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Inheriting from instantiated generic class causes mocking to fail #250
Description
My reproduction (python 2)
import mock
from typing import Generic, TypeVar
T = TypeVar('T')
class Bar(Generic[T]):
def __init__(self):
pass
def do_bar(self):
print("bar")
class Foo(Bar[int]):
def do_foo(self):
self.do_bar()
@mock.patch.object(Bar, 'do_bar')
def mocked(mock_do_bar):
mock_do_bar.return_value = None
foo = Foo()
foo.do_foo()
mocked()
will unexpectedly print bar.
The inheritance here is crucial.
Activity
gvanrossum commentedon Jul 20, 2016
(PS try to trim trailing whitespace when copy/pasting text into github. It causes spurious horizontal scroll bars to appear and weird line breaks. I cleaned it up for you this time.)
jhance commentedon Jul 20, 2016
Oh, I did not realize I somehow accrued trailing whitespace. Must have been because I pastebin'd it to Jukka then copied from there. Sorry about that :(
gvanrossum commentedon Jul 20, 2016
Anyway, I do think this is a bug, but I don't know how to fix it. Looking at the MRO for Foo, we have:
I think the double occurrence of Bar may be the problem -- you're patching the original, but the MRO search finds the unpatched copy in Bar[int].
I think here's a workaround:
jhance commentedon Jul 20, 2016
I see.
Well, a workaround is good enough for now. Thanks! (It has the somewhat unfortunate property that you have to mock all the instantiations being used - but in my case that is only 2 of them, which isn't so bad).
Edit: Confirmation that the workaround indeed works around.
A real fix for python#250
gvanrossum commentedon Oct 11, 2016
Sorry, this wasn't fixed by #289.
A real fix for issue #250 (failure with mock) (#295)
jhance commentedon Oct 28, 2016
Thanks :D