.eslintrc.js

// 2016 March 20
// https://github.com/bevry/base
// http://eslint.org
// This code must be able to run on Node 0.10
/* eslint no-warning-comments: 0 */
var IGNORE = 0, WARN = 1, ERROR = 2, MAX_PARAMS = 4

var config = {
  extends: ['eslint:recommended'],
  plugins: [],
  parserOptions: {
    sourceType: 'module',
    ecmaVersion: 6,
    ecmaFeatures: {
      jsx: true
    }
  },
  env: {
    browser: true,
    node: true,
    es6: true,
    commonjs: true,
    amd: true
  },
  rules: {
    // ----------------------------
    // Problems with these rules
    // If we can figure out how to enable the following, that would be great

    // Two spaces after one line if or else:
    // if ( blah )  return
    // Insead of one space:
    // if ( blah ) return

    // No spaces on embedded function:
    // .forEach(function(key, value){
    // instead of:
    // .forEach(function (key, value) {

    // Else and catch statements on the same line as closing brace:
    // } else {
    // } catch (e) {
    // instead of:
    // }
    // else {


    // --------------------------------------
    // Possible Errors
    // The following rules point out areas where you might have made mistakes.

    // ES6 supports dangling commas
    'comma-dangle': IGNORE,

    // Don't allow assignments in conditional statements (if, while, etc.)
    'no-cond-assign': [ERROR, 'always'],

    // Warn but don't error about console statements
    'no-console': WARN,

    // Allow while(true) loops
    'no-constant-condition': IGNORE,

    // Seems like a good idea to error about this
    'no-control-regex': ERROR,

    // Warn but don't error about console statements
    'no-debugger': WARN,

    // Don't allow duplicate arguments in a function, they can cause errors
    'no-dupe-args': ERROR,

    // Disallow duplicate keys in an object, they can cause errors
    'no-dupe-keys': ERROR,

    // Disallow duplicate case statements in a switch
    'no-duplicate-case': ERROR,

    // Allow empty block statements, they are useful for clarity
    'no-empty': IGNORE,

    // Disallow empty [] in regular expressions as they cause unexpected behaviour
    'no-empty-character-class': ERROR,

    // Overwriting the exception argument in a catch statement can cause memory leaks in some browsers
    'no-ex-assign': ERROR,

    // Disallow superflous boolean casts, they offer no value
    'no-extra-boolean-cast': ERROR,

    // Allow superflous parenthesis as they offer clarity in some cases
    'no-extra-parens': IGNORE,

    // Disallow superflous semicolons, they offer no value
    'no-extra-semi': IGNORE,

    // Seems like a good idea to error about this
    'no-func-assign': ERROR,

    // Seems like a good idea to error about this
    'no-inner-declarations': ERROR,

    // Seems like a good idea to error about this
    'no-invalid-regexp': ERROR,

    // Seems like a good idea to error about this
    'no-irregular-whitespace': ERROR,

    // Seems like a good idea to error about this
    'no-negated-in-lhs': ERROR,

    // Seems like a good idea to error about this
    'no-obj-calls': ERROR,

    // Seems like a good idea to error about this
    // Instead of /  /  used / {ERROR}/ instead
    'no-regex-spaces': ERROR,

    // Seems like a good idea to error about this
    'no-sparse-arrays': ERROR,

    // Seems like a good idea to error about this
    'no-unexpected-multiline': ERROR,

    // Seems like a good idea to error about this
    'no-unreachable': ERROR,

    // Seems like a good idea to error about this
    'use-isnan': ERROR,

    // We use JSDoc again
    'valid-jsdoc': [ERROR, {
      "requireParamDescription": false,
      "requireReturnDescription": false
    }],

    // Seems like a good idea to error about this
    'valid-typeof': ERROR,


    // --------------------------------------
    // Best Practices
    // These are rules designed to prevent you from making mistakes. They either prescribe a better way of doing something or help you avoid footguns.

    // Meh
    // Enforces getter/setter pairs in objects
    'accessor-pairs': IGNORE,

    // Seems sensible
    // Enforces return statements in callbacks of array's methods
    'array-callback-return': ERROR,

    // This rule seems buggy
    'block-scoped-var': IGNORE,

    // Disable complexity checks, they are annoying and not that useful in detecting actual complexity
    'complexity': IGNORE,

    // We use blank returns for break statements
    'consistent-return': IGNORE,

    // Always require curly braces unless the statement is all on a single line
    'curly': [ERROR, 'multi-line'],

    // If we don't have a default cause, it probably means we should throw an error
    'default-case': ERROR,

    // Dots should be on the newlines
    // chainableThingy
    //   .doSomething()
    //   .doSomethingElse()
    'dot-location': [ERROR, 'property'],

    // Use dot notation where possible
    'dot-notation': ERROR,

    // Unless you are doing == null, then force === to avoid truthy/falsey mistakes
    'eqeqeq': [ERROR, 'allow-null'],

    // Always use hasOwnProperty when doing for in
    'guard-for-in': ERROR,

    // Warn about alert statements in our code
    // Use one of the suggested alternatives instead
    // Reasoning is they could be mistaken for left over debugging statements
    'no-alert': WARN,

    // They are very slow
    'no-caller': ERROR,

    // Wow...
    'no-case-declarations': ERROR,

    // Seems like a good idea to error about this
    'no-div-regex': ERROR,

    // Returns in else statements offer code clarity, so disable this rule
    'no-else-return': IGNORE,

    // Up to developer sensibility
    // disallow use of empty functions
    'no-empty-function': IGNORE,

    // Seems sensible
    'no-labels': ERROR,

    // Seems sensible
    'no-empty-pattern': ERROR,

    // We know that == null is a null and undefined check
    'no-eq-null': IGNORE,

    // Eval is slow and unsafe, use vm's instead
    'no-eval': ERROR,

    // There is never a good reason for this
    'no-extend-native': ERROR,

    // Don't allow useless binds
    'no-extra-bind': ERROR,

    // Seems sensible
    'no-extra-label': ERROR,

    // Don't allow switch case statements to follow through, use continue keyword instead
    'no-fallthrough': ERROR,

    // Use zero when doing decimals, otherwise it is confusing
    'no-floating-decimal': ERROR,

    // Cleverness is unclear
    'no-implicit-coercion': ERROR,

    // Seems sensible providing detection works correctly
    'no-implicit-globals': ERROR,

    // A sneaky way to do evals
    'no-implied-eval': ERROR,

    // This throws for a lot of senseless things, like chainy functions
    'no-invalid-this': IGNORE,

    // Use proper iterators instead
    'no-iterator': ERROR,

    // We never use this, it seems silly to allow this
    'no-labels': ERROR,

    // We never use this, it seems silly to allow this
    'no-lone-blocks': ERROR,

    // Loop functions always cause problems, as the scope isn't clear through iterations
    'no-loop-func': ERROR,

    // Far too annoying
    'no-magic-numbers': IGNORE,

    // We like multi spaces for clarity
    // E.g. We like
    // if ( blah )  return foo
    // Instead of:
    // if ( blah ) return foo
    // @TODO would be great to enforce the above
    'no-multi-spaces': IGNORE,

    // Use ES6 template strings instead
    'no-multi-str': ERROR,

    // Would be silly to allow this
    'no-native-reassign': ERROR,

    // We never use this, it seems silly to allow this
    'no-new-func': ERROR,

    // We never use this, it seems silly to allow this
    'no-new-wrappers': ERROR,

    // We never use this, it seems silly to allow this
    'no-new': ERROR,

    // We never use this, it seems silly to allow this
    'no-octal-escape': ERROR,

    // We never use this, it seems silly to allow this
    'no-octal': ERROR,

    // We got to be pretty silly if we don't realise we are doing this
    // As such, take any usage as intentional and aware
    'no-param-reassign': IGNORE,

    // We use process.env wisely
    'no-process-env': IGNORE,

    // We never use this, it seems silly to allow this
    'no-proto': ERROR,

    // We never use this, it seems silly to allow this
    'no-redeclare': ERROR,

    // We never use this, it seems silly to allow this
    'no-return-assign': ERROR,

    // We never use this, it seems silly to allow this
    'no-script-url': ERROR,

    // Seems sensible
    'no-self-assign': ERROR,

    // We never use this, it seems silly to allow this
    'no-self-compare': ERROR,

    // We never use this, it seems silly to allow this
    'no-sequences': ERROR,

    // We always want proper error objects as they have stack traces and respond to instanceof Error checks
    'no-throw-literal': ERROR,

    // Could be a getter, so warn
    'no-unmodified-loop-condition': WARN,

    // We never use this, it seems silly to allow this
    'no-unused-expressions': ERROR,

    // Seems sensible
    'no-unused-labels': ERROR,

    // Seems sensible
    'no-useless-call': ERROR,

    // Seems sensible
    'no-useless-concat': ERROR,

    // We never use this, it seems silly to allow this
    'no-void': ERROR,

    // Warn about todos
    'no-warning-comments': [WARN, { terms: ['todo', 'fixme'], location: 'anywhere' }],

    // We never use this, it seems silly to allow this
    'no-with': ERROR,

    // Always specify a radix to avoid errors
    'radix': ERROR,

    // We appreciate the clarity late defines offer
    'vars-on-top': IGNORE,

    // Wrap instant called functions in parenthesis for clearer intent
    'wrap-iife': ERROR,

    // Because we force === and never allow assignments in conditions
    // we have no need for yoda statements, so disable them
    'yoda': [ERROR, 'never'],


    // --------------------------------------
    // Strict Mode
    // These rules relate to using strict mode.

    // Ensure that use strict is specified to prevent the runtime erorr:
    // SyntaxError: Block-scoped declarations (let, const, function, class) not yet supported outside strict mode
    'strict': [ERROR, 'global'],


    // --------------------------------------
    // Variables
    // These rules have to do with variable declarations.

    // We don't care
    'init-declaration': IGNORE,

    // Don't allow the catch method to shadow objects as browsers handle this differently
    // Update: We don't care for IE8
    'no-catch-shadow': IGNORE,

    // Don't use delete, it disables optimisations
    'no-delete-var': ERROR,

    // We never use this, it seems silly to allow this
    'no-label-var': ERROR,

    // We never use this, it seems silly to allow this
    'no-shadow-restricted-names': ERROR,

    // We use shadowing
    'no-shadow': IGNORE,

    // Makes sense
    'no-undef-init': ERROR,

    // Error when an undefined variable is used
    'no-undef': ERROR,

    // typeof blah === 'undefined' should always be used
    'no-undefined': ERROR,

    // Warn us when we don't use something
    'no-unused-vars': WARN,

    // Error when we try and use something before it is defined
    'no-use-before-define': ERROR,


    // --------------------------------------
    // Node.js and CommonJS
    // These rules are specific to JavaScript running on Node.js or using CommonJS in the browser.

    // Seems to difficult to enforce
    'callback-return': IGNORE,

    // We use require where it is appropriate to use it
    'global-require': IGNORE,

    // Force handling of callback errors
    'handle-callback-err': ERROR,

    // @TODO decide if this is good or not
    'no-mixed-requires': ERROR,

    // Disallow error prone syntax
    'no-new-require': ERROR,

    // Always use path.join for windows support
    'no-path-concat': ERROR,

    // We know what we are doing
    'no-process-exit': IGNORE,

    // No need to disallow any imports
    'no-restricted-imports': IGNORE,

    // No need to disallow any modules
    'no-restricted-modules': IGNORE,

    // Sometimes sync methods are useful, so warn but don't error
    'no-sync': WARN,


    // --------------------------------------
    // Stylistic
    // These rules are purely matters of style and are quite subjective.

    // We don't use spaces with brackets
    'array-bracket-spacing': [ERROR, 'never'],

    // Disallow or enforce spaces inside of single line blocks
    'block-spacing': [ERROR, 'always'],

    // Opening brace on same line, closing brace on its own line, except when statement is a single line
    'brace-style': [ERROR, 'stroustrup', { allowSingleLine: true }],

    // Use camel case
    'camelcase': ERROR,

    // Require a comma after always
    'comma-spacing': [ERROR, { before: false, after: true }],

    // Commas go last, we have tooling to detect if we forget a comma
    'comma-style': [ERROR, 'last'],

    // Require or disallow padding inside computed properties
    'computed-property-spacing': [ERROR, 'never'],

    // Enabling this was incredibly annoying when doing layers of nesting
    'consistent-this': IGNORE,

    // Enable to make UNIX people's lives easier
    'eol-last': ERROR,

    // We like anonymous functions
    'func-names': IGNORE,

    // Prefer to define functions via variables
    'func-style': [WARN, 'declaration'],

    // Nothing we want to blacklist
    // blacklist certain identifiers to prevent them being used
    'id-blacklist': IGNORE,

    // Sometimes short names are appropriate
    'id-length': IGNORE,

    // Camel case handles this for us
    'id-match': IGNORE,

    // Use tabs and indent case blocks
    // 'indent': [ERROR, 'tab', { SwitchCase: WARN }],
    // ^ broken

    // Prefer double qoutes for JSX properties: <a b="c" />, <a b='"' />
    'jsx-quotes': [ERROR, 'prefer-double'],

    // Space after the colon
    'key-spacing': [ERROR, {
      beforeColon: false,
      afterColon: true
    }],

    // Always force a space before and after a keyword
    'keyword-spacing': [ERROR],

    // Enforce unix line breaks
    'linebreak-style': [ERROR, 'unix'],

    // Enforce new lines before block comments
    'lines-around-comment': [ERROR, { beforeBlockComment: true, allowBlockStart: true }],

    // Disabled to ensure consistency with complexity option
    'max-depth': IGNORE,

    // We use soft wrap
    'max-len': IGNORE,

    // We are smart enough to know if this is bad or not
    'max-nested-callbacks': IGNORE,

    // Sometimes we have no control over this for compat reasons, so just warn
    'max-params': [WARN, MAX_PARAMS],

    // We should be able to use whatever feels right
    'max-statements': IGNORE,

    // Constructors should be CamelCase
    'new-cap': ERROR,

    // Always use parens when instantiating a class
    'new-parens': ERROR,

    // Too difficult to enforce correctly as too many edge-cases
    // require or disallow an empty newline after variable declarations
    'newline-after-var': IGNORE,

    // Let the author decide
    // enforce newline after each call when chaining the calls
    'newline-per-chained-call': IGNORE,

    // Don't use the array constructor when it is not needed
    'no-array-constructor': ERROR,

    // We never use bitwise, they are too clever
    'no-bitwise': ERROR,

    // We use continue
    'no-continue': IGNORE,

    // We like inline comments
    'no-inline-comments': IGNORE,

    // The code could be optimised if this error occurs
    'no-lonely-if': ERROR,

    // Don't mix spaces and tabs
    // @TODO maybe [ERROR, 'smart-tabs'] will be better, we will see
    'no-mixed-spaces-and-tabs': ERROR,

    // We use multiple empty lines for styling
    'no-multiple-empty-lines': IGNORE,

    // Sometimes it is more understandable with a negated condition
    'no-negated-condition': IGNORE,

    // Sometimes these are useful
    'no-nested-ternary': IGNORE,

    // Use {} instead of new Object()
    'no-new-object': ERROR,

    // We use plus plus
    'no-plusplus': IGNORE,

    // Handled by other rules
    'no-restricted-syntax': IGNORE,

    // We never use this, it seems silly to allow this
    'no-spaced-func': ERROR,

    // Sometimes ternaries are useful
    'no-ternary': IGNORE,

    // Disallow trailing spaces
    'no-trailing-spaces': ERROR,

    // Sometimes this is useful when avoiding shadowing
    'no-underscore-dangle': IGNORE,

    // Sensible
    'no-unneeded-ternary': ERROR,

    // Seems sensible
    'no-whitespace-before-property': ERROR,

    // Desirable, but too many edge cases it turns out where it is actually preferred
    'object-curly-spacing': IGNORE,

    // We like multiple var statements
    'one-var': IGNORE,
    'one-var-declaration-per-line': IGNORE,

    // Force use of shorthands when available
    'operator-assignment': [ERROR, 'always'],

    // Should be before, but not with =, *=, /=, += lines
    // @TODO figure out how to enforce
    'operator-linebreak': IGNORE,

    // This rule doesn't appear to work correclty
    'padded-blocks': IGNORE,

    // Seems like a good idea to error about this
    // 'quote-props': [ERROR, 'consistent-as-needed'],
    // ^ broken

    // Use single quotes where escaping isn't needed
    'quotes': [ERROR, 'single', 'avoid-escape'],

    // We use YUIdoc
    'require-jsdoc': IGNORE,

    // If semi's are used, then add spacing after
    'semi-spacing': [ERROR, { before: false, after: true }],

    // Up to dev
    'sort-imports': IGNORE,

    // Never use semicolons
    'semi': [ERROR, 'always'],

    // We don't care if our vars are alphabetical
    'sort-vars': IGNORE,

    // Always force a space before a {
    'space-before-blocks': [ERROR, 'always'],

    // function () {, get blah () {
    'space-before-function-paren': [ERROR, 'always'],

    // This is for spacing between [], so [ WARN, ERROR, 3 ] which we don't want
    'space-in-brackets': IGNORE,

    // This is for spacing between (), so doSomething( WARN, ERROR, 3 ) or if ( WARN === 3 )
    // which we want for ifs, but don't want for calls
    'space-in-parens': IGNORE,

    // We use this
    'space-infix-ops': ERROR,

    // We use this
    'space-unary-ops': ERROR,

    // We use this
    // 'spaced-line-comment': ERROR,
    'spaced-comment': ERROR,

    // We use this
    // @TODO revise this
    'wrap-regex': ERROR,


    // --------------------------------------
    // ECMAScript 6

    // Sensible to create more informed and clear code
    'arrow-body-style': [ERROR, 'as-needed'],

    // We do this, no reason why, just what we do
    'arrow-parens': [ERROR, 'always'],

    // Require consistent spacing for arrow functions
    'arrow-spacing': ERROR,

    // Makes sense as otherwise runtime error will occur
    'constructor-super': ERROR,

    // Seems the most consistent location for it
    'generator-star-spacing': [ERROR, 'before'],

    // Seems sensible
    'no-confusing-arrow': ERROR,

    // Sometimes useful for debugging
    'no-constant-condition': WARN,

    // Seems sensible
    'no-class-assign': ERROR,

    // Our developers should know the difference
    // disallow arrow functions where they could be confused with comparisons
    'no-confusing-arrow': IGNORE,

    // Makes sense as otherwise runtime error will occur
    'no-const-assign': ERROR,

    // Makes sense as otherwise runtime error will occur
    'no-dupe-class-members': ERROR,

    // Seems sensible
    'no-new-symbol': ERROR,

    // Makes sense as otherwise runtime error will occur
    'no-this-before-super': ERROR,

    // Seems sensible
    'no-useless-constructor': ERROR,

    // @TODO This probably should be an error
    // however it is useful for: for ( var key in obj ) {
    // which hopefully is more performant than let (@TODO check if it actually is more performant)
    'no-var': WARN,

    // Enforce ES6 object shorthand
    'object-shorthand': ERROR,

    // Better performance when running native
    // but horrible performance if not running native as could fallback to bind
    // https://travis-ci.org/bevry/es6-benchmarks
    'prefer-arrow-callback': IGNORE,

    // Sure, why not
    'prefer-const': WARN,

    // Controversial change, but makes sense to move towards to reduce the risk of bad people overwriting apply and call
    // https://github.com/eslint/eslint/issues/ERROR939
    // Ignoring because node does not yet support it, so we don't want to get the performance hit of using the compiled ES5 version
    'prefer-reflect': IGNORE,

    // Makes sense to enforce, exceptions should be opted out of on case by case
    'prefer-rest-params': ERROR,

    // Sure, why not
    'prefer-spread': ERROR,

    // Too annoying to enforce
    'prefer-template': IGNORE,

    // Makes sense
    'require-yield': ERROR,

    // Makes sense
    'template-curly-spacing': [ERROR, 'never'],

    // Our preference
    'yield-star-spacing': [ERROR, 'both'],


    // --------------------------------------
    // Plugins

    // Not sure why, but okay
      'no-await-in-loop': WARN,
      'flow-vars/define-flow-type': WARN,
      'flow-vars/use-flow-type': WARN
  }
}

// ------------------------------------
// Enhancements

var package = require('./package.json')

if ( 'babel-eslint' in package.devDependencies ) {
  config.parser = 'babel-eslint'
}

if ( 'eslint-plugin-react' in package.devDependencies ) {
  config.extends.push('plugin:react/recommended')
  config.plugins.push('react')
}

if ( 'eslint-plugin-babel' in package.devDependencies ) {
  config.plugins.push('babel')
  var replacements = [
    'new-cap',
    'object-curly-spacing'
  ]
  replacements.forEach(function (key) {
    if ( key in config.rules ) {
      config.rules['babel/' + key] = config.rules[key]
      config.rules[key] = IGNORE
    }
  })
}
else {
  Object.keys(config.rules).forEach(function (key) {
    if ( key.indexOf('babel/') === 0 ) {
      delete config.rules[key]
    }
  })
}

if ( 'eslint-plugin-flow-vars' in package.devDependencies ) {
  config.plugins.push('flow-vars')
}
else {
  Object.keys(config.rules).forEach(function (key) {
    if ( key.indexOf('flow-vars/') === 0 ) {
      delete config.rules[key]
    }
  })
}


// ------------------------------------
// Export

module.exports = config