Purpose of this package is to share common eslint configuration among other JS projects in our company. It should not be annoying but rather helpful when you understand "why" of each rule (please give us feedback if you disagree with some rules).

Usage

Before you start you should remove all Eslint plugins and Prettier from your package.json files. This package takes care of all the plugins that are necessary. You should install additional plugins only when you need to add some extra rules. It's a good idea to contribute these rules back to this package so everyone can benefit from it.

Install this package (as well as Eslint):

yarn add eslint @kiwicom/eslint-config --dev [--ignore-workspace-root-check]

And use it in your .eslintrc.js:

module.exports = {
  root: true,
  extends: [
    '@kiwicom/eslint-config',

    // - OR -
    // '@kiwicom/eslint-config/strict',

    // - OR -
    // '@kiwicom/eslint-config/nitro',
  ],
};

Strict version of the config turns some warnings into errors. We use warnings as a migration strategy for the future breaking release but you can make the config more strict even today (so your CI will fail). Not all warnings are turned into errors - only the ones considered to be errors in the future version. Please be aware that strict mode is like living on the edge: minor upgrade can break your CI (while others will get only warnings). You will be ready for the future major version though.

You can also set your eslint as needed with babel-eslint parser for example (you need to install it separately):

const OFF = 0;
const WARN = 1;
const ERROR = 2;

module.exports = {
  root: true,

  extends: ['@kiwicom/eslint-config'],

  // adjust the rules as needed
  parser: 'babel-eslint',
  env: {
    jest: true,
    node: true,
  },
  rules: {
    eqeqeq: [ERROR, 'smart'],
  },
};

It is important to report any issues with the eslint configuration back so we can improve it for everyone. These rules should be related only to how we write JS code so it's perfectly fine if you have some additional rules closely related to your project (no-restricted-imports for example).

Also please note that you should not ignore Eslint warnings! These warnings are helping you to migrate to the future major version. Some of them will turn into errors in the next major version bump.

Eslint runner

This package contains special runner for Jest to speedup Eslint checks. It executes Eslint in parallel thanks to Jest workers so it's much faster when you have many files with complicated rules. You have to create special Jest config in order to use this runner (.jest-eslint.config.js):

module.exports = {
  displayName: 'lint',
  runner: '@kiwicom/eslint-config/runner',
  testMatch: ['<rootDir>/src/**/*.js', '<rootDir>/scripts/**/*.js'],
};

It is of course possible to run this lint as yet another Jest project (using options.projects configuration). To execute this runner you have to call Jest like this:

{
  "scripts": {
    "lint": "yarn jest --config=.jest-eslint.config.js"
  }
}

It tries to detect files to lint because it's highly inefficient to test all the files everytime. However, you can do so by using --all flag like so: yarn run lint --all.

Please note: this Eslint runner not only runs all the tests much faster but it also performs automatic fixes. This is currently no-opt.

Tip

You can benefit from the main Jest executor much more. You can for example use watch mode to watch changes in one directory:

yarn run lint src/packages/relay --watch [--all]

Basically, every Jest watch option is available:

Watch Usage
 › Press a to run all tests.
 › Press f to run only failed tests.
 › Press o to only run tests related to changed files.
 › Press p to filter by a filename regex pattern.
 › Press t to filter by a test name regex pattern.
 › Press q to quit watch mode.
 › Press Enter to trigger a test run.