src/os/exec/lp_windows_test.go - go - Git at Google

 // Copyright 2013 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.

 // Use an external test to avoid os/exec -> internal/testenv -> os/exec
 // circular dependency.

 package exec_test

 import (
 	"errors"
 	"fmt"
 	"internal/testenv"
 	"io"
 	"os"
 	"os/exec"
 	"path/filepath"
 	"strconv"
 	"strings"
 	"testing"
 )

 func init() {
 	registerHelperCommand("exec", cmdExec)
 	registerHelperCommand("lookpath", cmdLookPath)
 }

 func cmdLookPath(args ...string) {
 	p, err := exec.LookPath(args[0])
 	if err != nil {
 		fmt.Fprintf(os.Stderr, "LookPath failed: %v\n", err)
 		os.Exit(1)
 	}
 	fmt.Print(p)
 }

 func cmdExec(args ...string) {
 	cmd := exec.Command(args[1])
 	cmd.Dir = args[0]
 	if errors.Is(cmd.Err, exec.ErrDot) {
 		cmd.Err = nil
 	}
 	output, err := cmd.CombinedOutput()
 	if err != nil {
 		fmt.Fprintf(os.Stderr, "Child: %s %s", err, string(output))
 		os.Exit(1)
 	}
 	fmt.Printf("%s", string(output))
 }

 func installExe(t *testing.T, dest, src string) {
 	fsrc, err := os.Open(src)
 	if err != nil {
 		t.Fatal("os.Open failed: ", err)
 	}
 	defer fsrc.Close()
 	fdest, err := os.Create(dest)
 	if err != nil {
 		t.Fatal("os.Create failed: ", err)
 	}
 	defer fdest.Close()
 	_, err = io.Copy(fdest, fsrc)
 	if err != nil {
 		t.Fatal("io.Copy failed: ", err)
 	}
 }

 func installBat(t *testing.T, dest string) {
 	f, err := os.Create(dest)
 	if err != nil {
 		t.Fatalf("failed to create batch file: %v", err)
 	}
 	defer f.Close()
 	fmt.Fprintf(f, "@echo %s\n", dest)
 }

 func installProg(t *testing.T, dest, srcExe string) {
 	err := os.MkdirAll(filepath.Dir(dest), 0700)
 	if err != nil {
 		t.Fatal("os.MkdirAll failed: ", err)
 	}
 	if strings.ToLower(filepath.Ext(dest)) == ".bat" {
 		installBat(t, dest)
 		return
 	}
 	installExe(t, dest, srcExe)
 }

 type lookPathTest struct {
 	rootDir   string
 	PATH      string
 	PATHEXT   string
 	files     []string
 	searchFor string
 	fails     bool // test is expected to fail
 }

 func (test lookPathTest) runProg(t *testing.T, env []string, cmd *exec.Cmd) (string, error) {
 	cmd.Env = env
 	cmd.Dir = test.rootDir
 	args := append([]string(nil), cmd.Args...)
 	args[0] = filepath.Base(args[0])
 	cmdText := fmt.Sprintf("%q command", strings.Join(args, " "))
 	out, err := cmd.CombinedOutput()
 	if (err != nil) != test.fails {
 		if test.fails {
 			t.Fatalf("test=%+v: %s succeeded, but expected to fail", test, cmdText)
 		}
 		t.Fatalf("test=%+v: %s failed, but expected to succeed: %v - %v", test, cmdText, err, string(out))
 	}
 	if err != nil {
 		return "", fmt.Errorf("test=%+v: %s failed: %v - %v", test, cmdText, err, string(out))
 	}
 	// normalise program output
 	p := string(out)
 	// trim terminating \r and \n that batch file outputs
 	for len(p) > 0 && (p[len(p)-1] == '\n' || p[len(p)-1] == '\r') {
 		p = p[:len(p)-1]
 	}
 	if !filepath.IsAbs(p) {
 		return p, nil
 	}
 	if p[:len(test.rootDir)] != test.rootDir {
 		t.Fatalf("test=%+v: %s output is wrong: %q must have %q prefix", test, cmdText, p, test.rootDir)
 	}
 	return p[len(test.rootDir)+1:], nil
 }

 func updateEnv(env []string, name, value string) []string {
 	for i, e := range env {
 		if strings.HasPrefix(strings.ToUpper(e), name+"=") {
 			env[i] = name + "=" + value
 			return env
 		}
 	}
 	return append(env, name+"="+value)
 }

 func createEnv(dir, PATH, PATHEXT string) []string {
 	env := os.Environ()
 	env = updateEnv(env, "PATHEXT", PATHEXT)
 	// Add dir in front of every directory in the PATH.
 	dirs := filepath.SplitList(PATH)
 	for i := range dirs {
 		dirs[i] = filepath.Join(dir, dirs[i])
 	}
 	path := strings.Join(dirs, ";")
 	env = updateEnv(env, "PATH", os.Getenv("SystemRoot")+"/System32;"+path)
 	return env
 }

 // createFiles copies srcPath file into multiply files.
 // It uses dir as prefix for all destination files.
 func createFiles(t *testing.T, dir string, files []string, srcPath string) {
 	for _, f := range files {
 		installProg(t, filepath.Join(dir, f), srcPath)
 	}
 }

 func (test lookPathTest) run(t *testing.T, tmpdir, printpathExe string) {
 	test.rootDir = tmpdir
 	createFiles(t, test.rootDir, test.files, printpathExe)
 	env := createEnv(test.rootDir, test.PATH, test.PATHEXT)
 	// Run "cmd.exe /c test.searchFor" with new environment and
 	// work directory set. All candidates are copies of printpath.exe.
 	// These will output their program paths when run.
 	should, errCmd := test.runProg(t, env, exec.Command("cmd", "/c", test.searchFor))
 	// Run the lookpath program with new environment and work directory set.
 	have, errLP := test.runProg(t, env, helperCommand(t, "lookpath", test.searchFor))
 	// Compare results.
 	if errCmd == nil && errLP == nil {
 		// both succeeded
 		if should != have {
 			t.Fatalf("test=%+v:\ncmd /c ran: %s\nlookpath found: %s", test, should, have)
 		}
 		return
 	}
 	if errCmd != nil && errLP != nil {
 		// both failed -> continue
 		return
 	}
 	if errCmd != nil {
 		t.Fatal(errCmd)
 	}
 	if errLP != nil {
 		t.Fatal(errLP)
 	}
 }

 var lookPathTests = []lookPathTest{
 	{
 		PATHEXT:   `.COM;.EXE;.BAT`,
 		PATH:      `p1;p2`,
 		files:     []string{`p1\a.exe`, `p2\a.exe`, `p2\a`},
 		searchFor: `a`,
 	},
 	{
 		PATHEXT:   `.COM;.EXE;.BAT`,
 		PATH:      `p1.dir;p2.dir`,
 		files:     []string{`p1.dir\a`, `p2.dir\a.exe`},
 		searchFor: `a`,
 	},
 	{
 		PATHEXT:   `.COM;.EXE;.BAT`,
 		PATH:      `p1;p2`,
 		files:     []string{`p1\a.exe`, `p2\a.exe`},
 		searchFor: `a.exe`,
 	},
 	{
 		PATHEXT:   `.COM;.EXE;.BAT`,
 		PATH:      `p1;p2`,
 		files:     []string{`p1\a.exe`, `p2\b.exe`},
 		searchFor: `b`,
 	},
 	{
 		PATHEXT:   `.COM;.EXE;.BAT`,
 		PATH:      `p1;p2`,
 		files:     []string{`p1\b`, `p2\a`},
 		searchFor: `a`,
 		fails:     true, // TODO(brainman): do not know why this fails
 	},
 	// If the command name specifies a path, the shell searches
 	// the specified path for an executable file matching
 	// the command name. If a match is found, the external
 	// command (the executable file) executes.
 	{
 		PATHEXT:   `.COM;.EXE;.BAT`,
 		PATH:      `p1;p2`,
 		files:     []string{`p1\a.exe`, `p2\a.exe`},
 		searchFor: `p2\a`,
 	},
 	// If the command name specifies a path, the shell searches
 	// the specified path for an executable file matching the command
 	// name. ... If no match is found, the shell reports an error
 	// and command processing completes.
 	{
 		PATHEXT:   `.COM;.EXE;.BAT`,
 		PATH:      `p1;p2`,
 		files:     []string{`p1\b.exe`, `p2\a.exe`},
 		searchFor: `p2\b`,
 		fails:     true,
 	},
 	// If the command name does not specify a path, the shell
 	// searches the current directory for an executable file
 	// matching the command name. If a match is found, the external
 	// command (the executable file) executes.
 	{
 		PATHEXT:   `.COM;.EXE;.BAT`,
 		PATH:      `p1;p2`,
 		files:     []string{`a`, `p1\a.exe`, `p2\a.exe`},
 		searchFor: `a`,
 	},
 	// The shell now searches each directory specified by the
 	// PATH environment variable, in the order listed, for an
 	// executable file matching the command name. If a match
 	// is found, the external command (the executable file) executes.
 	{
 		PATHEXT:   `.COM;.EXE;.BAT`,
 		PATH:      `p1;p2`,
 		files:     []string{`p1\a.exe`, `p2\a.exe`},
 		searchFor: `a`,
 	},
 	// The shell now searches each directory specified by the
 	// PATH environment variable, in the order listed, for an
 	// executable file matching the command name. If no match
 	// is found, the shell reports an error and command processing
 	// completes.
 	{
 		PATHEXT:   `.COM;.EXE;.BAT`,
 		PATH:      `p1;p2`,
 		files:     []string{`p1\a.exe`, `p2\a.exe`},
 		searchFor: `b`,
 		fails:     true,
 	},
 	// If the command name includes a file extension, the shell
 	// searches each directory for the exact file name specified
 	// by the command name.
 	{
 		PATHEXT:   `.COM;.EXE;.BAT`,
 		PATH:      `p1;p2`,
 		files:     []string{`p1\a.exe`, `p2\a.exe`},
 		searchFor: `a.exe`,
 	},
 	{
 		PATHEXT:   `.COM;.EXE;.BAT`,
 		PATH:      `p1;p2`,
 		files:     []string{`p1\a.exe`, `p2\a.exe`},
 		searchFor: `a.com`,
 		fails:     true, // includes extension and not exact file name match
 	},
 	{
 		PATHEXT:   `.COM;.EXE;.BAT`,
 		PATH:      `p1`,
 		files:     []string{`p1\a.exe.exe`},
 		searchFor: `a.exe`,
 	},
 	{
 		PATHEXT:   `.COM;.BAT`,
 		PATH:      `p1;p2`,
 		files:     []string{`p1\a.exe`, `p2\a.exe`},
 		searchFor: `a.exe`,
 	},
 	// If the command name does not include a file extension, the shell
 	// adds the extensions listed in the PATHEXT environment variable,
 	// one by one, and searches the directory for that file name. Note
 	// that the shell tries all possible file extensions in a specific
 	// directory before moving on to search the next directory
 	// (if there is one).
 	{
 		PATHEXT:   `.COM;.EXE`,
 		PATH:      `p1;p2`,
 		files:     []string{`p1\a.bat`, `p2\a.exe`},
 		searchFor: `a`,
 	},
 	{
 		PATHEXT:   `.COM;.EXE;.BAT`,
 		PATH:      `p1;p2`,
 		files:     []string{`p1\a.bat`, `p2\a.exe`},
 		searchFor: `a`,
 	},
 	{
 		PATHEXT:   `.COM;.EXE;.BAT`,
 		PATH:      `p1;p2`,
 		files:     []string{`p1\a.bat`, `p1\a.exe`, `p2\a.bat`, `p2\a.exe`},
 		searchFor: `a`,
 	},
 	{
 		PATHEXT:   `.COM`,
 		PATH:      `p1;p2`,
 		files:     []string{`p1\a.bat`, `p2\a.exe`},
 		searchFor: `a`,
 		fails:     true, // tried all extensions in PATHEXT, but none matches
 	},
 }

 func TestLookPathWindows(t *testing.T) {
 	if testing.Short() {
 		maySkipHelperCommand("lookpath")
 		t.Skipf("skipping test in short mode that would build a helper binary")
 	}
 	t.Parallel()

 	tmp := t.TempDir()
 	printpathExe := buildPrintPathExe(t, tmp)

 	// Run all tests.
 	for i, test := range lookPathTests {
 		i, test := i, test
 		t.Run(fmt.Sprint(i), func(t *testing.T) {
 			t.Parallel()

 			dir := filepath.Join(tmp, "d"+strconv.Itoa(i))
 			err := os.Mkdir(dir, 0700)
 			if err != nil {
 				t.Fatal("Mkdir failed: ", err)
 			}
 			test.run(t, dir, printpathExe)
 		})
 	}
 }

 type commandTest struct {
 	PATH  string
 	files []string
 	dir   string
 	arg0  string
 	want  string
 	fails bool // test is expected to fail
 }

 func (test commandTest) isSuccess(rootDir, output string, err error) error {
 	if err != nil {
 		return fmt.Errorf("test=%+v: exec: %v %v", test, err, output)
 	}
 	path := output
 	if path[:len(rootDir)] != rootDir {
 		return fmt.Errorf("test=%+v: %q must have %q prefix", test, path, rootDir)
 	}
 	path = path[len(rootDir)+1:]
 	if path != test.want {
 		return fmt.Errorf("test=%+v: want %q, got %q", test, test.want, path)
 	}
 	return nil
 }

 func (test commandTest) runOne(t *testing.T, rootDir string, env []string, dir, arg0 string) {
 	cmd := helperCommand(t, "exec", dir, arg0)
 	cmd.Dir = rootDir
 	cmd.Env = env
 	output, err := cmd.CombinedOutput()
 	err = test.isSuccess(rootDir, string(output), err)
 	if (err != nil) != test.fails {
 		if test.fails {
 			t.Errorf("test=%+v: succeeded, but expected to fail", test)
 		} else {
 			t.Error(err)
 		}
 	}
 }

 func (test commandTest) run(t *testing.T, rootDir, printpathExe string) {
 	createFiles(t, rootDir, test.files, printpathExe)
 	PATHEXT := `.COM;.EXE;.BAT`
 	env := createEnv(rootDir, test.PATH, PATHEXT)
 	test.runOne(t, rootDir, env, test.dir, test.arg0)
 }

 var commandTests = []commandTest{
 	// testing commands with no slash, like `a.exe`
 	{
 		// should find a.exe in current directory
 		files: []string{`a.exe`},
 		arg0:  `a.exe`,
 		want:  `a.exe`,
 	},
 	{
 		// like above, but add PATH in attempt to break the test
 		PATH:  `p2;p`,
 		files: []string{`a.exe`, `p\a.exe`, `p2\a.exe`},
 		arg0:  `a.exe`,
 		want:  `a.exe`,
 	},
 	{
 		// like above, but use "a" instead of "a.exe" for command
 		PATH:  `p2;p`,
 		files: []string{`a.exe`, `p\a.exe`, `p2\a.exe`},
 		arg0:  `a`,
 		want:  `a.exe`,
 	},
 	// testing commands with slash, like `.\a.exe`
 	{
 		// should find p\a.exe
 		files: []string{`p\a.exe`},
 		arg0:  `p\a.exe`,
 		want:  `p\a.exe`,
 	},
 	{
 		// like above, but adding `.` in front of executable should still be OK
 		files: []string{`p\a.exe`},
 		arg0:  `.\p\a.exe`,
 		want:  `p\a.exe`,
 	},
 	{
 		// like above, but with PATH added in attempt to break it
 		PATH:  `p2`,
 		files: []string{`p\a.exe`, `p2\a.exe`},
 		arg0:  `p\a.exe`,
 		want:  `p\a.exe`,
 	},
 	{
 		// like above, but make sure .exe is tried even for commands with slash
 		PATH:  `p2`,
 		files: []string{`p\a.exe`, `p2\a.exe`},
 		arg0:  `p\a`,
 		want:  `p\a.exe`,
 	},
 	// tests commands, like `a.exe`, with c.Dir set
 	{
 		// should not find a.exe in p, because LookPath(`a.exe`) will fail
 		files: []string{`p\a.exe`},
 		dir:   `p`,
 		arg0:  `a.exe`,
 		want:  `p\a.exe`,
 		fails: true,
 	},
 	{
 		// LookPath(`a.exe`) will find `.\a.exe`, but prefixing that with
 		// dir `p\a.exe` will refer to a non-existent file
 		files: []string{`a.exe`, `p\not_important_file`},
 		dir:   `p`,
 		arg0:  `a.exe`,
 		want:  `a.exe`,
 		fails: true,
 	},
 	{
 		// like above, but making test succeed by installing file
 		// in referred destination (so LookPath(`a.exe`) will still
 		// find `.\a.exe`, but we successfully execute `p\a.exe`)
 		files: []string{`a.exe`, `p\a.exe`},
 		dir:   `p`,
 		arg0:  `a.exe`,
 		want:  `p\a.exe`,
 	},
 	{
 		// like above, but add PATH in attempt to break the test
 		PATH:  `p2;p`,
 		files: []string{`a.exe`, `p\a.exe`, `p2\a.exe`},
 		dir:   `p`,
 		arg0:  `a.exe`,
 		want:  `p\a.exe`,
 	},
 	{
 		// like above, but use "a" instead of "a.exe" for command
 		PATH:  `p2;p`,
 		files: []string{`a.exe`, `p\a.exe`, `p2\a.exe`},
 		dir:   `p`,
 		arg0:  `a`,
 		want:  `p\a.exe`,
 	},
 	{
 		// finds `a.exe` in the PATH regardless of dir set
 		// because LookPath returns full path in that case
 		PATH:  `p2;p`,
 		files: []string{`p\a.exe`, `p2\a.exe`},
 		dir:   `p`,
 		arg0:  `a.exe`,
 		want:  `p2\a.exe`,
 	},
 	// tests commands, like `.\a.exe`, with c.Dir set
 	{
 		// should use dir when command is path, like ".\a.exe"
 		files: []string{`p\a.exe`},
 		dir:   `p`,
 		arg0:  `.\a.exe`,
 		want:  `p\a.exe`,
 	},
 	{
 		// like above, but with PATH added in attempt to break it
 		PATH:  `p2`,
 		files: []string{`p\a.exe`, `p2\a.exe`},
 		dir:   `p`,
 		arg0:  `.\a.exe`,
 		want:  `p\a.exe`,
 	},
 	{
 		// like above, but make sure .exe is tried even for commands with slash
 		PATH:  `p2`,
 		files: []string{`p\a.exe`, `p2\a.exe`},
 		dir:   `p`,
 		arg0:  `.\a`,
 		want:  `p\a.exe`,
 	},
 }

 func TestCommand(t *testing.T) {
 	if testing.Short() {
 		maySkipHelperCommand("exec")
 		t.Skipf("skipping test in short mode that would build a helper binary")
 	}
 	t.Parallel()

 	tmp := t.TempDir()
 	printpathExe := buildPrintPathExe(t, tmp)

 	// Run all tests.
 	for i, test := range commandTests {
 		i, test := i, test
 		t.Run(fmt.Sprint(i), func(t *testing.T) {
 			t.Parallel()

 			dir := filepath.Join(tmp, "d"+strconv.Itoa(i))
 			err := os.Mkdir(dir, 0700)
 			if err != nil {
 				t.Fatal("Mkdir failed: ", err)
 			}
 			test.run(t, dir, printpathExe)
 		})
 	}
 }

 // buildPrintPathExe creates a Go program that prints its own path.
 // dir is a temp directory where executable will be created.
 // The function returns full path to the created program.
 func buildPrintPathExe(t *testing.T, dir string) string {
 	const name = "printpath"
 	srcname := name + ".go"
 	err := os.WriteFile(filepath.Join(dir, srcname), []byte(printpathSrc), 0644)
 	if err != nil {
 		t.Fatalf("failed to create source: %v", err)
 	}
 	if err != nil {
 		t.Fatalf("failed to execute template: %v", err)
 	}
 	outname := name + ".exe"
 	cmd := exec.Command(testenv.GoToolPath(t), "build", "-o", outname, srcname)
 	cmd.Dir = dir
 	out, err := cmd.CombinedOutput()
 	if err != nil {
 		t.Fatalf("failed to build executable: %v - %v", err, string(out))
 	}
 	return filepath.Join(dir, outname)
 }

 const printpathSrc = `
 package main

 import (
 	"os"
 	"syscall"
 	"unicode/utf16"
 	"unsafe"
 )

 func getMyName() (string, error) {
 	var sysproc = syscall.MustLoadDLL("kernel32.dll").MustFindProc("GetModuleFileNameW")
 	b := make([]uint16, syscall.MAX_PATH)
 	r, _, err := sysproc.Call(0, uintptr(unsafe.Pointer(&b[0])), uintptr(len(b)))
 	n := uint32(r)
 	if n == 0 {
 		return "", err
 	}
 	return string(utf16.Decode(b[0:n])), nil
 }

 func main() {
 	path, err := getMyName()
 	if err != nil {
 		os.Stderr.Write([]byte("getMyName failed: " + err.Error() + "\n"))
 		os.Exit(1)
 	}
 	os.Stdout.Write([]byte(path))
 }
 `
	// Copyright 2013 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.

	// Use an external test to avoid os/exec -> internal/testenv -> os/exec
	// circular dependency.

	package exec_test

	import (
	"errors"
	"fmt"
	"internal/testenv"
	"io"
	"os"
	"os/exec"
	"path/filepath"
	"strconv"
	"strings"
	"testing"
	)

	func init() {
	registerHelperCommand("exec", cmdExec)
	registerHelperCommand("lookpath", cmdLookPath)
	}

	func cmdLookPath(args ...string) {
	p, err := exec.LookPath(args[0])
	if err != nil {
	fmt.Fprintf(os.Stderr, "LookPath failed: %v\n", err)
	os.Exit(1)
	}
	fmt.Print(p)
	}

	func cmdExec(args ...string) {
	cmd := exec.Command(args[1])
	cmd.Dir = args[0]
	if errors.Is(cmd.Err, exec.ErrDot) {
	cmd.Err = nil
	}
	output, err := cmd.CombinedOutput()
	if err != nil {
	fmt.Fprintf(os.Stderr, "Child: %s %s", err, string(output))
	os.Exit(1)
	}
	fmt.Printf("%s", string(output))
	}

	func installExe(t *testing.T, dest, src string) {
	fsrc, err := os.Open(src)
	if err != nil {
	t.Fatal("os.Open failed: ", err)
	}
	defer fsrc.Close()
	fdest, err := os.Create(dest)
	if err != nil {
	t.Fatal("os.Create failed: ", err)
	}
	defer fdest.Close()
	_, err = io.Copy(fdest, fsrc)
	if err != nil {
	t.Fatal("io.Copy failed: ", err)
	}
	}

	func installBat(t *testing.T, dest string) {
	f, err := os.Create(dest)
	if err != nil {
	t.Fatalf("failed to create batch file: %v", err)
	}
	defer f.Close()
	fmt.Fprintf(f, "@echo %s\n", dest)
	}

	func installProg(t *testing.T, dest, srcExe string) {
	err := os.MkdirAll(filepath.Dir(dest), 0700)
	if err != nil {
	t.Fatal("os.MkdirAll failed: ", err)
	}
	if strings.ToLower(filepath.Ext(dest)) == ".bat" {
	installBat(t, dest)
	return
	}
	installExe(t, dest, srcExe)
	}

	type lookPathTest struct {
	rootDir string
	PATH string
	PATHEXT string
	files []string
	searchFor string
	fails bool // test is expected to fail
	}

	func (test lookPathTest) runProg(t testing.T, env []string, cmd exec.Cmd) (string, error) {
	cmd.Env = env
	cmd.Dir = test.rootDir
	args := append([]string(nil), cmd.Args...)
	args[0] = filepath.Base(args[0])
	cmdText := fmt.Sprintf("%q command", strings.Join(args, " "))
	out, err := cmd.CombinedOutput()
	if (err != nil) != test.fails {
	if test.fails {
	t.Fatalf("test=%+v: %s succeeded, but expected to fail", test, cmdText)
	}
	t.Fatalf("test=%+v: %s failed, but expected to succeed: %v - %v", test, cmdText, err, string(out))
	}
	if err != nil {
	return "", fmt.Errorf("test=%+v: %s failed: %v - %v", test, cmdText, err, string(out))
	}
	// normalise program output
	p := string(out)
	// trim terminating \r and \n that batch file outputs
	for len(p) > 0 && (p[len(p)-1] == '\n' \|\| p[len(p)-1] == '\r') {
	p = p[:len(p)-1]
	}
	if !filepath.IsAbs(p) {
	return p, nil
	}
	if p[:len(test.rootDir)] != test.rootDir {
	t.Fatalf("test=%+v: %s output is wrong: %q must have %q prefix", test, cmdText, p, test.rootDir)
	}
	return p[len(test.rootDir)+1:], nil
	}

	func updateEnv(env []string, name, value string) []string {
	for i, e := range env {
	if strings.HasPrefix(strings.ToUpper(e), name+"=") {
	env[i] = name + "=" + value
	return env
	}
	}
	return append(env, name+"="+value)
	}

	func createEnv(dir, PATH, PATHEXT string) []string {
	env := os.Environ()
	env = updateEnv(env, "PATHEXT", PATHEXT)
	// Add dir in front of every directory in the PATH.
	dirs := filepath.SplitList(PATH)
	for i := range dirs {
	dirs[i] = filepath.Join(dir, dirs[i])
	}
	path := strings.Join(dirs, ";")
	env = updateEnv(env, "PATH", os.Getenv("SystemRoot")+"/System32;"+path)
	return env
	}

	// createFiles copies srcPath file into multiply files.
	// It uses dir as prefix for all destination files.
	func createFiles(t *testing.T, dir string, files []string, srcPath string) {
	for _, f := range files {
	installProg(t, filepath.Join(dir, f), srcPath)
	}
	}

	func (test lookPathTest) run(t *testing.T, tmpdir, printpathExe string) {
	test.rootDir = tmpdir
	createFiles(t, test.rootDir, test.files, printpathExe)
	env := createEnv(test.rootDir, test.PATH, test.PATHEXT)
	// Run "cmd.exe /c test.searchFor" with new environment and
	// work directory set. All candidates are copies of printpath.exe.
	// These will output their program paths when run.
	should, errCmd := test.runProg(t, env, exec.Command("cmd", "/c", test.searchFor))
	// Run the lookpath program with new environment and work directory set.
	have, errLP := test.runProg(t, env, helperCommand(t, "lookpath", test.searchFor))
	// Compare results.
	if errCmd == nil && errLP == nil {
	// both succeeded
	if should != have {
	t.Fatalf("test=%+v:\ncmd /c ran: %s\nlookpath found: %s", test, should, have)
	}
	return
	}
	if errCmd != nil && errLP != nil {
	// both failed -> continue
	return
	}
	if errCmd != nil {
	t.Fatal(errCmd)
	}
	if errLP != nil {
	t.Fatal(errLP)
	}
	}

	var lookPathTests = []lookPathTest{
	{
	PATHEXT: `.COM;.EXE;.BAT`,
	PATH: `p1;p2`,
	files: []string{`p1\a.exe`, `p2\a.exe`, `p2\a`},
	searchFor: `a`,
	},
	{
	PATHEXT: `.COM;.EXE;.BAT`,
	PATH: `p1.dir;p2.dir`,
	files: []string{`p1.dir\a`, `p2.dir\a.exe`},
	searchFor: `a`,
	},
	{
	PATHEXT: `.COM;.EXE;.BAT`,
	PATH: `p1;p2`,
	files: []string{`p1\a.exe`, `p2\a.exe`},
	searchFor: `a.exe`,
	},
	{
	PATHEXT: `.COM;.EXE;.BAT`,
	PATH: `p1;p2`,
	files: []string{`p1\a.exe`, `p2\b.exe`},
	searchFor: `b`,
	},
	{
	PATHEXT: `.COM;.EXE;.BAT`,
	PATH: `p1;p2`,
	files: []string{`p1\b`, `p2\a`},
	searchFor: `a`,
	fails: true, // TODO(brainman): do not know why this fails
	},
	// If the command name specifies a path, the shell searches
	// the specified path for an executable file matching
	// the command name. If a match is found, the external
	// command (the executable file) executes.
	{
	PATHEXT: `.COM;.EXE;.BAT`,
	PATH: `p1;p2`,
	files: []string{`p1\a.exe`, `p2\a.exe`},
	searchFor: `p2\a`,
	},
	// If the command name specifies a path, the shell searches
	// the specified path for an executable file matching the command
	// name. ... If no match is found, the shell reports an error
	// and command processing completes.
	{
	PATHEXT: `.COM;.EXE;.BAT`,
	PATH: `p1;p2`,
	files: []string{`p1\b.exe`, `p2\a.exe`},
	searchFor: `p2\b`,
	fails: true,
	},
	// If the command name does not specify a path, the shell
	// searches the current directory for an executable file
	// matching the command name. If a match is found, the external
	// command (the executable file) executes.
	{
	PATHEXT: `.COM;.EXE;.BAT`,
	PATH: `p1;p2`,
	files: []string{`a`, `p1\a.exe`, `p2\a.exe`},
	searchFor: `a`,
	},
	// The shell now searches each directory specified by the
	// PATH environment variable, in the order listed, for an
	// executable file matching the command name. If a match
	// is found, the external command (the executable file) executes.
	{
	PATHEXT: `.COM;.EXE;.BAT`,
	PATH: `p1;p2`,
	files: []string{`p1\a.exe`, `p2\a.exe`},
	searchFor: `a`,
	},
	// The shell now searches each directory specified by the
	// PATH environment variable, in the order listed, for an
	// executable file matching the command name. If no match
	// is found, the shell reports an error and command processing
	// completes.
	{
	PATHEXT: `.COM;.EXE;.BAT`,
	PATH: `p1;p2`,
	files: []string{`p1\a.exe`, `p2\a.exe`},
	searchFor: `b`,
	fails: true,
	},
	// If the command name includes a file extension, the shell
	// searches each directory for the exact file name specified
	// by the command name.
	{
	PATHEXT: `.COM;.EXE;.BAT`,
	PATH: `p1;p2`,
	files: []string{`p1\a.exe`, `p2\a.exe`},
	searchFor: `a.exe`,
	},
	{
	PATHEXT: `.COM;.EXE;.BAT`,
	PATH: `p1;p2`,
	files: []string{`p1\a.exe`, `p2\a.exe`},
	searchFor: `a.com`,
	fails: true, // includes extension and not exact file name match
	},
	{
	PATHEXT: `.COM;.EXE;.BAT`,
	PATH: `p1`,
	files: []string{`p1\a.exe.exe`},
	searchFor: `a.exe`,
	},
	{
	PATHEXT: `.COM;.BAT`,
	PATH: `p1;p2`,
	files: []string{`p1\a.exe`, `p2\a.exe`},
	searchFor: `a.exe`,
	},
	// If the command name does not include a file extension, the shell
	// adds the extensions listed in the PATHEXT environment variable,
	// one by one, and searches the directory for that file name. Note
	// that the shell tries all possible file extensions in a specific
	// directory before moving on to search the next directory
	// (if there is one).
	{
	PATHEXT: `.COM;.EXE`,
	PATH: `p1;p2`,
	files: []string{`p1\a.bat`, `p2\a.exe`},
	searchFor: `a`,
	},
	{
	PATHEXT: `.COM;.EXE;.BAT`,
	PATH: `p1;p2`,
	files: []string{`p1\a.bat`, `p2\a.exe`},
	searchFor: `a`,
	},
	{
	PATHEXT: `.COM;.EXE;.BAT`,
	PATH: `p1;p2`,
	files: []string{`p1\a.bat`, `p1\a.exe`, `p2\a.bat`, `p2\a.exe`},
	searchFor: `a`,
	},
	{
	PATHEXT: `.COM`,
	PATH: `p1;p2`,
	files: []string{`p1\a.bat`, `p2\a.exe`},
	searchFor: `a`,
	fails: true, // tried all extensions in PATHEXT, but none matches
	},
	}

	func TestLookPathWindows(t *testing.T) {
	if testing.Short() {
	maySkipHelperCommand("lookpath")
	t.Skipf("skipping test in short mode that would build a helper binary")
	}
	t.Parallel()

	tmp := t.TempDir()
	printpathExe := buildPrintPathExe(t, tmp)

	// Run all tests.
	for i, test := range lookPathTests {
	i, test := i, test
	t.Run(fmt.Sprint(i), func(t *testing.T) {
	t.Parallel()

	dir := filepath.Join(tmp, "d"+strconv.Itoa(i))
	err := os.Mkdir(dir, 0700)
	if err != nil {
	t.Fatal("Mkdir failed: ", err)
	}
	test.run(t, dir, printpathExe)
	})
	}
	}

	type commandTest struct {
	PATH string
	files []string
	dir string
	arg0 string
	want string
	fails bool // test is expected to fail
	}

	func (test commandTest) isSuccess(rootDir, output string, err error) error {
	if err != nil {
	return fmt.Errorf("test=%+v: exec: %v %v", test, err, output)
	}
	path := output
	if path[:len(rootDir)] != rootDir {
	return fmt.Errorf("test=%+v: %q must have %q prefix", test, path, rootDir)
	}
	path = path[len(rootDir)+1:]
	if path != test.want {
	return fmt.Errorf("test=%+v: want %q, got %q", test, test.want, path)
	}
	return nil
	}

	func (test commandTest) runOne(t *testing.T, rootDir string, env []string, dir, arg0 string) {
	cmd := helperCommand(t, "exec", dir, arg0)
	cmd.Dir = rootDir
	cmd.Env = env
	output, err := cmd.CombinedOutput()
	err = test.isSuccess(rootDir, string(output), err)
	if (err != nil) != test.fails {
	if test.fails {
	t.Errorf("test=%+v: succeeded, but expected to fail", test)
	} else {
	t.Error(err)
	}
	}
	}

	func (test commandTest) run(t *testing.T, rootDir, printpathExe string) {
	createFiles(t, rootDir, test.files, printpathExe)
	PATHEXT := `.COM;.EXE;.BAT`
	env := createEnv(rootDir, test.PATH, PATHEXT)
	test.runOne(t, rootDir, env, test.dir, test.arg0)
	}

	var commandTests = []commandTest{
	// testing commands with no slash, like `a.exe`
	{
	// should find a.exe in current directory
	files: []string{`a.exe`},
	arg0: `a.exe`,
	want: `a.exe`,
	},
	{
	// like above, but add PATH in attempt to break the test
	PATH: `p2;p`,
	files: []string{`a.exe`, `p\a.exe`, `p2\a.exe`},
	arg0: `a.exe`,
	want: `a.exe`,
	},
	{
	// like above, but use "a" instead of "a.exe" for command
	PATH: `p2;p`,
	files: []string{`a.exe`, `p\a.exe`, `p2\a.exe`},
	arg0: `a`,
	want: `a.exe`,
	},
	// testing commands with slash, like `.\a.exe`
	{
	// should find p\a.exe
	files: []string{`p\a.exe`},
	arg0: `p\a.exe`,
	want: `p\a.exe`,
	},
	{
	// like above, but adding `.` in front of executable should still be OK
	files: []string{`p\a.exe`},
	arg0: `.\p\a.exe`,
	want: `p\a.exe`,
	},
	{
	// like above, but with PATH added in attempt to break it
	PATH: `p2`,
	files: []string{`p\a.exe`, `p2\a.exe`},
	arg0: `p\a.exe`,
	want: `p\a.exe`,
	},
	{
	// like above, but make sure .exe is tried even for commands with slash
	PATH: `p2`,
	files: []string{`p\a.exe`, `p2\a.exe`},
	arg0: `p\a`,
	want: `p\a.exe`,
	},
	// tests commands, like `a.exe`, with c.Dir set
	{
	// should not find a.exe in p, because LookPath(`a.exe`) will fail
	files: []string{`p\a.exe`},
	dir: `p`,
	arg0: `a.exe`,
	want: `p\a.exe`,
	fails: true,
	},
	{
	// LookPath(`a.exe`) will find `.\a.exe`, but prefixing that with
	// dir `p\a.exe` will refer to a non-existent file
	files: []string{`a.exe`, `p\not_important_file`},
	dir: `p`,
	arg0: `a.exe`,
	want: `a.exe`,
	fails: true,
	},
	{
	// like above, but making test succeed by installing file
	// in referred destination (so LookPath(`a.exe`) will still
	// find `.\a.exe`, but we successfully execute `p\a.exe`)
	files: []string{`a.exe`, `p\a.exe`},
	dir: `p`,
	arg0: `a.exe`,
	want: `p\a.exe`,
	},
	{
	// like above, but add PATH in attempt to break the test
	PATH: `p2;p`,
	files: []string{`a.exe`, `p\a.exe`, `p2\a.exe`},
	dir: `p`,
	arg0: `a.exe`,
	want: `p\a.exe`,
	},
	{
	// like above, but use "a" instead of "a.exe" for command
	PATH: `p2;p`,
	files: []string{`a.exe`, `p\a.exe`, `p2\a.exe`},
	dir: `p`,
	arg0: `a`,
	want: `p\a.exe`,
	},
	{
	// finds `a.exe` in the PATH regardless of dir set
	// because LookPath returns full path in that case
	PATH: `p2;p`,
	files: []string{`p\a.exe`, `p2\a.exe`},
	dir: `p`,
	arg0: `a.exe`,
	want: `p2\a.exe`,
	},
	// tests commands, like `.\a.exe`, with c.Dir set
	{
	// should use dir when command is path, like ".\a.exe"
	files: []string{`p\a.exe`},
	dir: `p`,
	arg0: `.\a.exe`,
	want: `p\a.exe`,
	},
	{
	// like above, but with PATH added in attempt to break it
	PATH: `p2`,
	files: []string{`p\a.exe`, `p2\a.exe`},
	dir: `p`,
	arg0: `.\a.exe`,
	want: `p\a.exe`,
	},
	{
	// like above, but make sure .exe is tried even for commands with slash
	PATH: `p2`,
	files: []string{`p\a.exe`, `p2\a.exe`},
	dir: `p`,
	arg0: `.\a`,
	want: `p\a.exe`,
	},
	}

	func TestCommand(t *testing.T) {
	if testing.Short() {
	maySkipHelperCommand("exec")
	t.Skipf("skipping test in short mode that would build a helper binary")
	}
	t.Parallel()

	tmp := t.TempDir()
	printpathExe := buildPrintPathExe(t, tmp)

	// Run all tests.
	for i, test := range commandTests {
	i, test := i, test
	t.Run(fmt.Sprint(i), func(t *testing.T) {
	t.Parallel()

	dir := filepath.Join(tmp, "d"+strconv.Itoa(i))
	err := os.Mkdir(dir, 0700)
	if err != nil {
	t.Fatal("Mkdir failed: ", err)
	}
	test.run(t, dir, printpathExe)
	})
	}
	}

	// buildPrintPathExe creates a Go program that prints its own path.
	// dir is a temp directory where executable will be created.
	// The function returns full path to the created program.
	func buildPrintPathExe(t *testing.T, dir string) string {
	const name = "printpath"
	srcname := name + ".go"
	err := os.WriteFile(filepath.Join(dir, srcname), []byte(printpathSrc), 0644)
	if err != nil {
	t.Fatalf("failed to create source: %v", err)
	}
	if err != nil {
	t.Fatalf("failed to execute template: %v", err)
	}
	outname := name + ".exe"
	cmd := exec.Command(testenv.GoToolPath(t), "build", "-o", outname, srcname)
	cmd.Dir = dir
	out, err := cmd.CombinedOutput()
	if err != nil {
	t.Fatalf("failed to build executable: %v - %v", err, string(out))
	}
	return filepath.Join(dir, outname)
	}

	const printpathSrc = `
	package main

	import (
	"os"
	"syscall"
	"unicode/utf16"
	"unsafe"
	)

	func getMyName() (string, error) {
	var sysproc = syscall.MustLoadDLL("kernel32.dll").MustFindProc("GetModuleFileNameW")
	b := make([]uint16, syscall.MAX_PATH)
	r, _, err := sysproc.Call(0, uintptr(unsafe.Pointer(&b[0])), uintptr(len(b)))
	n := uint32(r)
	if n == 0 {
	return "", err
	}
	return string(utf16.Decode(b[0:n])), nil
	}

	func main() {
	path, err := getMyName()
	if err != nil {
	os.Stderr.Write([]byte("getMyName failed: " + err.Error() + "\n"))
	os.Exit(1)
	}
	os.Stdout.Write([]byte(path))
	}
	`