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__dir__ on unittest.mock not safe for all spec types #80762
Description
| BPO | 36581 |
|---|---|
| Nosy | @cjw296, @voidspace, @mariocj89, @tirkarthi, @dsem, @iritkatriel |
| PRs |
Note: 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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GitHub fields:
assignee = None
closed_at = None
created_at = <Date 2019-04-09.22:46:11.142>
labels = ['type-bug', 'library', '3.9', '3.10', '3.11']
title = '__dir__ on unittest.mock not safe for all spec types'
updated_at = <Date 2021-10-18.17:34:19.322>
user = 'https://github.com/dsem'bugs.python.org fields:
activity = <Date 2021-10-18.17:34:19.322>
actor = 'iritkatriel'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2019-04-09.22:46:11.142>
creator = 'Dylan Semler'
dependencies = []
files = []
hgrepos = []
issue_num = 36581
keywords = ['patch']
message_count = 4.0
messages = ['339813', '339815', '339819', '404202']
nosy_count = 6.0
nosy_names = ['cjw296', 'michael.foord', 'mariocj89', 'xtreak', 'Dylan Semler', 'iritkatriel']
pr_nums = ['12753']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue36581'
versions = ['Python 3.9', 'Python 3.10', 'Python 3.11']
Activity
dsem commentedon Apr 9, 2019
If a MagicMock is created with a spec or spec_set that is a non-list iterable of strings (like a tuple), calling dir() on said mock produces a Traceback. Here's a minimum example:
🡒 cat poc.py
from unittest.mock import MagicMock
tirkarthi commentedon Apr 9, 2019
https://docs.python.org/3/library/unittest.mock.html#unittest.mock.Mock
Docs state it should be list of strings. Can you please link to docs where an iterable of strings is mentioned? A simple patch would be to wrap it inside a list() call but I am not sure of making the interface more relaxed which was documented to accept list of strings. I am adding module mock devs to take a call on this.
diff --git a/Lib/unittest/mock.py b/Lib/unittest/mock.py
index 8684f1dfa5..35dc7b044e 100644
--- a/Lib/unittest/mock.py
+++ b/Lib/unittest/mock.py
@@ -679,7 +679,7 @@ class NonCallableMock(Base):
if not FILTER_DIR:
return object.__dir__(self)
dsem commentedon Apr 9, 2019
I agree docs only say "list of strings" and so this isn't a case where there's behavior that contrasts with the documentation. I merely ran into this issue in my project and found it difficult to get to the root of so wanted to fix it upstream. I made a patch and reported this bug only as a formality to accompany my patch.
iritkatriel commentedon Oct 18, 2021
Changing type as crash typically refers to segfault or hang or the like, and not an exception.
Reproduced on 3.11.
serhiy-storchaka commentedon Aug 12, 2026
Support of a tuple of strings was never documented, although it worked for most parts except
dir(). But since it was not documented, we can consider this as adding a new feature.gh-80762: Fix dir() on Mock with tuple specs (GH-12753)
[-]__dir__ on unittest.mock not safe for all spec types[/-][+]`__dir__` on unittest.mock not safe for all spec types[/+]pythongh-80762: Fix dir() on Mock with tuple specs (pythonGH-12753)