GH-1513 - Propagate delegate when executor threads are already created

spring-modulith-test/src/main/java/org/springframework/modulith/test/PublishedEventsParameterResolver.java

@@ -26,6 +26,8 @@
 import org.springframework.context.ApplicationEvent;
 import org.springframework.context.ApplicationListener;
 import org.springframework.context.support.AbstractApplicationContext;
+import org.springframework.core.task.TaskDecorator;
+import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;
 import org.springframework.test.context.junit.jupiter.SpringExtension;
 import org.springframework.util.Assert;
 
@@ -38,6 +40,7 @@ class PublishedEventsParameterResolver implements ParameterResolver, AfterEachCa
 
 	private final Function<ExtensionContext, ApplicationContext> lookup;
 	private @Nullable ThreadBoundApplicationListenerAdapter listener;
+	private @Nullable PropagateDelegateFromMainThreadTaskDecorator delegatePropagator;
 
 	PublishedEventsParameterResolver() {
 		this(ctx -> SpringExtension.getApplicationContext(ctx));
@@ -79,6 +82,9 @@ public PublishedEvents resolveParameter(ParameterContext parameterContext, Exten
 		if (listener != null) {
 			listener.registerDelegate(publishedEvents);
 		}
+		if (delegatePropagator != null) {
+			delegatePropagator.publishedEventsListener = publishedEvents;
+		}
 
 		return publishedEvents;
 	}
@@ -106,6 +112,12 @@ private void initializeListener(ExtensionContext extensionContext) {
 
 					return adapter;
 				});
+
+		delegatePropagator = new PropagateDelegateFromMainThreadTaskDecorator(listener);
+		ThreadPoolTaskExecutor taskExecutor = context.getBeanProvider(ThreadPoolTaskExecutor.class).getIfAvailable();
+		if (taskExecutor != null) {
+			taskExecutor.setTaskDecorator(delegatePropagator);
+		}
 	}
 
 	/*
@@ -165,4 +177,31 @@ public void onApplicationEvent(ApplicationEvent event) {
 			}
 		}
 	}
+
+	private static final class PropagateDelegateFromMainThreadTaskDecorator implements TaskDecorator {
+		private final ThreadBoundApplicationListenerAdapter adapter;
+		@Nullable
+		private ApplicationListener<ApplicationEvent> publishedEventsListener;
+
+		PropagateDelegateFromMainThreadTaskDecorator(ThreadBoundApplicationListenerAdapter adapter) {
+			this.adapter = adapter;
+		}
+
+		@Override
+		public Runnable decorate(Runnable task) {
+			return () -> {
+				if (publishedEventsListener == null) {
+					task.run();
+					return;
+				}
+				ApplicationListener<ApplicationEvent> previous = adapter.delegate.get();
+				try {
+					adapter.delegate.set(publishedEventsListener);
+					task.run();
+				} finally {
+					adapter.delegate.set(previous);
+				}
+			};
+		}
+	}
 }

spring-modulith-test/src/test/java/org/springframework/modulith/test/PublishedEventsIntegrationTests.java

@@ -24,11 +24,15 @@
 import lombok.RequiredArgsConstructor;
 
 import org.awaitility.Awaitility;
+import org.junit.jupiter.api.MethodOrderer;
+import org.junit.jupiter.api.Order;
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.TestMethodOrder;
 import org.junit.jupiter.api.extension.ExtendWith;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.boot.test.context.SpringBootTest;
 import org.springframework.context.ApplicationEventPublisher;
+import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;
 
 /**
  * Integration tests for {@link PublishedEvents}.
@@ -38,12 +42,25 @@
 @RequiredArgsConstructor
 @ExtendWith(PublishedEventsExtension.class)
 @SpringBootTest(classes = TestConfiguration.class)
+@TestMethodOrder(MethodOrderer.OrderAnnotation.class)
 class PublishedEventsIntegrationTests {
 
 	@Autowired ApplicationEventPublisher publisher;
 	@Autowired AsyncEventListener listener;
+	@Autowired ThreadPoolTaskExecutor taskExecutor;
+
+	@Test // #1513
+	@Order(1)
+	void initializeTaskThreadsBeforePublishedEventsAreInitialized() {
+		for (int i = 0; i < 20; ++i) {
+			taskExecutor.execute(() -> {
+				// no op
+			});
+		}
+	}
 
 	@Test // #116
+	@Order(2)
 	void capturesEventsTriggeredByAsyncEventListeners(PublishedEvents events) {
 
 		assertThatNoException().isThrownBy(() -> {