Issue 29822: inspect.isabstract does not work on abstract base classes during init_subclass (original) (raw)
Created on 2017-03-15 17:06 by So8res, last changed 2022-04-11 14:58 by admin. This issue is now closed.
Messages (8)
Author: Nate Soares (So8res) *
Date: 2017-03-15 17:06
Here's an example test that fails:
def test_isabstract_during_init_subclass(self): from abc import ABCMeta, abstractmethod
isabstract_checks = []
class AbstractChecker(metaclass=ABCMeta):
def __init_subclass__(cls):
abstract_checks.append(inspect.isabstract(cls))
class AbstractClassExample(AbstractChecker):
@abstractmethod
def foo(self):
pass
class ClassExample(AbstractClassExample):
def foo(self):
pass
self.assertEqual(isabstract_checks, [True, False])To run the test, you'll need to be on a version of python where bpo-29581 is fixed (e.g., a cpython branch with https://github.com/python/cpython/pull/527 merged) in order for init_subclass to work with ABCMeta at all in the first place. I have a simple patch to inspect.isabstract that fixes this, and will make a PR shortly.
Author: Ivan Levkivskyi (levkivskyi) * 
Date: 2017-03-18 01:09
Serhiy, sorry for a distraction, but it looks like here is one more situation where inspect.isabstract is problematic, similar to what was discussed in http://bugs.python.org/issue29638 recently.
Author: Serhiy Storchaka (serhiy.storchaka) *
Date: 2017-03-18 05:46
Is this an alternate fix of ?
Author: Nate Soares (So8res) *
Date: 2017-03-18 07:04
I didn't know about , and I'm not sure whether my PR fixes it. Looking at that bug, I don't think that my PR would fix it, because I still trust TPFLAGS_IS_ABSTRACT when abstractmethods exists. That said, I'm not clear on how the cache works, so it's possible that my PR would fix 29638.
My issue appears when one uses py3.6's new init_subclass hook with an ABC. init_subclass is run by type.new, which means that, as of py3.6, users can (in a natural/reasonable way) inspect ABCMeta classes before ABCMeta.new finishes executing. I didn't see any reasonable way to have ABCMeta.new finish setting up the ABC before calling super().new, so I figured the fix should go into inspect.isabstract. But there may be better solutions I just didn't think of.
Author: Serhiy Storchaka (serhiy.storchaka) *
Date: 2017-03-18 17:52
LGTM, but would be nice if Yury and Nick take a look.
Author: Serhiy Storchaka (serhiy.storchaka) *
Date: 2017-04-24 17:06
New changeset fcfe80ec2592fed8b3941c79056a8737abef7d3b by Serhiy Storchaka (Nate) in branch 'master': bpo-29822: Make inspect.isabstract() work during init_subclass. (#678) https://github.com/python/cpython/commit/fcfe80ec2592fed8b3941c79056a8737abef7d3b
Author: Serhiy Storchaka (serhiy.storchaka) *
Date: 2017-06-07 04:21
New changeset 09b6c0c71ea944f7e8b46998f3ebaf5b9fbe15f6 by Serhiy Storchaka (Nate) in branch '3.6': [3.6] bpo-29822: make inspect.isabstract() work during init_subclass (#1979) https://github.com/python/cpython/commit/09b6c0c71ea944f7e8b46998f3ebaf5b9fbe15f6
Author: Serhiy Storchaka (serhiy.storchaka) *
Date: 2017-06-07 04:22
Thank you for your contribution Nate.
History
Date
User
Action
Args
2022-04-11 14:58:44
admin
set
github: 74008
2017-06-07 04:22:59
serhiy.storchaka
set
status: open -> closed
resolution: fixed
messages: +
stage: backport needed -> resolved
2017-06-07 04:21:36
serhiy.storchaka
set
messages: +
2017-06-07 00:19:20
So8res
set
pull_requests: + <pull%5Frequest2045>
2017-04-24 17:09:07
serhiy.storchaka
set
stage: patch review -> backport needed
versions: - Python 3.5
2017-04-24 17:06:19
serhiy.storchaka
set
messages: +
2017-03-18 17:52:51
serhiy.storchaka
set
messages: +
2017-03-18 13:57:08
serhiy.storchaka
set
nosy: + ncoghlan
2017-03-18 07:04:13
So8res
set
messages: +
2017-03-18 05:46:49
serhiy.storchaka
set
type: behavior
components: + Library (Lib)
versions: + Python 3.5, Python 3.6
nosy: + yselivanov
messages: +
stage: patch review
2017-03-18 01:09:13
levkivskyi
set
nosy: + serhiy.storchaka, levkivskyi
messages: +
2017-03-15 18:50:05
So8res
set
pull_requests: + <pull%5Frequest556>
2017-03-15 17:06:09
So8res
create