os: add windows_volume function (#14721)

vlib/os/filepath.v

@@ -12,6 +12,7 @@ const (
 	bslash     = `\\`
 	dot        = `.`
 	qmark      = `?`
+	fslash_str = '/'
 	dot_dot    = '..'
 	empty_str  = ''
 	dot_str    = '.'
@@ -62,8 +63,13 @@ pub fn norm_path(path string) string {
 		return os.dot_str
 	}
 	rooted := is_abs_path(path)
-	volume := get_volume(path)
-	volume_len := volume.len
+	// get the volume name from the path
+	// if the current operating system is Windows
+	volume_len := win_volume_len(path)
+	mut volume := path[..volume_len]
+	if volume_len != 0 && volume.contains(os.fslash_str) {
+		volume = volume.replace(os.fslash_str, path_separator)
+	}
 	cpath := clean_path(path[volume_len..])
 	if cpath.len == 0 && volume_len == 0 {
 		return os.dot_str
@@ -217,6 +223,9 @@ fn clean_path(path string) string {
 // win_volume_len returns the length of the
 // Windows volume/drive from the given `path`.
 fn win_volume_len(path string) int {
+	$if !windows {
+		return 0
+	}
 	plen := path.len
 	if plen < 2 {
 		return 0
@@ -244,20 +253,6 @@ fn win_volume_len(path string) int {
 	return 0
 }
 
-fn get_volume(path string) string {
-	$if !windows {
-		return os.empty_str
-	}
-	volume := path[..win_volume_len(path)]
-	if volume.len == 0 {
-		return os.empty_str
-	}
-	if volume[0] == os.fslash {
-		return volume.replace('/', '\\')
-	}
-	return volume
-}
-
 fn is_slash(b u8) bool {
 	$if windows {
 		return b == os.bslash || b == os.fslash

vlib/os/filepath_test.v

@@ -152,3 +152,20 @@ fn test_existing_path() {
 	assert existing_path('$wd//././/.//') or { '' } == '$wd//././/.//'
 	assert existing_path('$wd//././/.//oh') or { '' } == '$wd//././/.//'
 }
+
+fn test_windows_volume() {
+	$if windows {
+		assert windows_volume('C:/path\\to/file.v') == 'C:'
+		assert windows_volume('D:\\.\\') == 'D:'
+		assert windows_volume('G:') == 'G:'
+		assert windows_volume('G') == ''
+		assert windows_volume(r'\\Host\share\files\file.v') == r'\\Host\share'
+		assert windows_volume('\\\\Host\\') == ''
+		assert windows_volume(r'\\.\BootPartition2\\files\.\\') == r'\\.\BootPartition2'
+		assert windows_volume(r'\/.\BootPartition2\\files\.\\') == r'\/.\BootPartition2'
+		assert windows_volume(r'\\\.\BootPartition2\\files\.\\') == ''
+		assert windows_volume('') == ''
+		assert windows_volume('\\') == ''
+		assert windows_volume('/') == ''
+	}
+}

vlib/os/filepath_windows.v

@@ -0,0 +1,18 @@
+module os
+
+// windows_volume returns the volume name from the given `path` on a Windows system.
+// An empty string is returned if no Windows volume is present.
+// NOTE: An error is returned if the current operating system is not Windows.
+// Examples (on a Windows system):
+// ```v
+// assert os.windows_volume(r'C:\path\to\file.v') == 'C:'
+// assert os.windows_volume('D:') == 'D:'
+// assert os.windows_volume(r'\\Host\share\files\file.v') == r'\\Host\share'
+// ```
+pub fn windows_volume(path string) string {
+	volume_len := win_volume_len(path)
+	if volume_len == 0 {
+		return empty_str
+	}
+	return path[..volume_len]
+}