https://github.com/python/cpython/commit/a8dc6d6d44a141a8f839deb248a02148dcfb509e
commit: a8dc6d6d44a141a8f839deb248a02148dcfb509e
branch: main
author: Alex Willmer <a...@moreati.org.uk>
committer: jaraco <jar...@jaraco.com>
date: 2025-01-26T19:00:28Z
summary:
gh-115911: Ignore PermissionError during import from cwd (#116131)
Ignore PermissionError when checking cwd during import
On macOS `getcwd(3)` can return EACCES if a path component isn't readable,
resulting in PermissionError. `PathFinder.find_spec()` now catches these and
ignores them - the same treatment as a missing/deleted cwd.
Introduces `test.support.os_helper.save_mode(path, ...)`, a context manager
that restores the mode of a path on exit.
This is allows finer control of exception handling and robust environment
restoration across platforms in `FinderTests.test_permission_error_cwd()`.
Co-authored-by: Jason R. Coombs <jar...@jaraco.com>
Co-authored-by: Brett Cannon <br...@python.org>
files:
A
Misc/NEWS.d/next/Core_and_Builtins/2024-02-29-16-55-52.gh-issue-115911.Vnkue_.rst
M Doc/reference/import.rst
M Lib/importlib/_bootstrap_external.py
M Lib/test/support/os_helper.py
M Lib/test/test_importlib/import_/test_path.py
diff --git a/Doc/reference/import.rst b/Doc/reference/import.rst
index ac363e8cfa00dc..48fdd0f5d021c7 100644
--- a/Doc/reference/import.rst
+++ b/Doc/reference/import.rst
@@ -762,10 +762,10 @@ module.
The current working directory -- denoted by an empty string -- is handled
slightly differently from other entries on :data:`sys.path`. First, if the
-current working directory is found to not exist, no value is stored in
-:data:`sys.path_importer_cache`. Second, the value for the current working
-directory is looked up fresh for each module lookup. Third, the path used for
-:data:`sys.path_importer_cache` and returned by
+current working directory cannot be determined or is found not to exist, no
+value is stored in :data:`sys.path_importer_cache`. Second, the value for the
+current working directory is looked up fresh for each module lookup. Third,
+the path used for :data:`sys.path_importer_cache` and returned by
:meth:`importlib.machinery.PathFinder.find_spec` will be the actual current
working directory and not the empty string.
diff --git a/Lib/importlib/_bootstrap_external.py
b/Lib/importlib/_bootstrap_external.py
index 697f7c55218a8f..8bcd741c446bd2 100644
--- a/Lib/importlib/_bootstrap_external.py
+++ b/Lib/importlib/_bootstrap_external.py
@@ -1244,7 +1244,7 @@ def _path_importer_cache(cls, path):
if path == '':
try:
path = _os.getcwd()
- except FileNotFoundError:
+ except (FileNotFoundError, PermissionError):
# Don't cache the failure as the cwd can easily change to
# a valid directory later on.
return None
diff --git a/Lib/test/support/os_helper.py b/Lib/test/support/os_helper.py
index 8071c248b9b67e..15dcdc9b1fddfb 100644
--- a/Lib/test/support/os_helper.py
+++ b/Lib/test/support/os_helper.py
@@ -294,6 +294,33 @@ def skip_unless_working_chmod(test):
return test if ok else unittest.skip(msg)(test)
+@contextlib.contextmanager
+def save_mode(path, *, quiet=False):
+ """Context manager that restores the mode (permissions) of *path* on exit.
+
+ Arguments:
+
+ path: Path of the file to restore the mode of.
+
+ quiet: if False (the default), the context manager raises an exception
+ on error. Otherwise, it issues only a warning and keeps the current
+ working directory the same.
+
+ """
+ saved_mode = os.stat(path)
+ try:
+ yield
+ finally:
+ try:
+ os.chmod(path, saved_mode.st_mode)
+ except OSError as exc:
+ if not quiet:
+ raise
+ warnings.warn(f'tests may fail, unable to restore the mode of '
+ f'{path!r} to {saved_mode.st_mode}: {exc}',
+ RuntimeWarning, stacklevel=3)
+
+
# Check whether the current effective user has the capability to override
# DAC (discretionary access control). Typically user root is able to
# bypass file read, write, and execute permission checks. The capability
diff --git a/Lib/test/test_importlib/import_/test_path.py
b/Lib/test/test_importlib/import_/test_path.py
index bcd5ad6e76005a..51ff6115e1281e 100644
--- a/Lib/test/test_importlib/import_/test_path.py
+++ b/Lib/test/test_importlib/import_/test_path.py
@@ -1,3 +1,4 @@
+from test.support import os_helper
from test.test_importlib import util
importlib = util.import_importlib('importlib')
@@ -153,6 +154,28 @@ def test_deleted_cwd(self):
# Do not want FileNotFoundError raised.
self.assertIsNone(self.machinery.PathFinder.find_spec('whatever'))
+ @os_helper.skip_unless_working_chmod
+ def test_permission_error_cwd(self):
+ # gh-115911: Test that an unreadable CWD does not break imports, in
+ # particular during early stages of interpreter startup.
+ with (
+ os_helper.temp_dir() as new_dir,
+ os_helper.save_mode(new_dir),
+ os_helper.change_cwd(new_dir),
+ util.import_state(path=['']),
+ ):
+ # chmod() is done here (inside the 'with' block) because the order
+ # of teardown operations cannot be the reverse of setup order. See
+ #
https://github.com/python/cpython/pull/116131#discussion_r1739649390
+ try:
+ os.chmod(new_dir, 0o000)
+ except OSError:
+ self.skipTest("platform does not allow "
+ "changing mode of the cwd")
+
+ # Do not want PermissionError raised.
+ self.assertIsNone(self.machinery.PathFinder.find_spec('whatever'))
+
def test_invalidate_caches_finders(self):
# Finders with an invalidate_caches() method have it called.
class FakeFinder:
diff --git
a/Misc/NEWS.d/next/Core_and_Builtins/2024-02-29-16-55-52.gh-issue-115911.Vnkue_.rst
b/Misc/NEWS.d/next/Core_and_Builtins/2024-02-29-16-55-52.gh-issue-115911.Vnkue_.rst
new file mode 100644
index 00000000000000..717804be95b18b
--- /dev/null
+++
b/Misc/NEWS.d/next/Core_and_Builtins/2024-02-29-16-55-52.gh-issue-115911.Vnkue_.rst
@@ -0,0 +1,3 @@
+If the current working directory cannot be determined due to permissions,
+then import will no longer raise :exc:`PermissionError`. Patch by Alex
+Willmer.
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