gh-107431: Make multiprocessing.managers.{DictProxy,ListProxy} generic (#107433)

Make `multiprocessing.managers.{DictProxy,ListProxy}` generic for type annotation use.  `ListProxy[str]` for example.

Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>
Co-authored-by: Gregory P. Smith <greg@krypto.org>

Author: 3 people

Diff for: Lib/multiprocessing/managers.py

@@ -1165,15 +1165,19 @@ def __imul__(self, value):
         self._callmethod('__imul__', (value,))
         return self
 
+    __class_getitem__ = classmethod(types.GenericAlias)
+
 
-DictProxy = MakeProxyType('DictProxy', (
+_BaseDictProxy = MakeProxyType('DictProxy', (
     '__contains__', '__delitem__', '__getitem__', '__iter__', '__len__',
     '__setitem__', 'clear', 'copy', 'get', 'items',
     'keys', 'pop', 'popitem', 'setdefault', 'update', 'values'
     ))
-DictProxy._method_to_typeid_ = {
+_BaseDictProxy._method_to_typeid_ = {
     '__iter__': 'Iterator',
     }
+class DictProxy(_BaseDictProxy):
+    __class_getitem__ = classmethod(types.GenericAlias)
 
 
 ArrayProxy = MakeProxyType('ArrayProxy', (

Diff for: Lib/test/test_genericalias.py

@@ -28,14 +28,16 @@
 from itertools import chain
 from http.cookies import Morsel
 try:
-    from multiprocessing.managers import ValueProxy
+    from multiprocessing.managers import ValueProxy, DictProxy, ListProxy
     from multiprocessing.pool import ApplyResult
     from multiprocessing.queues import SimpleQueue as MPSimpleQueue
     from multiprocessing.queues import Queue as MPQueue
     from multiprocessing.queues import JoinableQueue as MPJoinableQueue
 except ImportError:
     # _multiprocessing module is optional
     ValueProxy = None
+    DictProxy = None
+    ListProxy = None
     ApplyResult = None
     MPSimpleQueue = None
     MPQueue = None
@@ -134,7 +136,7 @@ class BaseTest(unittest.TestCase):
     if ctypes is not None:
         generic_types.extend((ctypes.Array, ctypes.LibraryLoader))
     if ValueProxy is not None:
-        generic_types.extend((ValueProxy, ApplyResult,
+        generic_types.extend((ValueProxy, DictProxy, ListProxy, ApplyResult,
                               MPSimpleQueue, MPQueue, MPJoinableQueue))
 
     def test_subscriptable(self):

Diff for: Misc/NEWS.d/next/Library/2023-07-29-19-00-39.gh-issue-107431.1GzJ2p.rst

@@ -0,0 +1,2 @@
+Make the ``DictProxy`` and ``ListProxy`` types in :mod:`multiprocessing.managers`
+:ref:`Generic Alias Types<types-genericalias>` for ``[]`` use in typing contexts.