PreInterruptCallback extension

Added PreInterruptCallback extension to allow to hook into the
@timeout extension before the executing Thread is interrupted.

The default implementation of PreInterruptCallback will simply print
the stacks of all Thread to System.err.
It is disabled by default and must be enabled with:
junit.jupiter.execution.timeout.threaddump.enabled = true

Issue: junit-team#2938

documentation/src/docs/asciidoc/release-notes/release-notes-5.12.0-M1.adoc

@@ -79,6 +79,7 @@ JUnit repository on GitHub.
   a test-scoped `ExtensionContext` in `Extension` methods called during test class
   instantiation. This behavior will become the default in future versions of JUnit.
 * `@TempDir` is now supported on test class constructors.
+* Added `PreInterruptCallback`
 
 
 [[release-notes-5.12.0-M1-junit-vintage]]

documentation/src/docs/asciidoc/user-guide/extensions.adoc

@@ -715,6 +715,21 @@ test methods.
 include::{testDir}/example/exception/MultipleHandlersTestCase.java[tags=user_guide]
 ----
 
+[[extensions-preinterrupt-callback]]
+=== PreInterrupt Callback
+
+`{PreInterruptCallback}` defines the API for `Extensions` that wish to react on
+`Thread.interrupt()` calls issued by Jupiter before the `Thread.interrupt()` is executed.
+
+This can be used to dump stacks for diagnostics, when the `Timeout` extension
+interrupts tests.
+
+There is also a default implementation available, which will dump the stacks of all
+`Threads` to `System.err`.
+This default implementation need to be enabled with the
+<<running-tests-config-params,configuration parameter>>:
+`junit.jupiter.execution.timeout.threaddump.enabled`
+
 [[extensions-intercepting-invocations]]
 === Intercepting Invocations
 

documentation/src/docs/asciidoc/user-guide/writing-tests.adoc

@@ -2658,6 +2658,12 @@ NOTE: If you need more control over polling intervals and greater flexibility wi
 asynchronous tests, consider using a dedicated library such as
 link:https://github.com/awaitility/awaitility[Awaitility].
 
+[[writing-tests-dump-stack-timeout]]
+=== Dump Stacks on Timeout
+
+It can be helpful for debugging to dump the stacks of all Threads, when a Timeout happened.
+The <<extensions-preinterrupt-callback, PreInterruptCallback>> provides a default
+implementation for that.
 
 [[writing-tests-declarative-timeouts-mode]]
 ==== Disable @Timeout Globally

junit-jupiter-api/src/main/java/org/junit/jupiter/api/extension/ExtensionContext.java

@@ -10,6 +10,7 @@
 
 package org.junit.jupiter.api.extension;
 
+import static org.apiguardian.api.API.Status.EXPERIMENTAL;
 import static org.apiguardian.api.API.Status.STABLE;
 
 import java.lang.reflect.AnnotatedElement;
@@ -401,6 +402,17 @@ default void publishReportEntry(String value) {
 	@API(status = STABLE, since = "5.11")
 	ExecutableInvoker getExecutableInvoker();
 
+	/**
+	 * Returns a list of registered extension at this context of the passed {@code extensionType}.
+	 *
+	 * @param <E> the extension type
+	 * @param extensionType the extension type
+	 * @return the list of extensions
+	 * @since 5.12
+	 */
+	@API(status = EXPERIMENTAL, since = "5.12")
+	<E extends Extension> List<E> getExtensions(Class<E> extensionType);
+
 	/**
 	 * {@code Store} provides methods for extensions to save and retrieve data.
 	 */

junit-jupiter-api/src/main/java/org/junit/jupiter/api/extension/PreInterruptCallback.java

@@ -0,0 +1,45 @@
+/*
+ * Copyright 2015-2024 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.jupiter.api.extension;
+
+import static org.apiguardian.api.API.Status.EXPERIMENTAL;
+
+import org.apiguardian.api.API;
+
+/**
+ * {@code PreInterruptCallback} defines the API for {@link Extension
+ * Extensions} that wish to react on {@link Thread#interrupt()} calls issued by Jupiter
+ * before the {@link Thread#interrupt()} is executed.
+ *
+ * <p>This can be used to e.g. dump stacks for diagnostics, when the {@link org.junit.jupiter.api.Timeout}
+ * extension is used.</p>
+ *
+ * <p>There is also a default implementation available, which will dump the stacks of all {@link Thread Threads}
+ * to {@code System.err}. This default implementation need to be enabled with the jupiter property:
+ * {@code junit.jupiter.execution.timeout.threaddump.enabled}
+ *
+ *
+ * @since 5.12
+ * @see org.junit.jupiter.api.Timeout
+ */
+@API(status = EXPERIMENTAL, since = "5.12")
+public interface PreInterruptCallback extends Extension {
+
+	/**
+	 * Callback that is invoked <em>before</em> a {@link Thread} is interrupted with {@link Thread#interrupt()}.
+	 *
+	 * <p>Caution: There is no guarantee on which {@link Thread} this callback will be executed.</p>
+	 *
+	 * @param threadToInterrupt  the target {@link Thread}, which will get interrupted.
+	 * @param context the current extension context; never {@code null}
+	 */
+	void beforeThreadInterrupt(Thread threadToInterrupt, ExtensionContext context) throws Exception;
+}

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

@@ -108,6 +108,17 @@ public final class Constants {
 	 */
 	public static final String EXTENSIONS_AUTODETECTION_ENABLED_PROPERTY_NAME = JupiterConfiguration.EXTENSIONS_AUTODETECTION_ENABLED_PROPERTY_NAME;
 
+	/**
+	 * Property name used to enable the default behavior of {@link org.junit.jupiter.api.extension.PreInterruptCallback}
+	 * extension to print the stacks of all {@link Thread}s to {@code System.err} before the test is interrupted.
+	 *
+	 * <p>The default behavior is not to enable the dump fo threads.
+	 *
+	 * @since 5.12
+	 */
+	@API(status = EXPERIMENTAL, since = "5.12")
+	public static final String EXTENSIONS_TIMEOUT_THREAD_DUMP_ENABLED_PROPERTY_NAME = JupiterConfiguration.EXTENSIONS_TIMEOUT_THREAD_DUMP_ENABLED_PROPERTY_NAME;
+
 	/**
 	 * Property name used to set the default test instance lifecycle mode: {@value}
 	 *
@@ -192,7 +203,6 @@ public final class Constants {
 	 * <p>When set to {@code false} the underlying fork-join pool will reject
 	 * additional tasks if all available workers are busy and the maximum
 	 * pool-size would be exceeded.
-
 	 * <p>Value must either {@code true} or {@code false}; defaults to {@code true}.
 	 *
 	 * <p>Note: This property only takes affect on Java 9+.

junit-jupiter-engine/src/main/java/org/junit/jupiter/engine/config/CachingJupiterConfiguration.java

@@ -68,6 +68,12 @@ public boolean isExtensionAutoDetectionEnabled() {
 			__ -> delegate.isExtensionAutoDetectionEnabled());
 	}
 
+	@Override
+	public boolean isExtensionTimeoutThreadDumpEnabled() {
+		return (boolean) cache.computeIfAbsent(EXTENSIONS_TIMEOUT_THREAD_DUMP_ENABLED_PROPERTY_NAME,
+			__ -> delegate.isExtensionTimeoutThreadDumpEnabled());
+	}
+
 	@Override
 	public ExecutionMode getDefaultExecutionMode() {
 		return (ExecutionMode) cache.computeIfAbsent(DEFAULT_EXECUTION_MODE_PROPERTY_NAME,

junit-jupiter-engine/src/main/java/org/junit/jupiter/engine/config/DefaultJupiterConfiguration.java

@@ -93,6 +93,11 @@ public boolean isExtensionAutoDetectionEnabled() {
 		return configurationParameters.getBoolean(EXTENSIONS_AUTODETECTION_ENABLED_PROPERTY_NAME).orElse(false);
 	}
 
+	@Override
+	public boolean isExtensionTimeoutThreadDumpEnabled() {
+		return configurationParameters.getBoolean(EXTENSIONS_TIMEOUT_THREAD_DUMP_ENABLED_PROPERTY_NAME).orElse(false);
+	}
+
 	@Override
 	public ExecutionMode getDefaultExecutionMode() {
 		return executionModeConverter.get(configurationParameters, DEFAULT_EXECUTION_MODE_PROPERTY_NAME,

junit-jupiter-engine/src/main/java/org/junit/jupiter/engine/config/JupiterConfiguration.java

@@ -40,6 +40,7 @@ public interface JupiterConfiguration {
 	String DEFAULT_EXECUTION_MODE_PROPERTY_NAME = Execution.DEFAULT_EXECUTION_MODE_PROPERTY_NAME;
 	String DEFAULT_CLASSES_EXECUTION_MODE_PROPERTY_NAME = Execution.DEFAULT_CLASSES_EXECUTION_MODE_PROPERTY_NAME;
 	String EXTENSIONS_AUTODETECTION_ENABLED_PROPERTY_NAME = "junit.jupiter.extensions.autodetection.enabled";
+	String EXTENSIONS_TIMEOUT_THREAD_DUMP_ENABLED_PROPERTY_NAME = "junit.jupiter.execution.timeout.threaddump.enabled";
 	String DEFAULT_TEST_INSTANCE_LIFECYCLE_PROPERTY_NAME = TestInstance.Lifecycle.DEFAULT_LIFECYCLE_PROPERTY_NAME;
 	String DEFAULT_DISPLAY_NAME_GENERATOR_PROPERTY_NAME = DisplayNameGenerator.DEFAULT_GENERATOR_PROPERTY_NAME;
 	String DEFAULT_TEST_METHOD_ORDER_PROPERTY_NAME = MethodOrderer.DEFAULT_ORDER_PROPERTY_NAME;
@@ -54,6 +55,8 @@ public interface JupiterConfiguration {
 
 	boolean isExtensionAutoDetectionEnabled();
 
+	boolean isExtensionTimeoutThreadDumpEnabled();
+
 	ExecutionMode getDefaultExecutionMode();
 
 	ExecutionMode getDefaultClassesExecutionMode();

junit-jupiter-engine/src/main/java/org/junit/jupiter/engine/descriptor/AbstractExtensionContext.java

@@ -15,17 +15,20 @@
 
 import java.util.Collections;
 import java.util.LinkedHashSet;
+import java.util.List;
 import java.util.Map;
 import java.util.Optional;
 import java.util.Set;
 import java.util.function.Function;
 
 import org.junit.jupiter.api.extension.ExecutableInvoker;
+import org.junit.jupiter.api.extension.Extension;
 import org.junit.jupiter.api.extension.ExtensionContext;
 import org.junit.jupiter.api.extension.ExtensionContext.Store.CloseableResource;
 import org.junit.jupiter.api.parallel.ExecutionMode;
 import org.junit.jupiter.engine.config.JupiterConfiguration;
 import org.junit.jupiter.engine.execution.NamespaceAwareStore;
+import org.junit.jupiter.engine.extension.ExtensionRegistry;
 import org.junit.platform.commons.JUnitException;
 import org.junit.platform.commons.util.Preconditions;
 import org.junit.platform.engine.EngineExecutionListener;
@@ -53,9 +56,10 @@ abstract class AbstractExtensionContext<T extends TestDescriptor> implements Ext
 	private final JupiterConfiguration configuration;
 	private final NamespacedHierarchicalStore<Namespace> valuesStore;
 	private final ExecutableInvoker executableInvoker;
+	private final ExtensionRegistry extensionRegistry;
 
 	AbstractExtensionContext(ExtensionContext parent, EngineExecutionListener engineExecutionListener, T testDescriptor,
-			JupiterConfiguration configuration,
+			JupiterConfiguration configuration, ExtensionRegistry extensionRegistry,
 			Function<ExtensionContext, ExecutableInvoker> executableInvokerFactory) {
 		this.executableInvoker = executableInvokerFactory.apply(this);
 
@@ -67,6 +71,7 @@ abstract class AbstractExtensionContext<T extends TestDescriptor> implements Ext
 		this.testDescriptor = testDescriptor;
 		this.configuration = configuration;
 		this.valuesStore = createStore(parent);
+		this.extensionRegistry = extensionRegistry;
 
 		// @formatter:off
 		this.tags = testDescriptor.getTags().stream()
@@ -152,6 +157,14 @@ public ExecutableInvoker getExecutableInvoker() {
 		return executableInvoker;
 	}
 
+	@Override
+	public <E extends Extension> List<E> getExtensions(Class<E> extensionType) {
+		if (extensionRegistry == null) {
+			return Collections.emptyList();
+		}
+		return extensionRegistry.getExtensions(extensionType);
+	}
+
 	protected abstract Node.ExecutionMode getPlatformExecutionMode();
 
 	private ExecutionMode toJupiterExecutionMode(Node.ExecutionMode mode) {

junit-jupiter-engine/src/main/java/org/junit/jupiter/engine/descriptor/ClassBasedTestDescriptor.java

@@ -181,8 +181,8 @@ public JupiterEngineExecutionContext prepare(JupiterEngineExecutionContext conte
 
 		ThrowableCollector throwableCollector = createThrowableCollector();
 		ClassExtensionContext extensionContext = new ClassExtensionContext(context.getExtensionContext(),
-			context.getExecutionListener(), this, this.lifecycle, context.getConfiguration(), throwableCollector,
-			it -> new DefaultExecutableInvoker(it, registry));
+			context.getExecutionListener(), this, this.lifecycle, context.getConfiguration(),
+			context.getExtensionRegistry(), throwableCollector, it -> new DefaultExecutableInvoker(it, registry));
 
 		// @formatter:off
 		return context.extend()

junit-jupiter-engine/src/main/java/org/junit/jupiter/engine/descriptor/ClassExtensionContext.java

@@ -20,6 +20,7 @@
 import org.junit.jupiter.api.extension.ExtensionContext;
 import org.junit.jupiter.api.extension.TestInstances;
 import org.junit.jupiter.engine.config.JupiterConfiguration;
+import org.junit.jupiter.engine.extension.ExtensionRegistry;
 import org.junit.platform.engine.EngineExecutionListener;
 import org.junit.platform.engine.support.hierarchical.Node;
 import org.junit.platform.engine.support.hierarchical.ThrowableCollector;
@@ -39,23 +40,24 @@ final class ClassExtensionContext extends AbstractExtensionContext<ClassBasedTes
 	 * Create a new {@code ClassExtensionContext} with {@link Lifecycle#PER_METHOD}.
 	 *
 	 * @see #ClassExtensionContext(ExtensionContext, EngineExecutionListener, ClassBasedTestDescriptor,
-	 * Lifecycle, JupiterConfiguration, ThrowableCollector, Function)
+	 * Lifecycle, JupiterConfiguration, ExtensionRegistry, ThrowableCollector, Function)
 	 */
 	ClassExtensionContext(ExtensionContext parent, EngineExecutionListener engineExecutionListener,
 			ClassBasedTestDescriptor testDescriptor, JupiterConfiguration configuration,
-			ThrowableCollector throwableCollector,
+			ExtensionRegistry extensionRegistry, ThrowableCollector throwableCollector,
 			Function<ExtensionContext, ExecutableInvoker> executableInvokerFactory) {
 
-		this(parent, engineExecutionListener, testDescriptor, Lifecycle.PER_METHOD, configuration, throwableCollector,
-			executableInvokerFactory);
+		this(parent, engineExecutionListener, testDescriptor, Lifecycle.PER_METHOD, configuration, extensionRegistry,
+			throwableCollector, executableInvokerFactory);
 	}
 
 	ClassExtensionContext(ExtensionContext parent, EngineExecutionListener engineExecutionListener,
 			ClassBasedTestDescriptor testDescriptor, Lifecycle lifecycle, JupiterConfiguration configuration,
-			ThrowableCollector throwableCollector,
+			ExtensionRegistry extensionRegistry, ThrowableCollector throwableCollector,
 			Function<ExtensionContext, ExecutableInvoker> executableInvokerFactory) {
 
-		super(parent, engineExecutionListener, testDescriptor, configuration, executableInvokerFactory);
+		super(parent, engineExecutionListener, testDescriptor, configuration, extensionRegistry,
+			executableInvokerFactory);
 
 		this.lifecycle = lifecycle;
 		this.throwableCollector = throwableCollector;

junit-jupiter-engine/src/main/java/org/junit/jupiter/engine/descriptor/DynamicExtensionContext.java

@@ -20,15 +20,18 @@
 import org.junit.jupiter.api.extension.ExtensionContext;
 import org.junit.jupiter.api.extension.TestInstances;
 import org.junit.jupiter.engine.config.JupiterConfiguration;
+import org.junit.jupiter.engine.extension.ExtensionRegistry;
 import org.junit.platform.engine.EngineExecutionListener;
 import org.junit.platform.engine.support.hierarchical.Node;
 
 class DynamicExtensionContext extends AbstractExtensionContext<DynamicNodeTestDescriptor> {
 
 	DynamicExtensionContext(ExtensionContext parent, EngineExecutionListener engineExecutionListener,
 			DynamicNodeTestDescriptor testDescriptor, JupiterConfiguration configuration,
+			ExtensionRegistry extensionRegistry,
 			Function<ExtensionContext, ExecutableInvoker> executableInvokerFactory) {
-		super(parent, engineExecutionListener, testDescriptor, configuration, executableInvokerFactory);
+		super(parent, engineExecutionListener, testDescriptor, configuration, extensionRegistry,
+			executableInvokerFactory);
 	}
 
 	@Override

junit-jupiter-engine/src/main/java/org/junit/jupiter/engine/descriptor/DynamicNodeTestDescriptor.java

@@ -46,7 +46,7 @@ public String getLegacyReportingName() {
 	@Override
 	public JupiterEngineExecutionContext prepare(JupiterEngineExecutionContext context) {
 		DynamicExtensionContext extensionContext = new DynamicExtensionContext(context.getExtensionContext(),
-			context.getExecutionListener(), this, context.getConfiguration(),
+			context.getExecutionListener(), this, context.getConfiguration(), context.getExtensionRegistry(),
 			it -> new DefaultExecutableInvoker(it, context.getExtensionRegistry()));
 		// @formatter:off
 		return context.extend()

junit-jupiter-engine/src/main/java/org/junit/jupiter/engine/descriptor/JupiterEngineDescriptor.java

@@ -53,7 +53,8 @@ public JupiterEngineExecutionContext prepare(JupiterEngineExecutionContext conte
 			context.getConfiguration());
 		EngineExecutionListener executionListener = context.getExecutionListener();
 		ExtensionContext extensionContext = new JupiterEngineExtensionContext(executionListener, this,
-			context.getConfiguration(), it -> new DefaultExecutableInvoker(it, extensionRegistry));
+			context.getConfiguration(), context.getExtensionRegistry(),
+			it -> new DefaultExecutableInvoker(it, extensionRegistry));
 
 		// @formatter:off
 		return context.extend()

junit-jupiter-engine/src/main/java/org/junit/jupiter/engine/descriptor/JupiterEngineExtensionContext.java

@@ -20,6 +20,7 @@
 import org.junit.jupiter.api.extension.ExtensionContext;
 import org.junit.jupiter.api.extension.TestInstances;
 import org.junit.jupiter.engine.config.JupiterConfiguration;
+import org.junit.jupiter.engine.extension.ExtensionRegistry;
 import org.junit.platform.engine.EngineExecutionListener;
 import org.junit.platform.engine.support.hierarchical.Node;
 
@@ -30,9 +31,11 @@ final class JupiterEngineExtensionContext extends AbstractExtensionContext<Jupit
 
 	JupiterEngineExtensionContext(EngineExecutionListener engineExecutionListener,
 			JupiterEngineDescriptor testDescriptor, JupiterConfiguration configuration,
+			ExtensionRegistry extensionRegistry,
 			Function<ExtensionContext, ExecutableInvoker> executableInvokerFactory) {
 
-		super(null, engineExecutionListener, testDescriptor, configuration, executableInvokerFactory);
+		super(null, engineExecutionListener, testDescriptor, configuration, extensionRegistry,
+			executableInvokerFactory);
 	}
 
 	@Override

junit-jupiter-engine/src/main/java/org/junit/jupiter/engine/descriptor/MethodExtensionContext.java

@@ -20,6 +20,7 @@
 import org.junit.jupiter.api.extension.ExtensionContext;
 import org.junit.jupiter.api.extension.TestInstances;
 import org.junit.jupiter.engine.config.JupiterConfiguration;
+import org.junit.jupiter.engine.extension.ExtensionRegistry;
 import org.junit.platform.engine.EngineExecutionListener;
 import org.junit.platform.engine.support.hierarchical.Node;
 import org.junit.platform.engine.support.hierarchical.ThrowableCollector;
@@ -35,10 +36,11 @@ final class MethodExtensionContext extends AbstractExtensionContext<TestMethodTe
 
 	MethodExtensionContext(ExtensionContext parent, EngineExecutionListener engineExecutionListener,
 			TestMethodTestDescriptor testDescriptor, JupiterConfiguration configuration,
-			ThrowableCollector throwableCollector,
+			ExtensionRegistry extensionRegistry, ThrowableCollector throwableCollector,
 			Function<ExtensionContext, ExecutableInvoker> executableInvokerFactory) {
 
-		super(parent, engineExecutionListener, testDescriptor, configuration, executableInvokerFactory);
+		super(parent, engineExecutionListener, testDescriptor, configuration, extensionRegistry,
+			executableInvokerFactory);
 
 		this.throwableCollector = throwableCollector;
 	}

junit-jupiter-engine/src/main/java/org/junit/jupiter/engine/descriptor/TestMethodTestDescriptor.java

@@ -99,8 +99,8 @@ public JupiterEngineExecutionContext prepare(JupiterEngineExecutionContext conte
 		MutableExtensionRegistry registry = populateNewExtensionRegistry(context);
 		ThrowableCollector throwableCollector = createThrowableCollector();
 		MethodExtensionContext extensionContext = new MethodExtensionContext(context.getExtensionContext(),
-			context.getExecutionListener(), this, context.getConfiguration(), throwableCollector,
-			it -> new DefaultExecutableInvoker(it, registry));
+			context.getExecutionListener(), this, context.getConfiguration(), context.getExtensionRegistry(),
+			throwableCollector, it -> new DefaultExecutableInvoker(it, registry));
 		// @formatter:off
 		JupiterEngineExecutionContext newContext = context.extend()
 				.withExtensionRegistry(registry)