CONTRIBUTING.md

Contributing to Astropy

Reporting Issues

When opening an issue to report a problem, please try to provide a minimal code example that reproduces the issue along with details of the operating system and the Python, NumPy, and astropy versions you are using.

Contributing

So you are interested in contributing code to the Astropy Project? Excellent! We love contributions! Astropy is open source, built on open source, and we'd love to have you hang out in our community.

Imposter syndrome disclaimer: We want your help. No, really.

There may be a little voice inside your head that is telling you that you're not ready to be an open source contributor; that your skills aren't nearly good enough to contribute. What could you possibly offer a project like this one?

We assure you - the little voice in your head is wrong. If you can write code at all, you can contribute code to open source. Contributing to open source projects is a fantastic way to advance one's coding skills. Writing perfect code isn't the measure of a good developer (that would disqualify all of us!); it's trying to create something, making mistakes, and learning from those mistakes. That's how we all improve, and we are happy to help others learn.

Being an open source contributor doesn't just mean writing code, either. You can help out by writing documentation, tests, or even giving feedback about the project (and yes - that includes giving feedback about the contribution process). Some of these contributions may be the most valuable to the project as a whole, because you're coming to the project with fresh eyes, so you can see the errors and assumptions that seasoned contributors have glossed over.

Note: This disclaimer was originally written by Adrienne Lowe for a PyCon talk, and was adapted by Astropy based on its use in the README file for the MetPy project.

How to Contribute, Best Practices

All contributions to Astropy are done via pull requests from GitHub users' "forks" (i.e., copies) of the astropy repository. If you are new to this style of development, you will want to read over our development workflow.

You may also/instead be interested in contributing to an astropy affiliated package. Affiliated packages are astronomy-related software packages that are not a part of the astropy core package, but build on it for more specialized applications and follow the Astropy guidelines for reuse, interoperability, and interfacing. Each affiliated package has its own developers/maintainers and its own specific guidelines for contributions, so be sure to read their docs.

Once you open a pull request (which should be opened against the main branch, not against any of the other branches), please make sure to include the following:

• Code: the code you are adding, which should follow our coding guidelines as much as possible.

• Tests: these are usually tests to ensure code that previously failed now works (regression tests), or tests that cover as much as possible of the new functionality to make sure it does not break in the future and also returns consistent results on all platforms (since we run these tests on many platforms/configurations). For more information about how to write tests, see our testing guidelines.

• Documentation: if you are adding new functionality, be sure to include a description in the main documentation (in docs/). Again, we have some detailed documentation guidelines to help you out.

• Performance improvements: if you are making changes that impact astropy performance, consider adding a performance benchmark in the astropy-benchmarks repository. You can find out more about how to do this in the README for that repository.

• Changelog entry: whether you are fixing a bug or adding new functionality, you should add a changelog fragment in the docs/changes/ directory. See docs/changes/README.rst for some guidance on the creation of this file.

  If you are opening a pull request you may not know the PR number yet, but you can add it once the pull request is open. If you are not sure where to put the changelog entry, wait until a maintainer has reviewed your PR and assigned it to a milestone.

  You do not need to include a changelog entry for fixes to bugs introduced in the developer version and therefore are not present in the stable releases. In general you do not need to include a changelog entry for minor documentation or test updates. Only user-visible changes (new features/API changes, fixed issues) need to be mentioned. If in doubt, ask the core maintainer reviewing your changes.

Other Tips

• Behind the scenes, we conduct a number of tests or checks with new pull requests. This is a technique that is called continuous integration, and we use GitHub Actions and CircleCI. To prevent the automated tests from running, you can add [ci skip] to your commit message. This is useful if your PR is a work in progress (WIP) and you are not yet ready for the tests to run. For example:

  $ git commit -m "WIP widget [ci skip]"
  

  • If you already made the commit without including this string, you can edit your existing commit message by running:

    $ git commit --amend
    

• Unfortunately, GitHub Actions ignores [ci skip] for a PR, so we recommend you only push your commits to GitHub when you are ready for the CI to run. Please do not push a lot of commits for every small WIP changes.

• If your commit makes substantial changes to the documentation but none of those changes include code snippets, then you can use [ci skip], which will skip all CI except RTD, where the documentation is built.

• When contributing trivial documentation fixes (i.e., fixes to typos, spelling, grammar) that don't contain any special markup and are not associated with code changes, please include the string [ci skip] in your commit message.

  $ git commit -m "Fixed typo [ci skip]"
  

• [ci skip] and [skip ci] are the same and can be used interchangeably.

Checklist for Contributed Code

A pull request for a new feature will be reviewed to see if it meets the following requirements. For any pull request, an astropy maintainer can help to make sure that the pull request meets the requirements for inclusion in the package.

Scientific Quality (when applicable)

• Is the submission relevant to astronomy?
• Are references included to the origin source for the algorithm?
• Does the code perform as expected?
• Has the code been tested against previously existing implementations?

Code Quality

• Are the coding guidelines followed?
• Is the code compatible with Python >=3.7?
• Are there dependencies other than the astropy core, the Python Standard Library, and NumPy 1.17.0 or later?
  • Is the package importable even if the C-extensions are not built?
  • Are additional dependencies handled appropriately?
  • Do functions that require additional dependencies raise an ImportError if they are not present?

Testing

• Are the testing guidelines followed?
• Are the inputs to the functions sufficiently tested?
• Are there tests for any exceptions raised?
• Are there tests for the expected performance?
• Are the sources for the tests documented?
• Have tests that require an optional dependency been marked as such?
• Does tox -e test run without failures?

Documentation

• Are the documentation guidelines followed?
• Is there a docstring in numpydoc format in the function describing:
  • What the code does?
  • The format of the inputs of the function?
  • The format of the outputs of the function?
  • References to the original algorithms?
  • Any exceptions which are raised?
  • An example of running the code?
• Is there any information needed to be added to the docs to describe the function?
• Does the documentation build without errors or warnings?

License

• Is the astropy license included at the top of the file?
• Are there any conflicts with this code and existing codes?

Astropy requirements

• Do all the GitHub Actions and CircleCI tests pass? If not, are they allowed to fail?
• If applicable, has an entry been added into the changelog?
• Can you check out the pull request and repeat the examples and tests?