Make parent_directory() of bare filename return . (#3313)

Author: casey

src/function.rs

@@ -496,10 +496,16 @@ fn os_family(_context: Context) -> FunctionResult {
 }
 
 fn parent_directory(_context: Context, path: &str) -> FunctionResult {
-  Utf8Path::new(path)
+  let parent = Utf8Path::new(path)
     .parent()
     .map(Utf8Path::to_string)
-    .ok_or_else(|| format!("Could not extract parent directory from `{path}`"))
+    .ok_or_else(|| format!("Could not extract parent directory from `{path}`"))?;
+
+  if parent.is_empty() {
+    Ok(".".into())
+  } else {
+    Ok(parent)
+  }
 }
 
 fn path_exists(context: Context, path: &str) -> FunctionResult {

tests/functions.rs

@@ -325,6 +325,19 @@ fn broken_directory_function2() {
     .failure();
 }
 
+#[test]
+fn parent_directory_of_bare_filename() {
+  Test::new()
+    .justfile(
+      "
+        foo:
+          @echo {{parent_directory('foo')}}
+      ",
+    )
+    .stdout(".\n")
+    .success();
+}
+
 #[test]
 fn env_var_functions_windows() {
   if cfg!(not(windows)) {