlint:-requires-automatic,-processing") // -requires-automatic: JUnit 4, -module: due to qualified exports, -processing: not all annotations need to be processed
 	}
 	compileTestFixturesGroovy {
 		javaLauncher = project.javaToolchains.launcherFor {

junit-vintage-engine/src/main/java/module-info.java

@@ -20,6 +20,7 @@
 module org.junit.vintage.engine {
 
 	requires static org.apiguardian.api;
+	requires static org.junit.platform.configuration.api;
 	requires static transitive org.jspecify;
 
 	requires junit; // 4

junit-vintage-engine/src/main/java/org/junit/vintage/engine/Constants.java

@@ -14,6 +14,7 @@
 import static org.apiguardian.api.API.Status.MAINTAINED;
 
 import org.apiguardian.api.API;
+import org.junit.platform.configuration.api.ConfigurationProperty;
 
 /**
  * Collection of constants related to the {@link VintageTestEngine}.
@@ -34,6 +35,7 @@ public final class Constants {
 	 * @since 5.12
 	 */
 	@API(status = MAINTAINED, since = "5.13.3")
+	@ConfigurationProperty
 	public static final String PARALLEL_EXECUTION_ENABLED = "junit.vintage.execution.parallel.enabled";
 
 	/**

platform-tooling-support-tests/projects/jar-describe-module/junit-jupiter-api.expected.txt

@@ -12,6 +12,7 @@ requires kotlin.stdlib static
 requires org.apiguardian.api static transitive
 requires org.jspecify static transitive
 requires org.junit.platform.commons transitive
+requires org.junit.platform.configuration.api static
 requires org.opentest4j transitive
 qualified exports org.junit.jupiter.api.timeout to org.junit.jupiter.engine
 qualified opens org.junit.jupiter.api.condition to org.junit.platform.commons

platform-tooling-support-tests/projects/jar-describe-module/junit-platform-configuration-api.expected.txt

@@ -0,0 +1,5 @@
+org.junit.platform.configuration.api@${version} jar:file:.+/junit-platform-configuration-api-\d.+\.jar..module-info\.class
+exports org.junit.platform.configuration.api
+requires java.base mandated
+requires org.apiguardian.api static transitive
+requires org.jspecify static transitive

platform-tooling-support-tests/projects/jar-describe-module/junit-platform-configuration-processor.expected.txt

@@ -0,0 +1,8 @@
+org.junit.platform.configuration.processor@${version} jar:file:.+/junit-platform-configuration-processor-\d.+\.jar..module-info\.class
+requires java.base mandated
+requires java.compiler
+requires org.apiguardian.api static transitive
+requires org.jspecify static transitive
+requires org.junit.platform.configuration.api
+provides javax.annotation.processing.Processor with org.junit.platform.configuration.processor.ConfigurationMetadataAnnotationProcessor
+contains org.junit.platform.configuration.processor