From bd583ef9857d99f9145ad0bb2c4424cc0baa63fc Mon Sep 17 00:00:00 2001 From: Nate Date: Wed, 15 Mar 2017 11:39:22 -0700 Subject: [PATCH] bpo-29581: Make ABCMeta.__new__ pass **kwargs to type.__new__ (#527) Many metaclasses in the standard library don't play nice with __init_subclass__. This bug makes ABCMeta in particular with __init_subclass__, which is an 80/20 solution for me personally. AFAICT, a general solution to this problem requires updating all metaclasses in the standard library to make sure they pass **kwargs to type.__new__, whereas this PR only fixes ABCMeta. For context, see https://bugs.python.org/issue29581. * added a test combining ABCMeta and __init_subclass__ * Added NEWS item --- Lib/abc.py | 4 ++-- Lib/test/test_abc.py | 12 ++++++++++++ Misc/NEWS | 3 +++ 3 files changed, 17 insertions(+), 2 deletions(-) diff --git a/Lib/abc.py b/Lib/abc.py index 1cbf96a61f..43a34a0bbd 100644 --- a/Lib/abc.py +++ b/Lib/abc.py @@ -129,8 +129,8 @@ class ABCMeta(type): # external code. _abc_invalidation_counter = 0 - def __new__(mcls, name, bases, namespace): - cls = super().__new__(mcls, name, bases, namespace) + def __new__(mcls, name, bases, namespace, **kwargs): + cls = super().__new__(mcls, name, bases, namespace, **kwargs) # Compute set of abstract method names abstracts = {name for name, value in namespace.items() diff --git a/Lib/test/test_abc.py b/Lib/test/test_abc.py index e1765f0d5a..4bc8382004 100644 --- a/Lib/test/test_abc.py +++ b/Lib/test/test_abc.py @@ -404,5 +404,17 @@ class TestABC(unittest.TestCase): self.assertEqual(B.counter, 1) +class TestABCWithInitSubclass(unittest.TestCase): + def test_works_with_init_subclass(self): + saved_kwargs = {} + class ReceivesClassKwargs: + def __init_subclass__(cls, **kwargs): + super().__init_subclass__() + saved_kwargs.update(kwargs) + class Receiver(ReceivesClassKwargs, abc.ABC, x=1, y=2, z=3): + pass + self.assertEqual(saved_kwargs, dict(x=1, y=2, z=3)) + + if __name__ == "__main__": unittest.main() diff --git a/Misc/NEWS b/Misc/NEWS index 2f7bd7ac7b..b7990c62e4 100644 --- a/Misc/NEWS +++ b/Misc/NEWS @@ -761,6 +761,9 @@ Library - Issue #24142: Reading a corrupt config file left configparser in an invalid state. Original patch by Florian Höch. +- Issue #29581: ABCMeta.__new__ now accepts **kwargs, allowing abstract base + classes to use keyword parameters in __init_subclass__. Patch by Nate Soares. + Windows ------- -- 2.50.0