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bpo-43757: Make pathlib use os.path.realpath() to resolve symlinks in a path (GH-25264)

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Also adds a new "strict" argument to realpath() to avoid changing the default behaviour of pathlib while sharing the implementation.
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Barney Gale 2021-04-28 16:50:17 +01:00 • committed by GitHub
parent 859577c249
commit baecfbd849
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7 changed files with 184 additions and 109 deletions
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125
Lib/pathlib.py
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@ -14,12 +14,6 @@ from stat import S_ISDIR, S_ISLNK, S_ISREG, S_ISSOCK, S_ISBLK, S_ISCHR, S_ISFIFO
from urllib.parse import quote_from_bytes as urlquote_from_bytes
if os.name == 'nt':
from nt import _getfinalpathname
else:
_getfinalpathname = None
__all__ = [
"PurePath", "PurePosixPath", "PureWindowsPath",
"Path", "PosixPath", "WindowsPath",
@ -29,14 +23,17 @@ __all__ = [
# Internals
#
_WINERROR_NOT_READY = 21 # drive exists but is not accessible
_WINERROR_INVALID_NAME = 123 # fix for bpo-35306
_WINERROR_CANT_RESOLVE_FILENAME = 1921 # broken symlink pointing to itself
# EBADF - guard against macOS `stat` throwing EBADF
_IGNORED_ERROS = (ENOENT, ENOTDIR, EBADF, ELOOP)
_IGNORED_WINERRORS = (
21, # ERROR_NOT_READY - drive exists but is not accessible
123, # ERROR_INVALID_NAME - fix for bpo-35306
1921, # ERROR_CANT_RESOLVE_FILENAME - fix for broken symlink pointing to itself
)
_WINERROR_NOT_READY,
_WINERROR_INVALID_NAME,
_WINERROR_CANT_RESOLVE_FILENAME)
def _ignore_error(exception):
return (getattr(exception, 'errno', None) in _IGNORED_ERROS or
@ -186,30 +183,6 @@ class _WindowsFlavour(_Flavour):
def compile_pattern(self, pattern):
return re.compile(fnmatch.translate(pattern), re.IGNORECASE).fullmatch
def resolve(self, path, strict=False):
s = str(path)
if not s:
return path._accessor.getcwd()
previous_s = None
if _getfinalpathname is not None:
if strict:
return self._ext_to_normal(_getfinalpathname(s))
else:
tail_parts = [] # End of the path after the first one not found
while True:
try:
s = self._ext_to_normal(_getfinalpathname(s))
except FileNotFoundError:
previous_s = s
s, tail = os.path.split(s)
tail_parts.append(tail)
if previous_s == s:
return path
else:
return os.path.join(s, *reversed(tail_parts))
# Means fallback on absolute
return None
def _split_extended_path(self, s, ext_prefix=ext_namespace_prefix):
prefix = ''
if s.startswith(ext_prefix):
@ -220,10 +193,6 @@ class _WindowsFlavour(_Flavour):
s = '\\' + s[3:]
return prefix, s
def _ext_to_normal(self, s):
# Turn back an extended path into a normal DOS-like path
return self._split_extended_path(s)[1]
def is_reserved(self, parts):
# NOTE: the rules for reserved names seem somewhat complicated
# (e.g. r"..\NUL" is reserved but not r"foo\NUL").
@ -281,54 +250,6 @@ class _PosixFlavour(_Flavour):
def compile_pattern(self, pattern):
return re.compile(fnmatch.translate(pattern)).fullmatch
def resolve(self, path, strict=False):
sep = self.sep
accessor = path._accessor
seen = {}
def _resolve(path, rest):
if rest.startswith(sep):
path = ''
for name in rest.split(sep):
if not name or name == '.':
# current dir
continue
if name == '..':
# parent dir
path, _, _ = path.rpartition(sep)
continue
if path.endswith(sep):
newpath = path + name
else:
newpath = path + sep + name
if newpath in seen:
# Already seen this path
path = seen[newpath]
if path is not None:
# use cached value
continue
# The symlink is not resolved, so we must have a symlink loop.
raise RuntimeError("Symlink loop from %r" % newpath)
# Resolve the symbolic link
try:
target = accessor.readlink(newpath)
except OSError as e:
if e.errno != EINVAL and strict:
raise
# Not a symlink, or non-strict mode. We just leave the path
# untouched.
path = newpath
else:
seen[newpath] = None # not resolved symlink
path = _resolve(path, target)
seen[newpath] = path # resolved symlink
return path
# NOTE: according to POSIX, getcwd() cannot contain path components
# which are symlinks.
base = '' if path.is_absolute() else accessor.getcwd()
return _resolve(base, str(path)) or sep
def is_reserved(self, parts):
return False
@ -424,6 +345,8 @@ class _NormalAccessor(_Accessor):
expanduser = staticmethod(os.path.expanduser)
realpath = staticmethod(os.path.realpath)
_normal_accessor = _NormalAccessor()
@ -1132,15 +1055,27 @@ class Path(PurePath):
normalizing it (for example turning slashes into backslashes under
Windows).
"""
s = self._flavour.resolve(self, strict=strict)
if s is None:
# No symlink resolution => for consistency, raise an error if
# the path doesn't exist or is forbidden
self.stat()
s = str(self.absolute())
# Now we have no symlinks in the path, it's safe to normalize it.
normed = self._flavour.pathmod.normpath(s)
return self._from_parts((normed,))
def check_eloop(e):
winerror = getattr(e, 'winerror', 0)
if e.errno == ELOOP or winerror == _WINERROR_CANT_RESOLVE_FILENAME:
raise RuntimeError("Symlink loop from %r" % e.filename)
try:
s = self._accessor.realpath(self, strict=strict)
except OSError as e:
check_eloop(e)
raise
p = self._from_parts((s,))
# In non-strict mode, realpath() doesn't raise on symlink loops.
# Ensure we get an exception by calling stat()
if not strict:
try:
p.stat()
except OSError as e:
check_eloop(e)
return p
def stat(self, *, follow_symlinks=True):
"""