gh-139134: Fix pathlib.Path.copy() Windows privilege errors with copyfile2 fallback

[dynamicy]

• Issue: Fix pathlib.Path.copy() Windows privilege errors with copyfile2 fallback #139134

[bedevere-app]

Most changes to Python require a NEWS entry. Add one using the blurb_it web app or the blurb command-line tool.

If this change has little impact on Python users, wait for a maintainer to apply the skip news label instead.

[python-cla-bot]

All commit authors signed the Contributor License Agreement.

[bedevere-app]

Most changes to Python require a NEWS entry. Add one using the blurb_it web app or the blurb command-line tool.

If this change has little impact on Python users, wait for a maintainer to apply the skip news label instead.

[barneygale]

Thanks for this :-)

[barneygale]

Suggested change

	try:
	copyfile2(source_fspath, str(self))
	except OSError as exc:
	winerror = getattr(exc, 'winerror', None)
	if (_winapi is not None and
	winerror in (_winapi.ERROR_PRIVILEGE_NOT_HELD,
	_winapi.ERROR_ACCESS_DENIED)):
	self._copy_from_file_fallback(source, preserve_metadata)
	return
	raise
	try:
	copyfile2(source_fspath, str(self))
	except OSError as exc:
	# Use fallback on ERROR_ACCESS_DENIED
	# or ERROR_PRIVILEGE_NOT_HELD
	if exc.winerror not in (5, 1314):
	raise
	else:
	return

This code is Windows-specific because of the if copyfile2: line above, so we can access exc.winerror directly I think.

We usually hard-code Windows error numbers rather than using _winapi in pathlib - I'm not sure if that's wise but I guess let's be consistent.

[dynamicy]

Thanks—good call. I switched to exc.winerror and check for 5/1314. If we hit either, we fall back to _copy_from_file_fallback; otherwise we re-raise. I also added a tiny comment mapping those to ERROR_ACCESS_DENIED and ERROR_PRIVILEGE_NOT_HELD. Still under the if copyfile2: guard, so Windows-only. Happy to tweak wording or style if you prefer.

[barneygale]

Suggested change

	try:
	import _winapi
	except ImportError:
	_winapi = None

This is unused now

[dynamicy]

Removing unused imports.

[barneygale]

Suggested change

	if hasattr(exc, "winerror") and exc.winerror in (5, 1314):
	if exc.winerror in (5, 1314):

IIUC winerror is guaranteed to exist for any OSError raised from CopyFile2().

[dynamicy]

Good catch! You're absolutely right. Since we're specifically catching OSError from copyfile2(), the winerror attribute is indeed guaranteed to exist, making the hasattr() check redundant.

The simplified condition if exc.winerror in (5, 1314): is cleaner and more direct. Thanks for the improvement - it makes the code more concise while maintaining the same functionality.

[barneygale]

Suggested change

	Fix ``pathlib.Path.copy()`` failing on Windows when copying files that require elevated privileges (e.g., hidden or system files) by adding a fallback mechanism when ``copyfile2`` encounters privilege-related errors.
	Fix :meth:`pathlib.Path.copy` failing on Windows when copying files that require elevated privileges (e.g., hidden or system files) by adding a fallback mechanism when ``CopyFile2()`` encounters privilege-related errors.

[dynamicy]

Updated the commit message to be more precise. Thanks for keeping the details accurate!