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//go:build !go1.20
// Copyright 2022 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package errors
// Join returns an error that wraps the given errors.
// Any nil error values are discarded.
// Join returns nil if every value in errs is nil.
// The error formats as the concatenation of the strings obtained
// by calling the Error method of each element of errs, with a newline
// between each string.
//
// A non-nil error returned by Join implements the Unwrap() []error method.
func Join(errs ...error) error {
n := 0
for _, err := range errs {
if err != nil {
n++
}
}
if n == 0 {
return nil
}
e := &joinError{
errs: make([]error, 0, n),
}
for _, err := range errs {
if err != nil {
e.errs = append(e.errs, err)
}
}
return e
}
type joinError struct {
errs []error
}
func (e *joinError) Error() string {
// Since Join returns nil if every value in errs is nil,
// e.errs cannot be empty.
if len(e.errs) == 1 {
return e.errs[0].Error()
}
b := []byte(e.errs[0].Error())
for _, err := range e.errs[1:] {
b = append(b, '\n')
b = append(b, err.Error()...)
}
// At this point, b has at least one byte '\n'.
// return unsafe.String(&b[0], len(b))
return string(b)
}
func (e *joinError) Unwrap() []error {
return e.errs
}
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