.eslintrc.yml

env:
    es6: true
    node: true
    mocha: true

parserOptions:
    ecmaVersion: 8
    sourceType: script

rules:

    # Errors break builds and prevent tests from running, so on occasion,
    # warn is used to allow tests/builds to run during development,
    # even though it's an error.

    # Possible Errors
    no-await-in-loop: error
    no-compare-neg-zero: error
    no-cond-assign: error
    no-console: warn # debugging happens
    no-constant-condition: error
    no-control-regex: off # too edge to care
    no-debugger: warn # debugging happens
    no-dupe-args: error
    no-dupe-keys: error
    no-duplicate-case: error
    no-empty: error
    no-empty-character-class: error
    no-ex-assign: error
    no-extra-boolean-cast: error
    no-extra-parens:
        - error
        - all
        - conditionalAssign: false
          nestedBinaryExpressions: false
          ignoreJSX: multi-line
    no-extra-semi: error
    no-func-assign: error
    no-inner-declarations: off # excellent way to control scope/code-complexity
    no-invalid-regexp: error
    no-irregular-whitespace: error
    no-obj-calls: error
    no-prototype-builtins: warn # prototype-less objects are a thing
    no-regex-spaces: error
    no-sparse-arrays: off # fixed length arrays are a thing
    no-template-curly-in-string: error
    no-unexpected-multiline: error
    no-unreachable: error
    no-unsafe-finally: error
    no-unsafe-negation: error
    use-isnan: error
    valid-jsdoc: off # in favor of docco
    valid-typeof: error

    # Best Practices
    accessor-pairs: error
    array-callback-return: error
    block-scoped-var: error
    class-methods-use-this: warn # disable in file if intentional
    complexity: [ warn, 20 ]
    consistent-return: error
    curly: [ error, all ]
    default-case: off # do not always make sense (i.e. which switches return)
    dot-location: [ error, property ]
    dot-notation: error
    eqeqeq: error
    guard-for-in: warn # just be careful and disable in file if intentional
    no-alert: error
    no-caller: error
    no-case-declarations: error
    no-div-regex: off # don't care
    no-else-return: error
    no-empty-function: error
    no-empty-pattern: error # irrelevant since destructuring is disallowed
    no-eq-null: error
    no-eval: error
    no-extend-native: error
    no-extra-bind: error
    no-extra-label: error
    no-fallthrough: error # this just forces a comment explaining why
    no-floating-decimal: error
    no-global-assign: error
    no-implicit-coercion: error
    no-implicit-globals: error
    no-implied-eval: error
    no-invalid-this: off # flags too many legitimate uses
    no-iterator: error
    no-labels: error
    no-lone-blocks: error
    no-loop-func: error
    no-magic-numbers: off # flags too many legitimate uses
    no-multi-spaces: error
    no-multi-str: error
    no-new: error
    no-new-func: error
    no-new-wrappers: error # disable in file & explain if need a primitive ref
    no-octal: error
    no-octal-escape: error
    no-param-reassign: error
    no-proto: error
    no-redeclare: error
    no-restricted-properties: off # maybe use this in the future
    no-return-assign: off # useful in memoization & setters
    no-return-await: error
    no-script-url: error
    no-self-assign: error
    no-self-compare: error
    no-sequences: error
    no-throw-literal: error
    no-unmodified-loop-condition: error
    no-unused-expressions: off # prevents expression chaining
    no-unused-labels: error
    no-useless-call: error
    no-useless-concat: error
    no-useless-escape: error
    no-useless-return: error
    no-void: error
    no-warning-comments:
        - warn
        - terms:
              - 'todo'
              - 'fixme'
              - 'xxx'
          location: 'anywhere'
    no-with: error
    prefer-promise-reject-errors: error
    radix: off # irrelevant in IE9+
    require-await: error
    vars-on-top: off # makes it unclear where vars come from and their scope
    wrap-iife: [ error, outside ]
    yoda: off
        # - error
        # - never
        # - onlyEquality: true # would prefer inequality also

    # Strict Mode
    strict: off # implied

    # Variables
    init-declarations: off # init'ed and non-init'd are needed
    no-catch-shadow: error
    no-delete-var: error
    no-label-var: error
    no-restricted-globals: error
    no-shadow: error
    no-shadow-restricted-names: error
    no-undef: error
    no-undef-init: error
    no-undefined: off # ecmascript 3 is too old to be a consideration
    no-unused-vars:
        - warn # mid-development unused vars shouldn't block the build
        - args: none
    no-use-before-define: off # hoisting helps make code more self-documenting,
                              # and also creates a nice header/toc

    # Node.js and CommonJS
    callback-return: error
    global-require: off # pass into an iife at the bottom of the module
    handle-callback-err: error
    no-mixed-requires: error
    no-new-require: error
    no-path-concat: error
    no-process-env: error
    no-process-exit: error
    no-restricted-modules: off # maybe use this in the future
    no-sync: error

    # Stylistic Issues
    array-bracket-spacing: [ error, always ]
    block-spacing: error
    brace-style: error
    camelcase: off # use snake_case for benefit of non-native English speakers
    capitalized-comments: off # usually, but not always, so...
    comma-dangle:
        - error
        - arrays: always-multiline
          objects: always-multiline
          imports: always-multiline
          exports: always-multiline
          functions: always-multiline
    comma-spacing: [ error, { before: false , after: true } ]
    comma-style: [ error, last ]
    computed-property-spacing: off # would prefer "always" unless var/literal
    consistent-this: off # use `thisThing` where "Thing" is descriptive
    eol-last: [ error, always ]
    func-call-spacing: [ error, never ]
    func-name-matching: off # not useful
    func-names: error
    func-style:
        - error
        - declaration
        - allowArrowFunctions: false
    id-blacklist: off # maybe use this in the future
    id-length: off # legitimate 1 char & many char ids
    id-match: off # maybe use this in the future
    indent:
        - error
        - 4 # 2 is difficult for some eyes to read + 4 discourages deep nesting
        - SwitchCase: 1
    jsx-quotes: [ error, prefer-double ]
    key-spacing:
        - error
        - beforeColon: false
          afterColon: true
    keyword-spacing:
        - error
        - before: true
          after: true
    line-comment-position: off # both are useful
    linebreak-style: error
    lines-around-comment: off # too troublesome during development
    lines-around-directive:
        - error
        - before: never
          after: always
    max-depth: [ warn, { max: 4 } ]
    max-len: [ error, 80 ]
    max-lines: [ warn, 300 ]
    max-nested-callbacks: [ warn, 3 ]
    max-params: [ error, 3 ]
    max-statements: [ warn, 15, { ignoreTopLevelFunctions: true } ]
    max-statements-per-line: [ warn, { max: 1 } ]
    multiline-ternary: off # multiline is more readable than single line
    new-cap: off # coercion happens (e.g. Integer(number))
    new-parens: off # does not reduce clarity to omit
    newline-after-var: off # both make sense
    newline-before-return: off # does not increase clarity
    newline-per-chained-call: off  # let line length govern this
    no-array-constructor: error
    no-bitwise: warn # sometimes it's a good idea, disable in file if needed
    no-continue: error
    no-inline-comments: off # useful for short comments
    no-lonely-if: error
    no-mixed-operators: off
    no-mixed-spaces-and-tabs: error
    no-multi-assign: off # sometimes good to do
    no-multiple-empty-lines:
        - warn
        - max: 3
          maxBOF: 0
          maxEOF: 1
    no-negated-condition: off # sometimes it's clearer
    no-nested-ternary: off # nested ternary is super readable and useful
    no-new-object: error
    no-plusplus: off # obviously
    no-restricted-syntax: off # maybe use this in the future
    no-tabs: error
    no-ternary: off # obviously
    no-trailing-spaces: error
    no-underscore-dangle: off
    no-unneeded-ternary: error
    no-whitespace-before-property: error
    nonblock-statement-body-position: off # irrelevant cause curly is set to all
    object-curly-newline: off # unpredictable behavior
    object-curly-spacing: [ error, always ]
    object-property-newline: off # if object can fit on a 80-char line, all good
    one-var: [ error, never ]
    one-var-declaration-per-line: [ error, initializations ]
    operator-assignment: [ error, always ]
    operator-linebreak: [ error, before ]
    padded-blocks: [ error, never ]
    quote-props: [ error, as-needed ]
    quotes: [ error , single, { allowTemplateLiterals: true } ]
    require-jsdoc: off # in favor of docco
    semi: [ error, always ]
    semi-spacing: error
    sort-keys: off # allow logical sorting
    sort-vars: off # allow logical sorting
    space-before-blocks: error
    space-before-function-paren:
        - error
        - anonymous: always
          named: never
          asyncArrow: always
    space-in-parens: off # sometimes use 'em, sometimes don't
    space-infix-ops: error
    space-unary-ops: error
    spaced-comment: [ error, always, { markers: [ '/' ] } ]
    template-tag-spacing: [ error, always ]
    unicode-bom: [ error, never ]
    wrap-regex: off # /foo/.test('bar') is clearly not division

    # ECMAScript 6+
    # Many ES6 features center around cramming logic into as few characters
    # as possible on a single line, at the expense of readability and clarity.
    # Discourage/ban those features where possible.
    arrow-body-style: [ error, never ] # irrelevant cause func-style
    arrow-parens: error # irrelevant cause func-style
    arrow-spacing: error # irrelevant cause func-style
    constructor-super: off # invalid call check is good, but don't require it
    generator-star-spacing: [ error, { before: true, after: false } ]
    no-class-assign: error
    no-confusing-arrow: error # irrelevant cause func-style
    no-const-assign: error
    no-dupe-class-members: error
    no-duplicate-imports: error
    no-new-symbol: error
    no-restricted-imports: off # maybe use this in the future
    no-this-before-super: off # logic may need to be before and/or after super
    no-useless-computed-key: error
    no-useless-constructor: error
    no-useless-rename: error # irrelevant cause force node require/module.export
    no-var: error
    object-shorthand: [ error, always ]
    prefer-arrow-callback: off # irrelevant cause func-style
    prefer-const: error
    prefer-destructuring: off # reduces clarity, sometimes dramatically #fuckit
    prefer-numeric-literals: error
    prefer-rest-params: error # disallow arguments magic variable
    prefer-spread: error
    prefer-template: error
    require-yield: error
    rest-spread-spacing: error
    sort-imports: off # allow logical sorting
    symbol-description: error
    template-curly-spacing: [ error, always ]
    yield-star-spacing: [ error, before ]