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gh-93156 - fix negative indexing into absolute pathlib.PurePath().parents (GH-93273)

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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.
(cherry picked from commit f32e6b48d1)

Co-authored-by: Barney Gale <barney.gale@gmail.com>
This commit is contained in:
Miss Islington (bot) 2022-06-03 14:53:00 -07:00 • committed by GitHub
parent 9cdfd1b01a
commit b382bf50c5
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5
Lib/test/test_pathlib.py
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@ -463,6 +463,9 @@ 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')))
@ -470,6 +473,8 @@ class _BasePurePathTest(object):
self.assertEqual(par[::2], (P('/a/b'), P('/')))
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]