Set up a Development Environment
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 https://nodejs.org/ to download and install the latest stable version for your operating system.
Most of the installers already come with npm but if for some reason npm doesn’t work on your system, you can install it manually using the instructions on the site.
Step 2: Fork and Checkout Your Own ESLint Repository
Clone your fork:
git clone https://github.com/<Your Github Username>/eslint
Once you’ve cloned the repository, run
npm install to get all the necessary dependencies:
You must be connected to the Internet for this step to work. You’ll see a lot of utilities being downloaded.
Note: It’s a good idea to re-run
npm install whenever you pull from the main repository to ensure you have the latest development dependencies.
Step 3: Add the Upstream Source
The upstream source is the main ESLint repository where active development happens. 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 minutes 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.
The ESLint directory and file structure is as follows:
bin- executable files that are available when ESLint is installed
conf- default configuration information
docs- documentation for the project
lib- contains the source code
formatters- all source files defining formatters
rules- all source files defining rules
tests- the main unit test folder
lib- tests for the source code
formatters- tests for the formatters
rules- tests for the rules
Once you have your development environment installed, you can make and submit changes to the ESLint source files. Doing this successfully requires careful adherence to our pull-request submission workflow.
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 webpack
build/eslint.js, a version of ESLint for use in the browser.