How to Contribute

React is one of Facebook’s first open source projects that is both under very active development and is also being used to ship code to everybody on facebook.com. We’re still working out the kinks to make contributing to this project as easy and transparent as possible, but we’re not quite there yet. Hopefully this document makes the process for contributing clear and answers some questions that you may have.

Code of Conduct

Facebook has adopted the Contributor Covenant as its Code of Conduct, and we expect project participants to adhere to it. Please read the full text so that you can understand what actions will and will not be tolerated.

Open Development

All work on React happens directly on GitHub. Both core team members and external contributors send pull requests which go through the same review process.

Semantic Versioning

React follows semantic versioning. We release patch versions for critical bugfixes, minor versions for new features or non-essential changes, and major versions for any breaking changes. When we make breaking changes, we also introduce deprecation warnings in a minor version so that our users learn about the upcoming changes and migrate their code in advance. Learn more about our commitment to stability and incremental migration in our versioning policy.

Every significant change is documented in the changelog file.

Branch Organization

Submit all changes directly to the master branch. We don’t use separate branches for development or for upcoming releases. We do our best to keep master in good shape, with all tests passing.

Code that lands in master must be compatible with the latest stable release. It may contain additional features, but no breaking changes. We should be able to release a new minor version from the tip of master at any time.

Feature Flags

To keep the master branch in a releasable state, breaking changes and experimental features must be gated behind a feature flag.

Feature flags are defined in packages/shared/ReactFeatureFlags.js. Some builds of React may enable different sets of feature flags; for example, the React Native build may be configured differently than React DOM. These flags are found in packages/shared/forks. Feature flags are statically typed by Flow, so you can run yarn flow to confirm that you’ve updated all the necessary files.

React’s build system will strip out disabled feature branches before publishing. A continuous integration job runs on every commit to check for changes in bundle size. You can use the change in size as a signal that a feature was gated correctly.

Bugs

Where to Find Known Issues

We are using GitHub Issues for our public bugs. We keep a close eye on this and try to make it clear when we have an internal fix in progress. Before filing a new task, try to make sure your problem doesn’t already exist.

Reporting New Issues

The best way to get your bug fixed is to provide a reduced test case. This JSFiddle template is a great starting point.

Security Bugs

Facebook has a bounty program for the safe disclosure of security bugs. With that in mind, please do not file public issues; go through the process outlined on that page.

How to Get in Touch

IRC: #reactjs on freenode
Discussion forums

There is also an active community of React users on the Discord chat platform in case you need help with React.

Proposing a Change

If you intend to change the public API, or make any non-trivial changes to the implementation, we recommend filing an issue. This lets us reach an agreement on your proposal before you put significant effort into it.

If you’re only fixing a bug, it’s fine to submit a pull request right away but we still recommend to file an issue detailing what you’re fixing. This is helpful in case we don’t accept that specific fix but want to keep track of the issue.

Your First Pull Request

Working on your first Pull Request? You can learn how from this free video series:

How to Contribute to an Open Source Project on GitHub

To help you get your feet wet and get you familiar with our contribution process, we have a list of good first issues that contain bugs that have a relatively limited scope. This is a great place to get started.

If you decide to fix an issue, please be sure to check the comment thread in case somebody is already working on a fix. If nobody is working on it at the moment, please leave a comment stating that you intend to work on it so other people don’t accidentally duplicate your effort.

If somebody claims an issue but doesn’t follow up for more than two weeks, it’s fine to take it over but you should still leave a comment.

Sending a Pull Request

The core team is monitoring for pull requests. We will review your pull request and either merge it, request changes to it, or close it with an explanation. For API changes we may need to fix our internal uses at Facebook.com, which could cause some delay. We’ll do our best to provide updates and feedback throughout the process.

Before submitting a pull request, please make sure the following is done:

Fork the repository and create your branch from master.
Run yarn in the repository root.
If you’ve fixed a bug or added code that should be tested, add tests!
Ensure the test suite passes (yarn test). Tip: yarn test --watch TestName is helpful in development.
Run yarn test --prod to test in the production environment.
If you need a debugger, run yarn debug-test --watch TestName, open chrome://inspect, and press “Inspect”.
Format your code with prettier (yarn prettier).
Make sure your code lints (yarn lint). Tip: yarn linc to only check changed files.
Run the Flow typechecks (yarn flow).
If you haven’t already, complete the CLA.

Contributor License Agreement (CLA)

In order to accept your pull request, we need you to submit a CLA. You only need to do this once, so if you’ve done this for another Facebook open source project, you’re good to go. If you are submitting a pull request for the first time, just let us know that you have completed the CLA and we can cross-check with your GitHub username.

Complete your CLA here.

Contribution Prerequisites

You have Node installed at v8.0.0+ and Yarn at v1.2.0+.
You have JDK installed.
You have gcc installed or are comfortable installing a compiler if needed. Some of our dependencies may require a compilation step. On OS X, the Xcode Command Line Tools will cover this. On Ubuntu, apt-get install build-essential will install the required packages. Similar commands should work on other Linux distros. Windows will require some additional steps, see the node-gyp installation instructions for details.
You are familiar with Git.

Development Workflow

After cloning React, run yarn to fetch its dependencies. Then, you can run several commands:

yarn lint checks the code style.
yarn linc is like yarn lint but faster because it only checks files that differ in your branch.
yarn test runs the complete test suite.
yarn test --watch runs an interactive test watcher.
yarn test --prod runs tests in the production environment.
yarn test <pattern> runs tests with matching filenames.
yarn debug-test is just like yarn test but with a debugger. Open chrome://inspect and press “Inspect”.
yarn flow runs the Flow typechecks.
yarn build creates a build folder with all the packages.
yarn build react/index,react-dom/index --type=UMD creates UMD builds of just React and ReactDOM.

We recommend running yarn test (or its variations above) to make sure you don’t introduce any regressions as you work on your change. However, it can be handy to try your build of React in a real project.

First, run yarn build. This will produce pre-built bundles in build folder, as well as prepare npm packages inside build/packages.

The easiest way to try your changes is to run yarn build react/index,react-dom/index --type=UMD and then open fixtures/packaging/babel-standalone/dev.html. This file already uses react.development.js from the build folder so it will pick up your changes.

If you want to try your changes in your existing React project, you may copy build/dist/react.development.js, build/dist/react-dom.development.js, or any other build products into your app and use them instead of the stable version.

If your project uses React from npm, you may delete react and react-dom in its dependencies and use yarn link to point them to your local build folder. Note that instead of --type=UMD you’ll want to pass --type=NODE when building. You’ll also need to build the scheduler package:

cd ~/path_to_your_react_clone/
yarn build react/index,react/jsx,react-dom/index,scheduler --type=NODE

cd build/node_modules/react
yarn link
cd build/node_modules/react-dom
yarn link

cd ~/path/to/your/project
yarn link react react-dom

Every time you run yarn build in the React folder, the updated versions will appear in your project’s node_modules. You can then rebuild your project to try your changes.

If some package is still missing (e.g. maybe you use react-dom/server in your project), you can always do a full build with yarn build. Note that running yarn build without options takes a long time.

We still require that your pull request contains unit tests for any new functionality. This way we can ensure that we don’t break your code in the future.

Style Guide

We use an automatic code formatter called Prettier. Run yarn prettier after making any changes to the code.

Then, our linter will catch most issues that may exist in your code. You can check the status of your code styling by simply running yarn linc.

However, there are still some styles that the linter cannot pick up. If you are unsure about something, looking at Airbnb’s Style Guide will guide you in the right direction.

Request for Comments (RFC)

Many changes, including bug fixes and documentation improvements can be implemented and reviewed via the normal GitHub pull request workflow.

Some changes though are “substantial”, and we ask that these be put through a bit of a design process and produce a consensus among the React core team.

The “RFC” (request for comments) process is intended to provide a consistent and controlled path for new features to enter the project. You can contribute by visiting the rfcs repository.

License

By contributing to React, you agree that your contributions will be licensed under its MIT license.

What Next?

Read the next section to learn how the codebase is organized.

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