[Python-checkins] bpo-33265: use an actual method instead of a method-like function in ExitStack (GH-6456)

Fri Apr 13 08:22:50 EDT 2018

https://github.com/python/cpython/commit/23ab5ee667a9b29014f6f7f01797c611f63ff743
commit: 23ab5ee667a9b29014f6f7f01797c611f63ff743
branch: master
author: jdemeyer <jdemeyer at cage.ugent.be>
committer: Nick Coghlan <ncoghlan at gmail.com>
date: 2018年04月13日T22:22:46+10:00
summary:
bpo-33265: use an actual method instead of a method-like function in ExitStack (GH-6456)
`MethodType` has the exact semantics that `ExitStack` needs,
so we can avoid creating a Python level closure.
files:
A Misc/NEWS.d/next/Library/2018-04-13-08-12-50.bpo-33265.KPQRk0.rst
M Lib/contextlib.py

diff --git a/Lib/contextlib.py b/Lib/contextlib.py
index 1ff8cdf1cecf..1a58b509f67c 100644
--- a/Lib/contextlib.py
+++ b/Lib/contextlib.py
@@ -4,6 +4,7 @@
 import _collections_abc
 from collections import deque
 from functools import wraps
+from types import MethodType
 
 __all__ = ["asynccontextmanager", "contextmanager", "closing", "nullcontext",
 "AbstractContextManager", "AbstractAsyncContextManager",
@@ -373,9 +374,7 @@ class _BaseExitStack:
 
 @staticmethod
 def _create_exit_wrapper(cm, cm_exit):
- def _exit_wrapper(exc_type, exc, tb):
- return cm_exit(cm, exc_type, exc, tb)
- return _exit_wrapper
+ return MethodType(cm_exit, cm)
 
 @staticmethod
 def _create_cb_wrapper(callback, *args, **kwds):
@@ -443,7 +442,6 @@ def callback(self, callback, *args, **kwds):
 def _push_cm_exit(self, cm, cm_exit):
 """Helper to correctly register callbacks to __exit__ methods."""
 _exit_wrapper = self._create_exit_wrapper(cm, cm_exit)
- _exit_wrapper.__self__ = cm
 self._push_exit_callback(_exit_wrapper, True)
 
 def _push_exit_callback(self, callback, is_sync=True):
@@ -535,9 +533,7 @@ class AsyncExitStack(_BaseExitStack, AbstractAsyncContextManager):
 
 @staticmethod
 def _create_async_exit_wrapper(cm, cm_exit):
- async def _exit_wrapper(exc_type, exc, tb):
- return await cm_exit(cm, exc_type, exc, tb)
- return _exit_wrapper
+ return MethodType(cm_exit, cm)
 
 @staticmethod
 def _create_async_cb_wrapper(callback, *args, **kwds):
@@ -596,7 +592,6 @@ def _push_async_cm_exit(self, cm, cm_exit):
 """Helper to correctly register coroutine function to __aexit__
 method."""
 _exit_wrapper = self._create_async_exit_wrapper(cm, cm_exit)
- _exit_wrapper.__self__ = cm
 self._push_exit_callback(_exit_wrapper, False)
 
 async def __aenter__(self):
diff --git a/Misc/NEWS.d/next/Library/2018-04-13-08-12-50.bpo-33265.KPQRk0.rst b/Misc/NEWS.d/next/Library/2018-04-13-08-12-50.bpo-33265.KPQRk0.rst
new file mode 100644
index 000000000000..523ceb9be1d6
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2018-04-13-08-12-50.bpo-33265.KPQRk0.rst
@@ -0,0 +1,2 @@
+``contextlib.ExitStack`` and ``contextlib.AsyncExitStack`` now use a method
+instead of a wrapper function for exit callbacks.
