status.go

/*
 *
 * Copyright 2017 gRPC authors.
 *
 * 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 status implements errors returned by gRPC.  These errors are
// serialized and transmitted on the wire between server and client, and allow
// for additional data to be transmitted via the Details field in the status
// proto.  gRPC service handlers should return an error created by this
// package, and gRPC clients should expect a corresponding error to be
// returned from the RPC call.
//
// This package upholds the invariants that a non-nil error may not
// contain an OK code, and an OK code must result in a nil error.
package status

import (
	"context"
	"errors"
	"fmt"

	spb "google.golang.org/genproto/googleapis/rpc/status"

	"google.golang.org/grpc/codes"
	"google.golang.org/grpc/internal/status"
)

// Status references google.golang.org/grpc/internal/status. It represents an
// RPC status code, message, and details.  It is immutable and should be
// created with New, Newf, or FromProto.
// https://godoc.org/google.golang.org/grpc/internal/status
type Status = status.Status

// New returns a Status representing c and msg.
func New(c codes.Code, msg string) *Status {
	return status.New(c, msg)
}

// Newf returns New(c, fmt.Sprintf(format, a...)).
func Newf(c codes.Code, format string, a ...interface{}) *Status {
	return New(c, fmt.Sprintf(format, a...))
}

// Error returns an error representing c and msg.  If c is OK, returns nil.
func Error(c codes.Code, msg string) error {
	return New(c, msg).Err()
}

// Errorf returns Error(c, fmt.Sprintf(format, a...)).
func Errorf(c codes.Code, format string, a ...interface{}) error {
	return Error(c, fmt.Sprintf(format, a...))
}

// ErrorProto returns an error representing s.  If s.Code is OK, returns nil.
func ErrorProto(s *spb.Status) error {
	return FromProto(s).Err()
}

// FromProto returns a Status representing s.
func FromProto(s *spb.Status) *Status {
	return status.FromProto(s)
}

// FromError returns a Status representation of err.
//
// - If err was produced by this package or implements the method `GRPCStatus()
//   *Status`, the appropriate Status is returned.
//
// - If err is nil, a Status is returned with codes.OK and no message.
//
// - Otherwise, err is an error not compatible with this package.  In this
//   case, a Status is returned with codes.Unknown and err's Error() message,
//   and ok is false.
func FromError(err error) (s *Status, ok bool) {
	if err == nil {
		return nil, true
	}
	if se, ok := err.(interface {
		GRPCStatus() *Status
	}); ok {
		return se.GRPCStatus(), true
	}
	return New(codes.Unknown, err.Error()), false
}

// Convert is a convenience function which removes the need to handle the
// boolean return value from FromError.
func Convert(err error) *Status {
	s, _ := FromError(err)
	return s
}

// Code returns the Code of the error if it is a Status error, codes.OK if err
// is nil, or codes.Unknown otherwise.
func Code(err error) codes.Code {
	// Don't use FromError to avoid allocation of OK status.
	if err == nil {
		return codes.OK
	}
	if se, ok := err.(interface {
		GRPCStatus() *Status
	}); ok {
		return se.GRPCStatus().Code()
	}
	return codes.Unknown
}

// FromContextError converts a context error or wrapped context error into a
// Status.  It returns a Status with codes.OK if err is nil, or a Status with
// codes.Unknown if err is non-nil and not a context error.
func FromContextError(err error) *Status {
	if err == nil {
		return nil
	}
	if errors.Is(err, context.DeadlineExceeded) {
		return New(codes.DeadlineExceeded, err.Error())
	}
	if errors.Is(err, context.Canceled) {
		return New(codes.Canceled, err.Error())
	}
	return New(codes.Unknown, err.Error())
}

// MustFromContextError is like FromContextError, except that it expects err to
// be non-nil, and it returns the status in form of an error.
func MustFromContextError(err error) error {
	if err == nil {
		return status.New(codes.Internal, "Expected non-nil context error").Err()
	}
	return FromContextError(err).Err()
}