Only clear request attribute when different

With this commit, we now make sure that the attributes are not cleared
if they are same as the nested request.

Issue: SPR-17304

spring-webflux/src/main/java/org/springframework/web/reactive/function/server/RouterFunctions.java

@@ -940,8 +940,11 @@ public abstract class RouterFunctions {
 								}
 								return this.routerFunction.route(nestedRequest)
 										.doOnNext(match -> {
-											serverRequest.attributes().clear();
-											serverRequest.attributes().putAll(nestedRequest.attributes());
+											if (nestedRequest != serverRequest) {
+												serverRequest.attributes().clear();
+												serverRequest.attributes()
+														.putAll(nestedRequest.attributes());
+											}
 										});
 							}
 					).orElseGet(Mono::empty);

spring-webflux/src/test/java/org/springframework/web/reactive/function/server/support/DispatcherHandlerIntegrationTests.java

@@ -0,0 +1,96 @@
+/*
+ * Copyright 2002-2018 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.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.web.reactive.function.server.support;
+
+import org.junit.Test;
+import reactor.core.publisher.Mono;
+
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.http.MediaType;
+import org.springframework.http.ResponseEntity;
+import org.springframework.http.server.reactive.AbstractHttpHandlerIntegrationTests;
+import org.springframework.http.server.reactive.HttpHandler;
+import org.springframework.web.client.RestTemplate;
+import org.springframework.web.reactive.DispatcherHandler;
+import org.springframework.web.reactive.config.EnableWebFlux;
+import org.springframework.web.reactive.function.server.RouterFunction;
+import org.springframework.web.reactive.function.server.ServerRequest;
+import org.springframework.web.reactive.function.server.ServerResponse;
+import org.springframework.web.server.adapter.WebHttpHandlerBuilder;
+
+import static org.junit.Assert.*;
+import static org.springframework.web.reactive.function.server.RequestPredicates.accept;
+import static org.springframework.web.reactive.function.server.RouterFunctions.route;
+
+/**
+ * @author Arjen Poutsma
+ */
+public class DispatcherHandlerIntegrationTests extends AbstractHttpHandlerIntegrationTests {
+
+	private final RestTemplate restTemplate = new RestTemplate();
+
+	@Override
+	protected HttpHandler createHttpHandler() {
+		AnnotationConfigApplicationContext wac = new AnnotationConfigApplicationContext();
+		wac.register(TestConfiguration.class);
+		wac.refresh();
+
+		return WebHttpHandlerBuilder.webHandler(new DispatcherHandler(wac)).build();
+	}
+
+	@Test
+	public void nested() {
+		ResponseEntity<String> result = this.restTemplate
+				.getForEntity("http://localhost:" + this.port + "/foo/bar", String.class);
+
+		assertEquals(200, result.getStatusCodeValue());
+	}
+
+
+	@Configuration
+	@EnableWebFlux
+	static class TestConfiguration {
+
+		@Bean
+		public RouterFunction<ServerResponse> router(Handler handler) {
+			return route()
+					.path("/foo", () -> route()
+							.nest(accept(MediaType.APPLICATION_JSON), builder -> builder
+									.GET("/bar", handler::handle))
+							.build())
+					.build();
+		}
+
+		@Bean
+		public Handler handler() {
+			return new Handler();
+		}
+	}
+
+	static class Handler {
+
+		public Mono<ServerResponse> handle(ServerRequest request) {
+			return ServerResponse.ok().build();
+		}
+	}
+
+
+
+
+}