pathlib.Path.resolve() mishandles symlink loops

[barneygale]

Bug report

Bug description:

Two closely-related issues in pathlib.Path.resolve():

First, resolve(strict=True) raises RuntimeError rather than OSError when a symlink loop is encountered. This is done only for backwards compatibility, since #25264 made pathlib call os.path.realpath(). It should raise OSError(ELOOP)

Second, resolve(strict=False) suppresses every kind of OS error except symlink loop errors. Again this is only for backwards compatibility. It should suppress exceptions about symlink loops.

Relevant code:

cpython/Lib/pathlib.py

Lines 1233 to 1252 in e21c89f

	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 = os.path.realpath(self, strict=strict)
	except OSError as e:
	check_eloop(e)
	raise
	p = self.with_segments(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

CPython versions tested on:

3.11, 3.12, CPython main branch

Operating systems tested on:

No response

Linked PRs

• GH-109187: Improve symlink loop handling in pathlib.Path.resolve() #109192

[barneygale]

Addressed in 3.13 / ecd813f / #109192