feat: add error helper that does not read the response body

googleapi/googleapi.go

@@ -145,22 +145,40 @@ func CheckResponse(res *http.Response) error {
 	}
 	slurp, err := io.ReadAll(res.Body)
 	if err == nil {
-		jerr := new(errorReply)
-		err = json.Unmarshal(slurp, jerr)
-		if err == nil && jerr.Error != nil {
-			if jerr.Error.Code == 0 {
-				jerr.Error.Code = res.StatusCode
-			}
-			jerr.Error.Body = string(slurp)
-			jerr.Error.Header = res.Header
-			return jerr.Error
-		}
+		return CheckResponseWithBody(res, slurp)
 	}
 	return &Error{
 		Code:   res.StatusCode,
 		Body:   string(slurp),
 		Header: res.Header,
 	}
+
+}
+
+// CheckResponseWithBody returns an error (of type *Error) if the response
+// status code is not 2xx. Distinct from CheckResponse to allow for checking
+// a previously-read body to maintain error detail content.
+func CheckResponseWithBody(res *http.Response, body []byte) error {
+	if res.StatusCode >= 200 && res.StatusCode <= 299 {
+		return nil
+	}
+
+	jerr := new(errorReply)
+	err := json.Unmarshal(body, jerr)
+	if err == nil && jerr.Error != nil {
+		if jerr.Error.Code == 0 {
+			jerr.Error.Code = res.StatusCode
+		}
+		jerr.Error.Body = string(body)
+		jerr.Error.Header = res.Header
+		return jerr.Error
+	}
+
+	return &Error{
+		Code:   res.StatusCode,
+		Body:   string(body),
+		Header: res.Header,
+	}
 }
 
 // IsNotModified reports whether err is the result of the

googleapi/googleapi_test.go

@@ -339,6 +339,32 @@ func TestCheckResponse(t *testing.T) {
 	}
 }
 
+func TestCheckResponseWithBody(t *testing.T) {
+	for _, test := range checkResponseTests {
+		res := test.in
+		var body []byte
+		if test.bodyText != "" {
+			body = []byte(test.bodyText)
+		}
+		g := CheckResponseWithBody(res, body)
+		if !reflect.DeepEqual(g, test.want) {
+			t.Errorf("CheckResponse: got %v, want %v", g, test.want)
+			gotJSON, err := json.Marshal(g)
+			if err != nil {
+				t.Error(err)
+			}
+			wantJSON, err := json.Marshal(test.want)
+			if err != nil {
+				t.Error(err)
+			}
+			t.Errorf("json(got):  %q\njson(want): %q", string(gotJSON), string(wantJSON))
+		}
+		if g != nil && g.Error() != test.errText {
+			t.Errorf("CheckResponse: unexpected error message.\nGot:  %q\nwant: %q", g, test.errText)
+		}
+	}
+}
+
 type VariantPoint struct {
 	Type        string
 	Coordinates []float64