[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)
diff --git a/Lib/inspect.py b/Lib/inspect.py
index a2dcb88..2894672 100644
--- a/Lib/inspect.py
+++ b/Lib/inspect.py
@@ -31,6 +31,7 @@
__author__ = ('Ka-Ping Yee <ping@lfw.org>',
'Yury Selivanov <yselivanov@sprymix.com>')
+import abc
import ast
import dis
import collections.abc
@@ -291,7 +292,27 @@
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.