Changes/DeprecatePythonMock

Deprecate python-mock

Summary

The python-mock (python3-mock) package will be deprecated in Fedora 34. The package is a standard library backport for older Pythons, Fedora packages should use unittest.mock instead. Many still depend on mock, so we cannot remove it yet. Packagers are encouraged to work with upstream to switch to unittest.mock when available. A simple sed can be applied in %prep as a temporary (or even permanent) downstream solution.

Owner

• Name: Miro Hrončok
• Email: mhroncok@redhat.com

Current status

• Targeted release: Fedora 34
• Last updated: 2021-02-02
• FESCo issue: #2566
• Tracker bug: #1924123
• Release notes tracker: #652

Detailed Description

The python-mock package is the 3rd party backport of the standard library unittest.mock module:

mock is now part of the Python standard library, available as unittest.mock in Python 3.3 onwards. This package contains a rolling backport of the standard library mock code compatible with Python 3.6 and up.

Fedora has recent enough versions of Python, hence using a library backport is redundant. Many packages only use it out of habit. We'd like to encourage both downstream packages and upstreams to switch to unittest.mock instead. Eventually, we'd like to drop python-mock from Fedora entirely, if possible. Before we attempt to remove the package, we need to stop new packages to (Build)Require python3-mock, hence we want to have it deprecated.

Note that the change owner does not currently officially maintain python-mock but the Python Maintenance team maintains the package in RHEL and contributes to the Fedora package when needed. The Fedora package maintainer has been contacted without response (the nonresponsive process is currently in progress).

How to migrate to unittest.mock

In most cases, performing the following replacement should be enough:

s/^(\s*)import mock/\1from unittest import mock/
s/^(\s*)from mock import /\1from unittest.mock import /

If upstream really needs to support Python versions without unittest.mock, we recommend using a try-import mechanism, such as:

try:
    from unittest import mock
except ImportError:
    import mock

If dual support for unittest.mock and mock is required, and the mock package is required in the metadata (such as in the testing extras), conditionalize it, with:

mock;python_version<"3.3"

Feedback

In the past, we've managed to migrate some packages away from python-mock, without a push back:

• https://src.fedoraproject.org/rpms/python-urllib3/pull-request/13
• https://src.fedoraproject.org/rpms/python-freezegun/pull-request/10
• https://src.fedoraproject.org/rpms/python-hypothesis/c/65a4191709

Benefit to Fedora

Eventually, we might be able to no longer maintain a standard library backport in a separate package.

Scope

• Proposal owners: Deprecate python3-mock and update the package description. Provide help migrating to unittest.mock to other packagers who ask for it.

• Other developers: No action needed. Don't add new dependencies on python3-mock. If interested, migrate existing packages to unittest.mock (feel free to ask for help).

• Release engineering: no impact on Release Engineering is anticipated

• Policies and guidelines: N/A (not a System Wide Change)

• Trademark approval: N/A (not needed for this Change)

• Alignment with Objectives: N/A (not needed for this Change)

Upgrade/compatibility impact

The package will remain available. Only new packages cannot depend on it. Once retired (in distant future), we don't plan to obsolete/provide python3-mock from python3-libs, because it cannot work as drop-in replacement (the import name is different). The package will eventually be obsoleted by fedora-obsolete-packages once Python is updated to 3.N+1 after the removal to avoid broken upgrades.

How To Test

$ repoquery --repo=rawhide --provides python3-mock
...
deprecated()
...

User Experience

No changes.

Dependencies

N/A (not a System Wide Change)

Contingency Plan

• Contingency mechanism: (What to do? Who will do it?) N/A (not a System Wide Change)
• Contingency deadline: N/A (not a System Wide Change)
• Blocks release? N/A (not a System Wide Change), Yes/No
• Blocks product? product

Documentation

N/A (not a System Wide Change)