GH-104102: Optimize `pathlib.Path.glob()` handling of `../` pattern segments (GH-104103)

These segments do not require a `stat()` call, as the selector's
`_select_from()` method is called after we've established that the
parent is a directory.

1 files changed, 12 insertions, 0 deletions

diff --git a/Lib/pathlib.py b/Lib/pathlib.py
index 61e7f3e..c69089f 100644
--- a/Lib/pathlib.py
+++ b/Lib/pathlib.py
@@ -74,6 +74,8 @@ def _make_selector(pattern_parts, flavour):
         return _TerminatingSelector()
     if pat == '**':
         cls = _RecursiveWildcardSelector
+    elif pat == '..':
+        cls = _ParentSelector
     elif '**' in pat:
         raise ValueError("Invalid pattern: '**' can only be an entire path component")
     elif _is_wildcard_pattern(pat):
@@ -114,6 +116,16 @@ class _TerminatingSelector:
         yield parent_path
 
 
+class _ParentSelector(_Selector):
+    def __init__(self, name, child_parts, flavour):
+        _Selector.__init__(self, child_parts, flavour)
+
+    def _select_from(self,  parent_path, is_dir, exists, scandir):
+        path = parent_path._make_child_relpath('..')
+        for p in self.successor._select_from(path, is_dir, exists, scandir):
+            yield p
+
+
 class _PreciseSelector(_Selector):
 
     def __init__(self, name, child_parts, flavour):