spring-projectsGH-3050: Delegating EH delegates compatibility

Fixes: spring-projects#3050

Correct CommonDelegatingErrorHandler validation for delegates compatibility.

Add documentation stating that delegates must be compatible with default error handler.

Author: antonin-arquey

spring-kafka-docs/src/main/antora/modules/ROOT/pages/kafka/annotation-error-handling.adoc

@@ -351,6 +351,8 @@ This is to cause the transaction to roll back (if transactions are enabled).
 The `CommonDelegatingErrorHandler` can delegate to different error handlers, depending on the exception type.
 For example, you may wish to invoke a `DefaultErrorHandler` for most exceptions, or a `CommonContainerStoppingErrorHandler` for others.
 
+All delegates must share the same compatible properties (`ackAfterHandle`, `seekAfterError` ...).
+
 [[log-eh]]
 == Logging Error Handler
 

spring-kafka/src/main/java/org/springframework/kafka/listener/CommonDelegatingErrorHandler.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2021-2023 the original author or authors.
+ * Copyright 2021-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -65,6 +65,7 @@ public CommonDelegatingErrorHandler(CommonErrorHandler defaultErrorHandler) {
 	 * Set the delegate error handlers; a {@link LinkedHashMap} argument is recommended so
 	 * that the delegates are searched in a known order.
 	 * @param delegates the delegates.
+	 * @throws IllegalArgumentException if any of the delegates is not compatible with the default error handler.
 	 */
 	public void setErrorHandlers(Map<Class<? extends Throwable>, CommonErrorHandler> delegates) {
 		Assert.notNull(delegates, "'delegates' cannot be null");
@@ -109,6 +110,7 @@ public void setAckAfterHandle(boolean ack) {
 	 * Add a delegate to the end of the current collection.
 	 * @param throwable the throwable for this handler.
 	 * @param handler the handler.
+	 * @throws IllegalArgumentException if the handler is not compatible with the default error handler.
 	 */
 	public void addDelegate(Class<? extends Throwable> throwable, CommonErrorHandler handler) {
 		Map<Class<? extends Throwable>, CommonErrorHandler> delegatesToCheck = new LinkedHashMap<>(this.delegates);
@@ -118,13 +120,12 @@ public void addDelegate(Class<? extends Throwable> throwable, CommonErrorHandler
 		this.delegates.putAll(delegatesToCheck);
 	}
 
-	@SuppressWarnings("deprecation")
 	private void checkDelegatesAndUpdateClassifier(Map<Class<? extends Throwable>,
 			CommonErrorHandler> delegatesToCheck) {
 
 		boolean ackAfterHandle = this.defaultErrorHandler.isAckAfterHandle();
 		boolean seeksAfterHandling = this.defaultErrorHandler.seeksAfterHandling();
-		this.delegates.values().forEach(handler -> {
+		delegatesToCheck.values().forEach(handler -> {
 			Assert.isTrue(ackAfterHandle == handler.isAckAfterHandle(),
 					"All delegates must return the same value when calling 'isAckAfterHandle()'");
 			Assert.isTrue(seeksAfterHandling == handler.seeksAfterHandling(),

spring-kafka/src/test/java/org/springframework/kafka/listener/CommonDelegatingErrorHandlerTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2021-2022 the original author or authors.
+ * Copyright 2021-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -17,7 +17,9 @@
 package org.springframework.kafka.listener;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
 import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.BDDMockito.given;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.never;
 import static org.mockito.Mockito.verify;
@@ -173,6 +175,48 @@ void testDefaultDelegateIsApplied() {
 		verify(defaultHandler).handleRemaining(any(), any(), any(), any());
 	}
 
+	@Test
+	void testAddIncompatibleAckAfterHandleDelegate() {
+		var defaultHandler = mock(CommonErrorHandler.class);
+		given(defaultHandler.isAckAfterHandle()).willReturn(true);
+		var delegatingErrorHandler = new CommonDelegatingErrorHandler(defaultHandler);
+		var delegate = mock(CommonErrorHandler.class);
+		given(delegate.isAckAfterHandle()).willReturn(false);
+
+		assertThatThrownBy(() -> delegatingErrorHandler.addDelegate(IllegalStateException.class, delegate))
+				.isInstanceOf(IllegalArgumentException.class)
+				.hasMessage("All delegates must return the same value when calling 'isAckAfterHandle()'");
+	}
+
+	@Test
+	void testAddIncompatibleSeeksAfterHandlingDelegate() {
+		var defaultHandler = mock(CommonErrorHandler.class);
+		given(defaultHandler.seeksAfterHandling()).willReturn(true);
+		var delegatingErrorHandler = new CommonDelegatingErrorHandler(defaultHandler);
+		var delegate = mock(CommonErrorHandler.class);
+		given(delegate.seeksAfterHandling()).willReturn(false);
+
+		assertThatThrownBy(() -> delegatingErrorHandler.addDelegate(IllegalStateException.class, delegate))
+				.isInstanceOf(IllegalArgumentException.class)
+				.hasMessage("All delegates must return the same value when calling 'seeksAfterHandling()'");
+	}
+
+	@Test
+	void testAddMultipleDelegatesWithOneIncompatible() {
+		var defaultHandler = mock(CommonErrorHandler.class);
+		given(defaultHandler.seeksAfterHandling()).willReturn(true);
+		var delegatingErrorHandler = new CommonDelegatingErrorHandler(defaultHandler);
+		var one = mock(CommonErrorHandler.class);
+		given(one.seeksAfterHandling()).willReturn(true);
+		var two = mock(CommonErrorHandler.class);
+		given(one.seeksAfterHandling()).willReturn(false);
+		Map<Class<? extends Throwable>, CommonErrorHandler> delegates = Map.of(IllegalStateException.class, one, IOException.class, two);
+
+		assertThatThrownBy(() -> delegatingErrorHandler.setErrorHandlers(delegates))
+				.isInstanceOf(IllegalArgumentException.class)
+				.hasMessage("All delegates must return the same value when calling 'seeksAfterHandling()'");
+	}
+
 	private Exception wrap(Exception ex) {
 		return new ListenerExecutionFailedException("test", ex);
 	}