// Copyright 2018 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 fmt_test import ( "errors" "fmt" "reflect" "testing" ) func TestErrorf(t *testing.T) { // noVetErrorf is an alias for fmt.Errorf that does not trigger vet warnings for // %w format strings. noVetErrorf := fmt.Errorf wrapped := errors.New("inner error") for _, test := range []struct { err error wantText string wantUnwrap error wantSplit []error }{{ err: fmt.Errorf("%w", wrapped), wantText: "inner error", wantUnwrap: wrapped, }, { err: fmt.Errorf("added context: %w", wrapped), wantText: "added context: inner error", wantUnwrap: wrapped, }, { err: fmt.Errorf("%w with added context", wrapped), wantText: "inner error with added context", wantUnwrap: wrapped, }, { err: fmt.Errorf("%s %w %v", "prefix", wrapped, "suffix"), wantText: "prefix inner error suffix", wantUnwrap: wrapped, }, { err: fmt.Errorf("%[2]s: %[1]w", wrapped, "positional verb"), wantText: "positional verb: inner error", wantUnwrap: wrapped, }, { err: fmt.Errorf("%v", wrapped), wantText: "inner error", }, { err: fmt.Errorf("added context: %v", wrapped), wantText: "added context: inner error", }, { err: fmt.Errorf("%v with added context", wrapped), wantText: "inner error with added context", }, { err: noVetErrorf("%w is not an error", "not-an-error"), wantText: "%!w(string=not-an-error) is not an error", }, { err: noVetErrorf("wrapped two errors: %w %w", errString("1"), errString("2")), wantText: "wrapped two errors: 1 2", wantSplit: []error{errString("1"), errString("2")}, }, { err: noVetErrorf("wrapped three errors: %w %w %w", errString("1"), errString("2"), errString("3")), wantText: "wrapped three errors: 1 2 3", wantSplit: []error{errString("1"), errString("2"), errString("3")}, }, { err: noVetErrorf("wrapped nil error: %w %w %w", errString("1"), nil, errString("2")), wantText: "wrapped nil error: 1 %!w() 2", wantSplit: []error{errString("1"), errString("2")}, }, { err: noVetErrorf("wrapped one non-error: %w %w %w", errString("1"), "not-an-error", errString("3")), wantText: "wrapped one non-error: 1 %!w(string=not-an-error) 3", wantSplit: []error{errString("1"), errString("3")}, }, { err: fmt.Errorf("wrapped errors out of order: %[3]w %[2]w %[1]w", errString("1"), errString("2"), errString("3")), wantText: "wrapped errors out of order: 3 2 1", wantSplit: []error{errString("1"), errString("2"), errString("3")}, }, { err: fmt.Errorf("wrapped several times: %[1]w %[1]w %[2]w %[1]w", errString("1"), errString("2")), wantText: "wrapped several times: 1 1 2 1", wantSplit: []error{errString("1"), errString("2")}, }, { err: fmt.Errorf("%w", nil), wantText: "%!w()", wantUnwrap: nil, // still nil }} { if got, want := errors.Unwrap(test.err), test.wantUnwrap; got != want { t.Errorf("Formatted error: %v\nerrors.Unwrap() = %v, want %v", test.err, got, want) } if got, want := splitErr(test.err), test.wantSplit; !reflect.DeepEqual(got, want) { t.Errorf("Formatted error: %v\nUnwrap() []error = %v, want %v", test.err, got, want) } if got, want := test.err.Error(), test.wantText; got != want { t.Errorf("err.Error() = %q, want %q", got, want) } } } func splitErr(err error) []error { if e, ok := err.(interface{ Unwrap() []error }); ok { return e.Unwrap() } return nil } type errString string func (e errString) Error() string { return string(e) }