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bpo-43153: Don't mask PermissionError with NotADirectoryError during tempdirectory cleanup #29940

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Merged
merged 12 commits into from
Dec 5, 2023
Merged

bpo-43153: Don't mask PermissionError with NotADirectoryError during tempdirectory cleanup #29940

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5111fa7
Don't mask PermissionError with IsADirectoryError during tempdirector…
Fidget-Spinner Dec 6, 2021
b3da7cd
fix Window spelling
Fidget-Spinner Dec 6, 2021
0673393
improve comment
Fidget-Spinner Dec 6, 2021
98725c8
fix comments IsADirectoryError -> NotADirectoryError
Fidget-Spinner Dec 6, 2021
283df0a
use os.path.isdir instead
Fidget-Spinner Dec 6, 2021
b9f074f
add issue number to comments
Fidget-Spinner Dec 7, 2021
b658bfc
Remove windows check
Fidget-Spinner Dec 7, 2021
11a31ac
Skip test on other OSes except Windows
Fidget-Spinner Dec 7, 2021
499e424
Merge remote-tracking branch 'upstream/main' into bpo-43153
Fidget-Spinner Dec 7, 2021
bfd39ea
Address Serhiy's code review
Fidget-Spinner Dec 8, 2021
45d5dea
Merge branch 'main' into bpo-43153
serhiy-storchaka Dec 5, 2023
77f5e8a
Test for junctions on Windows.
serhiy-storchaka Dec 5, 2023
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28 changes: 26 additions & 2 deletions Lib/tempfile.py
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Original file line number Diff line number Diff line change
Expand Up @@ -41,6 +41,7 @@
import io as _io
import os as _os
import shutil as _shutil
import stat as _stat
import errno as _errno
from random import Random as _Random
import sys as _sys
Expand Down Expand Up @@ -889,8 +890,31 @@ def resetperms(path):

try:
_os.unlink(path)
# PermissionError is raised on FreeBSD for directories
except (IsADirectoryError, PermissionError):
except IsADirectoryError:
cls._rmtree(path, ignore_errors=ignore_errors)
except PermissionError:
# The PermissionError handler was originally added for
# FreeBSD in directories, but it seems that it is raised
# on Windows too.
# bpo-43153: Calling _rmtree again may
# raise NotADirectoryError and mask the PermissionError.
# So we must re-raise the current PermissionError if
# path is not a directory.
try:
st = _os.lstat(path)
except OSError:
if ignore_errors:
return
raise
if (_stat.S_ISLNK(st.st_mode) or
not _stat.S_ISDIR(st.st_mode) or
(hasattr(st, 'st_file_attributes') and
st.st_file_attributes & _stat.FILE_ATTRIBUTE_REPARSE_POINT and
st.st_reparse_tag == _stat.IO_REPARSE_TAG_MOUNT_POINT)
):
if ignore_errors:
return
raise
cls._rmtree(path, ignore_errors=ignore_errors)
Comment on lines 891 to 918
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Why not go with an "ask-for-forgiveness-rather-than-permission" type of solution, e.g.:

try:
    _os.unlink(path)
except IsADirectoryError:
    cls._rmtree(path, ignore_errors=ignore_errors)
except PermissionError as pe:
    # PermissionError is raised on FreeBSD for directories
    # and by Windows on lock files used by other processes
    try:
        cls._rmtree(path, ignore_errors=ignore_errors)
    except NotADirectoryError:
        # NOTE: This is raised if PermissionError did not
        # correspond to a IsADirectoryError, e.g. on
        # Windows.
        if not ignore_errors:
            raise pe

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rmtree() is a complex function, and we cannot be sure whether NotADirectoryError was raised by the toplevel scandir() or somewhere deeper in the tree.

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Mmmh...

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Seems like a responsibility inversion to me. Sure there could be a bug deep down in _rmtree that ends up bubbling an unrelated NotADirectoryError, but that would technically be a bug in _rmtree. Maybe there are valid cases where such an unrelated error would be raised?

Also I see the diff I commented on is not the final version so I'll look at the final version.

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Not necessary a bug. It may be a race condition. Although the LBYL approach is also prone to race conditions, I think it has less chance to override error with a wrong exception.

I myself prefer the EAFP approach, but I do not think that it has advantages in this case.

except FileNotFoundError:
pass
Expand Down
11 changes: 11 additions & 0 deletions Lib/test/test_tempfile.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1641,6 +1641,17 @@ def test_explicit_cleanup_ignore_errors(self):
temp_path.exists(),
f"TemporaryDirectory {temp_path!s} exists after cleanup")

@unittest.skipUnless(os.name == "nt", "Only on Windows.")
def test_explicit_cleanup_correct_error(self):
with tempfile.TemporaryDirectory() as working_dir:
temp_dir = self.do_create(dir=working_dir)
with open(os.path.join(temp_dir.name, "example.txt"), 'wb'):
# Previously raised NotADirectoryError on some OSes
# (e.g. Windows). See bpo-43153.
with self.assertRaises(PermissionError):
temp_dir.cleanup()


@os_helper.skip_unless_symlink
def test_cleanup_with_symlink_to_a_directory(self):
# cleanup() should not follow symlinks to directories (issue #12464)
Expand Down
4 changes: 4 additions & 0 deletions Misc/NEWS.d/next/Library/2021-12-06-22-10-53.bpo-43153.J7mjSy.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,4 @@
On Windows, ``tempfile.TemporaryDirectory`` previously masked a
``PermissionError`` with ``NotADirectoryError`` during directory cleanup. It
now correctly raises ``PermissionError`` if errors are not ignored. Patch by
Andrei Kulakov and Ken Jin.