[issue45755] Mock spec with a specialized generic class does not mock class attributes

[Kevin Jamieson]

New submission from Kevin Jamieson :

This worked in Python 3.6, but in Python 3.7 and later creating a mock with a 
spec specifying a subscripted generic class does not mock any of the attributes 
of the class, because those attributes are not returned by dir().

For example:

# cat test.py
from typing import Generic, TypeVar
from unittest import mock

T = TypeVar('T')

class Foo(Generic[T]):
def bar(self) -> None:
pass

m = mock.MagicMock(spec=Foo[int])
m.bar()


# python3.11 test.py
Traceback (most recent call last):
  File "/root/test.py", line 11, in 
m.bar()
^^^
  File "/usr/lib/python3.11/unittest/mock.py", line 635, in __getattr__
raise AttributeError("Mock object has no attribute %r" % name)
^^
AttributeError: Mock object has no attribute 'bar'

--
components: Library (Lib)
messages: 405981
nosy: kjamieson
priority: normal
severity: normal
status: open
title: Mock spec with a specialized generic class does not mock class attributes
type: behavior
versions: Python 3.10, Python 3.11, Python 3.7, Python 3.8, Python 3.9

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[issue45756] mock raises exception when using a spec with an attribute that raises exception on access

[Kevin Jamieson]

New submission from Kevin Jamieson :

In 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 
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

--
messages: 405982
nosy: kjamieson
priority: normal
severity: normal
status: open
title: mock raises exception when using a spec with an attribute that raises 
exception on access
type: behavior
versions: Python 3.10, Python 3.11, Python 3.8, Python 3.9

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