gh-110495: ensure ntpath.realpath() result is a final, normalized pathname.

[moonsikpark]

By not breaking out of the loop when _readlink_deep() is successful, we can ensure that the result of ntpath.realpath() is a final, normalized pathname.

• Issue: Ensure ntpath.realpath() result is a final, normalized pathname. #110495

[moonsikpark]

@eryksun can you review this?

[encukou]

cc @serhiy-storchaka (os.path expert) & @barneygale (with the reproducer in the issue, pathlib.Path('C:\\testdir\\symlink2\\filelink.txt').resolve() also shows the symlink rather than file)

[eryksun]

I'm not having much luck getting this to work with a common seen set. I think an independent set is needed in _getfinalpathname_nonstrict(). For example:

def_getfinalpathname_nonstrict(path):
# These error codes indicate that we should stop resolving the# path and return the value we currently have.allowed_winerror= (
1, # ERROR_INVALID_FUNCTION2, # ERROR_FILE_NOT_FOUND3, # ERROR_DIRECTORY_NOT_FOUND5, # ERROR_ACCESS_DENIED21, # ERROR_NOT_READY (e.g. drive with no media)32, # ERROR_SHARING_VIOLATION (e.g. NTFS paging file)50, # ERROR_NOT_SUPPORTED53, # ERROR_BAD_NETPATH65, # ERROR_NETWORK_ACCESS_DENIED67, # ERROR_BAD_NET_NAME (e.g. remote server unavailable)87, # ERROR_INVALID_PARAMETER123, # ERROR_INVALID_NAME161, # ERROR_BAD_PATHNAME1920, # ERROR_CANT_ACCESS_FILE1921, # ERROR_CANT_RESOLVE_FILENAME (e.g. can't follow symlink)
)
# Non-strict algorithm is to find as much of the target# directory as we can and join the rest.tail=path[:0]
seen=set()
whilepathandnormcase(path) notinseen:
seen.add(normcase(path))
try:
path=_getfinalpathname(path)
returnjoin(path, tail) iftailelsepathexceptOSErrorasex:
ifex.winerrornotinallowed_winerror:
raise# Split off the base name, and break if it's root.parent_path, name=split(path)
ifnotname:
breaktry:
# Try resolving the final component as a link. If# successful, continue resolving the real path.new_path=_readlink_deep(path)
ifnew_path!=path:
path=new_pathcontinueexceptOSError:
pass# For some error cases, try to get the real name from# the directory entry.ifex.winerrorin (1, 5, 32, 50, 87, 1920, 1921):
try:
name=_findfirstfile(path)
exceptOSError:
passpath=parent_pathtail=join(name, tail) iftailelsenameifpath:
returnjoin(path, tail) iftailelsepathreturntail

[eryksun]

Some of the checks in test_realpath_broken_symlinks() that validate an incomplete resolution of the final path would need to be modified.

cpython/Lib/test/test_ntpath.py

Lines 471 to 480 in 73dc1c6

	# bpo-38453: We no longer recursively resolve segments of relative
	# symlinks that the OS cannot resolve.
	self.assertPathEqual(ntpath.realpath(r"broken1"),
	ABSTFN+r"\broken\bar")
	self.assertPathEqual(ntpath.realpath(r"broken1\baz"),
	ABSTFN+r"\broken\bar\baz")
	self.assertPathEqual(ntpath.realpath("broken2"),
	ABSTFN+r"\self\self\missing")
	self.assertPathEqual(ntpath.realpath("broken3"),
	ABSTFN+r"\subdir\parent\subdir\parent\missing")

New checks:

self.assertPathEqual(ntpath.realpath(r"broken1"),
ABSTFN+r"\missing\bar")
self.assertPathEqual(ntpath.realpath(r"broken1\baz"),
ABSTFN+r"\missing\bar\baz")
self.assertPathEqual(ntpath.realpath("broken2"),
ABSTFN+r"\missing")
self.assertPathEqual(ntpath.realpath("broken3"),
ABSTFN+r"\missing")

The corresponding bytes path checks would also have to be updated.

[github-actions]

This PR is stale because it has been open for 30 days with no activity.