Merge pull request #1393 from dmcgowan/multiple-differs

Add support for multiple differs

errdefs/errors.go

@@ -26,6 +26,7 @@ var (
 	ErrAlreadyExists      = errors.New("already exists")
 	ErrFailedPrecondition = errors.New("failed precondition")
 	ErrUnavailable        = errors.New("unavailable")
+	ErrNotSupported       = errors.New("not supported") // represents not supported and unimplemented
 )
 
 func IsInvalidArgument(err error) bool {
@@ -52,3 +53,7 @@ func IsFailedPrecondition(err error) bool {
 func IsUnavailable(err error) bool {
 	return errors.Cause(err) == ErrUnavailable
 }
+
+func IsNotSupported(err error) bool {
+	return errors.Cause(err) == ErrNotSupported
+}

errdefs/grpc.go

@@ -38,6 +38,8 @@ func ToGRPC(err error) error {
 		return grpc.Errorf(codes.FailedPrecondition, err.Error())
 	case IsUnavailable(err):
 		return grpc.Errorf(codes.Unavailable, err.Error())
+	case IsNotSupported(err):
+		return grpc.Errorf(codes.Unimplemented, err.Error())
 	}
 
 	return err
@@ -69,6 +71,8 @@ func FromGRPC(err error) error {
 		cls = ErrUnavailable
 	case codes.FailedPrecondition:
 		cls = ErrFailedPrecondition
+	case codes.Unimplemented:
+		cls = ErrNotSupported
 	default:
 		cls = ErrUnknown
 	}