pythongh-96290: Support partial/invalid UNC drives in ntpath.normpath…

…() and splitdrive() (pythonGH-100351)

This brings the Python implementation of `ntpath.normpath()` in line with the C implementation added in 99fcf15

Co-authored-by: Eryk Sun <eryksun@gmail.com>

Lib/ntpath.py

@@ -87,16 +87,20 @@ def normcase(s):
 def isabs(s):
  """Test whether a path is absolute"""
  s = os.fspath(s)
- # Paths beginning with \\?\ are always absolute, but do not
- # necessarily contain a drive.
  if isinstance(s, bytes):
- if s.replace(b'/', b'\\').startswith(b'\\\\?\\'):
- return True
+ sep = b'\\'
+ altsep = b'/'
+ colon_sep = b':\\'
  else:
- if s.replace('/', '\\').startswith('\\\\?\\'):
- return True
- s = splitdrive(s)[1]
- return len(s) > 0 and s[0] and s[0] in _get_bothseps(s)
+ sep = '\\'
+ altsep = '/'
+ colon_sep = ':\\'
+ s = s[:3].replace(altsep, sep)
+ # Absolute: UNC, device, and paths with a drive and root.
+ # LEGACY BUG: isabs("/x") should be false since the path has no drive.
+ if s.startswith(sep) or s.startswith(colon_sep, 1):
+ return True
+ return False
 
 
 # Join two (or more) paths.
@@ -172,28 +176,26 @@ def splitdrive(p):
  sep = b'\\'
  altsep = b'/'
  colon = b':'
+ unc_prefix = b'\\\\?\\UNC\\'
  else:
  sep = '\\'
  altsep = '/'
  colon = ':'
+ unc_prefix = '\\\\?\\UNC\\'
  normp = p.replace(altsep, sep)
- if (normp[0:2] == sep*2) and (normp[2:3] != sep):
- # is a UNC path:
- # vvvvvvvvvvvvvvvvvvvv drive letter or UNC path
- # \\machine\mountpoint\directory\etc\...
- # directory ^^^^^^^^^^^^^^^
- index = normp.find(sep, 2)
+ if normp[0:2] == sep * 2:
+ # UNC drives, e.g. \\server\share or \\?\UNC\server\share
+ # Device drives, e.g. \\.\device or \\?\device
+ start = 8 if normp[:8].upper() == unc_prefix else 2
+ index = normp.find(sep, start)
  if index == -1:
- return p[:0], p
+ return p, p[:0]
  index2 = normp.find(sep, index + 1)
- # a UNC path can't have two slashes in a row
- # (after the initial two)
- if index2 == index + 1:
- return p[:0], p
  if index2 == -1:
- index2 = len(p)
+ return p, p[:0]
  return p[:index2], p[index2:]
  if normp[1:2] == colon:
+ # Drive-letter drives, e.g. X:
  return p[:2], p[2:]
  return p[:0], p
 
@@ -499,20 +501,11 @@ def normpath(path):
  altsep = b'/'
  curdir = b'.'
  pardir = b'..'
- special_prefixes = (b'\\\\.\\', b'\\\\?\\')
  else:
  sep = '\\'
  altsep = '/'
  curdir = '.'
  pardir = '..'
- special_prefixes = ('\\\\.\\', '\\\\?\\')
- if path.startswith(special_prefixes):
- # in the case of paths with these prefixes:
- # \\.\ -> device names
- # \\?\ -> literal paths
- # do not do any normalization, but return the path
- # unchanged apart from the call to os.fspath()
- return path
  path = path.replace(altsep, sep)
  prefix, path = splitdrive(path)
 

Lib/test/test_ntpath.py

@@ -107,17 +107,50 @@ def test_splitdrive(self):
  tester('ntpath.splitdrive("//conky/mountpoint/foo/bar")',
  ('//conky/mountpoint', '/foo/bar'))
  tester('ntpath.splitdrive("\\\\\\conky\\mountpoint\\foo\\bar")',
- ('', '\\\\\\conky\\mountpoint\\foo\\bar'))
+ ('\\\\\\conky', '\\mountpoint\\foo\\bar'))
  tester('ntpath.splitdrive("///conky/mountpoint/foo/bar")',
- ('', '///conky/mountpoint/foo/bar'))
+ ('///conky', '/mountpoint/foo/bar'))
  tester('ntpath.splitdrive("\\\\conky\\\\mountpoint\\foo\\bar")',
- ('', '\\\\conky\\\\mountpoint\\foo\\bar'))
+ ('\\\\conky\\', '\\mountpoint\\foo\\bar'))
  tester('ntpath.splitdrive("//conky//mountpoint/foo/bar")',
- ('', '//conky//mountpoint/foo/bar'))
+ ('//conky/', '/mountpoint/foo/bar'))
  # Issue #19911: UNC part containing U+0130
  self.assertEqual(ntpath.splitdrive('//conky/MOUNTPOİNT/foo/bar'),
  ('//conky/MOUNTPOİNT', '/foo/bar'))
 
+ # gh-81790: support device namespace, including UNC drives.
+ tester('ntpath.splitdrive("//?/c:")', ("//?/c:", ""))
+ tester('ntpath.splitdrive("//?/c:/")', ("//?/c:", "/"))
+ tester('ntpath.splitdrive("//?/c:/dir")', ("//?/c:", "/dir"))
+ tester('ntpath.splitdrive("//?/UNC")', ("//?/UNC", ""))
+ tester('ntpath.splitdrive("//?/UNC/")', ("//?/UNC/", ""))
+ tester('ntpath.splitdrive("//?/UNC/server/")', ("//?/UNC/server/", ""))
+ tester('ntpath.splitdrive("//?/UNC/server/share")', ("//?/UNC/server/share", ""))
+ tester('ntpath.splitdrive("//?/UNC/server/share/dir")', ("//?/UNC/server/share", "/dir"))
+ tester('ntpath.splitdrive("//?/VOLUME{00000000-0000-0000-0000-000000000000}/spam")',
+ ('//?/VOLUME{00000000-0000-0000-0000-000000000000}', '/spam'))
+ tester('ntpath.splitdrive("//?/BootPartition/")', ("//?/BootPartition", "/"))
+
+ tester('ntpath.splitdrive("\\\\?\\c:")', ("\\\\?\\c:", ""))
+ tester('ntpath.splitdrive("\\\\?\\c:\\")', ("\\\\?\\c:", "\\"))
+ tester('ntpath.splitdrive("\\\\?\\c:\\dir")', ("\\\\?\\c:", "\\dir"))
+ tester('ntpath.splitdrive("\\\\?\\UNC")', ("\\\\?\\UNC", ""))
+ tester('ntpath.splitdrive("\\\\?\\UNC\\")', ("\\\\?\\UNC\\", ""))
+ tester('ntpath.splitdrive("\\\\?\\UNC\\server\\")', ("\\\\?\\UNC\\server\\", ""))
+ tester('ntpath.splitdrive("\\\\?\\UNC\\server\\share")', ("\\\\?\\UNC\\server\\share", ""))
+ tester('ntpath.splitdrive("\\\\?\\UNC\\server\\share\\dir")',
+ ("\\\\?\\UNC\\server\\share", "\\dir"))
+ tester('ntpath.splitdrive("\\\\?\\VOLUME{00000000-0000-0000-0000-000000000000}\\spam")',
+ ('\\\\?\\VOLUME{00000000-0000-0000-0000-000000000000}', '\\spam'))
+ tester('ntpath.splitdrive("\\\\?\\BootPartition\\")', ("\\\\?\\BootPartition", "\\"))
+
+ # gh-96290: support partial/invalid UNC drives
+ tester('ntpath.splitdrive("//")', ("//", "")) # empty server & missing share
+ tester('ntpath.splitdrive("///")', ("///", "")) # empty server & empty share
+ tester('ntpath.splitdrive("///y")', ("///y", "")) # empty server & non-empty share
+ tester('ntpath.splitdrive("//x")', ("//x", "")) # non-empty server & missing share
+ tester('ntpath.splitdrive("//x/")', ("//x/", "")) # non-empty server & empty share
+
  def test_split(self):
  tester('ntpath.split("c:\\foo\\bar")', ('c:\\foo', 'bar'))
  tester('ntpath.split("\\\\conky\\mountpoint\\foo\\bar")',
@@ -136,6 +169,10 @@ def test_isabs(self):
  tester('ntpath.isabs("\\foo")', 1)
  tester('ntpath.isabs("\\foo\\bar")', 1)
 
+ # gh-96290: normal UNC paths and device paths without trailing backslashes
+ tester('ntpath.isabs("\\\\conky\\mountpoint")', 1)
+ tester('ntpath.isabs("\\\\.\\C:")', 1)
+
  def test_commonprefix(self):
  tester('ntpath.commonprefix(["/home/swenson/spam", "/home/swen/spam"])',
  "/home/swen")
@@ -245,6 +282,12 @@ def test_normpath(self):
  tester("ntpath.normpath('//server/share/../..')", '\\\\server\\share\\')
  tester("ntpath.normpath('//server/share/../../')", '\\\\server\\share\\')
 
+ # gh-96290: don't normalize partial/invalid UNC drives as rooted paths.
+ tester("ntpath.normpath('\\\\foo\\\\')", '\\\\foo\\\\')
+ tester("ntpath.normpath('\\\\foo\\')", '\\\\foo\\')
+ tester("ntpath.normpath('\\\\foo')", '\\\\foo')
+ tester("ntpath.normpath('\\\\')", '\\\\')
+
  def test_realpath_curdir(self):
  expected = ntpath.normpath(os.getcwd())
  tester("ntpath.realpath('.')", expected)

Lib/test/test_zipfile.py

@@ -1468,10 +1468,10 @@ def test_extract_hackers_arcnames_windows_only(self):
  (r'C:\foo\bar', 'foo/bar'),
  (r'//conky/mountpoint/foo/bar', 'foo/bar'),
  (r'\\conky\mountpoint\foo\bar', 'foo/bar'),
- (r'///conky/mountpoint/foo/bar', 'conky/mountpoint/foo/bar'),
- (r'\\\conky\mountpoint\foo\bar', 'conky/mountpoint/foo/bar'),
- (r'//conky//mountpoint/foo/bar', 'conky/mountpoint/foo/bar'),
- (r'\\conky\\mountpoint\foo\bar', 'conky/mountpoint/foo/bar'),
+ (r'///conky/mountpoint/foo/bar', 'mountpoint/foo/bar'),
+ (r'\\\conky\mountpoint\foo\bar', 'mountpoint/foo/bar'),
+ (r'//conky//mountpoint/foo/bar', 'mountpoint/foo/bar'),
+ (r'\\conky\\mountpoint\foo\bar', 'mountpoint/foo/bar'),
  (r'//?/C:/foo/bar', 'foo/bar'),
  (r'\\?\C:\foo\bar', 'foo/bar'),
  (r'C:/../C:/foo/bar', 'C_/foo/bar'),

Misc/NEWS.d/next/Library/2022-12-19-23-19-26.gh-issue-96290.qFjsi6.rst

@@ -0,0 +1,5 @@
+Fix handling of partial and invalid UNC drives in ``ntpath.splitdrive()``, and in
+``ntpath.normpath()`` on non-Windows systems. Paths such as '\\server' and '\\' are now considered
+by ``splitdrive()`` to contain only a drive, and consequently are not modified by ``normpath()`` on
+non-Windows systems. The behaviour of ``normpath()`` on Windows systems is unaffected, as native
+OS APIs are used. Patch by Eryk Sun, with contributions by Barney Gale.