Source: annotate.go in package cloud.google.com/go/internal

Copyright 2017 Google LLC Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.


package internal

import (
	"fmt"

	"google.golang.org/api/googleapi"
	"google.golang.org/grpc/status"
)

Annotate prepends msg to the error message in err, attempting to preserve other information in err, like an error code. Annotate panics if err is nil. Annotate knows about these error types: - "google.golang.org/grpc/status".Status - "google.golang.org/api/googleapi".Error If the error is not one of these types, Annotate behaves like fmt.Errorf("%s: %v", msg, err)

func Annotate(err error, msg string) error {
	if err == nil {
		panic("Annotate called with nil")
	}
	if s, ok := status.FromError(err); ok {
		p := s.Proto()
		p.Message = msg + ": " + p.Message
		return status.ErrorProto(p)
	}
	if g, ok := err.(*googleapi.Error); ok {
		g.Message = msg + ": " + g.Message
		return g
	}
	return fmt.Errorf("%s: %v", msg, err)
}

Annotatef uses format and args to format a string, then calls Annotate.

func Annotatef(err error, format string, args ...interface{}) error {
	return Annotate(err, fmt.Sprintf(format, args...))