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pathlib ABCs: remove duplicate realpath() implementation. (#119178)

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Add private `posixpath._realpath()` function, which is a generic version of `realpath()` that can be parameterised with string tokens (`sep`, `curdir`, `pardir`) and query functions (`getcwd`, `lstat`, `readlink`). Also add support for limiting the number of symlink traversals.

In the private `pathlib._abc.PathBase` class, call `posixpath._realpath()` and remove our re-implementation of the same algorithm.

No change to any public APIs, either in `posixpath` or `pathlib`.

Co-authored-by: Nice Zombies <nineteendo19d0@gmail.com>
This commit is contained in:
Barney Gale 2024-06-05 18:54:50 +01:00 • committed by GitHub
parent 14e3c7071b
commit e83ce850f4
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2 changed files with 56 additions and 69 deletions
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40
Lib/posixpath.py
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@ -22,6 +22,7 @@ defpath = '/bin:/usr/bin'
altsep = None
devnull = '/dev/null'
import errno
import os
import sys
import stat
@ -401,7 +402,10 @@ symbolic links encountered in the path."""
curdir = '.'
pardir = '..'
getcwd = os.getcwd
return _realpath(filename, strict, sep, curdir, pardir, getcwd)
def _realpath(filename, strict=False, sep=sep, curdir=curdir, pardir=pardir,
getcwd=os.getcwd, lstat=os.lstat, readlink=os.readlink, maxlinks=None):
# The stack of unresolved path parts. When popped, a special value of None
# indicates that a symlink target has been resolved, and that the original
# symlink path can be retrieved by popping again. The [::-1] slice is a
@ -418,6 +422,10 @@ symbolic links encountered in the path."""
# the same links.
seen = {}
# Number of symlinks traversed. When the number of traversals is limited
# by *maxlinks*, this is used instead of *seen* to detect symlink loops.
link_count = 0
while rest:
name = rest.pop()
if name is None:
@ -436,11 +444,19 @@ symbolic links encountered in the path."""
else:
newpath = path + sep + name
try:
st = os.lstat(newpath)
st = lstat(newpath)
if not stat.S_ISLNK(st.st_mode):
path = newpath
continue
if newpath in seen:
elif maxlinks is not None:
link_count += 1
if link_count > maxlinks:
if strict:
raise OSError(errno.ELOOP, os.strerror(errno.ELOOP),
newpath)
path = newpath
continue
elif newpath in seen:
# Already seen this path
path = seen[newpath]
if path is not None:
@ -448,26 +464,28 @@ symbolic links encountered in the path."""
continue
# The symlink is not resolved, so we must have a symlink loop.
if strict:
# Raise OSError(errno.ELOOP)
os.stat(newpath)
raise OSError(errno.ELOOP, os.strerror(errno.ELOOP),
newpath)
path = newpath
continue
target = os.readlink(newpath)
target = readlink(newpath)
except OSError:
if strict:
raise
path = newpath
continue
# Resolve the symbolic link
seen[newpath] = None # not resolved symlink
if target.startswith(sep):
# Symlink target is absolute; reset resolved path.
path = sep
# Push the symlink path onto the stack, and signal its specialness by
# also pushing None. When these entries are popped, we'll record the
# fully-resolved symlink target in the 'seen' mapping.
rest.append(newpath)
rest.append(None)
if maxlinks is None:
# Mark this symlink as seen but not fully resolved.
seen[newpath] = None
# Push the symlink path onto the stack, and signal its specialness
# by also pushing None. When these entries are popped, we'll
# record the fully-resolved symlink target in the 'seen' mapping.
rest.append(newpath)
rest.append(None)
# Push the unresolved symlink target parts onto the stack.
rest.extend(target.split(sep)[::-1])