.eslintrc.js

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

// We use eslint-loader so even warnings are very visibile.
// 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.

var WARNING = 1;

module.exports = {
  root: true,

  parser: 'babel-eslint',

  // import plugin is termporarily disabled, scroll below to see why
  plugins: ['react', 'flowtype', 'import'/*, 'import'*/],

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

  parserOptions: {
    ecmaVersion: 6,
    sourceType: 'module',
    ecmaFeatures: {
      jsx: true,
      generators: true,
      experimentalObjectRestSpread: true
    }
  },

  settings: {
    'import/ignore': [
      'node_modules',
      '\\.(json|css|jpg|png|gif|eot|svg|ttf|woff|woff2|mp4|webm)$',
    ],
    'import/extensions': ['.js'],
    'import/resolver': {
      node: {
        extensions: ['.js', '.json']
      }
    }
  },

  rules: {
    // http://eslint.org/docs/rules/
    'array-callback-return': WARNING,
    'default-case': [WARNING, { commentPattern: '^no default$' }],
    'dot-location': [WARNING, 'property'],
    eqeqeq: [WARNING, 'allow-null'],
    'guard-for-in': WARNING,
    'new-cap': [WARNING, { newIsCap: true }],
    'new-parens': WARNING,
    'no-array-constructor': WARNING,
    'no-caller': WARNING,
    'no-cond-assign': [WARNING, 'always'],
    'no-const-assign': WARNING,
    'no-control-regex': WARNING,
    'no-delete-var': WARNING,
    'no-dupe-args': WARNING,
    'no-dupe-class-members': WARNING,
    'no-dupe-keys': WARNING,
    'no-duplicate-case': WARNING,
    'no-empty-character-class': WARNING,
    'no-empty-pattern': WARNING,
    'no-eval': WARNING,
    'no-ex-assign': WARNING,
    'no-extend-native': WARNING,
    'no-extra-bind': WARNING,
    'no-extra-label': WARNING,
    'no-fallthrough': WARNING,
    'no-func-assign': WARNING,
    'no-implied-eval': WARNING,
    'no-invalid-regexp': WARNING,
    'no-iterator': WARNING,
    'no-label-var': WARNING,
    'no-labels': [WARNING, { allowLoop: false, allowSwitch: false }],
    'no-lone-blocks': WARNING,
    'no-loop-func': WARNING,
    'no-mixed-operators': [WARNING, {
      groups: [
        ['+', '-', '*', '/', '%', '**'],
        ['&', '|', '^', '~', '<<', '>>', '>>>'],
        ['==', '!=', '===', '!==', '>', '>=', '<', '<='],
        ['&&', '||'],
        ['in', 'instanceof']
      ],
      allowSamePrecedence: false
    }],
    'no-multi-str': WARNING,
    'no-native-reassign': WARNING,
    'no-negated-in-lhs': WARNING,
    'no-new-func': WARNING,
    'no-new-object': WARNING,
    'no-new-symbol': WARNING,
    'no-new-wrappers': WARNING,
    'no-obj-calls': WARNING,
    'no-octal': WARNING,
    'no-octal-escape': WARNING,
    'no-redeclare': WARNING,
    'no-regex-spaces': WARNING,
    'no-restricted-syntax': [
      WARNING,
      'LabeledStatement',
      'WithStatement',
    ],
    'no-return-assign': WARNING,
    'no-script-url': WARNING,
    'no-self-assign': WARNING,
    'no-self-compare': WARNING,
    'no-sequences': WARNING,
    'no-shadow-restricted-names': WARNING,
    'no-sparse-arrays': WARNING,
    'no-this-before-super': WARNING,
    'no-throw-literal': WARNING,
    'no-undef': WARNING,
    'no-unexpected-multiline': WARNING,
    'no-unreachable': WARNING,
    'no-unused-expressions': WARNING,
    'no-unused-labels': WARNING,
    'no-unused-vars': [WARNING, { vars: 'local', args: 'none' }],
    'no-use-before-define': [WARNING, 'nofunc'],
    'no-useless-computed-key': WARNING,
    'no-useless-concat': WARNING,
    'no-useless-constructor': WARNING,
    'no-useless-escape': WARNING,
    'no-useless-rename': [WARNING, {
      ignoreDestructuring: false,
      ignoreImport: false,
      ignoreExport: false,
    }],
    'no-with': WARNING,
    'no-whitespace-before-property': WARNING,
    'operator-assignment': [WARNING, 'always'],
    radix: WARNING,
    'require-yield': WARNING,
    'rest-spread-spacing': [WARNING, 'never'],
    strict: [WARNING, 'never'],
    'unicode-bom': [WARNING, 'never'],
    'use-isnan': WARNING,
    'valid-typeof': WARNING,

    // flow rules
    "flowtype/require-parameter-type": WARNING,
    "flowtype/require-return-type": [WARNING, "always", { "annotateUndefined": "never" }],
    "flowtype/space-after-type-colon": [WARNING, "always"],
    "flowtype/space-before-type-colon": [WARNING, "never"],
    // "flowtype/type-id-match": [WARNING, "^([A-Z][a-z0-9]+)+Type$"],

    // https://github.com/benmosher/eslint-plugin-import/blob/master/docs/rules/

    // TODO: import rules are temporarily disabled because they don't play well
    // with how eslint-loader only checks the file you change. So if module A
    // imports module B, and B is missing a default export, the linter will
    // record this as an issue in module A. Now if you fix module B, the linter
    // will not be aware that it needs to re-lint A as well, so the error
    // will stay until the next restart, which is really confusing.

    // This is probably fixable with a patch to eslint-loader.
    // When file A is saved, we want to invalidate all files that import it
    // *and* that currently have lint errors. This should fix the problem.

    // 'import/default': WARNING,
    // 'import/export': WARNING,
    // 'import/named': WARNING,
    // 'import/namespace': WARNING,
    // 'import/no-amd': WARNING,
    // 'import/no-duplicates': WARNING,
    // 'import/no-extraneous-dependencies': WARNING,
    // 'import/no-named-as-default': WARNING,
    // 'import/no-named-as-default-member': WARNING,
    // 'import/no-unresolved': [WARNING, { commonjs: true }],

    // https://github.com/yannickcr/eslint-plugin-react/tree/master/docs/rules
    'react/jsx-equals-spacing': [WARNING, 'never'],
    'react/jsx-handler-names': [WARNING, {
      eventHandlerPrefix: 'handle',
      eventHandlerPropPrefix: 'on',
    }],
    'react/jsx-no-duplicate-props': [WARNING, { ignoreCase: true }],
    'react/jsx-no-undef': WARNING,
    'react/jsx-pascal-case': [WARNING, {
      allowAllCaps: true,
      ignore: [],
    }],
    'react/jsx-uses-react': WARNING,
    'react/jsx-uses-vars': WARNING,
    'react/no-deprecated': WARNING,
    'react/no-direct-mutation-state': WARNING,
    'react/no-is-mounted': WARNING,
    'react/react-in-jsx-scope': WARNING,
    'react/require-render-return': WARNING
  }
};