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mock raises exception when using a spec with an attribute that raises exception on access #89917
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kjamieson commented
on Nov 8, 2021 kjamiesonmannequinMannequinAuthorIn Python 3.8 and later creating a mock with a spec specifying an object containing a property that happens to raise an exception when accessed will fail, because _mock_add_spec calls getattr() on every attribute of the spec. This did not happen in Python 3.6/3.7.
This is likely a fairly unusual scenario (and in the particular case where I encountered this I could just use a class instead of an instance for the spec), but it was surprising.
For example:
# cat test.py from unittest import mock class Foo: @property def bar(self) -> str: raise Exception('xxx') m = mock.MagicMock(spec=Foo())
# python3.11 test.py Traceback (most recent call last): File "/root/test.py", line 8, in <module> m = mock.MagicMock(spec=Foo()) ^^^^^^^^^^^^^^^^^^^^^^^^^^ File "/usr/lib/python3.11/unittest/mock.py", line 2069, in __init__ _safe_super(MagicMixin, self).__init__(*args, **kw) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "/usr/lib/python3.11/unittest/mock.py", line 1087, in __init__ _safe_super(CallableMixin, self).__init__( ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "/usr/lib/python3.11/unittest/mock.py", line 442, in __init__ self._mock_add_spec(spec, spec_set, _spec_as_instance, _eat_self) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "/usr/lib/python3.11/unittest/mock.py", line 497, in _mock_add_spec if iscoroutinefunction(getattr(spec, attr, None)): ^^^^^^^^^^^^^^^^^^^^^^^^^ File "/root/test.py", line 6, in bar raise Exception('xxx') ^^^^^^^^^^^^^^^^^^^^^^ Exception: xxx
jaap3 commented
on Nov 13, 2021 jaap3mannequinMannequinI think I encountered this when trying to mock
requests.Response: psf/requests#5944This seems to be similar to https://bugs.python.org/issue41768 .
@propertydescrs while creating mock autospecs #29901Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.
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