.eslintrc.js

module.exports = {
  extends: [
    'prettier',
    'airbnb',
    'plugin:flowtype/recommended',
    'prettier/react',
    'prettier/flowtype',
    'plugin:jest/recommended',
    'plugin:prettier/recommended',
  ],
  parser: 'babel-eslint',
  plugins: ['prettier', 'flowtype', 'react', 'import', 'jest'],
  env: {
    es6: true,
    browser: true,
    node: true,
    'jest/globals': true,
  },
  globals: {
    // flow globals
    TimeoutID: true,
    IntervalID: true,
    AnimationFrameID: true,
  },
  rules: {
    // Error on prettier violations
    'prettier/prettier': 'error',

    // New eslint style rules that is not disabled by prettier:
    'lines-between-class-members': 'off',

    // Allowing warning and error console logging
    'no-console': ['error', { allow: ['warn', 'error'] }],

    // Opting out of prefer destructuring (nicer with flow in lots of cases)
    'prefer-destructuring': 'off',

    // Disallowing the use of variables starting with `_` unless it called on `this`.
    // Allowed: `this._secret = Symbol()`
    // Not allowed: `const _secret = Symbol()`
    'no-underscore-dangle': ['error', { allowAfterThis: true }],

    // Cannot reassign function parameters but allowing modification
    'no-param-reassign': ['error', { props: false }],

    // Allowing ++ on numbers
    'no-plusplus': 'off',

    // Allowing Math.pow rather than forcing `**`
    'no-restricted-properties': [
      'off',
      {
        object: 'Math',
        property: 'pow',
      },
    ],

    // Allowing jsx in files with any file extension (old components have jsx but not the extension)
    'react/jsx-filename-extension': 'off',

    // Not requiring default prop declarations all the time
    'react/require-default-props': 'off',

    // Opt out of preferring stateless functions
    'react/prefer-stateless-function': 'off',

    // Allowing files to have multiple components in it
    'react/no-multi-comp': 'off',

    // Sometimes we use the PropTypes.object PropType for simplicity
    'react/forbid-prop-types': 'off',

    // Allowing the non function setState approach
    'react/no-access-state-in-setstate': 'off',

    // Opting out of this
    'react/destructuring-assignment': 'off',

    // Adding 'skipShapeProps' as the rule has issues with correctly handling PropTypes.shape
    'react/no-unused-prop-types': ['error', { skipShapeProps: true }],

    // Require // @flow at the top of files
    'flowtype/require-valid-file-annotation': [
      'error',
      'always',
      { annotationStyle: 'line' },
    ],

    // Allowing importing from dev deps (for stories and tests)
    'import/no-extraneous-dependencies': 'off',
  },
};