bpo-30266: support "= None" pattern in AbstractContextManager (#1448) · python/cpython@57161aa (original) (raw)

3 files changed

lines changed

Original file line number	Diff line number	Diff line change
@@ -1,6 +1,7 @@
1	1	"""Utilities for with-statement contexts. See PEP 343."""
2	2	import abc
3	3	import sys
	4	+import _collections_abc
4	5	from collections import deque
5	6	from functools import wraps
6	7
@@ -25,9 +26,7 @@ def __exit__(self, exc_type, exc_value, traceback):
25	26	@classmethod
26	27	def __subclasshook__(cls, C):
27	28	if cls is AbstractContextManager:
28		-if (any("__enter__" in B.__dict__ for B in C.__mro__) and
29		-any("__exit__" in B.__dict__ for B in C.__mro__)):
30		-return True
	29	+return _collections_abc._check_methods(C, "__enter__", "__exit__")
31	30	return NotImplemented
32	31
33	32

Original file line number	Diff line number	Diff line change
@@ -44,6 +44,16 @@ def __exit__(self, *args):
44	44
45	45	self.assertTrue(issubclass(DefaultEnter, AbstractContextManager))
46	46
	47	+class NoEnter(ManagerFromScratch):
	48	+__enter__ = None
	49	+
	50	+self.assertFalse(issubclass(NoEnter, AbstractContextManager))
	51	+
	52	+class NoExit(ManagerFromScratch):
	53	+__exit__ = None
	54	+
	55	+self.assertFalse(issubclass(NoExit, AbstractContextManager))
	56	+
47	57
48	58	class ContextManagerTestCase(unittest.TestCase):
49	59

Original file line number	Diff line number	Diff line change
@@ -410,6 +410,10 @@ Library
410	410	- bpo-30048: Fixed ``Task.cancel()`` can be ignored when the task is
411	411	running coroutine and the coroutine returned without any more ``await``.
412	412
	413	+- bpo-30266: contextlib.AbstractContextManager now supports anti-registration
	414	+ by setting __enter__ = None or __exit__ = None, following the pattern
	415	+ introduced in bpo-25958. Patch by Jelle Zijlstra.
	416	+
413	417	- bpo-30340: Enhanced regular expressions optimization. This increased
414	418	the performance of matching some patterns up to 25 times.
415	419