.eslintrc.js

// vim: foldmethod=marker:foldmarker={{{,}}}
/**
 * @license
 * Copyright 2016 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

// ESlint config

// This is a matcher (usable in no-restricted-syntax) that matches either a
// test or a before/after block.
const testNameRegex =
    '/^([fx]?it|(drm|quarantined)It|(before|after)(Each|All))$/';
const testCall = `CallExpression[callee.name=${testNameRegex}]`;

module.exports = {
  'env': {
    'browser': true,
    'es6': true,
  },
  'parserOptions': {
    'ecmaVersion': 2017,
  },
  'extends': ['eslint:recommended', 'google'],
  'rules': {
    // Things the compiler already takes care of, with more precision: {{{
    'no-console': 'off',
    'no-eq-null': 'off',
    'no-eval': 'off',
    'no-undef': 'off',
    'valid-jsdoc': 'off',
    // }}}

    // Things we should probably fix, but in stages in multiple commits: {{{

    // These could catch real bugs
    'default-case': 'off',
    // TODO: Enable no-loop-func in next eslint release.  We can't use it
    // now since it doesn't allow capturing "const" variables, which is safe
    'no-loop-func': 'off',
    'no-unused-expressions': 'off',  // Conflicts with some Closure declarations
    'prefer-promise-reject-errors': 'off',

    // These could improve readability
    'complexity': 'off',
    'no-negated-condition': 'off',
    'no-shadow': 'off',
    // }}}

    // Temporary Google style overrides while we get in compliance with the
    // latest style guide {{{
    'prefer-spread': 'off',
    'require-jsdoc': 'off',
    // }}}

    // "Possible error" rules: {{{
    'no-async-promise-executor': 'error',
    'no-await-in-loop': 'error',
    'no-empty': ['error', {'allowEmptyCatch': true}],
    'no-misleading-character-class': 'error',
    'no-template-curly-in-string': 'error',
    'require-atomic-updates': 'error',
    // }}}

    // "Best practices" rules: {{{
    'accessor-pairs': 'error',
    'array-callback-return': 'error',
    // causes issues when implementing an interface
    'class-methods-use-this': 'off',
    'consistent-return': 'error',
    'dot-location': ['error', 'property'],
    'dot-notation': 'off',  // We use bracket notation in tests on purpose
    'eqeqeq': 'off',        // Compiler handles type checking in advance
    'guard-for-in': 'off',
    'no-alert': 'error',
    'no-caller': 'error',
    'no-div-regex': 'error',
    'no-extend-native': 'error',  // May conflict with future polyfills
    'no-extra-label': 'error',
    'no-floating-decimal': 'error',
    'no-implicit-coercion': ['error', {'allow': ['!!']}],
    'no-implied-eval': 'error',
    'no-invalid-this': 'error',
    'no-iterator': 'error',
    'no-labels': 'error',
    'no-lone-blocks': 'error',
    'no-multi-spaces': ['error', {'ignoreEOLComments': true}],
    'no-multi-str': 'error',
    'no-new': 'error',
    'no-new-func': 'error',
    'no-new-wrappers': 'error',
    'no-octal-escape': 'error',
    'no-proto': 'error',
    'no-return-assign': 'error',
    'no-return-await': 'error',
    'no-script-url': 'error',
    'no-self-compare': 'error',
    'no-sequences': 'error',
    'no-throw-literal': 'error',
    'no-unmodified-loop-condition': 'error',
    'no-unused-vars': 'off',  // Interface impls may not require all args
    'no-useless-call': 'error',
    'no-useless-catch': 'error',
    'no-useless-concat': 'error',
    'no-useless-return': 'error',
    'no-void': 'error',
    'no-warning-comments': 'off',  // TODO and FIXME are fine
    'radix': ['error', 'always'],
    'require-await': 'error',
    'wrap-iife': ['error', 'inside'],
    'yoda': ['error', 'never'],
    // }}}

    // "Variables" rules: {{{
    'no-label-var': 'error',
    'no-shadow-restricted-names': 'error',
    'no-undef-init': 'off',  // Sometimes necessary with hacky compiler casts
    'no-undefined': 'off',   // We use undefined in many places, legitimately
    // Does not know when things are executed, false positives
    'no-use-before-define': 'off',
    // }}}

    // "Stylistic Issues" rules: {{{
    'array-bracket-newline': ['error', 'consistent'],
    'block-spacing': ['error', 'always'],
    'brace-style': ['error', '1tbs', {'allowSingleLine': true}],
    'lines-between-class-members': 'error',
    'max-statements-per-line': ['error', {'max': 1}],
    'new-parens': 'error',
    'no-mixed-operators': [
      'error', {
        'groups': [['&', '|', '^', '~', '<<', '>>', '>>>', '&&', '||']],
        'allowSamePrecedence': false,
      },
    ],
    'no-restricted-syntax': [
      'error',
      {
        'selector': 'CallExpression[callee.name="beforeAll"] ' +
                    ':matches(' +
                    'CallExpression[callee.property.name="createSpy"],' +
                    'CallExpression[callee.name="spyOn"])',
        'message': 'Create spies in beforeEach, not beforeAll.',
      },
      {
        'selector': testCall + ' > :function[async=true][params.length>0]',
        'message': 'Don\'t use both async and done.',
      },
      {
        'selector': testCall + ' > CallExpression',
        'message': 'Use filterDescribe instead of checkAndRun calls',
      },
    ],
    'no-whitespace-before-property': 'error',
    'nonblock-statement-body-position': ['error', 'below'],
    'operator-assignment': 'error',
    // }}}

    // "ECMAScript 6" rules: {{{
    'arrow-spacing': 'error',
    'no-useless-constructor': 'error',
    'prefer-arrow-callback': 'error',
    'prefer-const': ['error', {'ignoreReadBeforeAssign': true}],
    // }}}
  },
  'overrides': [
    {
      'rules': {
        'no-var': 'off',
      },
      'files': [
        // Closure requires using var in externs.
        'ui/externs/*.js',
        'externs/**/*.js',
        'test/test/externs/*.js',
        // Use var in load.js so it works in old browsers.  We'll use
        // compiled mode for the main library and the demo.
        'demo/load.js',
      ],
    },
    {
      'rules': {
        'prefer-rest-params': 'off',
      },
      'files': [
        // Test code should still use "arguments", since the alternate
        // "rest parameter" syntax won't work in uncompiled code on IE.
        'test/**/*.js',
        // These two files use "arguments" to patch over functions.  It
        // is difficult to reason about whether or not these instances
        // would always work with rest parameters, so just allow them to
        // use "arguments".
        'demo/log_section.js',
        'lib/debug/asserts.js',
      ],
    },
    {
      'files': ['externs/*', 'externs/shaka/*'],
      'rules': {
        // Disable rules on useless constructors so we can use ES6 classes in
        // externs.
        'no-useless-constructor': 'off',
      },
    },
  ],
};