ESLint has a very lightweight development environment that makes updating code fast and easy. This is a step-by-step guide to setting up a local development environment that will let you contribute back to the project.
Step 1: Install Node.js
Go to http://nodejs.org/ to download and install the latest stable version for your operating system.
Most of the installers come with npm already installed, but if for some reason it doesn’t work on your system, you can install it manually using the instructions on the website.
Step 2: Fork and checkout your own ESLint repository
Go to https://github.com/eslint/eslint and click the “Fork” button. Follow the GitHub documentation for forking and cloning.
Once you’ve cloned the repository, run
npm install to get all the necessary dependencies:
$ cd eslint $ npm install
You must be connected to the Internet for this step to work. You’ll see a lot of utilities being downloaded.
Step 3: Add the upstream source
The upstream source is the main ESLint repository that active development happens on. While you won’t have push access to upstream, you will have pull access, allowing you to pull in the latest code whenever you want.
To add the upstream source for ESLint, run the following in your repository:
git remote add upstream email@example.com:eslint/eslint.git
Now, the remote
upstream points to the upstream source.
Step 4: Install the Yeoman Generator
Yeoman is a scaffold generator that ESLint uses to help streamline development of new rules. If you don’t already have Yeoman installed, you can install it via npm:
npm install -g yo
Then, you can install the ESLint Yeoman generator:
npm install -g generator-eslint
Please see the generator documentation for instructions on how to use it.
Step 5: Run the tests
Running the tests is the best way to ensure you have correctly set up your development environment. Make sure you’re in the
eslint directory and run:
The testing takes a few seconds to complete. If any tests fail, that likely means one or more parts of the environment setup didn’t complete correctly. The upstream tests always pass.
ESLint has several build scripts that help with various parts of development.
The primary script to use is
npm test, which does several things:
- Runs all tests on Node.js
- Checks code coverage targets
build/eslint.jsfor use in a browser
- Runs a subset of tests in PhantomJS
Be sure to run this after making changes and before sending a pull request with your changes.
Note: The full code coverage report is output into
npm run lint
npm run browserify
build/eslint.js, a version of ESLint for use in the browser
npm run docs
Generates JSDoc documentation and places it into
npm run profile
This command is used for intensive profiling of ESLint using Chrome Developer Tools. It starts a development server that runs through three profiles:
- Large - Runs ESLint on JSHint
- Medium - Runs ESLint on jQuery
- Small - Runs ESLint on KnockoutJS
Your browser should automatically open to the page in question. When that happens:
- Open up developer tools
- Click on Profiles
You should start to see profiles for each run show up on the left side. If not, reload the page in the browser. Once all three profiles have completed, they will be available for inspection.
Whenever you make changes to the ESLint source files, you’ll need to run
npm test to rerun the tests. The workflow is:
- Make changes
npm testto run tests on the command line
You’ll have to do this each time you make a change. The tests are run automatically whenever a pull request is received, so make sure to verify your changes work before submitting them.