vlib.os: fix join-path

Closes #20231

Co-authored-by: Turiiya <34311583+ttytm@users.noreply.github.com>

vlib/os/os.v

@@ -576,25 +576,34 @@ pub fn join_path(base string, dirs ...string) string {
 	defer {
 		unsafe { sb.free() }
 	}
-	sbase := base.trim_right('\\/')
-	defer {
-		unsafe { sbase.free() }
+	mut i := 0
+	mut needs_sep := false
+	if base != '' {
+		sb.write_string(base)
+		needs_sep = !base.ends_with(path_separator)
+	} else {
+		for i < dirs.len {
+			d := dirs[i]
+			i++
+			if d != '' {
+				sb.write_string(d)
+				needs_sep = !base.ends_with(path_separator)
+				break
+			}
+		}
 	}
-	sb.write_string(sbase)
-	for d in dirs {
+	for i < dirs.len {
+		d := dirs[i]
 		if d != '' {
-			sb.write_string(path_separator)
+			if needs_sep {
+				sb.write_string(path_separator)
+			}
 			sb.write_string(d)
+			needs_sep = !d.ends_with(path_separator)
 		}
+		i++
 	}
-	mut res := sb.str()
-	if sbase == '' {
-		res = res.trim_left(path_separator)
-	}
-	if res.contains('/./') {
-		// Fix `join_path("/foo/bar", "./file.txt")` => `/foo/bar/./file.txt`
-		res = res.replace('/./', '/')
-	}
+	res := sb.str()
 	return res
 }
 

vlib/os/os_test.c.v

@@ -621,9 +621,10 @@ fn test_join() {
 		assert os.join_path('v', '', 'dir') == 'v\\dir'
 	} $else {
 		assert os.join_path('v', 'vlib', 'os') == 'v/vlib/os'
-		assert os.join_path('/foo/bar', './file.txt') == '/foo/bar/file.txt'
+		assert os.join_path('/foo/bar', './file.txt') == '/foo/bar/./file.txt'
 		assert os.join_path('', 'f1', 'f2') == 'f1/f2'
 		assert os.join_path('v', '', 'dir') == 'v/dir'
+		assert os.join_path('/', 'test') == '/test'
 	}
 }