Use system.ToSlash() instead of filepath.ToSlash()

When running on Linux, filepath.ToSlash() is not suitable to convert paths
containing Windows path delimiter to Unix delimiters. To enable this, we
export system.ToSlash() that takes a platform flag, based on which we use
the proper file path separator, regardless of the platform we run on.

Signed-off-by: Gabriel Adrian Samfira <gsamfira@cloudbasesolutions.com>

Author: gabriel-samfira

frontend/dockerfile/dockerfile2llb/convert.go

@@ -1003,7 +1003,7 @@ func dispatchWorkdir(d *dispatchState, c *instructions.WorkdirCommand, commit bo
 	d.image.Config.WorkingDir = wd
 
 	// From this point forward, we can use UNIX style paths.
-	wd = filepath.ToSlash(wd)
+	wd = system.ToSlash(wd, d.platform.OS)
 	d.state = d.state.Dir(wd)
 
 	if commit {
@@ -1421,7 +1421,6 @@ func pathRelativeToWorkingDir(s llb.State, p string, platform ocispecs.Platform)
 	if len(p) == 0 {
 		return dir, nil
 	}
-
 	p, err = system.CheckSystemDriveAndRemoveDriveLetter(p, platform.OS)
 	if err != nil {
 		return "", errors.Wrap(err, "remving drive letter")

util/system/path.go

@@ -37,8 +37,8 @@ func NormalizePath(parent, newPath, inputOS string, keepSlash bool) (string, err
 		inputOS = "linux"
 	}
 
-	newPath = toSlash(newPath, inputOS)
-	parent = toSlash(parent, inputOS)
+	newPath = ToSlash(newPath, inputOS)
+	parent = ToSlash(parent, inputOS)
 	origPath := newPath
 
 	if parent == "" {
@@ -82,18 +82,18 @@ func NormalizePath(parent, newPath, inputOS string, keepSlash bool) (string, err
 		}
 	}
 
-	return toSlash(newPath, inputOS), nil
+	return ToSlash(newPath, inputOS), nil
 }
 
-func toSlash(inputPath, inputOS string) string {
+func ToSlash(inputPath, inputOS string) string {
 	separator := "/"
 	if inputOS == "windows" {
 		separator = "\\"
 	}
 	return strings.Replace(inputPath, separator, "/", -1)
 }
 
-func fromSlash(inputPath, inputOS string) string {
+func FromSlash(inputPath, inputOS string) string {
 	separator := "/"
 	if inputOS == "windows" {
 		separator = "\\"
@@ -119,7 +119,7 @@ func NormalizeWorkdir(current, wd string, inputOS string) (string, error) {
 
 	// Make sure we use the platform specific path separator. HCS does not like forward
 	// slashes in CWD.
-	return fromSlash(wd, inputOS), nil
+	return FromSlash(wd, inputOS), nil
 }
 
 // IsAbs returns a boolean value indicating whether or not the path
@@ -142,7 +142,7 @@ func IsAbs(pth, inputOS string) bool {
 	if err != nil {
 		return false
 	}
-	cleanedPath = toSlash(cleanedPath, inputOS)
+	cleanedPath = ToSlash(cleanedPath, inputOS)
 	// We stripped any potential drive letter and converted any backslashes to
 	// forward slashes. We can safely use path.IsAbs() for both Windows and Linux.
 	return path.IsAbs(cleanedPath)
@@ -189,14 +189,14 @@ func CheckSystemDriveAndRemoveDriveLetter(path string, inputOS string) (string,
 	}
 
 	// UNC paths should error out
-	if len(path) >= 2 && toSlash(path[:2], inputOS) == "//" {
+	if len(path) >= 2 && ToSlash(path[:2], inputOS) == "//" {
 		return "", errors.Errorf("UNC paths are not supported")
 	}
 
 	parts := strings.SplitN(path, ":", 2)
 	// Path does not have a drive letter. Just return it.
 	if len(parts) < 2 {
-		return toSlash(filepath.Clean(path), inputOS), nil
+		return ToSlash(filepath.Clean(path), inputOS), nil
 	}
 
 	// We expect all paths to be in C:
@@ -221,5 +221,5 @@ func CheckSystemDriveAndRemoveDriveLetter(path string, inputOS string) (string,
 	//
 	// We must return the second element of the split path, as is, without attempting to convert
 	// it to an absolute path. We have no knowledge of the CWD; that is treated elsewhere.
-	return toSlash(filepath.Clean(parts[1]), inputOS), nil
+	return ToSlash(filepath.Clean(parts[1]), inputOS), nil
 }