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Reviewers guideline

Pull request checklist

Branch selection

  • In general, simple bugfixes that are unlikely to introduce new bugs of their own should be merged onto the maintenance branch. New features, or anything that changes the API, should be made against master. The rules are fuzzy here – when in doubt, target master.
  • Once changes are merged into the maintenance branch, they should be merged into master.


  • Every new feature should be documented. If it’s a new module, don’t forget to add a new rst file to the API docs.
  • Each high-level plotting function should have a small example in the Example section of the docstring. This should be as simple as possible to demonstrate the method. More complex examples should go in the examples section of the documentation.
  • Build the docs and make sure all formatting warnings are addressed.
  • See Writing documentation for our documentation style guide.
  • If your change is a major new feature, add an entry to doc/users/whats_new.rst.
  • If you change the API in a backward-incompatible way, please document it in doc/api/api_changes.rst.

PR Review guidelines

  • If you have commit rights, then you are trusted to use them. Please help review and merge PRs!

  • For code changes (anything in src or lib) two developers (those with commit rights) should review all pull requests. If you are the first to review a PR and approve of the changes use the github ‘approve review’ tool to mark it as such. If you are a subsequent reviewer and you approve, either merge (and backport if needed) or select 'approve review'.

    Ensure that all API changes are documented in doc/api/api_changes and significant new features have and entry in doc/user/whats_new.

  • Documentation and examples may be merged by the first reviewer. Use the threshold “is this better than it was?” as the review criteria.

  • Make sure the Travis, Appvyor, and codecov tests are passing before merging.

    • Whenever a pull request is created or updated, Travis and Appveyor automatically runs the test suite on all versions of Python supported by Matplotlib. The tox support in Matplotlib may be useful for testing locally.
  • Do not self merge, except for ‘small’ patches to un-break the CI.

  • Squashing is case-by-case. The balance is between burden on the contributor, keeping a relatively clean history, and keeping a history usable for bisecting. The only time we are really strict about it is to eliminate binary files (ex multiple test image re-generations) and to remove upstream merges.

  • Be patient with contributors.

  • Do not let perfect be the enemy of the good, particularly for documentation or example PRs. If you find yourself making many small suggestions, either open a PR against the original branch or merge the PR and then open a new PR against upstream.


When doing backports please include the branch you backported the commit to along with the SHA in a comment on the original PR.

We do a backport from master to v2.0.x assuming:

  • matplotlib is a read-only remote branch of the matplotlib/matplotlib repo
  • DANGER is a read/write remote branch of the matplotlib/matplotlib repo

The TARGET_SHA is the hash of the merge commit you would like to backport. This can be read off of the github PR page (in the UI with the merge notification) or through the git CLI tools.:

git fetch matplotlib
git checkout v2.0.x
git merge --ff-only matplotlib/v2.0.x
git cherry-pick -m 1 TARGET_SHA
git log --graph --decorate  # to look at it
# local tests? (use your judgment)
git push DANGER v2.0.x
# leave a comment on PR noting sha of the resulting commit
# from the cherry-pick + branch it was moved to

These commands work on git 2.7.1.