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

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`MethodType` has the exact semantics that `ExitStack` needs,
so we can avoid creating a Python level closure.
This commit is contained in:
jdemeyer 2018-04-13 14:22:46 +02:00 • committed by Nick Coghlan
parent ffa2c3e2c4
commit 23ab5ee667
2 changed files with 5 additions and 8 deletions
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11
Lib/contextlib.py
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@ -4,6 +4,7 @@ import sys
import _collections_abc import _collections_abc
from collections import deque from collections import deque
from functools import wraps from functools import wraps
from types import MethodType
__all__ = ["asynccontextmanager", "contextmanager", "closing", "nullcontext", __all__ = ["asynccontextmanager", "contextmanager", "closing", "nullcontext",
"AbstractContextManager", "AbstractAsyncContextManager", "AbstractContextManager", "AbstractAsyncContextManager",
@ -373,9 +374,7 @@ class _BaseExitStack:
@staticmethod @staticmethod
def _create_exit_wrapper(cm, cm_exit): def _create_exit_wrapper(cm, cm_exit):
def _exit_wrapper(exc_type, exc, tb): return MethodType(cm_exit, cm)
return cm_exit(cm, exc_type, exc, tb)
return _exit_wrapper
@staticmethod @staticmethod
def _create_cb_wrapper(callback, *args, **kwds): def _create_cb_wrapper(callback, *args, **kwds):
@ -443,7 +442,6 @@ class _BaseExitStack:
def _push_cm_exit(self, cm, cm_exit): def _push_cm_exit(self, cm, cm_exit):
"""Helper to correctly register callbacks to __exit__ methods.""" """Helper to correctly register callbacks to __exit__ methods."""
_exit_wrapper = self._create_exit_wrapper(cm, cm_exit) _exit_wrapper = self._create_exit_wrapper(cm, cm_exit)
_exit_wrapper.__self__ = cm
self._push_exit_callback(_exit_wrapper, True) self._push_exit_callback(_exit_wrapper, True)
def _push_exit_callback(self, callback, is_sync=True): def _push_exit_callback(self, callback, is_sync=True):
@ -535,9 +533,7 @@ class AsyncExitStack(_BaseExitStack, AbstractAsyncContextManager):
@staticmethod @staticmethod
def _create_async_exit_wrapper(cm, cm_exit): def _create_async_exit_wrapper(cm, cm_exit):
async def _exit_wrapper(exc_type, exc, tb): return MethodType(cm_exit, cm)
return await cm_exit(cm, exc_type, exc, tb)
return _exit_wrapper
@staticmethod @staticmethod
def _create_async_cb_wrapper(callback, *args, **kwds): def _create_async_cb_wrapper(callback, *args, **kwds):
@ -596,7 +592,6 @@ class AsyncExitStack(_BaseExitStack, AbstractAsyncContextManager):
"""Helper to correctly register coroutine function to __aexit__ """Helper to correctly register coroutine function to __aexit__
method.""" method."""
_exit_wrapper = self._create_async_exit_wrapper(cm, cm_exit) _exit_wrapper = self._create_async_exit_wrapper(cm, cm_exit)
_exit_wrapper.__self__ = cm
self._push_exit_callback(_exit_wrapper, False) self._push_exit_callback(_exit_wrapper, False)
async def __aenter__(self): async def __aenter__(self):

2
Misc/NEWS.d/next/Library/2018-04-13-08-12-50.bpo-33265.KPQRk0.rst Normal file
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@ -0,0 +1,2 @@
``contextlib.ExitStack`` and ``contextlib.AsyncExitStack`` now use a method
instead of a wrapper function for exit callbacks.