eslint-plugin-rules-example

An example plugin for developing custom eslint rules based on the recommended setup from eslint.

Installation and Setup

Installation

Eslint will always look for plugins in node_modules by searching for eslint-plugin-*. You do not have to include eslint-plugin in the plugin name in the eslint configuration, rules-example works.

npm install eslint-plugin-rules-example --save-dev

Setup eslintrc.js to use rules example

Modify your eslintrc.js to include the plugin:

  plugins: [
    "rules-example"
  ],

Add a custom eslint rule:

  'rules': {
    'rules-example/require-emit-prefix': 2
  }

NOTE: This package was created based on the recommendations from eslint: https://eslint.org/docs/latest/extend/plugins

Development:

Creating a new rule:

NOTE: Eslint has a tutorial which is a great place to start: https://eslint.org/docs/latest/extend/custom-rule-tutorial

All rules are currently stored in the rules directory. Try creating a new rule file based off a current rule. A minimal rule stub looks like:

module.exports = {
  meta: {
    //add metadata
  },
  create(context) {
    return {
      //add callback functions
    };
  },
};

Always add a unit test for a rule

Create a new file in the tests/ directory by the same name but add .test.js as the file affix. Make sure to at least add a valid case and an invalid case.

The entire test suite can be run with

npm run test

OR you can run your individual test with JEST:

npx jest test/require-emit-prefix.test.js

OR you can use node:

node require-emit-prefix.test.js

npm link - running the package locally

• Make sure you are at the root of the project (eslint-plugin-rules-example) and run:

npm link

NOTE: This will create a symbolic link to the npm package as specified here: https://docs.npmjs.com/cli/v9/commands/npm-link

Change over to the project you intend on linking this package to and link the package by PACKAGE name (eslint-plugin-rules-example)

cd ~/projects/app
npm link eslint-plugin-rules-example

NOTE: at this step it's a good idea to test the new rules are picked up in the application. Look for an example that breaks the rule or create one

Pre-commit hooks and required checks

We have a pre-commit hook defined using husky (you can view these rules here: .husky/pre-commit) which will run:

1. A prettier format on all staged git files and update the git index.
2. The unit tests with npm run test
3. The eslinter on this plugin project specifically with npm run lint

Please make sure all checks pass prior to creating a merge request.