1 files changed, 327 insertions, 0 deletions
diff --git a/src/errors/wrap_test.go b/src/errors/wrap_test.go
new file mode 100644
index 0000000..9efbe45
--- /dev/null
+++ b/src/errors/wrap_test.go
@@ -0,0 +1,327 @@
+// 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},
+		{multiErr{}, err1, false},
+		{multiErr{err1, err3}, err1, true},
+		{multiErr{err3, err1}, err1, true},
+		{multiErr{err1, err3}, errors.New("x"), false},
+		{multiErr{err3, errb}, errb, true},
+		{multiErr{err3, errb}, erra, true},
+		{multiErr{err3, errb}, err1, true},
+		{multiErr{errb, err3}, err1, true},
+		{multiErr{poser}, err1, true},
+		{multiErr{poser}, err3, true},
+		{multiErr{nil}, nil, 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,
+	}, {
+		multiErr{},
+		&errT,
+		false,
+		nil,
+	}, {
+		multiErr{errors.New("a"), errorT{"T"}},
+		&errT,
+		true,
+		errorT{"T"},
+	}, {
+		multiErr{errorT{"T"}, errors.New("a")},
+		&errT,
+		true,
+		errorT{"T"},
+	}, {
+		multiErr{errorT{"a"}, errorT{"b"}},
+		&errT,
+		true,
+		errorT{"a"},
+	}, {
+		multiErr{multiErr{errors.New("a"), errorT{"a"}}, errorT{"b"}},
+		&errT,
+		true,
+		errorT{"a"},
+	}, {
+		multiErr{wrapped{"path error", errF}},
+		&timeout,
+		true,
+		errF,
+	}, {
+		multiErr{nil},
+		&errT,
+		false,
+		nil,
+	}}
+	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 multiErr []error
+
+func (m multiErr) Error() string   { return "multiError" }
+func (m multiErr) Unwrap() []error { return []error(m) }
+
+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
+}