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// 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 errors_test
import (
"errors"
"fmt"
"io/fs"
"os"
"reflect"
"testing"
)
func TestIs(t *testing.T) {
err1 := errors.New("1")
erra := wrapped{"wrap 2", err1}
errb := wrapped{"wrap 3", erra}
err3 := errors.New("3")
poser := &poser{"either 1 or 3", func(err error) bool {
return err == err1 || err == err3
}}
testCases := []struct {
err error
target error
match bool
}{
{nil, nil, true},
{err1, nil, false},
{err1, err1, true},
{erra, err1, true},
{errb, err1, true},
{err1, err3, false},
{erra, err3, false},
{errb, err3, false},
{poser, err1, true},
{poser, err3, true},
{poser, erra, false},
{poser, errb, false},
{errorUncomparable{}, errorUncomparable{}, true},
{errorUncomparable{}, &errorUncomparable{}, false},
{&errorUncomparable{}, errorUncomparable{}, true},
{&errorUncomparable{}, &errorUncomparable{}, false},
{errorUncomparable{}, err1, false},
{&errorUncomparable{}, err1, false},
}
for _, tc := range testCases {
t.Run("", func(t *testing.T) {
if got := errors.Is(tc.err, tc.target); got != tc.match {
t.Errorf("Is(%v, %v) = %v, want %v", tc.err, tc.target, got, tc.match)
}
})
}
}
type poser struct {
msg string
f func(error) bool
}
var poserPathErr = &fs.PathError{Op: "poser"}
func (p *poser) Error() string { return p.msg }
func (p *poser) Is(err error) bool { return p.f(err) }
func (p *poser) As(err any) bool {
switch x := err.(type) {
case **poser:
*x = p
case *errorT:
*x = errorT{"poser"}
case **fs.PathError:
*x = poserPathErr
default:
return false
}
return true
}
func TestAs(t *testing.T) {
var errT errorT
var errP *fs.PathError
var timeout interface{ Timeout() bool }
var p *poser
_, errF := os.Open("non-existing")
poserErr := &poser{"oh no", nil}
testCases := []struct {
err error
target any
match bool
want any // value of target on match
}{{
nil,
&errP,
false,
nil,
}, {
wrapped{"pitied the fool", errorT{"T"}},
&errT,
true,
errorT{"T"},
}, {
errF,
&errP,
true,
errF,
}, {
errorT{},
&errP,
false,
nil,
}, {
wrapped{"wrapped", nil},
&errT,
false,
nil,
}, {
&poser{"error", nil},
&errT,
true,
errorT{"poser"},
}, {
&poser{"path", nil},
&errP,
true,
poserPathErr,
}, {
poserErr,
&p,
true,
poserErr,
}, {
errors.New("err"),
&timeout,
false,
nil,
}, {
errF,
&timeout,
true,
errF,
}, {
wrapped{"path error", errF},
&timeout,
true,
errF,
}}
for i, tc := range testCases {
name := fmt.Sprintf("%d:As(Errorf(..., %v), %v)", i, tc.err, tc.target)
// Clear the target pointer, in case it was set in a previous test.
rtarget := reflect.ValueOf(tc.target)
rtarget.Elem().Set(reflect.Zero(reflect.TypeOf(tc.target).Elem()))
t.Run(name, func(t *testing.T) {
match := errors.As(tc.err, tc.target)
if match != tc.match {
t.Fatalf("match: got %v; want %v", match, tc.match)
}
if !match {
return
}
if got := rtarget.Elem().Interface(); got != tc.want {
t.Fatalf("got %#v, want %#v", got, tc.want)
}
})
}
}
func TestAsValidation(t *testing.T) {
var s string
testCases := []any{
nil,
(*int)(nil),
"error",
&s,
}
err := errors.New("error")
for _, tc := range testCases {
t.Run(fmt.Sprintf("%T(%v)", tc, tc), func(t *testing.T) {
defer func() {
recover()
}()
if errors.As(err, tc) {
t.Errorf("As(err, %T(%v)) = true, want false", tc, tc)
return
}
t.Errorf("As(err, %T(%v)) did not panic", tc, tc)
})
}
}
func TestUnwrap(t *testing.T) {
err1 := errors.New("1")
erra := wrapped{"wrap 2", err1}
testCases := []struct {
err error
want error
}{
{nil, nil},
{wrapped{"wrapped", nil}, nil},
{err1, nil},
{erra, err1},
{wrapped{"wrap 3", erra}, erra},
}
for _, tc := range testCases {
if got := errors.Unwrap(tc.err); got != tc.want {
t.Errorf("Unwrap(%v) = %v, want %v", tc.err, got, tc.want)
}
}
}
type errorT struct{ s string }
func (e errorT) Error() string { return fmt.Sprintf("errorT(%s)", e.s) }
type wrapped struct {
msg string
err error
}
func (e wrapped) Error() string { return e.msg }
func (e wrapped) Unwrap() error { return e.err }
type errorUncomparable struct {
f []string
}
func (errorUncomparable) Error() string {
return "uncomparable error"
}
func (errorUncomparable) Is(target error) bool {
_, ok := target.(errorUncomparable)
return ok
}
func ExampleIs() {
if _, err := os.Open("non-existing"); err != nil {
if errors.Is(err, fs.ErrNotExist) {
fmt.Println("file does not exist")
} else {
fmt.Println(err)
}
}
// Output:
// file does not exist
}
func ExampleAs() {
if _, err := os.Open("non-existing"); err != nil {
var pathError *fs.PathError
if errors.As(err, &pathError) {
fmt.Println("Failed at path:", pathError.Path)
} else {
fmt.Println(err)
}
}
// Output:
// Failed at path: non-existing
}
func ExampleUnwrap() {
err1 := errors.New("error1")
err2 := fmt.Errorf("error2: [%w]", err1)
fmt.Println(err2)
fmt.Println(errors.Unwrap(err2))
// Output
// error2: [error1]
// error1
}
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