From 09b6c0c71ea944f7e8b46998f3ebaf5b9fbe15f6 Mon Sep 17 00:00:00 2001 From: Nate Date: Tue, 6 Jun 2017 21:21:34 -0700 Subject: [PATCH] [3.6] bpo-29822: make inspect.isabstract() work during __init_subclass__ (#1979) At the time when an abstract base class' __init_subclass__ runs, ABCMeta.__new__ has not yet finished running, so in the presence of __init_subclass__, inspect.isabstract() can no longer depend only on TPFLAGS_IS_ABSTRACT. (cherry picked from commit fcfe80ec2592fed8b3941c79056a8737abef7d3b) --- Lib/inspect.py | 23 ++++++++++++++++++++++- Lib/test/test_inspect.py | 24 ++++++++++++++++++++++++ Misc/NEWS | 3 +++ 3 files changed, 49 insertions(+), 1 deletion(-) diff --git a/Lib/inspect.py b/Lib/inspect.py index a2dcb888a0..2894672f50 100644 --- a/Lib/inspect.py +++ b/Lib/inspect.py @@ -31,6 +31,7 @@ Here are some of the useful functions provided by this module: __author__ = ('Ka-Ping Yee ', 'Yury Selivanov ') +import abc import ast import dis import collections.abc @@ -291,7 +292,27 @@ def isroutine(object): def isabstract(object): """Return true if the object is an abstract base class (ABC).""" - return bool(isinstance(object, type) and object.__flags__ & TPFLAGS_IS_ABSTRACT) + if not isinstance(object, type): + return False + if object.__flags__ & TPFLAGS_IS_ABSTRACT: + return True + if not issubclass(type(object), abc.ABCMeta): + return False + if hasattr(object, '__abstractmethods__'): + # It looks like ABCMeta.__new__ has finished running; + # TPFLAGS_IS_ABSTRACT should have been accurate. + return False + # It looks like ABCMeta.__new__ has not finished running yet; we're + # probably in __init_subclass__. We'll look for abstractmethods manually. + for name, value in object.__dict__.items(): + if getattr(value, "__isabstractmethod__", False): + return True + for base in object.__bases__: + for name in getattr(base, "__abstractmethods__", ()): + value = getattr(object, name, None) + if getattr(value, "__isabstractmethod__", False): + return True + return False def getmembers(object, predicate=None): """Return all members of an object as (name, value) pairs sorted by name. diff --git a/Lib/test/test_inspect.py b/Lib/test/test_inspect.py index cfea281c70..37e451188a 100644 --- a/Lib/test/test_inspect.py +++ b/Lib/test/test_inspect.py @@ -232,6 +232,30 @@ class TestPredicates(IsTestBase): self.assertFalse(inspect.isabstract(int)) self.assertFalse(inspect.isabstract(5)) + def test_isabstract_during_init_subclass(self): + from abc import ABCMeta, abstractmethod + isabstract_checks = [] + class AbstractChecker(metaclass=ABCMeta): + def __init_subclass__(cls): + isabstract_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]) + + isabstract_checks.clear() + class AbstractChild(AbstractClassExample): + pass + class AbstractGrandchild(AbstractChild): + pass + class ConcreteGrandchild(ClassExample): + pass + self.assertEqual(isabstract_checks, [True, True, False]) + class TestInterpreterStack(IsTestBase): def __init__(self, *args, **kwargs): diff --git a/Misc/NEWS b/Misc/NEWS index 515960daf7..b819c6db73 100644 --- a/Misc/NEWS +++ b/Misc/NEWS @@ -45,6 +45,9 @@ Core and Builtins Library ------- +- bpo-29822: inspect.isabstract() now works during __init_subclass__. Patch + by Nate Soares. + - bpo-29581: ABCMeta.__new__ now accepts ``**kwargs``, allowing abstract base classes to use keyword parameters in __init_subclass__. Patch by Nate Soares. -- 2.40.0