Add Func to Read Error

json_response.go

@@ -110,3 +110,18 @@ func ReadResponse(r io.Reader, v interface{}) error {
 _, err := ReadResponsePage(r, v)
 return err
 }
+
+// ReadError attempts to unmarshal JSON-encoded error details from the supplied reader. It returns
+// nil if an error could not be parsed from the response, or if the parsed error was nil.
+func ReadError(r io.Reader) error {
+var u struct {
+Error *Error `json:"error"`
+}
+if err := json.NewDecoder(r).Decode(&u); err != nil {
+return nil
+}
+if u.Error == nil {
+return nil
+}
+return u.Error
+}

json_response_test.go

@@ -284,15 +284,14 @@ func TestReadResponseNil(t *testing.T) {
 }
 
 tests := []struct {
-name string
-r io.Reader
-wantErr bool
-wantValue string
+name string
+r io.Reader
+wantErr bool
 }{
-{"Empty", bytes.NewReader(nil), true, ""},
-{"Nil", getResponseBody(nil), false, "blah"},
-{"Response", getResponseBody(TestStruct{"blah"}), false, "blah"},
-{"Error", getErrorBody("blah", http.StatusNotFound), true, ""},
+{"Empty", bytes.NewReader(nil), true},
+{"Nil", getResponseBody(nil), false},
+{"Response", getResponseBody(TestStruct{"blah"}), false},
+{"Error", getErrorBody("blah", http.StatusNotFound), true},
 }
 for _, tt := range tests {
 t.Run(tt.name, func(t *testing.T) {
@@ -303,3 +302,42 @@ func TestReadResponseNil(t *testing.T) {
 })
 }
 }
+
+func TestReadError(t *testing.T) {
+type TestStruct struct {
+Value string
+}
+
+tests := []struct {
+name string
+r io.Reader
+wantErr bool
+wantMessage string
+wantCode int
+}{
+{"Empty", bytes.NewReader(nil), false, "", 0},
+{"Response", getResponseBody(TestStruct{"blah"}), false, "", 0},
+{"Error", getErrorBody("blah", http.StatusNotFound), true, "blah", http.StatusNotFound},
+}
+for _, tt := range tests {
+t.Run(tt.name, func(t *testing.T) {
+err := ReadError(tt.r)
+if (err != nil) != tt.wantErr {
+t.Errorf("ReadError() error = %v, wantErr %v", err, tt.wantErr)
+}
+
+if err != nil {
+err, ok := err.(*Error)
+if !ok {
+t.Fatal("invalid error type")
+}
+if got, want := err.Message, tt.wantMessage; got != want {
+t.Errorf("got message %v, want %v", got, want)
+}
+if got, want := err.Code, tt.wantCode; got != want {
+t.Errorf("got code %v, want %v", got, want)
+}
+}
+})
+}
+}