[3.14] GH-133789: Fix unpickling of pathlib objects pickled in Python 3.13 (GH-133831) (#140276)

GH-133789: Fix unpickling of pathlib objects pickled in Python 3.13 (GH-133831)

In Python 3.13 (but not 3.12 or 3.14), pathlib classes are defined in
`pathlib._local` rather than `pathlib`. In hindsight this was a mistake,
but it was difficult to predict how the abstract/local split would pan out.

In this patch we re-introduce `pathlib._local` as a stub module that
re-exports the classes from `pathlib`. This allows path objects pickled in
3.13 to be unpicked in 3.14+
(cherry picked from commit f4e51f253a)

Co-authored-by: Barney Gale <barney.gale@gmail.com>

Lib/pathlib/_local.py

@@ -0,0 +1,12 @@
+"""
+This module exists so that pathlib objects pickled under Python 3.13 can be
+unpickled in 3.14+.
+"""
+
+from pathlib import *
+
+__all__ = [
+    "UnsupportedOperation",
+    "PurePath", "PurePosixPath", "PureWindowsPath",
+    "Path", "PosixPath", "WindowsPath",
+]

Lib/test/test_free_threading/test_uuid.py

@@ -0,0 +1,60 @@
+import os
+import unittest
+
+from test.support import import_helper, threading_helper
+from test.support.threading_helper import run_concurrently
+from uuid import SafeUUID
+
+c_uuid = import_helper.import_module("_uuid")
+
+NTHREADS = 10
+UUID_PER_THREAD = 1000
+
+
+@threading_helper.requires_working_threading()
+class UUIDTests(unittest.TestCase):
+    @unittest.skipUnless(os.name == "posix", "POSIX only")
+    def test_generate_time_safe(self):
+        uuids = []
+
+        def worker():
+            local_uuids = []
+            for _ in range(UUID_PER_THREAD):
+                uuid, is_safe = c_uuid.generate_time_safe()
+                self.assertIs(type(uuid), bytes)
+                self.assertEqual(len(uuid), 16)
+                # Collect the UUID only if it is safe. If not, we cannot ensure
+                # UUID uniqueness. According to uuid_generate_time_safe() man
+                # page, it is theoretically possible for two concurrently
+                # running processes to generate the same UUID(s) if the return
+                # value is not 0.
+                if is_safe == SafeUUID.safe:
+                    local_uuids.append(uuid)
+
+            # Merge all safe uuids
+            uuids.extend(local_uuids)
+
+        run_concurrently(worker_func=worker, nthreads=NTHREADS)
+        self.assertEqual(len(uuids), len(set(uuids)))
+
+    @unittest.skipUnless(os.name == "nt", "Windows only")
+    def test_UuidCreate(self):
+        uuids = []
+
+        def worker():
+            local_uuids = []
+            for _ in range(UUID_PER_THREAD):
+                uuid = c_uuid.UuidCreate()
+                self.assertIs(type(uuid), bytes)
+                self.assertEqual(len(uuid), 16)
+                local_uuids.append(uuid)
+
+            # Merge all uuids
+            uuids.extend(local_uuids)
+
+        run_concurrently(worker_func=worker, nthreads=NTHREADS)
+        self.assertEqual(len(uuids), len(set(uuids)))
+
+
+if __name__ == "__main__":
+    unittest.main()

Lib/test/test_pathlib/test_pathlib.py

@@ -293,6 +293,12 @@ def test_pickling_common(self):
                     self.assertEqual(hash(pp), hash(p))
                     self.assertEqual(str(pp), str(p))
 
+    def test_unpicking_3_13(self):
+        data = (b"\x80\x04\x95'\x00\x00\x00\x00\x00\x00\x00\x8c\x0e"
+                b"pathlib._local\x94\x8c\rPurePosixPath\x94\x93\x94)R\x94.")
+        p = pickle.loads(data)
+        self.assertIsInstance(p, pathlib.PurePosixPath)
+
     def test_repr_common(self):
         for pathstr in ('a', 'a/b', 'a/b/c', '/', '/a/b', '/a/b/c'):
             with self.subTest(pathstr=pathstr):

Misc/NEWS.d/next/Library/2025-05-10-15-10-54.gh-issue-133789.I-ZlUX.rst

@@ -0,0 +1 @@
+Fix unpickling of :mod:`pathlib` objects that were pickled in Python 3.13.