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
5package fmt_test
6
7import (
8	"errors"
9	"fmt"
10	"reflect"
11	"testing"
12)
13
14func TestErrorf(t *testing.T) {
15	// noVetErrorf is an alias for fmt.Errorf that does not trigger vet warnings for
16	// %w format strings.
17	noVetErrorf := fmt.Errorf
18
19	wrapped := errors.New("inner error")
20	for _, test := range []struct {
21		err        error
22		wantText   string
23		wantUnwrap error
24		wantSplit  []error
25	}{{
26		err:        fmt.Errorf("%w", wrapped),
27		wantText:   "inner error",
28		wantUnwrap: wrapped,
29	}, {
30		err:        fmt.Errorf("added context: %w", wrapped),
31		wantText:   "added context: inner error",
32		wantUnwrap: wrapped,
33	}, {
34		err:        fmt.Errorf("%w with added context", wrapped),
35		wantText:   "inner error with added context",
36		wantUnwrap: wrapped,
37	}, {
38		err:        fmt.Errorf("%s %w %v", "prefix", wrapped, "suffix"),
39		wantText:   "prefix inner error suffix",
40		wantUnwrap: wrapped,
41	}, {
42		err:        fmt.Errorf("%[2]s: %[1]w", wrapped, "positional verb"),
43		wantText:   "positional verb: inner error",
44		wantUnwrap: wrapped,
45	}, {
46		err:      fmt.Errorf("%v", wrapped),
47		wantText: "inner error",
48	}, {
49		err:      fmt.Errorf("added context: %v", wrapped),
50		wantText: "added context: inner error",
51	}, {
52		err:      fmt.Errorf("%v with added context", wrapped),
53		wantText: "inner error with added context",
54	}, {
55		err:      noVetErrorf("%w is not an error", "not-an-error"),
56		wantText: "%!w(string=not-an-error) is not an error",
57	}, {
58		err:       noVetErrorf("wrapped two errors: %w %w", errString("1"), errString("2")),
59		wantText:  "wrapped two errors: 1 2",
60		wantSplit: []error{errString("1"), errString("2")},
61	}, {
62		err:       noVetErrorf("wrapped three errors: %w %w %w", errString("1"), errString("2"), errString("3")),
63		wantText:  "wrapped three errors: 1 2 3",
64		wantSplit: []error{errString("1"), errString("2"), errString("3")},
65	}, {
66		err:       noVetErrorf("wrapped nil error: %w %w %w", errString("1"), nil, errString("2")),
67		wantText:  "wrapped nil error: 1 %!w(<nil>) 2",
68		wantSplit: []error{errString("1"), errString("2")},
69	}, {
70		err:       noVetErrorf("wrapped one non-error: %w %w %w", errString("1"), "not-an-error", errString("3")),
71		wantText:  "wrapped one non-error: 1 %!w(string=not-an-error) 3",
72		wantSplit: []error{errString("1"), errString("3")},
73	}, {
74		err:       fmt.Errorf("wrapped errors out of order: %[3]w %[2]w %[1]w", errString("1"), errString("2"), errString("3")),
75		wantText:  "wrapped errors out of order: 3 2 1",
76		wantSplit: []error{errString("1"), errString("2"), errString("3")},
77	}, {
78		err:       fmt.Errorf("wrapped several times: %[1]w %[1]w %[2]w %[1]w", errString("1"), errString("2")),
79		wantText:  "wrapped several times: 1 1 2 1",
80		wantSplit: []error{errString("1"), errString("2")},
81	}, {
82		err:        fmt.Errorf("%w", nil),
83		wantText:   "%!w(<nil>)",
84		wantUnwrap: nil, // still nil
85	}} {
86		if got, want := errors.Unwrap(test.err), test.wantUnwrap; got != want {
87			t.Errorf("Formatted error: %v\nerrors.Unwrap() = %v, want %v", test.err, got, want)
88		}
89		if got, want := splitErr(test.err), test.wantSplit; !reflect.DeepEqual(got, want) {
90			t.Errorf("Formatted error: %v\nUnwrap() []error = %v, want %v", test.err, got, want)
91		}
92		if got, want := test.err.Error(), test.wantText; got != want {
93			t.Errorf("err.Error() = %q, want %q", got, want)
94		}
95	}
96}
97
98func splitErr(err error) []error {
99	if e, ok := err.(interface{ Unwrap() []error }); ok {
100		return e.Unwrap()
101	}
102	return nil
103}
104
105type errString string
106
107func (e errString) Error() string { return string(e) }
108