index.js

/**
 * Copyright (c) 2015-present, Facebook, Inc.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 */

'use strict';

// Inspired by https://github.com/airbnb/javascript but less opinionated.

// We use eslint-loader so even warnings are very visible.
// This is why we only use "WARNING" level for potential errors,
// and we don't use "ERROR" level at all.

// In the future, we might create a separate list of rules for production.
// It would probably be more strict.

// The ESLint browser environment defines all browser globals as valid,
// even though most people don't know some of them exist (e.g. `name` or `status`).
// This is dangerous as it hides accidentally undefined variables.
// We blacklist the globals that we deem potentially confusing.
// To use them, explicitly reference them, e.g. `window.name` or `window.status`.
const restrictedGlobals = require('confusing-browser-globals');

module.exports = {
  root: true,

  parser: 'babel-eslint',

  plugins: ['import', 'flowtype', 'jsx-a11y', 'react', 'react-hooks'],

  env: {
    browser: true,
    commonjs: true,
    es6: true,
    jest: true,
    node: true,
  },

  parserOptions: {
    ecmaVersion: 2018,
    sourceType: 'module',
    ecmaFeatures: {
      jsx: true,
    },
  },

  settings: {
    react: {
      version: 'detect',
    },
  },

  overrides: [
    {
      files: ['**/*.ts?(x)'],
      parser: '@typescript-eslint/parser',
      parserOptions: {
        ecmaVersion: 2018,
        sourceType: 'module',
        ecmaFeatures: {
          jsx: true,
        },

        // typescript-eslint specific options
        warnOnUnsupportedTypeScriptVersion: true,
      },
      plugins: ['@typescript-eslint'],
      // If adding a typescript-eslint version of an existing ESLint rule,
      // make sure to disable the ESLint rule here.
      rules: {
        // TypeScript's `noFallthroughCasesInSwitch` option is more robust (#6906)
        'default-case': 'off',
        // 'tsc' already handles this (https://github.com/typescript-eslint/typescript-eslint/issues/291)
        'no-dupe-class-members': 'off',
        // 'tsc' already handles this (https://github.com/typescript-eslint/typescript-eslint/issues/477)
        'no-undef': 'off',

        // Add TypeScript specific rules (and turn off ESLint equivalents)
        '@typescript-eslint/no-angle-bracket-type-assertion': 'warn',
        'no-array-constructor': 'off',
        '@typescript-eslint/no-array-constructor': 'warn',
        '@typescript-eslint/no-namespace': 'error',
        'no-use-before-define': 'off',
        '@typescript-eslint/no-use-before-define': [
          'warn',
          {
            functions: false,
            classes: false,
            variables: false,
            typedefs: false,
          },
        ],
        'no-unused-vars': 'off',
        '@typescript-eslint/no-unused-vars': [
          'warn',
          {
            args: 'none',
            ignoreRestSiblings: true,
          },
        ],
        'no-useless-constructor': 'off',
        '@typescript-eslint/no-useless-constructor': 'warn',
      },
    },
  ],

  // NOTE: When adding rules here, you need to make sure they are compatible with
  // `typescript-eslint`, as some rules such as `no-array-constructor` aren't compatible.
  rules: {
    // http://eslint.org/docs/rules/
    'array-callback-return': 'warn',
    'default-case': ['warn', { commentPattern: '^no default$' }],
    'dot-location': ['warn', 'property'],
    eqeqeq: ['warn', 'smart'],
    'new-parens': 'warn',
    'no-array-constructor': 'warn',
    'no-caller': 'warn',
    'no-cond-assign': ['warn', 'except-parens'],
    'no-const-assign': 'warn',
    'no-control-regex': 'warn',
    'no-delete-var': 'warn',
    'no-dupe-args': 'warn',
    'no-dupe-class-members': 'warn',
    'no-dupe-keys': 'warn',
    'no-duplicate-case': 'warn',
    'no-empty-character-class': 'warn',
    'no-empty-pattern': 'warn',
    'no-eval': 'warn',
    'no-ex-assign': 'warn',
    'no-extend-native': 'warn',
    'no-extra-bind': 'warn',
    'no-extra-label': 'warn',
    'no-fallthrough': 'warn',
    'no-func-assign': 'warn',
    'no-implied-eval': 'warn',
    'no-invalid-regexp': 'warn',
    'no-iterator': 'warn',
    'no-label-var': 'warn',
    'no-labels': ['warn', { allowLoop: true, allowSwitch: false }],
    'no-lone-blocks': 'warn',
    'no-loop-func': 'warn',
    'no-mixed-operators': [
      'warn',
      {
        groups: [
          ['&', '|', '^', '~', '<<', '>>', '>>>'],
          ['==', '!=', '===', '!==', '>', '>=', '<', '<='],
          ['&&', '||'],
          ['in', 'instanceof'],
        ],
        allowSamePrecedence: false,
      },
    ],
    'no-multi-str': 'warn',
    'no-native-reassign': 'warn',
    'no-negated-in-lhs': 'warn',
    'no-new-func': 'warn',
    'no-new-object': 'warn',
    'no-new-symbol': 'warn',
    'no-new-wrappers': 'warn',
    'no-obj-calls': 'warn',
    'no-octal': 'warn',
    'no-octal-escape': 'warn',
    // TODO: Remove this option in the next major release of CRA.
    // https://eslint.org/docs/user-guide/migrating-to-6.0.0#-the-no-redeclare-rule-is-now-more-strict-by-default
    'no-redeclare': ['warn', { builtinGlobals: false }],
    'no-regex-spaces': 'warn',
    'no-restricted-syntax': ['warn', 'WithStatement'],
    'no-script-url': 'warn',
    'no-self-assign': 'warn',
    'no-self-compare': 'warn',
    'no-sequences': 'warn',
    'no-shadow-restricted-names': 'warn',
    'no-sparse-arrays': 'warn',
    'no-template-curly-in-string': 'warn',
    'no-this-before-super': 'warn',
    'no-throw-literal': 'warn',
    'no-undef': 'error',
    'no-restricted-globals': ['error'].concat(restrictedGlobals),
    'no-unexpected-multiline': 'warn',
    'no-unreachable': 'warn',
    'no-unused-expressions': [
      'error',
      {
        allowShortCircuit: true,
        allowTernary: true,
        allowTaggedTemplates: true,
      },
    ],
    'no-unused-labels': 'warn',
    'no-unused-vars': [
      'warn',
      {
        args: 'none',
        ignoreRestSiblings: true,
      },
    ],
    'no-use-before-define': [
      'warn',
      {
        functions: false,
        classes: false,
        variables: false,
      },
    ],
    'no-useless-computed-key': 'warn',
    'no-useless-concat': 'warn',
    'no-useless-constructor': 'warn',
    'no-useless-escape': 'warn',
    'no-useless-rename': [
      'warn',
      {
        ignoreDestructuring: false,
        ignoreImport: false,
        ignoreExport: false,
      },
    ],
    'no-with': 'warn',
    'no-whitespace-before-property': 'warn',
    'react-hooks/exhaustive-deps': 'warn',
    'require-yield': 'warn',
    'rest-spread-spacing': ['warn', 'never'],
    strict: ['warn', 'never'],
    'unicode-bom': ['warn', 'never'],
    'use-isnan': 'warn',
    'valid-typeof': 'warn',
    'no-restricted-properties': [
      'error',
      {
        object: 'require',
        property: 'ensure',
        message:
          'Please use import() instead. More info: https://facebook.github.io/create-react-app/docs/code-splitting',
      },
      {
        object: 'System',
        property: 'import',
        message:
          'Please use import() instead. More info: https://facebook.github.io/create-react-app/docs/code-splitting',
      },
    ],
    'getter-return': 'warn',

    // https://github.com/benmosher/eslint-plugin-import/tree/master/docs/rules
    'import/first': 'error',
    'import/no-amd': 'error',
    'import/no-webpack-loader-syntax': 'error',

    // https://github.com/yannickcr/eslint-plugin-react/tree/master/docs/rules
    'react/forbid-foreign-prop-types': ['warn', { allowInPropTypes: true }],
    'react/jsx-no-comment-textnodes': 'warn',
    'react/jsx-no-duplicate-props': 'warn',
    'react/jsx-no-target-blank': 'warn',
    'react/jsx-no-undef': 'error',
    'react/jsx-pascal-case': [
      'warn',
      {
        allowAllCaps: true,
        ignore: [],
      },
    ],
    'react/jsx-uses-react': 'warn',
    'react/jsx-uses-vars': 'warn',
    'react/no-danger-with-children': 'warn',
    // Disabled because of undesirable warnings
    // See https://github.com/facebook/create-react-app/issues/5204 for
    // blockers until its re-enabled
    // 'react/no-deprecated': 'warn',
    'react/no-direct-mutation-state': 'warn',
    'react/no-is-mounted': 'warn',
    'react/no-typos': 'error',
    'react/react-in-jsx-scope': 'error',
    'react/require-render-return': 'error',
    'react/style-prop-object': 'warn',

    // https://github.com/evcohen/eslint-plugin-jsx-a11y/tree/master/docs/rules
    'jsx-a11y/accessible-emoji': 'warn',
    'jsx-a11y/alt-text': 'warn',
    'jsx-a11y/anchor-has-content': 'warn',
    'jsx-a11y/anchor-is-valid': [
      'warn',
      {
        aspects: ['noHref', 'invalidHref'],
      },
    ],
    'jsx-a11y/aria-activedescendant-has-tabindex': 'warn',
    'jsx-a11y/aria-props': 'warn',
    'jsx-a11y/aria-proptypes': 'warn',
    'jsx-a11y/aria-role': ['warn', { ignoreNonDOM: true }],
    'jsx-a11y/aria-unsupported-elements': 'warn',
    'jsx-a11y/heading-has-content': 'warn',
    'jsx-a11y/iframe-has-title': 'warn',
    'jsx-a11y/img-redundant-alt': 'warn',
    'jsx-a11y/no-access-key': 'warn',
    'jsx-a11y/no-distracting-elements': 'warn',
    'jsx-a11y/no-redundant-roles': 'warn',
    'jsx-a11y/role-has-required-aria-props': 'warn',
    'jsx-a11y/role-supports-aria-props': 'warn',
    'jsx-a11y/scope': 'warn',

    // https://github.com/facebook/react/tree/master/packages/eslint-plugin-react-hooks
    'react-hooks/rules-of-hooks': 'error',

    // https://github.com/gajus/eslint-plugin-flowtype
    'flowtype/define-flow-type': 'warn',
    'flowtype/require-valid-file-annotation': 'warn',
    'flowtype/use-flow-type': 'warn',
  },
};