1// Copyright (c) 2017-2023 Uber Technologies, Inc.
 2//
 3// Permission is hereby granted, free of charge, to any person obtaining a copy
 4// of this software and associated documentation files (the "Software"), to deal
 5// in the Software without restriction, including without limitation the rights
 6// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 7// copies of the Software, and to permit persons to whom the Software is
 8// furnished to do so, subject to the following conditions:
 9//
10// The above copyright notice and this permission notice shall be included in
11// all copies or substantial portions of the Software.
12//
13// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
14// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
15// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
16// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
17// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
18// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
19// THE SOFTWARE.
20
21//go:build !go1.20
22// +build !go1.20
23
24package multierr
25
26import "errors"
27
28// Versions of Go before 1.20 did not support the Unwrap() []error method.
29// This provides a similar behavior by implementing the Is(..) and As(..)
30// methods.
31// See the errors.Join proposal for details:
32// https://github.com/golang/go/issues/53435
33
34// As attempts to find the first error in the error list that matches the type
35// of the value that target points to.
36//
37// This function allows errors.As to traverse the values stored on the
38// multierr error.
39func (merr *multiError) As(target interface{}) bool {
40	for _, err := range merr.Errors() {
41		if errors.As(err, target) {
42			return true
43		}
44	}
45	return false
46}
47
48// Is attempts to match the provided error against errors in the error list.
49//
50// This function allows errors.Is to traverse the values stored on the
51// multierr error.
52func (merr *multiError) Is(target error) bool {
53	for _, err := range merr.Errors() {
54		if errors.Is(err, target) {
55			return true
56		}
57	}
58	return false
59}
60
61func extractErrors(err error) []error {
62	if err == nil {
63		return nil
64	}
65
66	// Note that we're casting to multiError, not errorGroup. Our contract is
67	// that returned errors MAY implement errorGroup. Errors, however, only
68	// has special behavior for multierr-specific error objects.
69	//
70	// This behavior can be expanded in the future but I think it's prudent to
71	// start with as little as possible in terms of contract and possibility
72	// of misuse.
73	eg, ok := err.(*multiError)
74	if !ok {
75		return []error{err}
76	}
77
78	return append(([]error)(nil), eg.Errors()...)
79}