Release process

Release Cadence

The pip project has a release cadence of releasing whatever is on master every 3 months. This gives users a predictable pattern for when releases are going to happen and prevents locking up improvements for fixes for long periods of time, while still preventing massively fracturing the user base with version numbers.

Our release months are January, April, July, October. The release date within that month will be up to the release manager for that release. If there are no changes, then that release month is skipped and the next release will be 3 month later.

The release manager may, at their discretion, choose whether or not there will be a pre-release period for a release, and if there is may extend that period into the next month if needed.

Because releases are made direct from the master branch, it is essential that master is always in a releasable state. It is acceptable to merge PRs that partially implement a new feature, but only if the partially implemented version is usable in that state (for example, with reduced functionality or disabled by default). In the case where a merged PR is found to need extra work before being released, the release manager always has the option to back out the partial change prior to a release. The PR can then be reworked and resubmitted for the next release.

Deprecation Policy

Any change to pip that removes or significantly alters user-visible behavior that is described in the pip documentation will be deprecated for a minimum of 6 months before the change occurs. Deprecation will take the form of a warning being issued by pip when the feature is used. Longer deprecation periods, or deprecation warnings for behavior changes that would not normally be covered by this policy, are also possible depending on circumstances, but this is at the discretion of the pip developers.

Note that the documentation is the sole reference for what counts as agreed behavior. If something isn’t explicitly mentioned in the documentation, it can be changed without warning, or any deprecation period, in a pip release. However, we are aware that the documentation isn’t always complete - PRs that document existing behavior with the intention of covering that behavior with the above deprecation process are always acceptable, and will be considered on their merits.

Note

pip has a helper function for making deprecation easier for pip maintainers. The supporting documentation can be found in the source code of pip._internal.utils.deprecation.deprecated. The function is not a part of pip’s public API.

Python 2 support

pip will continue to ensure that it runs on Python 2.7 after the CPython 2.7 EOL date. Support for Python 2.7 will be dropped, if bugs in Python 2.7 itself make this necessary (which is unlikely) or in pip 21.0 (Jan 2021), whichever is earlier.

However, bugs reported with pip which only occur on Python 2.7 would likely not be addressed directly by pip’s maintainers. Pull Requests to fix Python 2.7 only bugs will be considered, and merged (subject to normal review processes). Note that there may be delays due to the lack of developer resources for reviewing such pull requests.

Feature Flags

--use-deprecated

Example: --use-deprecated=legacy-resolver

Use for features that will be deprecated. Deprecated features should remain available behind this flag for at least six months, as per the deprecation policy.

Features moved behind this flag should always include a warning that indicates when the feature is scheduled to be removed.

Once the feature is removed, users who use the flag should be shown an error.

--use-feature

Example: --use-feature=2020-resolver

Use for new features that users can test before they become pip’s default behaviour (e.g. alpha or beta releases).

Once the feature becomes the default behaviour, this flag can remain in place, but should issue a warning telling the user that it is no longer necessary.

Release Process

Creating a new release

  1. Checkout the current pip master branch.

  2. Ensure you have the latest nox installed.

  3. Prepare for release using nox -s prepare-release -- YY.N. This will update the relevant files and tag the correct commit.

  4. Build the release artifacts using nox -s build-release -- YY.N. This will checkout the tag, generate the distribution files to be uploaded and checkout the master branch again.

  5. Upload the release to PyPI using nox -s upload-release -- YY.N.

  6. Push all of the changes including the tag.

  7. Regenerate the get-pip.py script in the get-pip repository (as documented there) and commit the results.

  8. Submit a Pull Request to CPython adding the new version of pip (and upgrading setuptools) to Lib/ensurepip/_bundled, removing the existing version, and adjusting the versions listed in Lib/ensurepip/__init__.py.

Note

If the release dropped the support of an obsolete Python version M.m, a new M.m/get-pip.py needs to be published: update the all task from tasks/generate.py in get-pip repository and make a pull request to psf-salt repository to add the new get-pip.py (and its directory) to salt/pypa/bootstrap/init.sls.

Note

If the get-pip.py script needs to be updated due to changes in pip internals and if the last M.m/get-pip.py published still uses the default template, make sure to first duplicate templates/default.py as templates/pre-YY.N.py before updating it and specify in tasks/generate.py that M.m/get-pip.py now needs to use templates/pre-YY.N.py.

Creating a bug-fix release

Sometimes we need to release a bugfix release of the form YY.N.Z+1. In order to create one of these the changes should already be merged into the master branch.

  1. Create a new release/YY.N.Z+1 branch off of the YY.N tag using the command git checkout -b release/YY.N.Z+1 YY.N.

  2. Cherry pick the fixed commits off of the master branch, fixing any conflicts.

  3. Run nox -s prepare-release -- YY.N.Z+1.

  4. Merge master into your release branch and drop the news files that have been included in your release (otherwise they would also appear in the YY.N+1 changelog)

  5. Push the release/YY.N.Z+1 branch to github and submit a PR for it against the master branch and wait for the tests to run.

  6. Once tests run, merge the release/YY.N.Z+1 branch into master, and follow the above release process starting with step 4.