[3.12] gh-126451: Revert backports of ABC registrations for contextvars.Context and multiprocessing proxies (#126735)

Author: AlexWaygood

Lib/contextvars.py

@@ -1,8 +1,4 @@
-import _collections_abc
 from _contextvars import Context, ContextVar, Token, copy_context
 
 
 __all__ = ('Context', 'ContextVar', 'Token', 'copy_context')
-
-
-_collections_abc.Mapping.register(Context)

Lib/multiprocessing/managers.py

@@ -18,7 +18,6 @@
 import threading
 import signal
 import array
-import collections.abc
 import queue
 import time
 import types
@@ -1161,8 +1160,6 @@ def __imul__(self, value):
         return self
 
 
-collections.abc.MutableSequence.register(BaseListProxy)
-
 DictProxy = MakeProxyType('DictProxy', (
     '__contains__', '__delitem__', '__getitem__', '__iter__', '__len__',
     '__setitem__', 'clear', 'copy', 'get', 'items',
@@ -1172,7 +1169,6 @@ def __imul__(self, value):
     '__iter__': 'Iterator',
     }
 
-collections.abc.MutableMapping.register(DictProxy)
 
 ArrayProxy = MakeProxyType('ArrayProxy', (
     '__len__', '__getitem__', '__setitem__'

Lib/test/_test_multiprocessing.py

@@ -17,7 +17,6 @@
 import functools
 import signal
 import array
-import collections.abc
 import socket
 import random
 import logging
@@ -2460,10 +2459,6 @@ def test_list(self):
         a.append('hello')
         self.assertEqual(f[0][:], [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 'hello'])
 
-    def test_list_isinstance(self):
-        a = self.list()
-        self.assertIsInstance(a, collections.abc.MutableSequence)
-
     def test_list_iter(self):
         a = self.list(list(range(10)))
         it = iter(a)
@@ -2504,10 +2499,6 @@ def test_dict(self):
         self.assertEqual(sorted(d.values()), [chr(i) for i in indices])
         self.assertEqual(sorted(d.items()), [(i, chr(i)) for i in indices])
 
-    def test_dict_isinstance(self):
-        a = self.dict()
-        self.assertIsInstance(a, collections.abc.MutableMapping)
-
     def test_dict_iter(self):
         d = self.dict()
         indices = list(range(65, 70))

Lib/test/test_context.py

@@ -1,4 +1,3 @@
-import collections.abc
 import concurrent.futures
 import contextvars
 import functools
@@ -343,19 +342,6 @@ def ctx2_fun():
 
         ctx1.run(ctx1_fun)
 
-    def test_context_isinstance(self):
-        ctx = contextvars.Context()
-        self.assertIsInstance(ctx, collections.abc.Mapping)
-        self.assertTrue(issubclass(contextvars.Context, collections.abc.Mapping))
-
-        mapping_methods = (
-            '__contains__', '__eq__', '__getitem__', '__iter__', '__len__',
-            '__ne__', 'get', 'items', 'keys', 'values',
-        )
-        for name in mapping_methods:
-            with self.subTest(name=name):
-                self.assertTrue(callable(getattr(ctx, name)))
-
     @isolated_context
     @threading_helper.requires_working_threading()
     def test_context_threads_1(self):

Misc/ACKS

@@ -1259,7 +1259,6 @@ Emily Morehouse
 Derek Morr
 James A Morrison
 Martin Morrison
-Stephen Morton
 Derek McTavish Mounce
 Alessandro Moura
 Pablo Mouzo