From 55408f86d78259f18c56c5e1ea51e0f8dcdbeb67 Mon Sep 17 00:00:00 2001
From: Grigoriev Semyon <33061489+grigoriev-semyon@users.noreply.github.com>
Date: Sun, 16 Jul 2023 18:30:39 +0300
Subject: gh-105726: Add `__slots__` to `AbstractContextManager` and
 `AbstractAsyncContextManager` (#106771)

Co-authored-by: Kumar Aditya <kumaraditya@python.org>
---
 Lib/contextlib.py                                            |  4 ++++
 Lib/test/test_contextlib.py                                  | 10 ++++++++++
 Lib/test/test_contextlib_async.py                            | 12 ++++++++++++
 .../Library/2023-07-15-12-52-50.gh-issue-105726.NGthO8.rst   |  3 +++
 4 files changed, 29 insertions(+)
 create mode 100644 Misc/NEWS.d/next/Library/2023-07-15-12-52-50.gh-issue-105726.NGthO8.rst

diff --git a/Lib/contextlib.py b/Lib/contextlib.py
index b5acbcb..95947ac 100644
--- a/Lib/contextlib.py
+++ b/Lib/contextlib.py
@@ -20,6 +20,8 @@ class AbstractContextManager(abc.ABC):
 
     __class_getitem__ = classmethod(GenericAlias)
 
+    __slots__ = ()
+
     def __enter__(self):
         """Return `self` upon entering the runtime context."""
         return self
@@ -42,6 +44,8 @@ class AbstractAsyncContextManager(abc.ABC):
 
     __class_getitem__ = classmethod(GenericAlias)
 
+    __slots__ = ()
+
     async def __aenter__(self):
         """Return `self` upon entering the runtime context."""
         return self
diff --git a/Lib/test/test_contextlib.py b/Lib/test/test_contextlib.py
index 0f8351a..ecc5a43 100644
--- a/Lib/test/test_contextlib.py
+++ b/Lib/test/test_contextlib.py
@@ -24,6 +24,16 @@ class TestAbstractContextManager(unittest.TestCase):
         manager = DefaultEnter()
         self.assertIs(manager.__enter__(), manager)
 
+    def test_slots(self):
+        class DefaultContextManager(AbstractContextManager):
+            __slots__ = ()
+
+            def __exit__(self, *args):
+                super().__exit__(*args)
+
+        with self.assertRaises(AttributeError):
+            DefaultContextManager().var = 42
+
     def test_exit_is_abstract(self):
         class MissingExit(AbstractContextManager):
             pass
diff --git a/Lib/test/test_contextlib_async.py b/Lib/test/test_contextlib_async.py
index 3d43ed0..bb72ae7 100644
--- a/Lib/test/test_contextlib_async.py
+++ b/Lib/test/test_contextlib_async.py
@@ -38,6 +38,18 @@ class TestAbstractAsyncContextManager(unittest.TestCase):
             self.assertIs(manager, context)
 
     @_async_test
+    async def test_slots(self):
+        class DefaultAsyncContextManager(AbstractAsyncContextManager):
+            __slots__ = ()
+
+            async def __aexit__(self, *args):
+                await super().__aexit__(*args)
+
+        with self.assertRaises(AttributeError):
+            manager = DefaultAsyncContextManager()
+            manager.var = 42
+
+    @_async_test
     async def test_async_gen_propagates_generator_exit(self):
         # A regression test for https://bugs.python.org/issue33786.
 
diff --git a/Misc/NEWS.d/next/Library/2023-07-15-12-52-50.gh-issue-105726.NGthO8.rst b/Misc/NEWS.d/next/Library/2023-07-15-12-52-50.gh-issue-105726.NGthO8.rst
new file mode 100644
index 0000000..434f932
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2023-07-15-12-52-50.gh-issue-105726.NGthO8.rst
@@ -0,0 +1,3 @@
+Added ``__slots__`` to :class:`contextlib.AbstractContextManager` and :class:`contextlib.AbstractAsyncContextManager`
+so that child classes can use ``__slots__``.
+
-- 
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