Suppress body when handling a no content (204) "error"

Fixes gh-18136

Author: wilkinsona

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/servlet/error/BasicErrorController.java

@@ -94,8 +94,11 @@ public ModelAndView errorHtml(HttpServletRequest request, HttpServletResponse re
 
 	@RequestMapping
 	public ResponseEntity<Map<String, Object>> error(HttpServletRequest request) {
-		Map<String, Object> body = getErrorAttributes(request, isIncludeStackTrace(request, MediaType.ALL));
 		HttpStatus status = getStatus(request);
+		if (status == HttpStatus.NO_CONTENT) {
+			return new ResponseEntity<Map<String, Object>>(status);
+		}
+		Map<String, Object> body = getErrorAttributes(request, isIncludeStackTrace(request, MediaType.ALL));
 		return new ResponseEntity<>(body, status);
 	}
 

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/web/servlet/error/BasicErrorControllerMockMvcTests.java

@@ -92,13 +92,23 @@ public void testDirectAccessForMachineClient() throws Exception {
 	}
 
 	@Test
-	public void testErrorWithResponseStatus() throws Exception {
+	public void testErrorWithNotFoundResponseStatus() throws Exception {
 		MvcResult result = this.mockMvc.perform(get("/bang")).andExpect(status().isNotFound()).andReturn();
 		MvcResult response = this.mockMvc.perform(new ErrorDispatcher(result, "/error")).andReturn();
 		String content = response.getResponse().getContentAsString();
 		assertThat(content).contains("Expected!");
 	}
 
+	@Test
+	public void testErrorWithNoContentResponseStatus() throws Exception {
+		MvcResult result = this.mockMvc.perform(get("/noContent").accept("some/thing"))
+				.andExpect(status().isNoContent()).andReturn();
+		MvcResult response = this.mockMvc.perform(new ErrorDispatcher(result, "/error"))
+				.andExpect(status().isNoContent()).andReturn();
+		String content = response.getResponse().getContentAsString();
+		assertThat(content).isEmpty();
+	}
+
 	@Test
 	public void testBindingExceptionForMachineClient() throws Exception {
 		// In a real server the response is carried over into the error dispatcher, but
@@ -174,6 +184,11 @@ public String bind() throws Exception {
 				throw error;
 			}
 
+			@RequestMapping("/noContent")
+			public void noContent() throws Exception {
+				throw new NoContentException("Expected!");
+			}
+
 		}
 
 	}
@@ -187,6 +202,15 @@ private static class NotFoundException extends RuntimeException {
 
 	}
 
+	@ResponseStatus(HttpStatus.NO_CONTENT)
+	private static class NoContentException extends RuntimeException {
+
+		NoContentException(String string) {
+			super(string);
+		}
+
+	}
+
 	private class ErrorDispatcher implements RequestBuilder {
 
 		private MvcResult result;
@@ -203,6 +227,7 @@ public MockHttpServletRequest buildRequest(ServletContext servletContext) {
 			MockHttpServletRequest request = this.result.getRequest();
 			request.setDispatcherType(DispatcherType.ERROR);
 			request.setRequestURI(this.path);
+			request.setAttribute("javax.servlet.error.status_code", this.result.getResponse().getStatus());
 			return request;
 		}