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Notes for Julia Contributors

Hi! Thanks for checking out Julia. If you have questions or problems, the Julia dev list is a good place to post them, but you should check out the online Julia docs first. If you have changes you'd like to contribute, you'll need a free GitHub account. (If you're reading this on GitHub, you probably already have one.) You'll also want a working copy of Julia, built from source (you can still contribute with a binary install, but it's harder and not really recommended). In list form, here's what to do to become a contributor:

  • Join the dev list.

  • Create a GitHub account.

  • Fork Julia.

  • Build the software and libraries (the first time takes a while, but it's fast after that). Detailed build instructions are in the README. Julia depends on several external packages; most are automatically downloaded and installed, but are less frequently updated than Julia itself.

  • Keep Julia current. Julia is a fast-moving target, and many details of the language are still settling out. Keep your repository up-to-date and rebase your work in progress frequently.

  • Learn to use git, the version control system used by GitHub and the Julia project. Try a tutorial such as the one provided by GitHub.

  • Relax and have fun.

Submitting your contributions

Contributing a Julia package

Julia has a built-in package manager based on git. A number of packages across many domains are already available for Julia. Developers are encouraged to provide their libraries as a Julia package. The Julia manual provides instructions on creating Julia packages.

For developers who need to wrap C libraries so that they can be called from Julia, the Clang.jl package can help generate the wrappers automatically from the C header files.

Improving documentation

By contributing documentation to Julia, you are agreeing to release it under the MIT License.

Julia's documentation is stored in the doc directory, and like everything else can be modified using git. However, for small changes one can also use GitHub's web interface:

  • Navigate to
  • Click doc
  • If you want to modify an entry in the help for Julia's standard library, click stdlib
  • Pick the file you want to edit (for example, base.rst)
  • Select the master branch (if not browsing it already)
  • Click "Edit"
  • Click on the icon that looks like a fullscreen symbol ("Zen" mode)
  • Search for the function you want to change
  • Make your changes
  • Exit Zen mode
  • Provide a title, and optionally a longer description of your change
  • Submit your change

Contributing to core functionality or base libraries

By contributing code to Julia, you are agreeing to release it under the MIT License.

The Julia community uses GitHub issues to track and discuss problems, feature requests, and pull requests. You can make pull requests for incomplete features to get code review. The convention is to prefix the pull request title with "WIP:" for Work In Progress, or "RFC:" for Request for Comments when work is completed and ready for merging. This will prevent accidental merging of work that is in progress.

Note: These instructions are for adding functionality to the base library. Usually, this is not encouraged, and before doing so, it is essential to discuss the proposed changes or additions on the mailing list or in a github issue. Changing stuff in the base can potentially break a lot of things. Make sure you test your code as described here, together with the latest Julia updates, to avoid problems. Add new code to Julia's base libraries as follows:

  1. Add files to the base/ directory, and tests into test/. Often, this may not be necessary and you may be able to add your code to an existing file in base/.

  2. Add any new files to sysimg.jl in order to build them into the Julia system image and export necessary symbols in exports.jl.

  3. Include your tests in test/Makefile and test/runtests.jl.

Build as usual, and do make clean testall to test your contribution. If your contribution includes changes to Makefiles or external dependencies, make sure you can build Julia from a clean tree using git clean -fdx or equivalent (be careful – this command will delete any files lying around that aren't checked into git). Make sure that Travis greenlights the pull request with a Good to merge message.

Getting help

While getting familiar with Julia, remember to check out the docs, keeping in mind that they are searchable. (If you use a script blocker then you'll have to unblock that page.) The source code is an excellent source of examples (and it's mostly pretty approachable). If you're still stumped, post something on the dev list, but you may want to search the archives first to see if there's already been a discussion about what you're stuck on.


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