fix(googleapi): add JSON array support to CheckResponseWithBody (#3075)

fixes: googleapis/gax-go#389

Author: quartzmo

googleapi/googleapi.go

@@ -163,8 +163,7 @@ func CheckResponseWithBody(res *http.Response, body []byte) error {
 		return nil
 	}
 
-	jerr := new(errorReply)
-	err := json.Unmarshal(body, jerr)
+	jerr, err := errorReplyFromBody(body)
 	if err == nil && jerr.Error != nil {
 		if jerr.Error.Code == 0 {
 			jerr.Error.Code = res.StatusCode
@@ -181,6 +180,21 @@ func CheckResponseWithBody(res *http.Response, body []byte) error {
 	}
 }
 
+// errorReplyFromBody attempts to get the error from body. The body
+// may be a JSON object or JSON array, or may be something else.
+func errorReplyFromBody(body []byte) (*errorReply, error) {
+	jerr := new(errorReply)
+	if len(body) > 0 && body[0] == '[' {
+		// Attempt JSON array
+		jsonArr := []*errorReply{jerr}
+		err := json.Unmarshal(body, &jsonArr)
+		return jerr, err
+	}
+	// Attempt JSON object
+	err := json.Unmarshal(body, jerr)
+	return jerr, err
+}
+
 // IsNotModified reports whether err is the result of the
 // server replying with http.StatusNotModified.
 // Such error values are sometimes returned by "Do" methods

googleapi/googleapi_test.go

@@ -312,6 +312,32 @@ Details:
 		},
 		`googleapi: got HTTP response code 500 with body: {"error":{}}`,
 	},
+	{
+		// Case: Error in JSON object in body.
+		&http.Response{
+			StatusCode: http.StatusTooManyRequests,
+		},
+		`{"error":{"code": 429,"message": "Resource has been exhausted (e.g. check quota).","status": "RESOURCE_EXHAUSTED"}}`,
+		&Error{
+			Code:    http.StatusTooManyRequests,
+			Message: "Resource has been exhausted (e.g. check quota).",
+			Body:    `{"error":{"code": 429,"message": "Resource has been exhausted (e.g. check quota).","status": "RESOURCE_EXHAUSTED"}}`,
+		},
+		`googleapi: Error 429: Resource has been exhausted (e.g. check quota).`,
+	},
+	{
+		// Case: Streaming error in JSON array in body.
+		&http.Response{
+			StatusCode: http.StatusTooManyRequests,
+		},
+		`[{"error":{"code": 429,"message": "Resource has been exhausted (e.g. check quota).","status": "RESOURCE_EXHAUSTED"}}]`,
+		&Error{
+			Code:    http.StatusTooManyRequests,
+			Message: "Resource has been exhausted (e.g. check quota).",
+			Body:    `[{"error":{"code": 429,"message": "Resource has been exhausted (e.g. check quota).","status": "RESOURCE_EXHAUSTED"}}]`,
+		},
+		`googleapi: Error 429: Resource has been exhausted (e.g. check quota).`,
+	},
 }
 
 func TestCheckResponse(t *testing.T) {