errors.go

Documentation: google.golang.org/protobuf/internal/errors

     1  // Copyright 2018 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  // Package errors implements functions to manipulate errors.
     6  package errors
     7  
     8  import (
     9  	"errors"
    10  	"fmt"
    11  
    12  	"google.golang.org/protobuf/internal/detrand"
    13  )
    14  
    15  // Error is a sentinel matching all errors produced by this package.
    16  var Error = errors.New("protobuf error")
    17  
    18  // New formats a string according to the format specifier and arguments and
    19  // returns an error that has a "proto" prefix.
    20  func New(f string, x ...interface{}) error {
    21  	return &prefixError{s: format(f, x...)}
    22  }
    23  
    24  type prefixError struct{ s string }
    25  
    26  var prefix = func() string {
    27  	// Deliberately introduce instability into the error message string to
    28  	// discourage users from performing error string comparisons.
    29  	if detrand.Bool() {
    30  		return "proto: " // use non-breaking spaces (U+00a0)
    31  	} else {
    32  		return "proto: " // use regular spaces (U+0020)
    33  	}
    34  }()
    35  
    36  func (e *prefixError) Error() string {
    37  	return prefix + e.s
    38  }
    39  
    40  func (e *prefixError) Unwrap() error {
    41  	return Error
    42  }
    43  
    44  // Wrap returns an error that has a "proto" prefix, the formatted string described
    45  // by the format specifier and arguments, and a suffix of err. The error wraps err.
    46  func Wrap(err error, f string, x ...interface{}) error {
    47  	return &wrapError{
    48  		s:   format(f, x...),
    49  		err: err,
    50  	}
    51  }
    52  
    53  type wrapError struct {
    54  	s   string
    55  	err error
    56  }
    57  
    58  func (e *wrapError) Error() string {
    59  	return format("%v%v: %v", prefix, e.s, e.err)
    60  }
    61  
    62  func (e *wrapError) Unwrap() error {
    63  	return e.err
    64  }
    65  
    66  func (e *wrapError) Is(target error) bool {
    67  	return target == Error
    68  }
    69  
    70  func format(f string, x ...interface{}) string {
    71  	// avoid "proto: " prefix when chaining
    72  	for i := 0; i < len(x); i++ {
    73  		switch e := x[i].(type) {
    74  		case *prefixError:
    75  			x[i] = e.s
    76  		case *wrapError:
    77  			x[i] = format("%v: %v", e.s, e.err)
    78  		}
    79  	}
    80  	return fmt.Sprintf(f, x...)
    81  }
    82  
    83  func InvalidUTF8(name string) error {
    84  	return New("field %v contains invalid UTF-8", name)
    85  }
    86  
    87  func RequiredNotSet(name string) error {
    88  	return New("required field %v not set", name)
    89  }
    90
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