GH-1021: Fix @SendTo after error is handled

Fixes https://github.com/spring-projects/spring-amqp/issues/1021

Sending the result from a `RabbitListenerErrorHandler` was broken
for class-level `@RabbitListener` because the send to expression
was lost.

**cherry-pick to 2.1.x**

* * Also capture the generic return type after the error is handled

spring-rabbit/src/main/java/org/springframework/amqp/rabbit/listener/adapter/DelegatingInvocableHandler.java

@@ -272,4 +272,14 @@ public class DelegatingInvocableHandler {
 		return this.defaultHandler != null;
 	}
 
+	@Nullable
+	public InvocationResult getInvocationResultFor(Object result, Object inboundPayload) {
+		InvocableHandlerMethod handler = findHandlerForPayload(inboundPayload.getClass());
+		if (handler != null) {
+			return new InvocationResult(result, this.handlerSendTo.get(handler),
+					handler.getMethod().getGenericReturnType());
+		}
+		return null;
+	}
+
 }

spring-rabbit/src/main/java/org/springframework/amqp/rabbit/listener/adapter/HandlerAdapter.java

@@ -16,6 +16,7 @@
 
 package org.springframework.amqp.rabbit.listener.adapter;
 
+import org.springframework.lang.Nullable;
 import org.springframework.messaging.Message;
 import org.springframework.messaging.handler.invocation.InvocableHandlerMethod;
 
@@ -94,5 +95,14 @@ public class HandlerAdapter {
 		}
 	}
 
+	@Nullable
+	public InvocationResult getInvocationResultFor(Object result, Object inboundPayload) {
+		if (this.invokerHandlerMethod != null) {
+			return new InvocationResult(result, null, this.invokerHandlerMethod.getMethod().getGenericReturnType());
+		}
+		else {
+			return this.delegatingHandler.getInvocationResultFor(result, inboundPayload);
+		}
+	}
 
 }

spring-rabbit/src/main/java/org/springframework/amqp/rabbit/listener/adapter/MessagingMessageListenerAdapter.java

@@ -149,7 +149,8 @@ public class MessagingMessageListenerAdapter extends AbstractAdaptableMessageLis
 							.build();
 					Object errorResult = this.errorHandler.handleError(amqpMessage, message, e);
 					if (errorResult != null) {
-						handleResult(new InvocationResult(errorResult, null, null), amqpMessage, channel, message);
+						handleResult(this.handlerAdapter.getInvocationResultFor(errorResult, message.getPayload()),
+								amqpMessage, channel, message);
 					}
 					else {
 						logger.trace("Error handler returned no result");

spring-rabbit/src/test/java/org/springframework/amqp/rabbit/annotation/EnableRabbitIntegrationTests.java

@@ -345,6 +345,11 @@ public class EnableRabbitIntegrationTests {
 		rabbitTemplate.convertAndSend("multi.exch", "multi.rk", bar);
 		rabbitTemplate.setReceiveTimeout(10000);
 		assertThat(this.rabbitTemplate.receiveAndConvert("sendTo.replies")).isEqualTo("BAR: bar");
+		bar.field = "crash";
+		rabbitTemplate.convertAndSend("multi.exch", "multi.rk", bar);
+		assertThat(this.rabbitTemplate.receiveAndConvert("sendTo.replies"))
+			.isEqualTo("CRASHCRASH Test reply from error handler");
+		bar.field = "bar";
 		Baz baz = new Baz();
 		baz.field = "baz";
 		assertThat(rabbitTemplate.convertSendAndReceive("multi.exch", "multi.rk", baz)).isEqualTo("BAZ: baz");
@@ -1550,14 +1555,22 @@ public class EnableRabbitIntegrationTests {
 
 		@Bean
 		public RabbitListenerErrorHandler alwaysBARHandler() {
-			return (m, sm, e) -> "BAR";
+			return (msg, springMsg, ex) -> "BAR";
+		}
+
+		@Bean
+		public RabbitListenerErrorHandler upcaseAndRepeatErrorHandler() {
+			return (msg, springMsg, ex) -> {
+				String payload = ((Bar) springMsg.getPayload()).field.toUpperCase();
+				return payload + payload + " " + ex.getCause().getMessage();
+ 			};
 		}
 
 		@Bean
 		public RabbitListenerErrorHandler throwANewException() {
-			return (m, sm, e) -> {
-				this.errorHandlerChannel = sm.getHeaders().get(AmqpHeaders.CHANNEL, Channel.class);
-				throw new RuntimeException("from error handler", e.getCause());
+			return (msg, springMsg, ex) -> {
+				this.errorHandlerChannel = springMsg.getHeaders().get(AmqpHeaders.CHANNEL, Channel.class);
+				throw new RuntimeException("from error handler", ex.getCause());
 			};
 		}
 
@@ -1637,7 +1650,7 @@ public class EnableRabbitIntegrationTests {
 
 		@Bean
 		public org.springframework.amqp.core.Queue sendToReplies() {
-			return new org.springframework.amqp.core.Queue(sendToRepliesBean(), false, false, true);
+			return new org.springframework.amqp.core.Queue(sendToRepliesBean(), false, false, false);
 		}
 
 		@Bean
@@ -1672,12 +1685,15 @@ public class EnableRabbitIntegrationTests {
 	@RabbitListener(bindings = @QueueBinding
 			(value = @Queue,
 					exchange = @Exchange(value = "multi.exch", autoDelete = "true"),
-					key = "multi.rk"))
+					key = "multi.rk"), errorHandler = "upcaseAndRepeatErrorHandler")
 	static class MultiListenerBean {
 
 		@RabbitHandler
 		@SendTo("${foo.bar:#{sendToRepliesBean}}")
 		public String bar(@NonNull Bar bar) {
+			if (bar.field.equals("crash")) {
+				throw new RuntimeException("Test reply from error handler");
+			}
 			return "BAR: " + bar.field;
 		}