errors

errors

Builds on Go 1.13 errors by adding HTTP statuses and GRPC codes to them.

Installation

go get -u github.com/stackus/errors

Prerequisites

Go 1.13

Adding HTTP status and GRPC codes to your errors

The errors.Wrap(error, string) error function is used to embed an errors.Error or to wrap other errors. When used with an errors.Error the desired message is not altered. Wrapping other errors will prefix the message before the wrapped error message.

err := errors.Wrap(errors.ErrNotFound, "found nothing")
fmt.Println(err) // Outputs: "found nothing"
err = errors.Wrap(err, "a prefixed message")
fmt.Println(err) // Outputs: "a prefixed message: found nothing"

HTTP Statuses

The wrapped errors.Error can be checked with errors.As() and the errors.HTTPCoder interface to locate the HTTP status.

err := errors.Wrap(errors.ErrNotFound, "found nothing")
var coder errors.HTTPCoder
if errors.As(err, &coder) {
    fmt.Println(coder.HTTPCode()) // Outputs: 404
}

GRPC Codes

A similar method can be used to get the GRPC codes with the errors.GRPCCoder interface.

err := errors.Wrap(errors.NotFound, "found nothing")
var coder errors.GRPCCoder
if errors.As(err, &coder) {
    fmt.Println(coder.GRPCCode()) // Outputs: 5

Transmitting errors with GRPC

The methods SendGRPCError(error) error and ReceiveGRPCError(error) error provide a way to convert a status.Status and its error into an errors.Error and vice versa. You can use these in your server and client handlers directly, or they can be used with GRPC interceptors.

Server Example:

func serverErrorUnaryInterceptor() grpc.UnaryServerInterceptor {
    return func(ctx context.Context, req interface{}, info *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (resp interface{}, err error) {
	    return resp, errors.SendGRPCError(err)
	}
}

server := grpc.NewServer(grpc.ChainUnaryInterceptor(serverErrorUnaryInterceptor()))

Client Example:

func clientErrorUnaryInterceptor() grpc.UnaryClientInterceptor {
    return func(ctx context.Context, method string, req, reply interface{}, cc *grpc.ClientConn, invoker grpc.UnaryInvoker, opts ...grpc.CallOption) error {
	    return errors.ReceiveGRPCError(invoker(ctx, method, req, reply, cc, opts...))
	}
}

cc, err := grpc.Dial(uri, grpc.WithChainUnaryInterceptor(clientErrorUnaryInterceptor()))

There is no requirement that both the server and client use this library to benefit from coded errors.

Contributing

Pull requests are welcome. For major changes, please open an issue first to discuss what you would like to change.

Please make sure to update tests as appropriate.

License

MIT