.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

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 {{{
        "indent": "off",
        "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",
        "class-methods-use-this": "off",  // causes issues when implementing an interface
        "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
        "no-use-before-define": "off",  // Does not know when things are executed, false positives
        // }}}

        // "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-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",
            ],
        },
    ],
};