1 files changed, 212 insertions, 0 deletions
diff --git a/src/os/exec/lp_windows.go b/src/os/exec/lp_windows.go
new file mode 100644
index 0000000..698a97c
--- /dev/null
+++ b/src/os/exec/lp_windows.go
@@ -0,0 +1,212 @@
+// Copyright 2010 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 exec
+
+import (
+	"errors"
+	"io/fs"
+	"os"
+	"path/filepath"
+	"strings"
+	"syscall"
+)
+
+// ErrNotFound is the error resulting if a path search failed to find an executable file.
+var ErrNotFound = errors.New("executable file not found in %PATH%")
+
+func chkStat(file string) error {
+	d, err := os.Stat(file)
+	if err != nil {
+		return err
+	}
+	if d.IsDir() {
+		return fs.ErrPermission
+	}
+	return nil
+}
+
+func hasExt(file string) bool {
+	i := strings.LastIndex(file, ".")
+	if i < 0 {
+		return false
+	}
+	return strings.LastIndexAny(file, `:\/`) < i
+}
+
+func findExecutable(file string, exts []string) (string, error) {
+	if len(exts) == 0 {
+		return file, chkStat(file)
+	}
+	if hasExt(file) {
+		if chkStat(file) == nil {
+			return file, nil
+		}
+		// Keep checking exts below, so that programs with weird names
+		// like "foo.bat.exe" will resolve instead of failing.
+	}
+	for _, e := range exts {
+		if f := file + e; chkStat(f) == nil {
+			return f, nil
+		}
+	}
+	if hasExt(file) {
+		return "", fs.ErrNotExist
+	}
+	return "", ErrNotFound
+}
+
+// LookPath searches for an executable named file in the
+// directories named by the PATH environment variable.
+// LookPath also uses PATHEXT environment variable to match
+// a suitable candidate.
+// If file contains a slash, it is tried directly and the PATH is not consulted.
+// Otherwise, on success, the result is an absolute path.
+//
+// In older versions of Go, LookPath could return a path relative to the current directory.
+// As of Go 1.19, LookPath will instead return that path along with an error satisfying
+// errors.Is(err, ErrDot). See the package documentation for more details.
+func LookPath(file string) (string, error) {
+	return lookPath(file, pathExt())
+}
+
+// lookExtensions finds windows executable by its dir and path.
+// It uses LookPath to try appropriate extensions.
+// lookExtensions does not search PATH, instead it converts `prog` into `.\prog`.
+//
+// If the path already has an extension found in PATHEXT,
+// lookExtensions returns it directly without searching
+// for additional extensions. For example,
+// "C:\foo\example.com" would be returned as-is even if the
+// program is actually "C:\foo\example.com.exe".
+func lookExtensions(path, dir string) (string, error) {
+	if filepath.Base(path) == path {
+		path = "." + string(filepath.Separator) + path
+	}
+	exts := pathExt()
+	if ext := filepath.Ext(path); ext != "" {
+		for _, e := range exts {
+			if strings.EqualFold(ext, e) {
+				// Assume that path has already been resolved.
+				return path, nil
+			}
+		}
+	}
+	if dir == "" {
+		return lookPath(path, exts)
+	}
+	if filepath.VolumeName(path) != "" {
+		return lookPath(path, exts)
+	}
+	if len(path) > 1 && os.IsPathSeparator(path[0]) {
+		return lookPath(path, exts)
+	}
+	dirandpath := filepath.Join(dir, path)
+	// We assume that LookPath will only add file extension.
+	lp, err := lookPath(dirandpath, exts)
+	if err != nil {
+		return "", err
+	}
+	ext := strings.TrimPrefix(lp, dirandpath)
+	return path + ext, nil
+}
+
+func pathExt() []string {
+	var exts []string
+	x := os.Getenv(`PATHEXT`)
+	if x != "" {
+		for _, e := range strings.Split(strings.ToLower(x), `;`) {
+			if e == "" {
+				continue
+			}
+			if e[0] != '.' {
+				e = "." + e
+			}
+			exts = append(exts, e)
+		}
+	} else {
+		exts = []string{".com", ".exe", ".bat", ".cmd"}
+	}
+	return exts
+}
+
+// lookPath implements LookPath for the given PATHEXT list.
+func lookPath(file string, exts []string) (string, error) {
+	if strings.ContainsAny(file, `:\/`) {
+		f, err := findExecutable(file, exts)
+		if err == nil {
+			return f, nil
+		}
+		return "", &Error{file, err}
+	}
+
+	// On Windows, creating the NoDefaultCurrentDirectoryInExePath
+	// environment variable (with any value or no value!) signals that
+	// path lookups should skip the current directory.
+	// In theory we are supposed to call NeedCurrentDirectoryForExePathW
+	// "as the registry location of this environment variable can change"
+	// but that seems exceedingly unlikely: it would break all users who
+	// have configured their environment this way!
+	// https://docs.microsoft.com/en-us/windows/win32/api/processenv/nf-processenv-needcurrentdirectoryforexepathw
+	// See also go.dev/issue/43947.
+	var (
+		dotf   string
+		dotErr error
+	)
+	if _, found := syscall.Getenv("NoDefaultCurrentDirectoryInExePath"); !found {
+		if f, err := findExecutable(filepath.Join(".", file), exts); err == nil {
+			if execerrdot.Value() == "0" {
+				execerrdot.IncNonDefault()
+				return f, nil
+			}
+			dotf, dotErr = f, &Error{file, ErrDot}
+		}
+	}
+
+	path := os.Getenv("path")
+	for _, dir := range filepath.SplitList(path) {
+		if dir == "" {
+			// Skip empty entries, consistent with what PowerShell does.
+			// (See https://go.dev/issue/61493#issuecomment-1649724826.)
+			continue
+		}
+
+		if f, err := findExecutable(filepath.Join(dir, file), exts); err == nil {
+			if dotErr != nil {
+				// https://go.dev/issue/53536: if we resolved a relative path implicitly,
+				// and it is the same executable that would be resolved from the explicit %PATH%,
+				// prefer the explicit name for the executable (and, likely, no error) instead
+				// of the equivalent implicit name with ErrDot.
+				//
+				// Otherwise, return the ErrDot for the implicit path as soon as we find
+				// out that the explicit one doesn't match.
+				dotfi, dotfiErr := os.Lstat(dotf)
+				fi, fiErr := os.Lstat(f)
+				if dotfiErr != nil || fiErr != nil || !os.SameFile(dotfi, fi) {
+					return dotf, dotErr
+				}
+			}
+
+			if !filepath.IsAbs(f) {
+				if execerrdot.Value() != "0" {
+					// If this is the same relative path that we already found,
+					// dotErr is non-nil and we already checked it above.
+					// Otherwise, record this path as the one to which we must resolve,
+					// with or without a dotErr.
+					if dotErr == nil {
+						dotf, dotErr = f, &Error{file, ErrDot}
+					}
+					continue
+				}
+				execerrdot.IncNonDefault()
+			}
+			return f, nil
+		}
+	}
+
+	if dotErr != nil {
+		return dotf, dotErr
+	}
+	return "", &Error{file, ErrNotFound}
+}