[Python-checkins] [3.12] gh-104797: Allow Protocols to inherit from collections.abc.Buffer (GH-104827) (#104841)

[AlexWaygood]

https://github.com/python/cpython/commit/d10d1e3b10737a8426f92221e2788e40ad05b4e0
commit: d10d1e3b10737a8426f92221e2788e40ad05b4e0
branch: 3.12
author: Miss Islington (bot) <31488909+miss-islington at users.noreply.github.com>
committer: AlexWaygood <Alex.Waygood at Gmail.com>
date: 2023-05-24T09:05:34Z
summary:

[3.12] gh-104797: Allow Protocols to inherit from collections.abc.Buffer (GH-104827) (#104841)

gh-104797: Allow Protocols to inherit from collections.abc.Buffer (GH-104827)
(cherry picked from commit c0ab7d401c736c37bf4462eef7c7d69fef8fab93)

Co-authored-by: Jelle Zijlstra <jelle.zijlstra at gmail.com>

files:
A Misc/NEWS.d/next/Library/2023-05-23-17-43-52.gh-issue-104797.NR7KzF.rst
M Lib/test/test_typing.py
M Lib/typing.py

diff --git a/Lib/test/test_typing.py b/Lib/test/test_typing.py
index 9a3e64289ee8..a3fad6f35e71 100644
--- a/Lib/test/test_typing.py
+++ b/Lib/test/test_typing.py
@@ -3546,6 +3546,22 @@ def close(self):
         self.assertIsSubclass(B, Custom)
         self.assertNotIsSubclass(A, Custom)
 
+        @runtime_checkable
+        class ReleasableBuffer(collections.abc.Buffer, Protocol):
+            def __release_buffer__(self, mv: memoryview) -> None: ...
+
+        class C: pass
+        class D:
+            def __buffer__(self, flags: int) -> memoryview:
+                return memoryview(b'')
+            def __release_buffer__(self, mv: memoryview) -> None:
+                pass
+
+        self.assertIsSubclass(D, ReleasableBuffer)
+        self.assertIsInstance(D(), ReleasableBuffer)
+        self.assertNotIsSubclass(C, ReleasableBuffer)
+        self.assertNotIsInstance(C(), ReleasableBuffer)
+
     def test_builtin_protocol_allowlist(self):
         with self.assertRaises(TypeError):
             class CustomProtocol(TestCase, Protocol):
diff --git a/Lib/typing.py b/Lib/typing.py
index 96393d6a0281..88837db4b744 100644
--- a/Lib/typing.py
+++ b/Lib/typing.py
@@ -1745,7 +1745,7 @@ def _allow_reckless_class_checks(depth=3):
 _PROTO_ALLOWLIST = {
     'collections.abc': [
         'Callable', 'Awaitable', 'Iterable', 'Iterator', 'AsyncIterable',
-        'Hashable', 'Sized', 'Container', 'Collection', 'Reversible',
+        'Hashable', 'Sized', 'Container', 'Collection', 'Reversible', 'Buffer',
     ],
     'contextlib': ['AbstractContextManager', 'AbstractAsyncContextManager'],
 }
diff --git a/Misc/NEWS.d/next/Library/2023-05-23-17-43-52.gh-issue-104797.NR7KzF.rst b/Misc/NEWS.d/next/Library/2023-05-23-17-43-52.gh-issue-104797.NR7KzF.rst
new file mode 100644
index 000000000000..60c9a0601cdc
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2023-05-23-17-43-52.gh-issue-104797.NR7KzF.rst
@@ -0,0 +1,2 @@
+Allow :class:`typing.Protocol` classes to inherit from
+:class:`collections.abc.Buffer`. Patch by Jelle Zijlstra.