python / python/cpython

unittest.mock.patch('path') neither forwards or backwards compatible starting from Python >= v3.11

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topic-importlib type-bug
Dominant language
Python
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Description

Bug report

Bug description:

Issue

It appears that Python v3.11 and v3.12 are not respecting project functions and classes relative to the module root (module.__init__) when running tests and leveraging unittest.mock.

Proof of Failure

👉 I created a project that can be found here which demonstrates the entire situation.

You can review the import failures across the multiple versions of Python here

Expected Behavior

That the following would work in Python >= 3.11 as it does with all previous versions:

import sys
from unittest import mock


# This actually retrieves apprise.Apprise.Apprise().notify when using
# earlier versions of py.test (hence apprise.__init__.__all__ is respected)
@mock.patch("apprise.Apprise.notify")
def test_py11_and_higher_fails(mock_notify):
    """
    Only works with Python v3.10

    Python v3.11+ produces (where ?? is swapped with 11, or 12 respectively to whichever version of Python is being tested):
    AttributeError: <module 'apprise.Apprise' from '/usr/local/lib/python3.??/site-packages/apprise/Apprise.py'> does not have the attribute 'notify
    """
    pass

For it to work in newer versions of Python, the modules internal object placements are ignored. The following does however work (but incompatible with Python v3.10 and less):

# ...
@mock.patch("apprise.Apprise.Apprise.notify")
def test_py10_and_lower_fails(mock_notify):
     ...

Apprise Background

I'm not sure if this information is relavant; but perhaps the issue is centered around the module itself I'm testing against that makes use of the __all__ setting. Just incase; here are details that surround it:

The __init__ residing in the Apprise Module identifies:

# Get our class Apprise() from within the Apprise.py file
from .Apprise import Apprise

__all__ = [
 'Apprise',  #...
]

Regular Usage Works

Despite testing failing, all versions of the Python continue to respect import and correctly source the class/function refernced within the modules (inconsisent with unittest). The following works great:

# pip install apprise

# All versions of Python correctly respect module definitions here.
from apprise import Apprise

# Do our magic with it. 
obj = Apprise()

After Thoughts

At first I thought there was an issue with py.test but since Pytest v8.1.1 works in Python v3.10 but not in Python v3.11 or v3.12, I decided to open the ticket here. But the issue seems to be related to unittest.mock.patch and centers around Python v3.11 and higher.

Personally, I feel I've exhausted all avenues with my own research, so hopefully you can help me share what could have been introduced. Any tips/help would be much appreciated. 🙏

CPython versions tested on:

3.6, 3.7, 3.8, 3.9, 3.10, 3.11, 3.12

  • bolded are impacted by issue.
Operating systems tested on:

Linux

Linked PRs
  • gh-118176
  • gh-118432

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Reproduce the behavior using unittest.mock.patch with the Apprise example and compare the Python 3.10, 3.11, and 3.12 results shown in the linked project and GitHub Actions run. Read apprise/init.py and the patch target-resolution entry point, then review linked PRs gh-118176 and gh-118432. Done means the intended patch target behavior is established across the reported Python versions with regression coverage.

Written by the indexing model from the issue text.

Assessment

Tech stack
python
Domain
testing-qa
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
30/100

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