join.go

     1  // Copyright 2022 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
     6  
     7  // Join returns an error that wraps the given errors.
     8  // Any nil error values are discarded.
     9  // Join returns nil if errs contains no non-nil values.
    10  // The error formats as the concatenation of the strings obtained
    11  // by calling the Error method of each element of errs, with a newline
    12  // between each string.
    13  func Join(errs ...error) error {
    14  	n := 0
    15  	for _, err := range errs {
    16  		if err != nil {
    17  			n++
    18  		}
    19  	}
    20  	if n == 0 {
    21  		return nil
    22  	}
    23  	e := &joinError{
    24  		errs: make([]error, 0, n),
    25  	}
    26  	for _, err := range errs {
    27  		if err != nil {
    28  			e.errs = append(e.errs, err)
    29  		}
    30  	}
    31  	return e
    32  }
    33  
    34  type joinError struct {
    35  	errs []error
    36  }
    37  
    38  func (e *joinError) Error() string {
    39  	var b []byte
    40  	for i, err := range e.errs {
    41  		if i > 0 {
    42  			b = append(b, '\n')
    43  		}
    44  		b = append(b, err.Error()...)
    45  	}
    46  	return string(b)
    47  }
    48  
    49  func (e *joinError) Unwrap() []error {
    50  	return e.errs
    51  }
    52
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