httpx.Error response without body (#982)

* httpx.Error support response without body

* fix doc

CONTRIBUTING.md

@@ -90,7 +90,7 @@ After that, run these local verifications before submitting pull request to pred
 fail of continuous integration.
 
 * Format the code with `gofmt`
-* Run the test with data race enabled `go test -race ./…`
+* Run the test with data race enabled `go test -race ./...`
 
 ## Code Review
 

rest/httpx/responses.go

@@ -25,6 +25,11 @@ func Error(w http.ResponseWriter, err error) {
 	}
 
 	code, body := errorHandler(err)
+	if body == nil {
+		w.WriteHeader(code)
+		return
+	}
+
 	e, ok := body.(error)
 	if ok {
 		http.Error(w, e.Error(), code)

rest/httpx/responses_test.go

@@ -28,12 +28,14 @@ func TestError(t *testing.T) {
 		name           string
 		input          string
 		errorHandler   func(error) (int, interface{})
+		expectHaveBody bool
 		expectBody     string
 		expectCode     int
 	}{
 		{
 			name:           "default error handler",
 			input:          body,
+			expectHaveBody: true,
 			expectBody:     body,
 			expectCode:     http.StatusBadRequest,
 		},
@@ -43,6 +45,7 @@ func TestError(t *testing.T) {
 			errorHandler: func(err error) (int, interface{}) {
 				return http.StatusForbidden, err.Error()
 			},
+			expectHaveBody: true,
 			expectBody:     wrappedBody,
 			expectCode:     http.StatusForbidden,
 		},
@@ -52,9 +55,20 @@ func TestError(t *testing.T) {
 			errorHandler: func(err error) (int, interface{}) {
 				return http.StatusForbidden, err
 			},
+			expectHaveBody: true,
 			expectBody:     body,
 			expectCode:     http.StatusForbidden,
 		},
+		{
+			name:  "customized error handler return nil",
+			input: body,
+			errorHandler: func(err error) (int, interface{}) {
+				return http.StatusForbidden, nil
+			},
+			expectHaveBody: false,
+			expectBody:     "",
+			expectCode:     http.StatusForbidden,
+		},
 	}
 
 	for _, test := range tests {
@@ -75,6 +89,7 @@ func TestError(t *testing.T) {
 			}
 			Error(&w, errors.New(test.input))
 			assert.Equal(t, test.expectCode, w.code)
+			assert.Equal(t, test.expectHaveBody, w.haveBody)
 			assert.Equal(t, test.expectBody, strings.TrimSpace(w.builder.String()))
 		})
 	}
@@ -122,6 +137,7 @@ func TestWriteJsonLessWritten(t *testing.T) {
 type tracedResponseWriter struct {
 	headers     map[string][]string
 	builder     strings.Builder
+	haveBody    bool
 	code        int
 	lessWritten bool
 	timeout     bool
@@ -140,6 +156,7 @@ func (w *tracedResponseWriter) Write(bytes []byte) (n int, err error) {
 	if w.lessWritten {
 		n -= 1
 	}
+	w.haveBody = true
 	return
 }