Contributor’s Guide

Thank you very much for your interest in contributing to Flycheck! We’d like to warmly welcome you in the Flycheck community, and hope that you enjoy your time with us!

There are many ways to contribute to Flycheck, and we appreciate all of them. We hope that this document helps you to contribute. If you have questions, please ask on our issue tracker or in our Gitter chatroom.

For a gentle start please take a look at all the things we need your help with and look for beginner-friendly tasks.

Please note that all contributors are expected to follow our Code of Conduct.

Bug reports

Bugs are a sad reality in software, but we strive to have as few as possible in Flycheck. Please liberally report any bugs you find. If you are not sure whether something is a bug or not, please report anyway.

If you have the chance and time please search existing issues, as it’s possible that someone else already reported your issue. Of course, this doesn’t always work, and sometimes it’s very hard to know what to search for, so this is absolutely optional. We definitely don’t mind duplicates, please report liberally.

To open an issue simply fill out the issue form. To help us fix the issue, include as much information as possible. When in doubt, better include too much than too little. Here’s a list of facts that are important:

  • What you did, and what you expected to happen instead
  • Whether and how you were able to reproduce the issue in emacs -Q
  • Your Flycheck setup from M-x flycheck-verify-setup
  • Your operating system
  • Your Emacs version from M-x emacs-version
  • Your Flycheck version from M-x flycheck-version

Windows-only issues

As Flycheck does not support Windows officially we generally do not attempt to fix issues that only occur on Windows. We will move all Windows-only issues to the list of open Windows issues, and leave them to Windows users and developers.

We welcome anyone who wants to fix open Windows issues, and we will merge pull requests for improved Windows compatibility. If you know Windows and Emacs, please take a look at the list of open Windows issues and try to fix any of these.

Feature requests

To request a new feature please open a new issue through our issue form.

A feature request needs to find a core developer or maintainer who adopts and implements it. Otherwise we will move the issue to the S-needs your love column of our Waffle board where issues sit that wait for a pull request from the community.

The Build system

Flycheck provides a Makefile with some convenient targets to compile and test Flycheck. The Makefile requires Cask, the Emacs Lisp dependency manager. Run make help to see a list of all available targets. Some common ones are:

  • make init initialises the project by installing local Emacs Lisp dependencies.
  • make compile compiles Flycheck and its libraries to byte code.
  • make specs runs all Buttercup specs for Flycheck. Set PATTERN to run only specs matching a specific regular expression, e.g. make PATTERN='^Mode Line' specs to run only tests for the mode line.
  • make test runs all ERT unit tests for Flycheck. We are phasing ERT out in favour of Buttercup; no new ERT unit tests will be added and this target will eventually be removed.
  • make integ runs all integration tests for Flycheck syntax checkers. These tests are very dependent on the checker programs and their versions; expect failures when running this target. Set SELECTOR to run only tests matching a specific ERT selector, e.g. make SELECTOR='(language haskell)' integ to run only integration tests for Haskell. make LANGUAGE=haskell integ is a shortcut for this.

Pull requests

Pull Requests are the primary mechanism to submit your own changes to Flycheck. Github provides great documentation about Pull Requests.

Please make your pull requests against the master branch.

Use make specs test to test your pull request locally. When making changes to syntax checkers of a specific language, it’s also a good idea to run make LANGUAGE=language integ and check whether the tests for the particular language still work. A successful make integ is by no means mandatory for pull requests, though, we will test your changes, too.

All pull requests are reviewed by a maintainer. Feel free to mention individual developers (e.g. @lunaryorn) to request a review from a specific person, or @flycheck/maintainers if you have general questions or if your pull request was waiting for review too long.

Additionally, all pull requests go through automated tests on Travis CI which check code style, run unit tests, etc. After the pull request was reviewed and if all tests passed a maintainer will eventually cherry-pick or merge your changes and close the pull request.

Commit guidelines

The art of writing good commit messages is a wide subject. This model commit message illustrates our style:

Fix a foo bug

The first line is the summary, 50 characters or less.  Write in the
imperative and in present tense: “Fix bug”, not “fixed bug” or “fixes

After the summary more paragraphs with detailed explanations may follow,
wrapped at 72 characters.  Separate multiple paragraphs by blank lines.

You may use simple formatting like *emphasis* or _underline_, but keep
it to a minimum.  Commit messages are not in Markdown :)

Commit messages may reference issues by number, like this: See GH-42.
Please use `GH-` to prefix issue numbers.  You may also close issues
like this: Fixes GH-42 and closes GH-42.

Git Commit and Magit provide Emacs mode for Git commit messages, which helps you to comply to these guidelines.

Writing documentation

Documentation improvements are very welcome. Flycheck’s manual is written in reStructuredText and built with Sphinx. The source of the manual resides in the doc/ directory.

You need Python 3.4 or newer to install Sphinx for Flycheck’s documentation. On OS X it is recommended that you use Homebrew to install the latest Python version with brew install python3. On Linux you should be able to obtain Python 3.4 from the package manager of your distribution.

With Python 3 installed change into the doc/ directory and run make init to install Sphinx and related tools required for Flycheck’s documentation. We recommend that you use virtualenv to avoid a global installation of Python modules. make init will warn you if you do not.

When editing documentation run make html-auto to view the results of your edits. This target runs a local webserver at http://localhost:8000 which serves the HTML documentation and watches the documentation sources for changes to rebuild automatically. When you finished your edits it is a good idea to run make linkcheck to verify all links in the documentation. Note that this target can take a while especially when run on a clean build.

Run make help to see a list of all available Make targets for the documentation.

Documentation pull requests work in the same way as other pull requests. To find documentation issues sort by the A-documentation label.

Issue management

We manage all issues and pull requests on our Waffle board. The board has six columns which correspond to S- labels on Github:

  • The Backlog (no S label) holds all incoming issues. Pull requests waiting for review sit here, as well as bugs that were reported or stories and tasks that are not ready to work on yet.
  • Community (S-needs your love label) issues are those that we will not work on ourselves. These issues need pull requests from the community to be solved. Look at this column to find spots to contribute to.
  • Blocked (S-blocked label) issues are waiting for something, like a change in an upstream project or a feedback from another developer. A B- label may provide additional clue why the issue is blocked. Blocked issues may also appear in the backlog, but in this column we actively seek to remove the blockers and move the issue to Ready.
  • In Ready (S-ready label) we keep issues that we are ready to work on. This includes bugs which we can reproduce and fix, and pull requests that were reviewed and are ready to be merged now. Look at this column to see what’s coming next to Flycheck.
  • When we start to work on an issue it moves into In Progress (S-in progress label).
  • Open pull requests, whether from contributors or core developers, start in the S-to review column for review by maintainers. Once review is complete we will either merge the pull request and thus move it to Done, or move the issue back to S-in progress if the pull request still needs work.
  • Eventually issues move into Done when they are closed.

In addition to these columns which reflect the basic issue workflow we also use a variety of labels to group issues:

  • Yellow, A-prefixed labels describes the area of Flycheck the issue belongs to.
  • Orange, B-prefixed labels gives reasons why an issue is blocked.
  • Green, E-prefixed labels denotes the level of experience necessary to address an issue.
  • Blue, K-prefixed labels tells the kind of an issue, i.e. whether it’s a bug, a feature request, etc.
  • Grey, R-prefixed labels inform about the resolution of an issue.

Out of tree contributions

There are many ways that you can contribute to Flycheck that go beyond this repository.

Answer questions in our Gitter channel or on StackExchange.

Participate in Flycheck discussions in other Emacs communities and help users with troubles.

Write extensions for Flycheck.

This contributing guide is heavily inspired by Rust’s excellent contributing information.