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	"testing"
11)
12
13func TestErrorf(t *testing.T) {
14	// noVetErrorf is an alias for fmt.Errorf that does not trigger vet warnings for
15	// %w format strings.
16	noVetErrorf := fmt.Errorf
17
18	wrapped := errors.New("inner error")
19	for _, test := range []struct {
20		err        error
21		wantText   string
22		wantUnwrap error
23	}{{
24		err:        fmt.Errorf("%w", wrapped),
25		wantText:   "inner error",
26		wantUnwrap: wrapped,
27	}, {
28		err:        fmt.Errorf("added context: %w", wrapped),
29		wantText:   "added context: inner error",
30		wantUnwrap: wrapped,
31	}, {
32		err:        fmt.Errorf("%w with added context", wrapped),
33		wantText:   "inner error with added context",
34		wantUnwrap: wrapped,
35	}, {
36		err:        fmt.Errorf("%s %w %v", "prefix", wrapped, "suffix"),
37		wantText:   "prefix inner error suffix",
38		wantUnwrap: wrapped,
39	}, {
40		err:        fmt.Errorf("%[2]s: %[1]w", wrapped, "positional verb"),
41		wantText:   "positional verb: inner error",
42		wantUnwrap: wrapped,
43	}, {
44		err:      fmt.Errorf("%v", wrapped),
45		wantText: "inner error",
46	}, {
47		err:      fmt.Errorf("added context: %v", wrapped),
48		wantText: "added context: inner error",
49	}, {
50		err:      fmt.Errorf("%v with added context", wrapped),
51		wantText: "inner error with added context",
52	}, {
53		err:      noVetErrorf("%w is not an error", "not-an-error"),
54		wantText: "%!w(string=not-an-error) is not an error",
55	}, {
56		err:      noVetErrorf("wrapped two errors: %w %w", errString("1"), errString("2")),
57		wantText: "wrapped two errors: 1 %!w(fmt_test.errString=2)",
58	}, {
59		err:      noVetErrorf("wrapped three errors: %w %w %w", errString("1"), errString("2"), errString("3")),
60		wantText: "wrapped three errors: 1 %!w(fmt_test.errString=2) %!w(fmt_test.errString=3)",
61	}, {
62		err:        fmt.Errorf("%w", nil),
63		wantText:   "%!w(<nil>)",
64		wantUnwrap: nil, // still nil
65	}} {
66		if got, want := errors.Unwrap(test.err), test.wantUnwrap; got != want {
67			t.Errorf("Formatted error: %v\nerrors.Unwrap() = %v, want %v", test.err, got, want)
68		}
69		if got, want := test.err.Error(), test.wantText; got != want {
70			t.Errorf("err.Error() = %q, want %q", got, want)
71		}
72	}
73}
74
75type errString string
76
77func (e errString) Error() string { return string(e) }
78