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GH-118289: Fix handling of non-directories in posixpath.realpath() (#120127)

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In strict mode, raise `NotADirectoryError` if we encounter a non-directory
while we still have path parts left to process.

We use a `part_count` variable rather than `len(rest)` because the `rest`
stack also contains markers for unresolved symlinks.
This commit is contained in:
Barney Gale 2024-11-13 22:59:32 +00:00 • committed by GitHub
parent c695e37a3f
commit fd4b5453df
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3 changed files with 75 additions and 4 deletions
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18
Lib/posixpath.py
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@ -412,6 +412,10 @@ def _realpath(filename, strict=False, sep=sep, curdir=curdir, pardir=pardir,
# very fast way of spelling list(reversed(...)).
rest = filename.split(sep)[::-1]
# Number of unprocessed parts in 'rest'. This can differ from len(rest)
# later, because 'rest' might contain markers for unresolved symlinks.
part_count = len(rest)
# The resolved path, which is absolute throughout this function.
# Note: getcwd() returns a normalized and symlink-free path.
path = sep if filename.startswith(sep) else getcwd()
@ -426,12 +430,13 @@ def _realpath(filename, strict=False, sep=sep, curdir=curdir, pardir=pardir,
# by *maxlinks*, this is used instead of *seen* to detect symlink loops.
link_count = 0
while rest:
while part_count:
name = rest.pop()
if name is None:
# resolved symlink target
seen[rest.pop()] = path
continue
part_count -= 1
if not name or name == curdir:
# current dir
continue
@ -444,8 +449,11 @@ def _realpath(filename, strict=False, sep=sep, curdir=curdir, pardir=pardir,
else:
newpath = path + sep + name
try:
st = lstat(newpath)
if not stat.S_ISLNK(st.st_mode):
st_mode = lstat(newpath).st_mode
if not stat.S_ISLNK(st_mode):
if strict and part_count and not stat.S_ISDIR(st_mode):
raise OSError(errno.ENOTDIR, os.strerror(errno.ENOTDIR),
newpath)
path = newpath
continue
elif maxlinks is not None:
@ -487,7 +495,9 @@ def _realpath(filename, strict=False, sep=sep, curdir=curdir, pardir=pardir,
rest.append(newpath)
rest.append(None)
# Push the unresolved symlink target parts onto the stack.
rest.extend(target.split(sep)[::-1])
target_parts = target.split(sep)[::-1]
rest.extend(target_parts)
part_count += len(target_parts)
return path