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GH-78079: Fix UNC device path root normalization in pathlib by barneygale · Pull Request #102003 · python/cpython · GitHub
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GH-78079: Fix UNC device path root normalization in pathlib #102003

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Merged
barneygale merged 10 commits into from
Apr 14, 2023
+43 −3
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GH-78079: Fix UNC device path root normalization in pathlib #102003

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99f62bc
GH-78079: Fix UNC device path root normalization in pathlib
barneygale Feb 2, 2023
6651b67
A few more test cases
barneygale Feb 20, 2023
87519ba
Merge branch 'main' into gh-78079-win-device-path-roots
barneygale Feb 20, 2023
c444a3c
Update Lib/pathlib.py
barneygale Mar 10, 2023
36623c0
Fix handling of UNC paths with incomplete drives in glob(), walk(), etc.
barneygale Mar 10, 2023
aea236e
Test handling of UNC paths with incomplete drives in joinpath()
barneygale Mar 10, 2023
bb0af91
Merge branch 'main' into gh-78079-win-device-path-roots
barneygale Mar 10, 2023
f412f87
Merge branch 'main' into gh-78079-win-device-path-roots
barneygale Apr 3, 2023
8ff07fc
Merge branch 'main' into gh-78079-win-device-path-roots
barneygale Apr 9, 2023
723a5aa
Merge branch 'main' into gh-78079-win-device-path-roots
barneygale Apr 11, 2023
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Merge branch 'main' into gh-78079-win-device-path-roots
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@barneygale
barneygale committed Apr 9, 2023
commit 8ff07fc8f6ca204e6a948fd7da51b67e9ec19069
3 changes: 1 addition & 2 deletions Lib/pathlib.py
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Original file line number Diff line number Diff line change
Expand Up @@ -330,8 +330,7 @@ def _parse_path(cls, path):
elif len(drv_parts) == 6:
# e.g. //?/unc/server/share
root = sep
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unfiltered_parsed = [drv + root] + rel.split(sep)
parsed = [sys.intern(x) for x in unfiltered_parsed if x and x != '.']
parsed = [sys.intern(str(x)) for x in rel.split(sep) if x and x != '.']

@zooba zooba Apr 11, 2023

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Whoa, we sys.intern everything? That seems like a painful memory leak. Would we be better off with a class level lru_cache'd function1?

Don't we already know that rel will be str here? If it's bytes, str(x) is the wrong conversion anyway. Maybe the intern function should be cls._flavour.str_and_intern?

Footnotes

  1. @lru_cache(max_size=REASONABLE_VALUE) def intern(x): return x ↩

@barneygale barneygale Apr 11, 2023 •
edited
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The interning of the path parts is longstanding pathlib behaviour. Honestly I don't know enough about the benefits/drawbacks of interning to say whether it's reasonable.

Don't we already know that rel will be str here?

We know that it's an instance of str (and not bytes), but we don't know whether it's a true str object (required by sys.intern()).

@eryksun eryksun Apr 11, 2023

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Whoa, we sys.intern everything? That seems like a painful memory leak.

Is it really all that bad? sys.intern() calls PyUnicode_InternInPlace(), not PyUnicode_InternImmortal(). An interned string gets deallocated based on its reference count, like any other object. For example:

>>> s = sys.intern('spam and eggs')
>>> t = sys.intern('spam and eggs')
>>> s is t
True
>>> id(s)
139835455199152
>>> del s, t
>>> s = sys.intern('spam and eggs')
>>> id(s)
139835455198912

return drv, root, parsed

def _load_parts(self):
Expand Down
144 changes: 17 additions & 127 deletions Lib/test/test_pathlib.py
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Original file line number Diff line number Diff line change
Expand Up @@ -24,133 +24,6 @@
grp = pwd = None


class _BaseFlavourTest(object):

def _check_parse_parts(self, arg, expected):
def f(parts):
path = self.cls(*parts)._raw_path
return self.cls._parse_path(path)
sep = self.flavour.sep
altsep = self.flavour.altsep
actual = f([x.replace('/', sep) for x in arg])
self.assertEqual(actual, expected)
if altsep:
actual = f([x.replace('/', altsep) for x in arg])
self.assertEqual(actual, expected)

def test_parse_parts_common(self):
check = self._check_parse_parts
sep = self.flavour.sep
# Unanchored parts.
check([], ('', '', []))
check(['a'], ('', '', ['a']))
check(['a/'], ('', '', ['a']))
check(['a', 'b'], ('', '', ['a', 'b']))
# Expansion.
check(['a/b'], ('', '', ['a', 'b']))
check(['a/b/'], ('', '', ['a', 'b']))
check(['a', 'b/c', 'd'], ('', '', ['a', 'b', 'c', 'd']))
# Collapsing and stripping excess slashes.
check(['a', 'b//c', 'd'], ('', '', ['a', 'b', 'c', 'd']))
check(['a', 'b/c/', 'd'], ('', '', ['a', 'b', 'c', 'd']))
# Eliminating standalone dots.
check(['.'], ('', '', []))
check(['.', '.', 'b'], ('', '', ['b']))
check(['a', '.', 'b'], ('', '', ['a', 'b']))
check(['a', '.', '.'], ('', '', ['a']))
# The first part is anchored.
check(['/a/b'], ('', sep, [sep, 'a', 'b']))
check(['/a', 'b'], ('', sep, [sep, 'a', 'b']))
check(['/a/', 'b'], ('', sep, [sep, 'a', 'b']))
# Ignoring parts before an anchored part.
check(['a', '/b', 'c'], ('', sep, [sep, 'b', 'c']))
check(['a', '/b', '/c'], ('', sep, [sep, 'c']))


class PosixFlavourTest(_BaseFlavourTest, unittest.TestCase):
cls = pathlib.PurePosixPath
flavour = pathlib.PurePosixPath._flavour

def test_parse_parts(self):
check = self._check_parse_parts
# Collapsing of excess leading slashes, except for the double-slash
# special case.
check(['//a', 'b'], ('', '//', ['//', 'a', 'b']))
check(['///a', 'b'], ('', '/', ['/', 'a', 'b']))
check(['////a', 'b'], ('', '/', ['/', 'a', 'b']))
# Paths which look like NT paths aren't treated specially.
check(['c:a'], ('', '', ['c:a']))
check(['c:\\a'], ('', '', ['c:\\a']))
check(['\\a'], ('', '', ['\\a']))


class NTFlavourTest(_BaseFlavourTest, unittest.TestCase):
cls = pathlib.PureWindowsPath
flavour = pathlib.PureWindowsPath._flavour

def test_parse_parts(self):
check = self._check_parse_parts
# First part is anchored.
check(['c:'], ('c:', '', ['c:']))
check(['c:/'], ('c:', '\\', ['c:\\']))
check(['/'], ('', '\\', ['\\']))
check(['c:a'], ('c:', '', ['c:', 'a']))
check(['c:/a'], ('c:', '\\', ['c:\\', 'a']))
check(['/a'], ('', '\\', ['\\', 'a']))
# UNC paths.
check(['//'], ('\\\\', '', ['\\\\']))
check(['//a'], ('\\\\a', '', ['\\\\a']))
check(['//a/'], ('\\\\a\\', '', ['\\\\a\\']))
check(['//a/b'], ('\\\\a\\b', '\\', ['\\\\a\\b\\']))
check(['//a/b/'], ('\\\\a\\b', '\\', ['\\\\a\\b\\']))
check(['//a/b/c'], ('\\\\a\\b', '\\', ['\\\\a\\b\\', 'c']))
# Second part is anchored, so that the first part is ignored.
check(['a', 'Z:b', 'c'], ('Z:', '', ['Z:', 'b', 'c']))
check(['a', 'Z:/b', 'c'], ('Z:', '\\', ['Z:\\', 'b', 'c']))
# UNC paths.
check(['a', '//b/c', 'd'], ('\\\\b\\c', '\\', ['\\\\b\\c\\', 'd']))
# Collapsing and stripping excess slashes.
check(['a', 'Z://b//c/', 'd/'], ('Z:', '\\', ['Z:\\', 'b', 'c', 'd']))
# UNC paths.
check(['a', '//b/c//', 'd'], ('\\\\b\\c', '\\', ['\\\\b\\c\\', 'd']))
# Extended paths.
check(['//./c:'], ('\\\\.\\c:', '', ['\\\\.\\c:']))
check(['//?/c:/'], ('\\\\?\\c:', '\\', ['\\\\?\\c:\\']))
check(['//?/c:/a'], ('\\\\?\\c:', '\\', ['\\\\?\\c:\\', 'a']))
check(['//?/c:/a', '/b'], ('\\\\?\\c:', '\\', ['\\\\?\\c:\\', 'b']))
# Extended UNC paths (format is "\\?\UNC\server\share").
check(['//?'], ('\\\\?', '', ['\\\\?']))
check(['//?/'], ('\\\\?\\', '', ['\\\\?\\']))
check(['//?/UNC'], ('\\\\?\\UNC', '', ['\\\\?\\UNC']))
check(['//?/UNC/'], ('\\\\?\\UNC\\', '', ['\\\\?\\UNC\\']))
check(['//?/UNC/b'], ('\\\\?\\UNC\\b', '', ['\\\\?\\UNC\\b']))
check(['//?/UNC/b/'], ('\\\\?\\UNC\\b\\', '', ['\\\\?\\UNC\\b\\']))
check(['//?/UNC/b/c'], ('\\\\?\\UNC\\b\\c', '\\', ['\\\\?\\UNC\\b\\c\\']))
check(['//?/UNC/b/c/'], ('\\\\?\\UNC\\b\\c', '\\', ['\\\\?\\UNC\\b\\c\\']))
check(['//?/UNC/b/c/d'], ('\\\\?\\UNC\\b\\c', '\\', ['\\\\?\\UNC\\b\\c\\', 'd']))
# UNC device paths
check(['//./BootPartition/'], ('\\\\.\\BootPartition', '\\', ['\\\\.\\BootPartition\\']))
check(['//?/BootPartition/'], ('\\\\?\\BootPartition', '\\', ['\\\\?\\BootPartition\\']))
check(['//./PhysicalDrive0'], ('\\\\.\\PhysicalDrive0', '', ['\\\\.\\PhysicalDrive0']))
check(['//?/Volume{}/'], ('\\\\?\\Volume{}', '\\', ['\\\\?\\Volume{}\\']))
check(['//./nul'], ('\\\\.\\nul', '', ['\\\\.\\nul']))
# Second part has a root but not drive.
check(['a', '/b', 'c'], ('', '\\', ['\\', 'b', 'c']))
check(['Z:/a', '/b', 'c'], ('Z:', '\\', ['Z:\\', 'b', 'c']))
check(['//?/Z:/a', '/b', 'c'], ('\\\\?\\Z:', '\\', ['\\\\?\\Z:\\', 'b', 'c']))
# Joining with the same drive => the first path is appended to if
# the second path is relative.
check(['c:/a/b', 'c:x/y'], ('c:', '\\', ['c:\\', 'a', 'b', 'x', 'y']))
check(['c:/a/b', 'c:/x/y'], ('c:', '\\', ['c:\\', 'x', 'y']))
# Paths to files with NTFS alternate data streams
check(['./c:s'], ('', '', ['c:s']))
check(['cc:s'], ('', '', ['cc:s']))
check(['C:c:s'], ('C:', '', ['C:', 'c:s']))
check(['C:/c:s'], ('C:', '\\', ['C:\\', 'c:s']))
check(['D:a', './c:b'], ('D:', '', ['D:', 'a', 'c:b']))
check(['D:/a', './c:b'], ('D:', '\\', ['D:\\', 'a', 'c:b']))


#
# Tests for the pure classes.
#
Expand Down Expand Up @@ -937,6 +810,9 @@ def test_drive_root_parts(self):
check(('c:/a',), 'c:', '\\', ('c:\\', 'a'))
check(('/a',), '', '\\', ('\\', 'a'))
# UNC paths.
check(('//',), '\\\\', '', ('\\\\',))
check(('//a',), '\\\\a', '', ('\\\\a',))
check(('//a/',), '\\\\a\\', '', ('\\\\a\\',))
check(('//a/b',), '\\\\a\\b', '\\', ('\\\\a\\b\\',))
check(('//a/b/',), '\\\\a\\b', '\\', ('\\\\a\\b\\',))
check(('//a/b/c',), '\\\\a\\b', '\\', ('\\\\a\\b\\', 'c'))
Expand All @@ -950,12 +826,26 @@ def test_drive_root_parts(self):
# UNC paths.
check(('a', '//b/c//', 'd'), '\\\\b\\c', '\\', ('\\\\b\\c\\', 'd'))
# Extended paths.
check(('//./c:',), '\\\\.\\c:', '', ('\\\\.\\c:',))
check(('//?/c:/',), '\\\\?\\c:', '\\', ('\\\\?\\c:\\',))
check(('//?/c:/a',), '\\\\?\\c:', '\\', ('\\\\?\\c:\\', 'a'))
check(('//?/c:/a', '/b'), '\\\\?\\c:', '\\', ('\\\\?\\c:\\', 'b'))
# Extended UNC paths (format is "\\?\UNC\server\share").
check(('//?',), '\\\\?', '', ('\\\\?',))
check(('//?/',), '\\\\?\\', '', ('\\\\?\\',))
check(('//?/UNC',), '\\\\?\\UNC', '', ('\\\\?\\UNC',))
check(('//?/UNC/',), '\\\\?\\UNC\\', '', ('\\\\?\\UNC\\',))
check(('//?/UNC/b',), '\\\\?\\UNC\\b', '', ('\\\\?\\UNC\\b',))
check(('//?/UNC/b/',), '\\\\?\\UNC\\b\\', '', ('\\\\?\\UNC\\b\\',))
check(('//?/UNC/b/c',), '\\\\?\\UNC\\b\\c', '\\', ('\\\\?\\UNC\\b\\c\\',))
check(('//?/UNC/b/c/',), '\\\\?\\UNC\\b\\c', '\\', ('\\\\?\\UNC\\b\\c\\',))
check(('//?/UNC/b/c/d',), '\\\\?\\UNC\\b\\c', '\\', ('\\\\?\\UNC\\b\\c\\', 'd'))
# UNC device paths
check(('//./BootPartition/',), '\\\\.\\BootPartition', '\\', ('\\\\.\\BootPartition\\',))
check(('//?/BootPartition/',), '\\\\?\\BootPartition', '\\', ('\\\\?\\BootPartition\\',))
check(('//./PhysicalDrive0',), '\\\\.\\PhysicalDrive0', '', ('\\\\.\\PhysicalDrive0',))
check(('//?/Volume{}/',), '\\\\?\\Volume{}', '\\', ('\\\\?\\Volume{}\\',))
check(('//./nul',), '\\\\.\\nul', '', ('\\\\.\\nul',))
# Second part has a root but not drive.
check(('a', '/b', 'c'), '', '\\', ('\\', 'b', 'c'))
check(('Z:/a', '/b', 'c'), 'Z:', '\\', ('Z:\\', 'b', 'c'))
Expand Down
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