Adding upstream version 1.21.8.upstream/1.21.8

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1925 insertions, 0 deletions

diff --git a/src/path/filepath/path_test.go b/src/path/filepath/path_test.go
new file mode 100644
index 0000000..bd1904c
--- /dev/null
+++ b/src/path/filepath/path_test.go
@@ -0,0 +1,1925 @@
+// Copyright 2009 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 filepath_test
+
+import (
+	"errors"
+	"fmt"
+	"internal/testenv"
+	"io/fs"
+	"os"
+	"path/filepath"
+	"reflect"
+	"runtime"
+	"slices"
+	"sort"
+	"strings"
+	"syscall"
+	"testing"
+)
+
+type PathTest struct {
+	path, result string
+}
+
+var cleantests = []PathTest{
+	// Already clean
+	{"abc", "abc"},
+	{"abc/def", "abc/def"},
+	{"a/b/c", "a/b/c"},
+	{".", "."},
+	{"..", ".."},
+	{"../..", "../.."},
+	{"../../abc", "../../abc"},
+	{"/abc", "/abc"},
+	{"/", "/"},
+
+	// Empty is current dir
+	{"", "."},
+
+	// Remove trailing slash
+	{"abc/", "abc"},
+	{"abc/def/", "abc/def"},
+	{"a/b/c/", "a/b/c"},
+	{"./", "."},
+	{"../", ".."},
+	{"../../", "../.."},
+	{"/abc/", "/abc"},
+
+	// Remove doubled slash
+	{"abc//def//ghi", "abc/def/ghi"},
+	{"abc//", "abc"},
+
+	// Remove . elements
+	{"abc/./def", "abc/def"},
+	{"/./abc/def", "/abc/def"},
+	{"abc/.", "abc"},
+
+	// Remove .. elements
+	{"abc/def/ghi/../jkl", "abc/def/jkl"},
+	{"abc/def/../ghi/../jkl", "abc/jkl"},
+	{"abc/def/..", "abc"},
+	{"abc/def/../..", "."},
+	{"/abc/def/../..", "/"},
+	{"abc/def/../../..", ".."},
+	{"/abc/def/../../..", "/"},
+	{"abc/def/../../../ghi/jkl/../../../mno", "../../mno"},
+	{"/../abc", "/abc"},
+	{"a/../b:/../../c", `../c`},
+
+	// Combinations
+	{"abc/./../def", "def"},
+	{"abc//./../def", "def"},
+	{"abc/../../././../def", "../../def"},
+}
+
+var nonwincleantests = []PathTest{
+	// Remove leading doubled slash
+	{"//abc", "/abc"},
+	{"///abc", "/abc"},
+	{"//abc//", "/abc"},
+}
+
+var wincleantests = []PathTest{
+	{`c:`, `c:.`},
+	{`c:\`, `c:\`},
+	{`c:\abc`, `c:\abc`},
+	{`c:abc\..\..\.\.\..\def`, `c:..\..\def`},
+	{`c:\abc\def\..\..`, `c:\`},
+	{`c:\..\abc`, `c:\abc`},
+	{`c:..\abc`, `c:..\abc`},
+	{`c:\b:\..\..\..\d`, `c:\d`},
+	{`\`, `\`},
+	{`/`, `\`},
+	{`\\i\..\c$`, `\\i\..\c$`},
+	{`\\i\..\i\c$`, `\\i\..\i\c$`},
+	{`\\i\..\I\c$`, `\\i\..\I\c$`},
+	{`\\host\share\foo\..\bar`, `\\host\share\bar`},
+	{`//host/share/foo/../baz`, `\\host\share\baz`},
+	{`\\host\share\foo\..\..\..\..\bar`, `\\host\share\bar`},
+	{`\\.\C:\a\..\..\..\..\bar`, `\\.\C:\bar`},
+	{`\\.\C:\\\\a`, `\\.\C:\a`},
+	{`\\a\b\..\c`, `\\a\b\c`},
+	{`\\a\b`, `\\a\b`},
+	{`.\c:`, `.\c:`},
+	{`.\c:\foo`, `.\c:\foo`},
+	{`.\c:foo`, `.\c:foo`},
+	{`//abc`, `\\abc`},
+	{`///abc`, `\\\abc`},
+	{`//abc//`, `\\abc\\`},
+	{`\\?\C:\`, `\\?\C:\`},
+	{`\\?\C:\a`, `\\?\C:\a`},
+
+	// Don't allow cleaning to move an element with a colon to the start of the path.
+	{`a/../c:`, `.\c:`},
+	{`a\..\c:`, `.\c:`},
+	{`a/../c:/a`, `.\c:\a`},
+	{`a/../../c:`, `..\c:`},
+	{`foo:bar`, `foo:bar`},
+
+	// Don't allow cleaning to create a Root Local Device path like \??\a.
+	{`/a/../??/a`, `\.\??\a`},
+}
+
+func TestClean(t *testing.T) {
+	tests := cleantests
+	if runtime.GOOS == "windows" {
+		for i := range tests {
+			tests[i].result = filepath.FromSlash(tests[i].result)
+		}
+		tests = append(tests, wincleantests...)
+	} else {
+		tests = append(tests, nonwincleantests...)
+	}
+	for _, test := range tests {
+		if s := filepath.Clean(test.path); s != test.result {
+			t.Errorf("Clean(%q) = %q, want %q", test.path, s, test.result)
+		}
+		if s := filepath.Clean(test.result); s != test.result {
+			t.Errorf("Clean(%q) = %q, want %q", test.result, s, test.result)
+		}
+	}
+
+	if testing.Short() {
+		t.Skip("skipping malloc count in short mode")
+	}
+	if runtime.GOMAXPROCS(0) > 1 {
+		t.Log("skipping AllocsPerRun checks; GOMAXPROCS>1")
+		return
+	}
+
+	for _, test := range tests {
+		allocs := testing.AllocsPerRun(100, func() { filepath.Clean(test.result) })
+		if allocs > 0 {
+			t.Errorf("Clean(%q): %v allocs, want zero", test.result, allocs)
+		}
+	}
+}
+
+type IsLocalTest struct {
+	path    string
+	isLocal bool
+}
+
+var islocaltests = []IsLocalTest{
+	{"", false},
+	{".", true},
+	{"..", false},
+	{"../a", false},
+	{"/", false},
+	{"/a", false},
+	{"/a/../..", false},
+	{"a", true},
+	{"a/../a", true},
+	{"a/", true},
+	{"a/.", true},
+	{"a/./b/./c", true},
+	{`a/../b:/../../c`, false},
+}
+
+var winislocaltests = []IsLocalTest{
+	{"NUL", false},
+	{"nul", false},
+	{"nul ", false},
+	{"nul.", false},
+	{"a/nul:", false},
+	{"a/nul : a", false},
+	{"com0", true},
+	{"com1", false},
+	{"com2", false},
+	{"com3", false},
+	{"com4", false},
+	{"com5", false},
+	{"com6", false},
+	{"com7", false},
+	{"com8", false},
+	{"com9", false},
+	{"com¹", false},
+	{"com²", false},
+	{"com³", false},
+	{"com¹ : a", false},
+	{"cOm1", false},
+	{"lpt1", false},
+	{"LPT1", false},
+	{"lpt³", false},
+	{"./nul", false},
+	{`\`, false},
+	{`\a`, false},
+	{`C:`, false},
+	{`C:\a`, false},
+	{`..\a`, false},
+	{`a/../c:`, false},
+	{`CONIN$`, false},
+	{`conin$`, false},
+	{`CONOUT$`, false},
+	{`conout$`, false},
+	{`dollar$`, true}, // not a special file name
+}
+
+var plan9islocaltests = []IsLocalTest{
+	{"#a", false},
+}
+
+func TestIsLocal(t *testing.T) {
+	tests := islocaltests
+	if runtime.GOOS == "windows" {
+		tests = append(tests, winislocaltests...)
+	}
+	if runtime.GOOS == "plan9" {
+		tests = append(tests, plan9islocaltests...)
+	}
+	for _, test := range tests {
+		if got := filepath.IsLocal(test.path); got != test.isLocal {
+			t.Errorf("IsLocal(%q) = %v, want %v", test.path, got, test.isLocal)
+		}
+	}
+}
+
+const sep = filepath.Separator
+
+var slashtests = []PathTest{
+	{"", ""},
+	{"/", string(sep)},
+	{"/a/b", string([]byte{sep, 'a', sep, 'b'})},
+	{"a//b", string([]byte{'a', sep, sep, 'b'})},
+}
+
+func TestFromAndToSlash(t *testing.T) {
+	for _, test := range slashtests {
+		if s := filepath.FromSlash(test.path); s != test.result {
+			t.Errorf("FromSlash(%q) = %q, want %q", test.path, s, test.result)
+		}
+		if s := filepath.ToSlash(test.result); s != test.path {
+			t.Errorf("ToSlash(%q) = %q, want %q", test.result, s, test.path)
+		}
+	}
+}
+
+type SplitListTest struct {
+	list   string
+	result []string
+}
+
+const lsep = filepath.ListSeparator
+
+var splitlisttests = []SplitListTest{
+	{"", []string{}},
+	{string([]byte{'a', lsep, 'b'}), []string{"a", "b"}},
+	{string([]byte{lsep, 'a', lsep, 'b'}), []string{"", "a", "b"}},
+}
+
+var winsplitlisttests = []SplitListTest{
+	// quoted
+	{`"a"`, []string{`a`}},
+
+	// semicolon
+	{`";"`, []string{`;`}},
+	{`"a;b"`, []string{`a;b`}},
+	{`";";`, []string{`;`, ``}},
+	{`;";"`, []string{``, `;`}},
+
+	// partially quoted
+	{`a";"b`, []string{`a;b`}},
+	{`a; ""b`, []string{`a`, ` b`}},
+	{`"a;b`, []string{`a;b`}},
+	{`""a;b`, []string{`a`, `b`}},
+	{`"""a;b`, []string{`a;b`}},
+	{`""""a;b`, []string{`a`, `b`}},
+	{`a";b`, []string{`a;b`}},
+	{`a;b";c`, []string{`a`, `b;c`}},
+	{`"a";b";c`, []string{`a`, `b;c`}},
+}
+
+func TestSplitList(t *testing.T) {
+	tests := splitlisttests
+	if runtime.GOOS == "windows" {
+		tests = append(tests, winsplitlisttests...)
+	}
+	for _, test := range tests {
+		if l := filepath.SplitList(test.list); !reflect.DeepEqual(l, test.result) {
+			t.Errorf("SplitList(%#q) = %#q, want %#q", test.list, l, test.result)
+		}
+	}
+}
+
+type SplitTest struct {
+	path, dir, file string
+}
+
+var unixsplittests = []SplitTest{
+	{"a/b", "a/", "b"},
+	{"a/b/", "a/b/", ""},
+	{"a/", "a/", ""},
+	{"a", "", "a"},
+	{"/", "/", ""},
+}
+
+var winsplittests = []SplitTest{
+	{`c:`, `c:`, ``},
+	{`c:/`, `c:/`, ``},
+	{`c:/foo`, `c:/`, `foo`},
+	{`c:/foo/bar`, `c:/foo/`, `bar`},
+	{`//host/share`, `//host/share`, ``},
+	{`//host/share/`, `//host/share/`, ``},
+	{`//host/share/foo`, `//host/share/`, `foo`},
+	{`\\host\share`, `\\host\share`, ``},
+	{`\\host\share\`, `\\host\share\`, ``},
+	{`\\host\share\foo`, `\\host\share\`, `foo`},
+}
+
+func TestSplit(t *testing.T) {
+	var splittests []SplitTest
+	splittests = unixsplittests
+	if runtime.GOOS == "windows" {
+		splittests = append(splittests, winsplittests...)
+	}
+	for _, test := range splittests {
+		if d, f := filepath.Split(test.path); d != test.dir || f != test.file {
+			t.Errorf("Split(%q) = %q, %q, want %q, %q", test.path, d, f, test.dir, test.file)
+		}
+	}
+}
+
+type JoinTest struct {
+	elem []string
+	path string
+}
+
+var jointests = []JoinTest{
+	// zero parameters
+	{[]string{}, ""},
+
+	// one parameter
+	{[]string{""}, ""},
+	{[]string{"/"}, "/"},
+	{[]string{"a"}, "a"},
+
+	// two parameters
+	{[]string{"a", "b"}, "a/b"},
+	{[]string{"a", ""}, "a"},
+	{[]string{"", "b"}, "b"},
+	{[]string{"/", "a"}, "/a"},
+	{[]string{"/", "a/b"}, "/a/b"},
+	{[]string{"/", ""}, "/"},
+	{[]string{"/a", "b"}, "/a/b"},
+	{[]string{"a", "/b"}, "a/b"},
+	{[]string{"/a", "/b"}, "/a/b"},
+	{[]string{"a/", "b"}, "a/b"},
+	{[]string{"a/", ""}, "a"},
+	{[]string{"", ""}, ""},
+
+	// three parameters
+	{[]string{"/", "a", "b"}, "/a/b"},
+}
+
+var nonwinjointests = []JoinTest{
+	{[]string{"//", "a"}, "/a"},
+}
+
+var winjointests = []JoinTest{
+	{[]string{`directory`, `file`}, `directory\file`},
+	{[]string{`C:\Windows\`, `System32`}, `C:\Windows\System32`},
+	{[]string{`C:\Windows\`, ``}, `C:\Windows`},
+	{[]string{`C:\`, `Windows`}, `C:\Windows`},
+	{[]string{`C:`, `a`}, `C:a`},
+	{[]string{`C:`, `a\b`}, `C:a\b`},
+	{[]string{`C:`, `a`, `b`}, `C:a\b`},
+	{[]string{`C:`, ``, `b`}, `C:b`},
+	{[]string{`C:`, ``, ``, `b`}, `C:b`},
+	{[]string{`C:`, ``}, `C:.`},
+	{[]string{`C:`, ``, ``}, `C:.`},
+	{[]string{`C:`, `\a`}, `C:\a`},
+	{[]string{`C:`, ``, `\a`}, `C:\a`},
+	{[]string{`C:.`, `a`}, `C:a`},
+	{[]string{`C:a`, `b`}, `C:a\b`},
+	{[]string{`C:a`, `b`, `d`}, `C:a\b\d`},
+	{[]string{`\\host\share`, `foo`}, `\\host\share\foo`},
+	{[]string{`\\host\share\foo`}, `\\host\share\foo`},
+	{[]string{`//host/share`, `foo/bar`}, `\\host\share\foo\bar`},
+	{[]string{`\`}, `\`},
+	{[]string{`\`, ``}, `\`},
+	{[]string{`\`, `a`}, `\a`},
+	{[]string{`\\`, `a`}, `\\a`},
+	{[]string{`\`, `a`, `b`}, `\a\b`},
+	{[]string{`\\`, `a`, `b`}, `\\a\b`},
+	{[]string{`\`, `\\a\b`, `c`}, `\a\b\c`},
+	{[]string{`\\a`, `b`, `c`}, `\\a\b\c`},
+	{[]string{`\\a\`, `b`, `c`}, `\\a\b\c`},
+	{[]string{`//`, `a`}, `\\a`},
+	{[]string{`a:\b\c`, `x\..\y:\..\..\z`}, `a:\b\z`},
+	{[]string{`\`, `??\a`}, `\.\??\a`},
+}
+
+func TestJoin(t *testing.T) {
+	if runtime.GOOS == "windows" {
+		jointests = append(jointests, winjointests...)
+	} else {
+		jointests = append(jointests, nonwinjointests...)
+	}
+	for _, test := range jointests {
+		expected := filepath.FromSlash(test.path)
+		if p := filepath.Join(test.elem...); p != expected {
+			t.Errorf("join(%q) = %q, want %q", test.elem, p, expected)
+		}
+	}
+}
+
+type ExtTest struct {
+	path, ext string
+}
+
+var exttests = []ExtTest{
+	{"path.go", ".go"},
+	{"path.pb.go", ".go"},
+	{"a.dir/b", ""},
+	{"a.dir/b.go", ".go"},
+	{"a.dir/", ""},
+}
+
+func TestExt(t *testing.T) {
+	for _, test := range exttests {
+		if x := filepath.Ext(test.path); x != test.ext {
+			t.Errorf("Ext(%q) = %q, want %q", test.path, x, test.ext)
+		}
+	}
+}
+
+type Node struct {
+	name    string
+	entries []*Node // nil if the entry is a file
+	mark    int
+}
+
+var tree = &Node{
+	"testdata",
+	[]*Node{
+		{"a", nil, 0},
+		{"b", []*Node{}, 0},
+		{"c", nil, 0},
+		{
+			"d",
+			[]*Node{
+				{"x", nil, 0},
+				{"y", []*Node{}, 0},
+				{
+					"z",
+					[]*Node{
+						{"u", nil, 0},
+						{"v", nil, 0},
+					},
+					0,
+				},
+			},
+			0,
+		},
+	},
+	0,
+}
+
+func walkTree(n *Node, path string, f func(path string, n *Node)) {
+	f(path, n)
+	for _, e := range n.entries {
+		walkTree(e, filepath.Join(path, e.name), f)
+	}
+}
+
+func makeTree(t *testing.T) {
+	walkTree(tree, tree.name, func(path string, n *Node) {
+		if n.entries == nil {
+			fd, err := os.Create(path)
+			if err != nil {
+				t.Errorf("makeTree: %v", err)
+				return
+			}
+			fd.Close()
+		} else {
+			os.Mkdir(path, 0770)
+		}
+	})
+}
+
+func markTree(n *Node) { walkTree(n, "", func(path string, n *Node) { n.mark++ }) }
+
+func checkMarks(t *testing.T, report bool) {
+	walkTree(tree, tree.name, func(path string, n *Node) {
+		if n.mark != 1 && report {
+			t.Errorf("node %s mark = %d; expected 1", path, n.mark)
+		}
+		n.mark = 0
+	})
+}
+
+// Assumes that each node name is unique. Good enough for a test.
+// If clear is true, any incoming error is cleared before return. The errors
+// are always accumulated, though.
+func mark(d fs.DirEntry, err error, errors *[]error, clear bool) error {
+	name := d.Name()
+	walkTree(tree, tree.name, func(path string, n *Node) {
+		if n.name == name {
+			n.mark++
+		}
+	})
+	if err != nil {
+		*errors = append(*errors, err)
+		if clear {
+			return nil
+		}
+		return err
+	}
+	return nil
+}
+
+// chdir changes the current working directory to the named directory,
+// and then restore the original working directory at the end of the test.
+func chdir(t *testing.T, dir string) {
+	olddir, err := os.Getwd()
+	if err != nil {
+		t.Fatalf("getwd %s: %v", dir, err)
+	}
+	if err := os.Chdir(dir); err != nil {
+		t.Fatalf("chdir %s: %v", dir, err)
+	}
+
+	t.Cleanup(func() {
+		if err := os.Chdir(olddir); err != nil {
+			t.Errorf("restore original working directory %s: %v", olddir, err)
+			os.Exit(1)
+		}
+	})
+}
+
+func chtmpdir(t *testing.T) (restore func()) {
+	oldwd, err := os.Getwd()
+	if err != nil {
+		t.Fatalf("chtmpdir: %v", err)
+	}
+	d, err := os.MkdirTemp("", "test")
+	if err != nil {
+		t.Fatalf("chtmpdir: %v", err)
+	}
+	if err := os.Chdir(d); err != nil {
+		t.Fatalf("chtmpdir: %v", err)
+	}
+	return func() {
+		if err := os.Chdir(oldwd); err != nil {
+			t.Fatalf("chtmpdir: %v", err)
+		}
+		os.RemoveAll(d)
+	}
+}
+
+// tempDirCanonical returns a temporary directory for the test to use, ensuring
+// that the returned path does not contain symlinks.
+func tempDirCanonical(t *testing.T) string {
+	dir := t.TempDir()
+
+	cdir, err := filepath.EvalSymlinks(dir)
+	if err != nil {
+		t.Errorf("tempDirCanonical: %v", err)
+	}
+
+	return cdir
+}
+
+func TestWalk(t *testing.T) {
+	walk := func(root string, fn fs.WalkDirFunc) error {
+		return filepath.Walk(root, func(path string, info fs.FileInfo, err error) error {
+			return fn(path, &statDirEntry{info}, err)
+		})
+	}
+	testWalk(t, walk, 1)
+}
+
+type statDirEntry struct {
+	info fs.FileInfo
+}
+
+func (d *statDirEntry) Name() string               { return d.info.Name() }
+func (d *statDirEntry) IsDir() bool                { return d.info.IsDir() }
+func (d *statDirEntry) Type() fs.FileMode          { return d.info.Mode().Type() }
+func (d *statDirEntry) Info() (fs.FileInfo, error) { return d.info, nil }
+
+func (d *statDirEntry) String() string {
+	return fs.FormatDirEntry(d)
+}
+
+func TestWalkDir(t *testing.T) {
+	testWalk(t, filepath.WalkDir, 2)
+}
+
+func testWalk(t *testing.T, walk func(string, fs.WalkDirFunc) error, errVisit int) {
+	if runtime.GOOS == "ios" {
+		restore := chtmpdir(t)
+		defer restore()
+	}
+
+	tmpDir := t.TempDir()
+
+	origDir, err := os.Getwd()
+	if err != nil {
+		t.Fatal("finding working dir:", err)
+	}
+	if err = os.Chdir(tmpDir); err != nil {
+		t.Fatal("entering temp dir:", err)
+	}
+	defer os.Chdir(origDir)
+
+	makeTree(t)
+	errors := make([]error, 0, 10)
+	clear := true
+	markFn := func(path string, d fs.DirEntry, err error) error {
+		return mark(d, err, &errors, clear)
+	}
+	// Expect no errors.
+	err = walk(tree.name, markFn)
+	if err != nil {
+		t.Fatalf("no error expected, found: %s", err)
+	}
+	if len(errors) != 0 {
+		t.Fatalf("unexpected errors: %s", errors)
+	}
+	checkMarks(t, true)
+	errors = errors[0:0]
+
+	t.Run("PermErr", func(t *testing.T) {
+		// Test permission errors. Only possible if we're not root
+		// and only on some file systems (AFS, FAT).  To avoid errors during
+		// all.bash on those file systems, skip during go test -short.
+		// Chmod is not supported on wasip1.
+		if runtime.GOOS == "windows" || runtime.GOOS == "wasip1" {
+			t.Skip("skipping on " + runtime.GOOS)
+		}
+		if os.Getuid() == 0 {
+			t.Skip("skipping as root")
+		}
+		if testing.Short() {
+			t.Skip("skipping in short mode")
+		}
+
+		// introduce 2 errors: chmod top-level directories to 0
+		os.Chmod(filepath.Join(tree.name, tree.entries[1].name), 0)
+		os.Chmod(filepath.Join(tree.name, tree.entries[3].name), 0)
+
+		// 3) capture errors, expect two.
+		// mark respective subtrees manually
+		markTree(tree.entries[1])
+		markTree(tree.entries[3])
+		// correct double-marking of directory itself
+		tree.entries[1].mark -= errVisit
+		tree.entries[3].mark -= errVisit
+		err := walk(tree.name, markFn)
+		if err != nil {
+			t.Fatalf("expected no error return from Walk, got %s", err)
+		}
+		if len(errors) != 2 {
+			t.Errorf("expected 2 errors, got %d: %s", len(errors), errors)
+		}
+		// the inaccessible subtrees were marked manually
+		checkMarks(t, true)
+		errors = errors[0:0]
+
+		// 4) capture errors, stop after first error.
+		// mark respective subtrees manually
+		markTree(tree.entries[1])
+		markTree(tree.entries[3])
+		// correct double-marking of directory itself
+		tree.entries[1].mark -= errVisit
+		tree.entries[3].mark -= errVisit
+		clear = false // error will stop processing
+		err = walk(tree.name, markFn)
+		if err == nil {
+			t.Fatalf("expected error return from Walk")
+		}
+		if len(errors) != 1 {
+			t.Errorf("expected 1 error, got %d: %s", len(errors), errors)
+		}
+		// the inaccessible subtrees were marked manually
+		checkMarks(t, false)
+		errors = errors[0:0]
+
+		// restore permissions
+		os.Chmod(filepath.Join(tree.name, tree.entries[1].name), 0770)
+		os.Chmod(filepath.Join(tree.name, tree.entries[3].name), 0770)
+	})
+}
+
+func touch(t *testing.T, name string) {
+	f, err := os.Create(name)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := f.Close(); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestWalkSkipDirOnFile(t *testing.T) {
+	td := t.TempDir()
+
+	if err := os.MkdirAll(filepath.Join(td, "dir"), 0755); err != nil {
+		t.Fatal(err)
+	}
+	touch(t, filepath.Join(td, "dir/foo1"))
+	touch(t, filepath.Join(td, "dir/foo2"))
+
+	sawFoo2 := false
+	walker := func(path string) error {
+		if strings.HasSuffix(path, "foo2") {
+			sawFoo2 = true
+		}
+		if strings.HasSuffix(path, "foo1") {
+			return filepath.SkipDir
+		}
+		return nil
+	}
+	walkFn := func(path string, _ fs.FileInfo, _ error) error { return walker(path) }
+	walkDirFn := func(path string, _ fs.DirEntry, _ error) error { return walker(path) }
+
+	check := func(t *testing.T, walk func(root string) error, root string) {
+		t.Helper()
+		sawFoo2 = false
+		err := walk(root)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if sawFoo2 {
+			t.Errorf("SkipDir on file foo1 did not block processing of foo2")
+		}
+	}
+
+	t.Run("Walk", func(t *testing.T) {
+		Walk := func(root string) error { return filepath.Walk(td, walkFn) }
+		check(t, Walk, td)
+		check(t, Walk, filepath.Join(td, "dir"))
+	})
+	t.Run("WalkDir", func(t *testing.T) {
+		WalkDir := func(root string) error { return filepath.WalkDir(td, walkDirFn) }
+		check(t, WalkDir, td)
+		check(t, WalkDir, filepath.Join(td, "dir"))
+	})
+}
+
+func TestWalkSkipAllOnFile(t *testing.T) {
+	td := t.TempDir()
+
+	if err := os.MkdirAll(filepath.Join(td, "dir", "subdir"), 0755); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.MkdirAll(filepath.Join(td, "dir2"), 0755); err != nil {
+		t.Fatal(err)
+	}
+
+	touch(t, filepath.Join(td, "dir", "foo1"))
+	touch(t, filepath.Join(td, "dir", "foo2"))
+	touch(t, filepath.Join(td, "dir", "subdir", "foo3"))
+	touch(t, filepath.Join(td, "dir", "foo4"))
+	touch(t, filepath.Join(td, "dir2", "bar"))
+	touch(t, filepath.Join(td, "last"))
+
+	remainingWereSkipped := true
+	walker := func(path string) error {
+		if strings.HasSuffix(path, "foo2") {
+			return filepath.SkipAll
+		}
+
+		if strings.HasSuffix(path, "foo3") ||
+			strings.HasSuffix(path, "foo4") ||
+			strings.HasSuffix(path, "bar") ||
+			strings.HasSuffix(path, "last") {
+			remainingWereSkipped = false
+		}
+		return nil
+	}
+
+	walkFn := func(path string, _ fs.FileInfo, _ error) error { return walker(path) }
+	walkDirFn := func(path string, _ fs.DirEntry, _ error) error { return walker(path) }
+
+	check := func(t *testing.T, walk func(root string) error, root string) {
+		t.Helper()
+		remainingWereSkipped = true
+		if err := walk(root); err != nil {
+			t.Fatal(err)
+		}
+		if !remainingWereSkipped {
+			t.Errorf("SkipAll on file foo2 did not block processing of remaining files and directories")
+		}
+	}
+
+	t.Run("Walk", func(t *testing.T) {
+		Walk := func(_ string) error { return filepath.Walk(td, walkFn) }
+		check(t, Walk, td)
+		check(t, Walk, filepath.Join(td, "dir"))
+	})
+	t.Run("WalkDir", func(t *testing.T) {
+		WalkDir := func(_ string) error { return filepath.WalkDir(td, walkDirFn) }
+		check(t, WalkDir, td)
+		check(t, WalkDir, filepath.Join(td, "dir"))
+	})
+}
+
+func TestWalkFileError(t *testing.T) {
+	td := t.TempDir()
+
+	touch(t, filepath.Join(td, "foo"))
+	touch(t, filepath.Join(td, "bar"))
+	dir := filepath.Join(td, "dir")
+	if err := os.MkdirAll(filepath.Join(td, "dir"), 0755); err != nil {
+		t.Fatal(err)
+	}
+	touch(t, filepath.Join(dir, "baz"))
+	touch(t, filepath.Join(dir, "stat-error"))
+	defer func() {
+		*filepath.LstatP = os.Lstat
+	}()
+	statErr := errors.New("some stat error")
+	*filepath.LstatP = func(path string) (fs.FileInfo, error) {
+		if strings.HasSuffix(path, "stat-error") {
+			return nil, statErr
+		}
+		return os.Lstat(path)
+	}
+	got := map[string]error{}
+	err := filepath.Walk(td, func(path string, fi fs.FileInfo, err error) error {
+		rel, _ := filepath.Rel(td, path)
+		got[filepath.ToSlash(rel)] = err
+		return nil
+	})
+	if err != nil {
+		t.Errorf("Walk error: %v", err)
+	}
+	want := map[string]error{
+		".":              nil,
+		"foo":            nil,
+		"bar":            nil,
+		"dir":            nil,
+		"dir/baz":        nil,
+		"dir/stat-error": statErr,
+	}
+	if !reflect.DeepEqual(got, want) {
+		t.Errorf("Walked %#v; want %#v", got, want)
+	}
+}
+
+func TestWalkSymlinkRoot(t *testing.T) {
+	testenv.MustHaveSymlink(t)
+
+	td := t.TempDir()
+	dir := filepath.Join(td, "dir")
+	if err := os.MkdirAll(filepath.Join(td, "dir"), 0755); err != nil {
+		t.Fatal(err)
+	}
+	touch(t, filepath.Join(dir, "foo"))
+
+	link := filepath.Join(td, "link")
+	if err := os.Symlink("dir", link); err != nil {
+		t.Fatal(err)
+	}
+
+	abslink := filepath.Join(td, "abslink")
+	if err := os.Symlink(dir, abslink); err != nil {
+		t.Fatal(err)
+	}
+
+	linklink := filepath.Join(td, "linklink")
+	if err := os.Symlink("link", linklink); err != nil {
+		t.Fatal(err)
+	}
+
+	// Per https://pubs.opengroup.org/onlinepubs/9699919799.2013edition/basedefs/V1_chap04.html#tag_04_12:
+	// “A pathname that contains at least one non- <slash> character and that ends
+	// with one or more trailing <slash> characters shall not be resolved
+	// successfully unless the last pathname component before the trailing <slash>
+	// characters names an existing directory [...].”
+	//
+	// Since Walk does not traverse symlinks itself, its behavior should depend on
+	// whether the path passed to Walk ends in a slash: if it does not end in a slash,
+	// Walk should report the symlink itself (since it is the last pathname component);
+	// but if it does end in a slash, Walk should walk the directory to which the symlink
+	// refers (since it must be fully resolved before walking).
+	for _, tt := range []struct {
+		desc      string
+		root      string
+		want      []string
+		buggyGOOS []string
+	}{
+		{
+			desc: "no slash",
+			root: link,
+			want: []string{link},
+		},
+		{
+			desc: "slash",
+			root: link + string(filepath.Separator),
+			want: []string{link, filepath.Join(link, "foo")},
+		},
+		{
+			desc: "abs no slash",
+			root: abslink,
+			want: []string{abslink},
+		},
+		{
+			desc: "abs with slash",
+			root: abslink + string(filepath.Separator),
+			want: []string{abslink, filepath.Join(abslink, "foo")},
+		},
+		{
+			desc: "double link no slash",
+			root: linklink,
+			want: []string{linklink},
+		},
+		{
+			desc:      "double link with slash",
+			root:      linklink + string(filepath.Separator),
+			want:      []string{linklink, filepath.Join(linklink, "foo")},
+			buggyGOOS: []string{"darwin", "ios"}, // https://go.dev/issue/59586
+		},
+	} {
+		tt := tt
+		t.Run(tt.desc, func(t *testing.T) {
+			var walked []string
+			err := filepath.Walk(tt.root, func(path string, info fs.FileInfo, err error) error {
+				if err != nil {
+					return err
+				}
+				t.Logf("%#q: %v", path, info.Mode())
+				walked = append(walked, filepath.Clean(path))
+				return nil
+			})
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			if !reflect.DeepEqual(walked, tt.want) {
+				t.Logf("Walk(%#q) visited %#q; want %#q", tt.root, walked, tt.want)
+				if slices.Contains(tt.buggyGOOS, runtime.GOOS) {
+					t.Logf("(ignoring known bug on %v)", runtime.GOOS)
+				} else {
+					t.Fail()
+				}
+			}
+		})
+	}
+}
+
+var basetests = []PathTest{
+	{"", "."},
+	{".", "."},
+	{"/.", "."},
+	{"/", "/"},
+	{"////", "/"},
+	{"x/", "x"},
+	{"abc", "abc"},
+	{"abc/def", "def"},
+	{"a/b/.x", ".x"},
+	{"a/b/c.", "c."},
+	{"a/b/c.x", "c.x"},
+}
+
+var winbasetests = []PathTest{
+	{`c:\`, `\`},
+	{`c:.`, `.`},
+	{`c:\a\b`, `b`},
+	{`c:a\b`, `b`},
+	{`c:a\b\c`, `c`},
+	{`\\host\share\`, `\`},
+	{`\\host\share\a`, `a`},
+	{`\\host\share\a\b`, `b`},
+}
+
+func TestBase(t *testing.T) {
+	tests := basetests
+	if runtime.GOOS == "windows" {
+		// make unix tests work on windows
+		for i := range tests {
+			tests[i].result = filepath.Clean(tests[i].result)
+		}
+		// add windows specific tests
+		tests = append(tests, winbasetests...)
+	}
+	for _, test := range tests {
+		if s := filepath.Base(test.path); s != test.result {
+			t.Errorf("Base(%q) = %q, want %q", test.path, s, test.result)
+		}
+	}
+}
+
+var dirtests = []PathTest{
+	{"", "."},
+	{".", "."},
+	{"/.", "/"},
+	{"/", "/"},
+	{"/foo", "/"},
+	{"x/", "x"},
+	{"abc", "."},
+	{"abc/def", "abc"},
+	{"a/b/.x", "a/b"},
+	{"a/b/c.", "a/b"},
+	{"a/b/c.x", "a/b"},
+}
+
+var nonwindirtests = []PathTest{
+	{"////", "/"},
+}
+
+var windirtests = []PathTest{
+	{`c:\`, `c:\`},
+	{`c:.`, `c:.`},
+	{`c:\a\b`, `c:\a`},
+	{`c:a\b`, `c:a`},
+	{`c:a\b\c`, `c:a\b`},
+	{`\\host\share`, `\\host\share`},
+	{`\\host\share\`, `\\host\share\`},
+	{`\\host\share\a`, `\\host\share\`},
+	{`\\host\share\a\b`, `\\host\share\a`},
+	{`\\\\`, `\\\\`},
+}
+
+func TestDir(t *testing.T) {
+	tests := dirtests
+	if runtime.GOOS == "windows" {
+		// make unix tests work on windows
+		for i := range tests {
+			tests[i].result = filepath.Clean(tests[i].result)
+		}
+		// add windows specific tests
+		tests = append(tests, windirtests...)
+	} else {
+		tests = append(tests, nonwindirtests...)
+	}
+	for _, test := range tests {
+		if s := filepath.Dir(test.path); s != test.result {
+			t.Errorf("Dir(%q) = %q, want %q", test.path, s, test.result)
+		}
+	}
+}
+
+type IsAbsTest struct {
+	path  string
+	isAbs bool
+}
+
+var isabstests = []IsAbsTest{
+	{"", false},
+	{"/", true},
+	{"/usr/bin/gcc", true},
+	{"..", false},
+	{"/a/../bb", true},
+	{".", false},
+	{"./", false},
+	{"lala", false},
+}
+
+var winisabstests = []IsAbsTest{
+	{`C:\`, true},
+	{`c\`, false},
+	{`c::`, false},
+	{`c:`, false},
+	{`/`, false},
+	{`\`, false},
+	{`\Windows`, false},
+	{`c:a\b`, false},
+	{`c:\a\b`, true},
+	{`c:/a/b`, true},
+	{`\\host\share`, true},
+	{`\\host\share\`, true},
+	{`\\host\share\foo`, true},
+	{`//host/share/foo/bar`, true},
+	{`\\?\a\b\c`, true},
+	{`\??\a\b\c`, true},
+}
+
+func TestIsAbs(t *testing.T) {
+	var tests []IsAbsTest
+	if runtime.GOOS == "windows" {
+		tests = append(tests, winisabstests...)
+		// All non-windows tests should fail, because they have no volume letter.
+		for _, test := range isabstests {
+			tests = append(tests, IsAbsTest{test.path, false})
+		}
+		// All non-windows test should work as intended if prefixed with volume letter.
+		for _, test := range isabstests {
+			tests = append(tests, IsAbsTest{"c:" + test.path, test.isAbs})
+		}
+	} else {
+		tests = isabstests
+	}
+
+	for _, test := range tests {
+		if r := filepath.IsAbs(test.path); r != test.isAbs {
+			t.Errorf("IsAbs(%q) = %v, want %v", test.path, r, test.isAbs)
+		}
+	}
+}
+
+type EvalSymlinksTest struct {
+	// If dest is empty, the path is created; otherwise the dest is symlinked to the path.
+	path, dest string
+}
+
+var EvalSymlinksTestDirs = []EvalSymlinksTest{
+	{"test", ""},
+	{"test/dir", ""},
+	{"test/dir/link3", "../../"},
+	{"test/link1", "../test"},
+	{"test/link2", "dir"},
+	{"test/linkabs", "/"},
+	{"test/link4", "../test2"},
+	{"test2", "test/dir"},
+	// Issue 23444.
+	{"src", ""},
+	{"src/pool", ""},
+	{"src/pool/test", ""},
+	{"src/versions", ""},
+	{"src/versions/current", "../../version"},
+	{"src/versions/v1", ""},
+	{"src/versions/v1/modules", ""},
+	{"src/versions/v1/modules/test", "../../../pool/test"},
+	{"version", "src/versions/v1"},
+}
+
+var EvalSymlinksTests = []EvalSymlinksTest{
+	{"test", "test"},
+	{"test/dir", "test/dir"},
+	{"test/dir/../..", "."},
+	{"test/link1", "test"},
+	{"test/link2", "test/dir"},
+	{"test/link1/dir", "test/dir"},
+	{"test/link2/..", "test"},
+	{"test/dir/link3", "."},
+	{"test/link2/link3/test", "test"},
+	{"test/linkabs", "/"},
+	{"test/link4/..", "test"},
+	{"src/versions/current/modules/test", "src/pool/test"},
+}
+
+// simpleJoin builds a file name from the directory and path.
+// It does not use Join because we don't want ".." to be evaluated.
+func simpleJoin(dir, path string) string {
+	return dir + string(filepath.Separator) + path
+}
+
+func testEvalSymlinks(t *testing.T, path, want string) {
+	have, err := filepath.EvalSymlinks(path)
+	if err != nil {
+		t.Errorf("EvalSymlinks(%q) error: %v", path, err)
+		return
+	}
+	if filepath.Clean(have) != filepath.Clean(want) {
+		t.Errorf("EvalSymlinks(%q) returns %q, want %q", path, have, want)
+	}
+}
+
+func testEvalSymlinksAfterChdir(t *testing.T, wd, path, want string) {
+	cwd, err := os.Getwd()
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer func() {
+		err := os.Chdir(cwd)
+		if err != nil {
+			t.Fatal(err)
+		}
+	}()
+
+	err = os.Chdir(wd)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	have, err := filepath.EvalSymlinks(path)
+	if err != nil {
+		t.Errorf("EvalSymlinks(%q) in %q directory error: %v", path, wd, err)
+		return
+	}
+	if filepath.Clean(have) != filepath.Clean(want) {
+		t.Errorf("EvalSymlinks(%q) in %q directory returns %q, want %q", path, wd, have, want)
+	}
+}
+
+func TestEvalSymlinks(t *testing.T) {
+	testenv.MustHaveSymlink(t)
+
+	tmpDir := t.TempDir()
+
+	// /tmp may itself be a symlink! Avoid the confusion, although
+	// it means trusting the thing we're testing.
+	var err error
+	tmpDir, err = filepath.EvalSymlinks(tmpDir)
+	if err != nil {
+		t.Fatal("eval symlink for tmp dir:", err)
+	}
+
+	// Create the symlink farm using relative paths.
+	for _, d := range EvalSymlinksTestDirs {
+		var err error
+		path := simpleJoin(tmpDir, d.path)
+		if d.dest == "" {
+			err = os.Mkdir(path, 0755)
+		} else {
+			err = os.Symlink(d.dest, path)
+		}
+		if err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	// Evaluate the symlink farm.
+	for _, test := range EvalSymlinksTests {
+		path := simpleJoin(tmpDir, test.path)
+
+		dest := simpleJoin(tmpDir, test.dest)
+		if filepath.IsAbs(test.dest) || os.IsPathSeparator(test.dest[0]) {
+			dest = test.dest
+		}
+		testEvalSymlinks(t, path, dest)
+
+		// test EvalSymlinks(".")
+		testEvalSymlinksAfterChdir(t, path, ".", ".")
+
+		// test EvalSymlinks("C:.") on Windows
+		if runtime.GOOS == "windows" {
+			volDot := filepath.VolumeName(tmpDir) + "."
+			testEvalSymlinksAfterChdir(t, path, volDot, volDot)
+		}
+
+		// test EvalSymlinks(".."+path)
+		dotdotPath := simpleJoin("..", test.dest)
+		if filepath.IsAbs(test.dest) || os.IsPathSeparator(test.dest[0]) {
+			dotdotPath = test.dest
+		}
+		testEvalSymlinksAfterChdir(t,
+			simpleJoin(tmpDir, "test"),
+			simpleJoin("..", test.path),
+			dotdotPath)
+
+		// test EvalSymlinks(p) where p is relative path
+		testEvalSymlinksAfterChdir(t, tmpDir, test.path, test.dest)
+	}
+}
+
+func TestEvalSymlinksIsNotExist(t *testing.T) {
+	testenv.MustHaveSymlink(t)
+
+	defer chtmpdir(t)()
+
+	_, err := filepath.EvalSymlinks("notexist")
+	if !os.IsNotExist(err) {
+		t.Errorf("expected the file is not found, got %v\n", err)
+	}
+
+	err = os.Symlink("notexist", "link")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.Remove("link")
+
+	_, err = filepath.EvalSymlinks("link")
+	if !os.IsNotExist(err) {
+		t.Errorf("expected the file is not found, got %v\n", err)
+	}
+}
+
+func TestIssue13582(t *testing.T) {
+	testenv.MustHaveSymlink(t)
+
+	tmpDir := t.TempDir()
+
+	dir := filepath.Join(tmpDir, "dir")
+	err := os.Mkdir(dir, 0755)
+	if err != nil {
+		t.Fatal(err)
+	}
+	linkToDir := filepath.Join(tmpDir, "link_to_dir")
+	err = os.Symlink(dir, linkToDir)
+	if err != nil {
+		t.Fatal(err)
+	}
+	file := filepath.Join(linkToDir, "file")
+	err = os.WriteFile(file, nil, 0644)
+	if err != nil {
+		t.Fatal(err)
+	}
+	link1 := filepath.Join(linkToDir, "link1")
+	err = os.Symlink(file, link1)
+	if err != nil {
+		t.Fatal(err)
+	}
+	link2 := filepath.Join(linkToDir, "link2")
+	err = os.Symlink(link1, link2)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// /tmp may itself be a symlink!
+	realTmpDir, err := filepath.EvalSymlinks(tmpDir)
+	if err != nil {
+		t.Fatal(err)
+	}
+	realDir := filepath.Join(realTmpDir, "dir")
+	realFile := filepath.Join(realDir, "file")
+
+	tests := []struct {
+		path, want string
+	}{
+		{dir, realDir},
+		{linkToDir, realDir},
+		{file, realFile},
+		{link1, realFile},
+		{link2, realFile},
+	}
+	for i, test := range tests {
+		have, err := filepath.EvalSymlinks(test.path)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if have != test.want {
+			t.Errorf("test#%d: EvalSymlinks(%q) returns %q, want %q", i, test.path, have, test.want)
+		}
+	}
+}
+
+// Issue 57905.
+func TestRelativeSymlinkToAbsolute(t *testing.T) {
+	testenv.MustHaveSymlink(t)
+	// Not parallel: uses os.Chdir.
+
+	tmpDir := t.TempDir()
+	chdir(t, tmpDir)
+
+	// Create "link" in the current working directory as a symlink to an arbitrary
+	// absolute path. On macOS, this path is likely to begin with a symlink
+	// itself: generally either in /var (symlinked to "private/var") or /tmp
+	// (symlinked to "private/tmp").
+	if err := os.Symlink(tmpDir, "link"); err != nil {
+		t.Fatal(err)
+	}
+	t.Logf(`os.Symlink(%q, "link")`, tmpDir)
+
+	p, err := filepath.EvalSymlinks("link")
+	if err != nil {
+		t.Fatalf(`EvalSymlinks("link"): %v`, err)
+	}
+	want, err := filepath.EvalSymlinks(tmpDir)
+	if err != nil {
+		t.Fatalf(`EvalSymlinks(%q): %v`, tmpDir, err)
+	}
+	if p != want {
+		t.Errorf(`EvalSymlinks("link") = %q; want %q`, p, want)
+	}
+	t.Logf(`EvalSymlinks("link") = %q`, p)
+}
+
+// Test directories relative to temporary directory.
+// The tests are run in absTestDirs[0].
+var absTestDirs = []string{
+	"a",
+	"a/b",
+	"a/b/c",
+}
+
+// Test paths relative to temporary directory. $ expands to the directory.
+// The tests are run in absTestDirs[0].
+// We create absTestDirs first.
+var absTests = []string{
+	".",
+	"b",
+	"b/",
+	"../a",
+	"../a/b",
+	"../a/b/./c/../../.././a",
+	"../a/b/./c/../../.././a/",
+	"$",
+	"$/.",
+	"$/a/../a/b",
+	"$/a/b/c/../../.././a",
+	"$/a/b/c/../../.././a/",
+}
+
+func TestAbs(t *testing.T) {
+	root := t.TempDir()
+	wd, err := os.Getwd()
+	if err != nil {
+		t.Fatal("getwd failed: ", err)
+	}
+	err = os.Chdir(root)
+	if err != nil {
+		t.Fatal("chdir failed: ", err)
+	}
+	defer os.Chdir(wd)
+
+	for _, dir := range absTestDirs {
+		err = os.Mkdir(dir, 0777)
+		if err != nil {
+			t.Fatal("Mkdir failed: ", err)
+		}
+	}
+
+	if runtime.GOOS == "windows" {
+		vol := filepath.VolumeName(root)
+		var extra []string
+		for _, path := range absTests {
+			if strings.Contains(path, "$") {
+				continue
+			}
+			path = vol + path
+			extra = append(extra, path)
+		}
+		absTests = append(absTests, extra...)
+	}
+
+	err = os.Chdir(absTestDirs[0])
+	if err != nil {
+		t.Fatal("chdir failed: ", err)
+	}
+
+	for _, path := range absTests {
+		path = strings.ReplaceAll(path, "$", root)
+		info, err := os.Stat(path)
+		if err != nil {
+			t.Errorf("%s: %s", path, err)
+			continue
+		}
+
+		abspath, err := filepath.Abs(path)
+		if err != nil {
+			t.Errorf("Abs(%q) error: %v", path, err)
+			continue
+		}
+		absinfo, err := os.Stat(abspath)
+		if err != nil || !os.SameFile(absinfo, info) {
+			t.Errorf("Abs(%q)=%q, not the same file", path, abspath)
+		}
+		if !filepath.IsAbs(abspath) {
+			t.Errorf("Abs(%q)=%q, not an absolute path", path, abspath)
+		}
+		if filepath.IsAbs(abspath) && abspath != filepath.Clean(abspath) {
+			t.Errorf("Abs(%q)=%q, isn't clean", path, abspath)
+		}
+	}
+}
+
+// Empty path needs to be special-cased on Windows. See golang.org/issue/24441.
+// We test it separately from all other absTests because the empty string is not
+// a valid path, so it can't be used with os.Stat.
+func TestAbsEmptyString(t *testing.T) {
+	root := t.TempDir()
+
+	wd, err := os.Getwd()
+	if err != nil {
+		t.Fatal("getwd failed: ", err)
+	}
+	err = os.Chdir(root)
+	if err != nil {
+		t.Fatal("chdir failed: ", err)
+	}
+	defer os.Chdir(wd)
+
+	info, err := os.Stat(root)
+	if err != nil {
+		t.Fatalf("%s: %s", root, err)
+	}
+
+	abspath, err := filepath.Abs("")
+	if err != nil {
+		t.Fatalf(`Abs("") error: %v`, err)
+	}
+	absinfo, err := os.Stat(abspath)
+	if err != nil || !os.SameFile(absinfo, info) {
+		t.Errorf(`Abs("")=%q, not the same file`, abspath)
+	}
+	if !filepath.IsAbs(abspath) {
+		t.Errorf(`Abs("")=%q, not an absolute path`, abspath)
+	}
+	if filepath.IsAbs(abspath) && abspath != filepath.Clean(abspath) {
+		t.Errorf(`Abs("")=%q, isn't clean`, abspath)
+	}
+}
+
+type RelTests struct {
+	root, path, want string
+}
+
+var reltests = []RelTests{
+	{"a/b", "a/b", "."},
+	{"a/b/.", "a/b", "."},
+	{"a/b", "a/b/.", "."},
+	{"./a/b", "a/b", "."},
+	{"a/b", "./a/b", "."},
+	{"ab/cd", "ab/cde", "../cde"},
+	{"ab/cd", "ab/c", "../c"},
+	{"a/b", "a/b/c/d", "c/d"},
+	{"a/b", "a/b/../c", "../c"},
+	{"a/b/../c", "a/b", "../b"},
+	{"a/b/c", "a/c/d", "../../c/d"},
+	{"a/b", "c/d", "../../c/d"},
+	{"a/b/c/d", "a/b", "../.."},
+	{"a/b/c/d", "a/b/", "../.."},
+	{"a/b/c/d/", "a/b", "../.."},
+	{"a/b/c/d/", "a/b/", "../.."},
+	{"../../a/b", "../../a/b/c/d", "c/d"},
+	{"/a/b", "/a/b", "."},
+	{"/a/b/.", "/a/b", "."},
+	{"/a/b", "/a/b/.", "."},
+	{"/ab/cd", "/ab/cde", "../cde"},
+	{"/ab/cd", "/ab/c", "../c"},
+	{"/a/b", "/a/b/c/d", "c/d"},
+	{"/a/b", "/a/b/../c", "../c"},
+	{"/a/b/../c", "/a/b", "../b"},
+	{"/a/b/c", "/a/c/d", "../../c/d"},
+	{"/a/b", "/c/d", "../../c/d"},
+	{"/a/b/c/d", "/a/b", "../.."},
+	{"/a/b/c/d", "/a/b/", "../.."},
+	{"/a/b/c/d/", "/a/b", "../.."},
+	{"/a/b/c/d/", "/a/b/", "../.."},
+	{"/../../a/b", "/../../a/b/c/d", "c/d"},
+	{".", "a/b", "a/b"},
+	{".", "..", ".."},
+
+	// can't do purely lexically
+	{"..", ".", "err"},
+	{"..", "a", "err"},
+	{"../..", "..", "err"},
+	{"a", "/a", "err"},
+	{"/a", "a", "err"},
+}
+
+var winreltests = []RelTests{
+	{`C:a\b\c`, `C:a/b/d`, `..\d`},
+	{`C:\`, `D:\`, `err`},
+	{`C:`, `D:`, `err`},
+	{`C:\Projects`, `c:\projects\src`, `src`},
+	{`C:\Projects`, `c:\projects`, `.`},
+	{`C:\Projects\a\..`, `c:\projects`, `.`},
+	{`\\host\share`, `\\host\share\file.txt`, `file.txt`},
+}
+
+func TestRel(t *testing.T) {
+	tests := append([]RelTests{}, reltests...)
+	if runtime.GOOS == "windows" {
+		for i := range tests {
+			tests[i].want = filepath.FromSlash(tests[i].want)
+		}
+		tests = append(tests, winreltests...)
+	}
+	for _, test := range tests {
+		got, err := filepath.Rel(test.root, test.path)
+		if test.want == "err" {
+			if err == nil {
+				t.Errorf("Rel(%q, %q)=%q, want error", test.root, test.path, got)
+			}
+			continue
+		}
+		if err != nil {
+			t.Errorf("Rel(%q, %q): want %q, got error: %s", test.root, test.path, test.want, err)
+		}
+		if got != test.want {
+			t.Errorf("Rel(%q, %q)=%q, want %q", test.root, test.path, got, test.want)
+		}
+	}
+}
+
+type VolumeNameTest struct {
+	path string
+	vol  string
+}
+
+var volumenametests = []VolumeNameTest{
+	{`c:/foo/bar`, `c:`},
+	{`c:`, `c:`},
+	{`c:\`, `c:`},
+	{`2:`, `2:`},
+	{``, ``},
+	{`\\\host`, `\\\host`},
+	{`\\\host\`, `\\\host`},
+	{`\\\host\share`, `\\\host`},
+	{`\\\host\\share`, `\\\host`},
+	{`\\host`, `\\host`},
+	{`//host`, `\\host`},
+	{`\\host\`, `\\host\`},
+	{`//host/`, `\\host\`},
+	{`\\host\share`, `\\host\share`},
+	{`//host/share`, `\\host\share`},
+	{`\\host\share\`, `\\host\share`},
+	{`//host/share/`, `\\host\share`},
+	{`\\host\share\foo`, `\\host\share`},
+	{`//host/share/foo`, `\\host\share`},
+	{`\\host\share\\foo\\\bar\\\\baz`, `\\host\share`},
+	{`//host/share//foo///bar////baz`, `\\host\share`},
+	{`\\host\share\foo\..\bar`, `\\host\share`},
+	{`//host/share/foo/../bar`, `\\host\share`},
+	{`//.`, `\\.`},
+	{`//./`, `\\.\`},
+	{`//./NUL`, `\\.\NUL`},
+	{`//?`, `\\?`},
+	{`//?/`, `\\?\`},
+	{`//?/NUL`, `\\?\NUL`},
+	{`/??`, `\??`},
+	{`/??/`, `\??\`},
+	{`/??/NUL`, `\??\NUL`},
+	{`//./a/b`, `\\.\a`},
+	{`//./C:`, `\\.\C:`},
+	{`//./C:/`, `\\.\C:`},
+	{`//./C:/a/b/c`, `\\.\C:`},
+	{`//./UNC/host/share/a/b/c`, `\\.\UNC\host\share`},
+	{`//./UNC/host`, `\\.\UNC\host`},
+	{`//./UNC/host\`, `\\.\UNC\host\`},
+	{`//./UNC`, `\\.\UNC`},
+	{`//./UNC/`, `\\.\UNC\`},
+	{`\\?\x`, `\\?\x`},
+	{`\??\x`, `\??\x`},
+}
+
+func TestVolumeName(t *testing.T) {
+	if runtime.GOOS != "windows" {
+		return
+	}
+	for _, v := range volumenametests {
+		if vol := filepath.VolumeName(v.path); vol != v.vol {
+			t.Errorf("VolumeName(%q)=%q, want %q", v.path, vol, v.vol)
+		}
+	}
+}
+
+func TestDriveLetterInEvalSymlinks(t *testing.T) {
+	if runtime.GOOS != "windows" {
+		return
+	}
+	wd, _ := os.Getwd()
+	if len(wd) < 3 {
+		t.Errorf("Current directory path %q is too short", wd)
+	}
+	lp := strings.ToLower(wd)
+	up := strings.ToUpper(wd)
+	flp, err := filepath.EvalSymlinks(lp)
+	if err != nil {
+		t.Fatalf("EvalSymlinks(%q) failed: %q", lp, err)
+	}
+	fup, err := filepath.EvalSymlinks(up)
+	if err != nil {
+		t.Fatalf("EvalSymlinks(%q) failed: %q", up, err)
+	}
+	if flp != fup {
+		t.Errorf("Results of EvalSymlinks do not match: %q and %q", flp, fup)
+	}
+}
+
+func TestBug3486(t *testing.T) { // https://golang.org/issue/3486
+	if runtime.GOOS == "ios" {
+		t.Skipf("skipping on %s/%s", runtime.GOOS, runtime.GOARCH)
+	}
+	root := filepath.Join(testenv.GOROOT(t), "src", "unicode")
+	utf16 := filepath.Join(root, "utf16")
+	utf8 := filepath.Join(root, "utf8")
+	seenUTF16 := false
+	seenUTF8 := false
+	err := filepath.Walk(root, func(pth string, info fs.FileInfo, err error) error {
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		switch pth {
+		case utf16:
+			seenUTF16 = true
+			return filepath.SkipDir
+		case utf8:
+			if !seenUTF16 {
+				t.Fatal("filepath.Walk out of order - utf8 before utf16")
+			}
+			seenUTF8 = true
+		}
+		return nil
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !seenUTF8 {
+		t.Fatalf("%q not seen", utf8)
+	}
+}
+
+func testWalkSymlink(t *testing.T, mklink func(target, link string) error) {
+	tmpdir := t.TempDir()
+
+	wd, err := os.Getwd()
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.Chdir(wd)
+
+	err = os.Chdir(tmpdir)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	err = mklink(tmpdir, "link")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	var visited []string
+	err = filepath.Walk(tmpdir, func(path string, info fs.FileInfo, err error) error {
+		if err != nil {
+			t.Fatal(err)
+		}
+		rel, err := filepath.Rel(tmpdir, path)
+		if err != nil {
+			t.Fatal(err)
+		}
+		visited = append(visited, rel)
+		return nil
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	sort.Strings(visited)
+	want := []string{".", "link"}
+	if fmt.Sprintf("%q", visited) != fmt.Sprintf("%q", want) {
+		t.Errorf("unexpected paths visited %q, want %q", visited, want)
+	}
+}
+
+func TestWalkSymlink(t *testing.T) {
+	testenv.MustHaveSymlink(t)
+	testWalkSymlink(t, os.Symlink)
+}
+
+func TestIssue29372(t *testing.T) {
+	tmpDir := t.TempDir()
+
+	path := filepath.Join(tmpDir, "file.txt")
+	err := os.WriteFile(path, nil, 0644)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	pathSeparator := string(filepath.Separator)
+	tests := []string{
+		path + strings.Repeat(pathSeparator, 1),
+		path + strings.Repeat(pathSeparator, 2),
+		path + strings.Repeat(pathSeparator, 1) + ".",
+		path + strings.Repeat(pathSeparator, 2) + ".",
+		path + strings.Repeat(pathSeparator, 1) + "..",
+		path + strings.Repeat(pathSeparator, 2) + "..",
+	}
+
+	for i, test := range tests {
+		_, err = filepath.EvalSymlinks(test)
+		if err != syscall.ENOTDIR {
+			t.Fatalf("test#%d: want %q, got %q", i, syscall.ENOTDIR, err)
+		}
+	}
+}
+
+// Issue 30520 part 1.
+func TestEvalSymlinksAboveRoot(t *testing.T) {
+	testenv.MustHaveSymlink(t)
+
+	t.Parallel()
+
+	tmpDir := t.TempDir()
+
+	evalTmpDir, err := filepath.EvalSymlinks(tmpDir)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if err := os.Mkdir(filepath.Join(evalTmpDir, "a"), 0777); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.Symlink(filepath.Join(evalTmpDir, "a"), filepath.Join(evalTmpDir, "b")); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(evalTmpDir, "a", "file"), nil, 0666); err != nil {
+		t.Fatal(err)
+	}
+
+	// Count the number of ".." elements to get to the root directory.
+	vol := filepath.VolumeName(evalTmpDir)
+	c := strings.Count(evalTmpDir[len(vol):], string(os.PathSeparator))
+	var dd []string
+	for i := 0; i < c+2; i++ {
+		dd = append(dd, "..")
+	}
+
+	wantSuffix := strings.Join([]string{"a", "file"}, string(os.PathSeparator))
+
+	// Try different numbers of "..".
+	for _, i := range []int{c, c + 1, c + 2} {
+		check := strings.Join([]string{evalTmpDir, strings.Join(dd[:i], string(os.PathSeparator)), evalTmpDir[len(vol)+1:], "b", "file"}, string(os.PathSeparator))
+		resolved, err := filepath.EvalSymlinks(check)
+		switch {
+		case runtime.GOOS == "darwin" && errors.Is(err, fs.ErrNotExist):
+			// On darwin, the temp dir is sometimes cleaned up mid-test (issue 37910).
+			testenv.SkipFlaky(t, 37910)
+		case err != nil:
+			t.Errorf("EvalSymlinks(%q) failed: %v", check, err)
+		case !strings.HasSuffix(resolved, wantSuffix):
+			t.Errorf("EvalSymlinks(%q) = %q does not end with %q", check, resolved, wantSuffix)
+		default:
+			t.Logf("EvalSymlinks(%q) = %q", check, resolved)
+		}
+	}
+}
+
+// Issue 30520 part 2.
+func TestEvalSymlinksAboveRootChdir(t *testing.T) {
+	testenv.MustHaveSymlink(t)
+
+	tmpDir, err := os.MkdirTemp("", "TestEvalSymlinksAboveRootChdir")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(tmpDir)
+	chdir(t, tmpDir)
+
+	subdir := filepath.Join("a", "b")
+	if err := os.MkdirAll(subdir, 0777); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.Symlink(subdir, "c"); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(subdir, "file"), nil, 0666); err != nil {
+		t.Fatal(err)
+	}
+
+	subdir = filepath.Join("d", "e", "f")
+	if err := os.MkdirAll(subdir, 0777); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.Chdir(subdir); err != nil {
+		t.Fatal(err)
+	}
+
+	check := filepath.Join("..", "..", "..", "c", "file")
+	wantSuffix := filepath.Join("a", "b", "file")
+	if resolved, err := filepath.EvalSymlinks(check); err != nil {
+		t.Errorf("EvalSymlinks(%q) failed: %v", check, err)
+	} else if !strings.HasSuffix(resolved, wantSuffix) {
+		t.Errorf("EvalSymlinks(%q) = %q does not end with %q", check, resolved, wantSuffix)
+	} else {
+		t.Logf("EvalSymlinks(%q) = %q", check, resolved)
+	}
+}
+
+func TestIssue51617(t *testing.T) {
+	dir := t.TempDir()
+	for _, sub := range []string{"a", filepath.Join("a", "bad"), filepath.Join("a", "next")} {
+		if err := os.Mkdir(filepath.Join(dir, sub), 0755); err != nil {
+			t.Fatal(err)
+		}
+	}
+	bad := filepath.Join(dir, "a", "bad")
+	if err := os.Chmod(bad, 0); err != nil {
+		t.Fatal(err)
+	}
+	defer os.Chmod(bad, 0700) // avoid errors on cleanup
+	var saw []string
+	err := filepath.WalkDir(dir, func(path string, d fs.DirEntry, err error) error {
+		if err != nil {
+			return filepath.SkipDir
+		}
+		if d.IsDir() {
+			rel, err := filepath.Rel(dir, path)
+			if err != nil {
+				t.Fatal(err)
+			}
+			saw = append(saw, rel)
+		}
+		return nil
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	want := []string{".", "a", filepath.Join("a", "bad"), filepath.Join("a", "next")}
+	if !reflect.DeepEqual(saw, want) {
+		t.Errorf("got directories %v, want %v", saw, want)
+	}
+}
+
+func TestEscaping(t *testing.T) {
+	dir1 := t.TempDir()
+	dir2 := t.TempDir()
+	chdir(t, dir1)
+
+	for _, p := range []string{
+		filepath.Join(dir2, "x"),
+	} {
+		if !filepath.IsLocal(p) {
+			continue
+		}
+		f, err := os.Create(p)
+		if err != nil {
+			f.Close()
+		}
+		ents, err := os.ReadDir(dir2)
+		if err != nil {
+			t.Fatal(err)
+		}
+		for _, e := range ents {
+			t.Fatalf("found: %v", e.Name())
+		}
+	}
+}