Use nested path variables instead of Servlet's

Remove the overriden pathVariable method from the nested request
wrapper,so that the merged attributes are used instead of the ones
provided by servlet.

Closes gh-26163

Author: poutsma

spring-webmvc/src/main/java/org/springframework/web/servlet/function/RequestPredicates.java

@@ -1040,11 +1040,6 @@ public MultiValueMap<String, Part> multipartData() throws IOException, ServletEx
 			return this.request.multipartData();
 		}
 
-		@Override
-		public String pathVariable(String name) {
-			return this.request.pathVariable(name);
-		}
-
 		@Override
 		@SuppressWarnings("unchecked")
 		public Map<String, String> pathVariables() {

spring-webmvc/src/test/java/org/springframework/web/servlet/function/RouterFunctionsTests.java

@@ -22,6 +22,7 @@
 import org.junit.jupiter.api.Test;
 
 import org.springframework.web.servlet.handler.PathPatternsTestUtils;
+import org.springframework.web.testfixture.servlet.MockHttpServletRequest;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.mockito.BDDMockito.given;
@@ -97,4 +98,20 @@ public void nestNoMatch() {
 		assertThat(resultHandlerFunction.isPresent()).isFalse();
 	}
 
+	@Test
+	public void nestPathVariable() {
+		HandlerFunction<ServerResponse> handlerFunction = request -> ServerResponse.ok().build();
+		RequestPredicate requestPredicate = request -> request.pathVariable("foo").equals("bar");
+		RouterFunction<ServerResponse> nestedFunction = RouterFunctions.route(requestPredicate, handlerFunction);
+
+		RouterFunction<ServerResponse> result = RouterFunctions.nest(RequestPredicates.path("/{foo}"), nestedFunction);
+		assertThat(result).isNotNull();
+
+		MockHttpServletRequest servletRequest = new MockHttpServletRequest("GET", "/bar");
+		ServerRequest request = new DefaultServerRequest(servletRequest, Collections.emptyList());
+		Optional<HandlerFunction<ServerResponse>> resultHandlerFunction = result.route(request);
+		assertThat(resultHandlerFunction.isPresent()).isTrue();
+		assertThat(resultHandlerFunction.get()).isEqualTo(handlerFunction);
+	}
+
 }