classification
Title: unittest mock's reset_mock throws an error when an attribute has been deleted
Type: behavior Stage: patch review
Components: Library (Lib) Versions: Python 3.7, Python 3.6, Python 3.5
process
Status: open Resolution:
Dependencies: Superseder:
Assigned To: Nosy List: hmvp, xtreak
Priority: normal Keywords: patch

Created on 2017-08-10 14:22 by hmvp, last changed 2018-09-14 10:46 by xtreak.

Pull Requests
URL Status Linked Edit
PR 9302 open xtreak, 2018-09-14 10:46
Messages (2)
msg300090 - (view) Author: Hmvp (hmvp) Date: 2017-08-10 14:22
When using a mock and deleting a attribute reset_mock cannot be used anymore since it tries to call reset_mock on the _deleted sentinel value.

Reproduction path:
```
from unittest.mock import MagicMock
mock = MagicMock()
mock.a = 'test'
del mock.a
mock.reset_mock()
```

Gives:
```
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python3.5/unittest/mock.py", line 544, in reset_mock
    child.reset_mock(visited)
AttributeError: '_SentinelObject' object has no attribute 'reset_mock'
```

Expected result:
mock is reset without throwing an exception and the 'a' attribute is no longer in a deleted state

Only checked 3.5 and current master if bug is present
msg325340 - (view) Author: Karthikeyan Singaravelan (xtreak) * Date: 2018-09-14 10:10
Can confirm this behavior on CPython master as well. It seems that when an attribute is deleted then a deleted flag is set for the attribute at https://github.com/python/cpython/blob/73820a60cc3c990abb351540ca27bf7689bce8ac/Lib/unittest/mock.py#L737 . But when reset_mock is called it doesn't check for the deleted flag at https://github.com/python/cpython/blob/73820a60cc3c990abb351540ca27bf7689bce8ac/Lib/unittest/mock.py#L543

➜  cpython git:(master) ./python.exe ../backups/bpo31177.py
Traceback (most recent call last):
  File "../backups/bpo31177.py", line 5, in <module>
    m.reset_mock()
  File "/Users/karthikeyansingaravelan/stuff/python/cpython/Lib/unittest/mock.py", line 546, in reset_mock
    child.reset_mock(visited)
AttributeError: '_SentinelObject' object has no attribute 'reset_mock'

A simple patch would be to skip the deleted as below but some of the code in mock module raise an AttributeError. I don't know the correct behavior here. But applying the below patch and running tests with `./python.exe Lib/unittest/test/` doesn't cause any test failure.

diff --git a/Lib/unittest/mock.py b/Lib/unittest/mock.py
index db1e642c00..700e2fb8b9 100644
--- a/Lib/unittest/mock.py
+++ b/Lib/unittest/mock.py
@@ -541,7 +541,7 @@ class NonCallableMock(Base):
             self._mock_side_effect = None
 
         for child in self._mock_children.values():
-            if isinstance(child, _SpecState):
+            if isinstance(child, _SpecState) or child is _deleted:
                 continue
             child.reset_mock(visited)
 
I will try to make a PR if it's ok.

Thanks
History
Date User Action Args
2018-09-14 10:46:40xtreaksetkeywords: + patch
stage: patch review
pull_requests: + pull_request8731
2018-09-14 10:10:37xtreaksetnosy: + xtreak
messages: + msg325340
2017-08-10 14:22:19hmvpcreate