https://github.com/python/cpython/commit/b5e4c46be24d1fade0deda211785c04a74a722cc
commit: b5e4c46be24d1fade0deda211785c04a74a722cc
branch: main
author: Jason R. Coombs <[email protected]>
committer: jaraco <[email protected]>
date: 2026-03-20T20:10:50Z
summary:
gh-146228: Better fork support in cached FastPath (#146231)
* Apply changes from importlib_metadata 8.9.0
* Suppress deprecation warning in fork.
files:
A Misc/NEWS.d/next/Library/2026-03-20-14-53-00.gh-issue-146228.OJVEDL.rst
M Lib/importlib/metadata/__init__.py
M Lib/importlib/metadata/_adapters.py
M Lib/importlib/metadata/_functools.py
M Lib/test/test_importlib/metadata/fixtures.py
M Lib/test/test_importlib/metadata/test_api.py
M Lib/test/test_importlib/metadata/test_main.py
M Lib/test/test_importlib/metadata/test_zip.py
diff --git a/Lib/importlib/metadata/__init__.py
b/Lib/importlib/metadata/__init__.py
index e91acc065ba9ae..cde697e3dc7ab0 100644
--- a/Lib/importlib/metadata/__init__.py
+++ b/Lib/importlib/metadata/__init__.py
@@ -31,7 +31,7 @@
from . import _meta
from ._collections import FreezableDefaultDict, Pair
-from ._functools import method_cache, pass_none
+from ._functools import method_cache, noop, pass_none, passthrough
from ._itertools import always_iterable, bucket, unique_everseen
from ._meta import PackageMetadata, SimplePath
from ._typing import md_none
@@ -783,6 +783,20 @@ def find_distributions(self, context=Context()) ->
Iterable[Distribution]:
"""
+@passthrough
+def _clear_after_fork(cached):
+ """Ensure ``func`` clears cached state after ``fork`` when supported.
+
+ ``FastPath`` caches zip-backed ``pathlib.Path`` objects that retain a
+ reference to the parent's open ``ZipFile`` handle. Re-using a cached
+ instance in a forked child can therefore resurrect invalid file pointers
+ and trigger ``BadZipFile``/``OSError`` failures
(python/importlib_metadata#520).
+ Registering ``cache_clear`` with ``os.register_at_fork`` keeps each process
+ on its own cache.
+ """
+ getattr(os, 'register_at_fork', noop)(after_in_child=cached.cache_clear)
+
+
class FastPath:
"""
Micro-optimized class for searching a root for children.
@@ -799,7 +813,8 @@ class FastPath:
True
"""
- @functools.lru_cache() # type: ignore[misc]
+ @_clear_after_fork # type: ignore[misc]
+ @functools.lru_cache()
def __new__(cls, root):
return super().__new__(cls)
@@ -925,10 +940,12 @@ def __init__(self, name: str | None):
def normalize(name):
"""
PEP 503 normalization plus dashes as underscores.
+
+ Specifically avoids ``re.sub`` as prescribed for performance
+ benefits (see python/cpython#143658).
"""
- # Much faster than re.sub, and even faster than str.translate
value = name.lower().replace("-", "_").replace(".", "_")
- # Condense repeats (faster than regex)
+ # Condense repeats
while "__" in value:
value = value.replace("__", "_")
return value
diff --git a/Lib/importlib/metadata/_adapters.py
b/Lib/importlib/metadata/_adapters.py
index f5b30dd92cde69..dede395d79a38b 100644
--- a/Lib/importlib/metadata/_adapters.py
+++ b/Lib/importlib/metadata/_adapters.py
@@ -9,7 +9,8 @@
class RawPolicy(email.policy.EmailPolicy):
def fold(self, name, value):
folded = self.linesep.join(
- textwrap.indent(value, prefix=' ' * 8, predicate=lambda line: True)
+ textwrap
+ .indent(value, prefix=' ' * 8, predicate=lambda line: True)
.lstrip()
.splitlines()
)
diff --git a/Lib/importlib/metadata/_functools.py
b/Lib/importlib/metadata/_functools.py
index 5dda6a2199ad0b..c159b46e48959c 100644
--- a/Lib/importlib/metadata/_functools.py
+++ b/Lib/importlib/metadata/_functools.py
@@ -1,5 +1,7 @@
import functools
import types
+from collections.abc import Callable
+from typing import TypeVar
# from jaraco.functools 3.3
@@ -102,3 +104,33 @@ def wrapper(param, *args, **kwargs):
return func(param, *args, **kwargs)
return wrapper
+
+
+# From jaraco.functools 4.4
+def noop(*args, **kwargs):
+ """
+ A no-operation function that does nothing.
+
+ >>> noop(1, 2, three=3)
+ """
+
+
+_T = TypeVar('_T')
+
+
+# From jaraco.functools 4.4
+def passthrough(func: Callable[..., object]) -> Callable[[_T], _T]:
+ """
+ Wrap the function to always return the first parameter.
+
+ >>> passthrough(print)('3')
+ 3
+ '3'
+ """
+
+ @functools.wraps(func)
+ def wrapper(first: _T, *args, **kwargs) -> _T:
+ func(first, *args, **kwargs)
+ return first
+
+ return wrapper # type: ignore[return-value]
diff --git a/Lib/test/test_importlib/metadata/fixtures.py
b/Lib/test/test_importlib/metadata/fixtures.py
index ad0ab42e089a9d..3283697d418188 100644
--- a/Lib/test/test_importlib/metadata/fixtures.py
+++ b/Lib/test/test_importlib/metadata/fixtures.py
@@ -6,6 +6,7 @@
import shutil
import sys
import textwrap
+from importlib import resources
from test.support import import_helper
from test.support import os_helper
@@ -14,11 +15,6 @@
from . import _path
from ._path import FilesSpec
-if sys.version_info >= (3, 9):
- from importlib import resources
-else:
- import importlib_resources as resources
-
@contextlib.contextmanager
def tmp_path():
@@ -374,8 +370,6 @@ def setUp(self):
# Add self.zip_name to the front of sys.path.
self.resources = contextlib.ExitStack()
self.addCleanup(self.resources.close)
- # workaround for #138313
- self.addCleanup(lambda: None)
def parameterize(*args_set):
diff --git a/Lib/test/test_importlib/metadata/test_api.py
b/Lib/test/test_importlib/metadata/test_api.py
index 3c856a88b77bf6..5449f0484492fb 100644
--- a/Lib/test/test_importlib/metadata/test_api.py
+++ b/Lib/test/test_importlib/metadata/test_api.py
@@ -317,33 +317,31 @@ def test_invalidate_cache(self):
class PreparedTests(unittest.TestCase):
- def test_normalize(self):
- tests = [
- # Simple
- ("sample", "sample"),
- # Mixed case
- ("Sample", "sample"),
- ("SAMPLE", "sample"),
- ("SaMpLe", "sample"),
- # Separator conversions
- ("sample-pkg", "sample_pkg"),
- ("sample.pkg", "sample_pkg"),
- ("sample_pkg", "sample_pkg"),
- # Multiple separators
- ("sample---pkg", "sample_pkg"),
- ("sample___pkg", "sample_pkg"),
- ("sample...pkg", "sample_pkg"),
- # Mixed separators
- ("sample-._pkg", "sample_pkg"),
- ("sample_.-pkg", "sample_pkg"),
- # Complex
- ("Sample__Pkg-name.foo", "sample_pkg_name_foo"),
- ("Sample__Pkg.name__foo", "sample_pkg_name_foo"),
- # Uppercase with separators
- ("SAMPLE-PKG", "sample_pkg"),
- ("Sample.Pkg", "sample_pkg"),
- ("SAMPLE_PKG", "sample_pkg"),
- ]
- for name, expected in tests:
- with self.subTest(name=name):
- self.assertEqual(Prepared.normalize(name), expected)
+ @fixtures.parameterize(
+ # Simple
+ dict(input='sample', expected='sample'),
+ # Mixed case
+ dict(input='Sample', expected='sample'),
+ dict(input='SAMPLE', expected='sample'),
+ dict(input='SaMpLe', expected='sample'),
+ # Separator conversions
+ dict(input='sample-pkg', expected='sample_pkg'),
+ dict(input='sample.pkg', expected='sample_pkg'),
+ dict(input='sample_pkg', expected='sample_pkg'),
+ # Multiple separators
+ dict(input='sample---pkg', expected='sample_pkg'),
+ dict(input='sample___pkg', expected='sample_pkg'),
+ dict(input='sample...pkg', expected='sample_pkg'),
+ # Mixed separators
+ dict(input='sample-._pkg', expected='sample_pkg'),
+ dict(input='sample_.-pkg', expected='sample_pkg'),
+ # Complex
+ dict(input='Sample__Pkg-name.foo', expected='sample_pkg_name_foo'),
+ dict(input='Sample__Pkg.name__foo', expected='sample_pkg_name_foo'),
+ # Uppercase with separators
+ dict(input='SAMPLE-PKG', expected='sample_pkg'),
+ dict(input='Sample.Pkg', expected='sample_pkg'),
+ dict(input='SAMPLE_PKG', expected='sample_pkg'),
+ )
+ def test_normalize(self, input, expected):
+ self.assertEqual(Prepared.normalize(input), expected)
diff --git a/Lib/test/test_importlib/metadata/test_main.py
b/Lib/test/test_importlib/metadata/test_main.py
index 83b686babfdb7a..f6c4ab2e78fe47 100644
--- a/Lib/test/test_importlib/metadata/test_main.py
+++ b/Lib/test/test_importlib/metadata/test_main.py
@@ -2,12 +2,12 @@
import pickle
import re
import unittest
-from test.support import os_helper
try:
import pyfakefs.fake_filesystem_unittest as ffs
except ImportError:
from .stubs import fake_filesystem_unittest as ffs
+from test.support import os_helper
from importlib.metadata import (
Distribution,
diff --git a/Lib/test/test_importlib/metadata/test_zip.py
b/Lib/test/test_importlib/metadata/test_zip.py
index fcb649f3736076..9daa04173b843e 100644
--- a/Lib/test/test_importlib/metadata/test_zip.py
+++ b/Lib/test/test_importlib/metadata/test_zip.py
@@ -1,7 +1,12 @@
+import multiprocessing
+import os
import sys
import unittest
+from test.support import warnings_helper
+
from importlib.metadata import (
+ FastPath,
PackageNotFoundError,
distribution,
distributions,
@@ -47,6 +52,38 @@ def test_one_distribution(self):
dists = list(distributions(path=sys.path[:1]))
assert len(dists) == 1
+ @warnings_helper.ignore_fork_in_thread_deprecation_warnings()
+ @unittest.skipUnless(
+ hasattr(os, 'register_at_fork')
+ and 'fork' in multiprocessing.get_all_start_methods(),
+ 'requires fork-based multiprocessing support',
+ )
+ def test_fastpath_cache_cleared_in_forked_child(self):
+ zip_path = sys.path[0]
+
+ FastPath(zip_path)
+ assert FastPath.__new__.cache_info().currsize >= 1
+
+ ctx = multiprocessing.get_context('fork')
+ parent_conn, child_conn = ctx.Pipe()
+
+ def child(conn, root):
+ try:
+ before = FastPath.__new__.cache_info().currsize
+ FastPath(root)
+ after = FastPath.__new__.cache_info().currsize
+ conn.send((before, after))
+ finally:
+ conn.close()
+
+ proc = ctx.Process(target=child, args=(child_conn, zip_path))
+ proc.start()
+ child_conn.close()
+ cache_sizes = parent_conn.recv()
+ proc.join()
+
+ self.assertEqual(cache_sizes, (0, 1))
+
class TestEgg(TestZip):
def setUp(self):
diff --git
a/Misc/NEWS.d/next/Library/2026-03-20-14-53-00.gh-issue-146228.OJVEDL.rst
b/Misc/NEWS.d/next/Library/2026-03-20-14-53-00.gh-issue-146228.OJVEDL.rst
new file mode 100644
index 00000000000000..1356e2ca07d9ae
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2026-03-20-14-53-00.gh-issue-146228.OJVEDL.rst
@@ -0,0 +1,2 @@
+Cached FastPath objects in importlib.metadata are now cleared on fork,
+avoiding broken references to zip files during fork.
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