Description

assignee = None
closed_at = None
created_at = <Date 2021-11-08.19:47:53.494>
labels = ['type-bug', '3.8', '3.9', '3.10', '3.11']
title = 'mock raises exception when using a spec with an attribute that raises exception on access'
updated_at = <Date 2022-02-15.06:36:26.841>
user = 'https://bugs.python.org/kjamieson'

activity = <Date 2022-02-15.06:36:26.841>
actor = 'hongweipeng'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = []
creation = <Date 2021-11-08.19:47:53.494>
creator = 'kjamieson'
dependencies = []
files = []
hgrepos = []
issue_num = 45756
keywords = ['patch']
message_count = 3.0
messages = ['405982', '406284', '406452']
nosy_count = 6.0
nosy_names = ['lukasz.langa', 'hongweipeng', 'xtreak', 'sobolevn', 'kjamieson', 'jaap3']
pr_nums = ['29901', '31348']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue45756'
versions = ['Python 3.8', 'Python 3.9', 'Python 3.10', 'Python 3.11']

Activity

1. kjamieson commented on Nov 8, 2021

   

   kjamiesonmannequin

   on Nov 8, 2021

   MannequinAuthor

   More actions

   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 <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
2. kjamieson

   added

   3.8 (EOL)end of lifeend of life

   3.9 (EOL)end of lifeend of life

   3.10 (EOL)end of lifeend of life

   3.11only security fixesonly security fixes

   type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

   on Nov 8, 2021
3. jaap3 commented on Nov 13, 2021

   

   jaap3mannequin

   on Nov 13, 2021

   Mannequin

   More actions

   I think I encountered this when trying to mock requests.Response: psf/requests#5944
4. tirkarthi commented on Nov 17, 2021

   

   tirkarthi

   on Nov 17, 2021

   Member

   More actions

   This seems to be similar to https://bugs.python.org/issue41768 .
5. ezio-melotti

   transferred this issue fromon Apr 10, 2022
6. serhiy-storchaka

   added this to Unittest & doctest issueson May 20, 2022
7. carljm commented on May 5, 2023

   

   carljm

   on May 5, 2023

   Member

   More actions

   Closing as duplicate of #85934
8. carljm

   closed this as not plannedon May 5, 2023
9. github-project-automation

   moved this to Done in Unittest & doctest issueson May 5, 2023

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