Lukas Anzinger <l.anzin...@gmail.com> added the comment:
I can reproduce the problem and have analyzed it a bit. My use case is a bit
different, I want to use autospec=True and wraps= so that I can mock unbound
methods but return the result from the original method (see also
https://docs.python.org/3/library/unittest.mock-examples.html#mocking-unbound-methods).
The problem in the mock code is that mock.return_value actually calls
__get_return_value() which replaces the actual return value mock.DEFAULT (which
is stored in self._mock_return_value) with a new child mock. When the mock is
then called and _mock_call() is executed, the wrapped function is not executed
because self._mock_return_value is not mock.DEFAULT anymore:
if (self._mock_wraps is not None and
self._mock_return_value is DEFAULT):
return self._mock_wraps(*args, **kwargs)
if ret_val is DEFAULT:
ret_val = self.return_value
return ret_val
Since self._mock_return_value is not DEFAULT anymore it doesn't matter if the
mock wraps something and it will instead just return a new mock.
I think that the side effect of the assignment to self.return_value in
_setup_func() is not intentional, i.e. the child mock should actually be
created only if there is an outside access to return_value, but not when it is
just wrapped in a function. The assignment can be made side effect free by
assigning the internal attribute _mock_return_value (see attached patch). This
solves the problem for me.
I've attached a patch that fixes the problem and doesn't seem to introduce a
regression (all unittest.mock tests pass).
If somebody is interested in getting this merged, I'm happy to provide a
regression test and everything else that is needed to get this merged.
Cheers,
Lukas
----------
keywords: +patch
nosy: +Lukas Anzinger
versions: +Python 3.7
Added file:
https://bugs.python.org/file47267/0001-bpo-31807-unittest.mock-Fix-common-use-of-autospec-T.patch
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<https://bugs.python.org/issue31807>
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