From f32e6b48d12834ba3bde01ec21c14da33abd26d6 Mon Sep 17 00:00:00 2001 From: Barney Gale Date: Fri, 3 Jun 2022 22:33:20 +0100 Subject: gh-93156 - fix negative indexing into absolute `pathlib.PurePath().parents` (GH-93273) When a `_PathParents` object has a drive or a root, the length of the object is *one less* than than the length of `self._parts`, which resulted in an off-by-one error when `path.parents[-n]` was fed through to `self._parts[:-n - 1]`. In particular, `path.parents[-1]` was a malformed path object with spooky properties. This is addressed by adding `len(self)` to negative indices. --- Lib/pathlib.py | 2 ++ Lib/test/test_pathlib.py | 5 +++++ .../next/Library/2022-05-26-23-10-55.gh-issue-93156.4XfDVN.rst | 2 ++ 3 files changed, 9 insertions(+) create mode 100644 Misc/NEWS.d/next/Library/2022-05-26-23-10-55.gh-issue-93156.4XfDVN.rst diff --git a/Lib/pathlib.py b/Lib/pathlib.py index c608ba0..26da4ed 100644 --- a/Lib/pathlib.py +++ b/Lib/pathlib.py @@ -443,6 +443,8 @@ class _PathParents(Sequence): if idx >= len(self) or idx < -len(self): raise IndexError(idx) + if idx < 0: + idx += len(self) return self._pathcls._from_parsed_parts(self._drv, self._root, self._parts[:-idx - 1]) diff --git a/Lib/test/test_pathlib.py b/Lib/test/test_pathlib.py index 6694f1b..2215134 100644 --- a/Lib/test/test_pathlib.py +++ b/Lib/test/test_pathlib.py @@ -465,6 +465,9 @@ class _BasePurePathTest(object): self.assertEqual(par[0], P('/a/b')) self.assertEqual(par[1], P('/a')) self.assertEqual(par[2], P('/')) + self.assertEqual(par[-1], P('/')) + self.assertEqual(par[-2], P('/a')) + self.assertEqual(par[-3], P('/a/b')) self.assertEqual(par[0:1], (P('/a/b'),)) self.assertEqual(par[:2], (P('/a/b'), P('/a'))) self.assertEqual(par[:-1], (P('/a/b'), P('/a'))) @@ -473,6 +476,8 @@ class _BasePurePathTest(object): self.assertEqual(par[::-1], (P('/'), P('/a'), P('/a/b'))) self.assertEqual(list(par), [P('/a/b'), P('/a'), P('/')]) with self.assertRaises(IndexError): + par[-4] + with self.assertRaises(IndexError): par[3] def test_drive_common(self): diff --git a/Misc/NEWS.d/next/Library/2022-05-26-23-10-55.gh-issue-93156.4XfDVN.rst b/Misc/NEWS.d/next/Library/2022-05-26-23-10-55.gh-issue-93156.4XfDVN.rst new file mode 100644 index 0000000..165baa0 --- /dev/null +++ b/Misc/NEWS.d/next/Library/2022-05-26-23-10-55.gh-issue-93156.4XfDVN.rst @@ -0,0 +1,2 @@ +Accessing the :attr:`pathlib.PurePath.parents` sequence of an absolute path +using negative index values produced incorrect results. -- cgit v0.12