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GH-113528: Deoptimise pathlib._abc.PathBase.resolve() (#113782)

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Replace use of `_from_parsed_parts()` with `with_segments()` in
`resolve()`.

No effect on `Path.resolve()`, which uses `os.path.realpath()`.
This commit is contained in:
Barney Gale 2024-01-09 19:50:23 +00:00 committed by GitHub
parent 3a9096c337
commit 1092cfb201
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GPG Key ID: 4AEE18F83AFDEB23
1 changed files with 40 additions and 25 deletions
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65
Lib/pathlib/_abc.py
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@ -406,6 +406,23 @@ class PurePathBase:
except TypeError:
return NotImplemented
@property
def _stack(self):
"""
Split the path into a 2-tuple (anchor, parts), where *anchor* is the
uppermost parent of the path (equivalent to path.parents[-1]), and
*parts* is a reversed list of parts following the anchor.
"""
split = self.pathmod.split
path = str(self)
parent, name = split(path)
names = []
while path != parent:
names.append(name)
path = parent
parent, name = split(path)
return path, names
@property
def parent(self):
"""The logical parent of the path."""
@ -911,16 +928,6 @@ class PathBase(PurePathBase):
self._unsupported("readlink")
readlink._supported = False
def _split_stack(self):
"""
Split the path into a 2-tuple (anchor, parts), where *anchor* is the
uppermost parent of the path (equivalent to path.parents[-1]), and
*parts* is a reversed list of parts following the anchor.
"""
if not self._tail:
return self, []
return self._from_parsed_parts(self.drive, self.root, []), self._tail[::-1]
def resolve(self, strict=False):
"""
Make the path absolute, resolving all symlinks on the way and also
@ -928,11 +935,15 @@ class PathBase(PurePathBase):
"""
if self._resolving:
return self
path, parts = self._split_stack()
path_root, parts = self._stack
path = self.with_segments(path_root)
try:
path = path.absolute()
except UnsupportedOperation:
pass
path_tail = []
else:
path_root, path_tail = path._stack
path_tail.reverse()
# If the user has *not* overridden the `readlink()` method, then symlinks are unsupported
# and (in non-strict mode) we can improve performance by not calling `stat()`.
@ -940,31 +951,37 @@ class PathBase(PurePathBase):
link_count = 0
while parts:
part = parts.pop()
if not part or part == '.':
continue
if part == '..':
if not path._tail:
if path.root:
if not path_tail:
if path_root:
# Delete '..' segment immediately following root
continue
elif path._tail[-1] != '..':
elif path_tail[-1] != '..':
# Delete '..' segment and its predecessor
path = path.parent
path_tail.pop()
continue
next_path = path._make_child_relpath(part)
path_tail.append(part)
if querying and part != '..':
next_path._resolving = True
path = self.with_segments(path_root + self.pathmod.sep.join(path_tail))
path._resolving = True
try:
st = next_path.stat(follow_symlinks=False)
st = path.stat(follow_symlinks=False)
if S_ISLNK(st.st_mode):
# Like Linux and macOS, raise OSError(errno.ELOOP) if too many symlinks are
# encountered during resolution.
link_count += 1
if link_count >= self._max_symlinks:
raise OSError(ELOOP, "Too many symbolic links in path", str(self))
target, target_parts = next_path.readlink()._split_stack()
target_root, target_parts = path.readlink()._stack
# If the symlink target is absolute (like '/etc/hosts'), set the current
# path to its uppermost parent (like '/').
if target.root:
path = target
if target_root:
path_root = target_root
path_tail.clear()
else:
path_tail.pop()
# Add the symlink target's reversed tail parts (like ['hosts', 'etc']) to
# the stack of unresolved path parts.
parts.extend(target_parts)
@ -976,9 +993,7 @@ class PathBase(PurePathBase):
raise
else:
querying = False
next_path._resolving = False
path = next_path
return path
return self.with_segments(path_root + self.pathmod.sep.join(path_tail))
def symlink_to(self, target, target_is_directory=False):
"""