Add eslint plus very tolerant starting config (#4872)

* Add eslint plus very tolerant starting config

Addresses GH #1865

This adds eslint as a developer dependency, plus a generated eslint
config that doesn't take a very strong stance on much of anything.  The
goal here to get started using automated style checking, add eslint
checking to the testing flow, and gradually introduce stricter checks
over time.

* eslint: Fix ecmaVersion

See
https://github.com/Jermolene/TiddlyWiki5/pull/4421#issuecomment-587002325,
where @Jermolene declared TiddlyWiki targets EcmaScript 5

.eslintignore

@@ -0,0 +1,15 @@
+# Known minified files
+/boot/sjcl.js
+/core/modules/utils/base64-utf8/base64-utf8.module.min.js
+/core/modules/utils/diff-match-patch/diff_match_patch.js
+/plugins/tiddlywiki/async/files/async.min.v1.5.0.js
+/plugins/tiddlywiki/codemirror-autocomplete/files/addon/hint/anyword-hint.js
+/plugins/tiddlywiki/codemirror-autocomplete/files/addon/hint/css-hint.js
+/plugins/tiddlywiki/codemirror-autocomplete/files/addon/hint/html-hint.js
+/plugins/tiddlywiki/codemirror-autocomplete/files/addon/hint/javascript-hint.js
+/plugins/tiddlywiki/codemirror-autocomplete/files/addon/hint/show-hint.js
+/plugins/tiddlywiki/codemirror-autocomplete/files/addon/hint/xml-hint.js
+/plugins/tiddlywiki/codemirror-closebrackets/files/addon/edit/closebrackets.js
+/plugins/tiddlywiki/codemirror-closebrackets/files/addon/edit/matchbrackets.js
+/plugins/tiddlywiki/codemirror-closetag/files/addon/edit/closetag.js
+/plugins/tiddlywiki/codemirror-closetag/files/addon/fold/xml-fold.js

.eslintrc.yml

@@ -0,0 +1,267 @@
+env:
+  browser: true
+  commonjs: true
+  es2021: true
+  node: true
+extends: 'eslint:recommended'
+globals:
+  "$tw": "writable" # temporary
+parserOptions:
+  ecmaVersion: 5
+rules:
+  array-bracket-newline: 'off'
+  array-bracket-spacing: 'off'
+  array-callback-return: 'off'
+  array-element-newline: 'off'
+  arrow-body-style: error
+  arrow-parens:
+    - error
+    - as-needed
+  arrow-spacing:
+    - error
+    - after: true
+      before: true
+  block-scoped-var: 'off'
+  block-spacing: 'off'
+  brace-style: 'off'
+  callback-return: 'off'
+  camelcase: 'off'
+  capitalized-comments: 'off'
+  class-methods-use-this: error
+  comma-dangle: 'off'
+  comma-spacing: 'off'
+  comma-style: 'off'
+  complexity: 'off'
+  computed-property-spacing: 'off'
+  consistent-return: 'off'
+  consistent-this: 'off'
+  curly: 'off'
+  default-case: 'off'
+  default-case-last: error
+  default-param-last: error
+  dot-location: 'off'
+  dot-notation: 'off'
+  eol-last: 'off'
+  eqeqeq: 'off'
+  func-call-spacing: 'off'
+  func-name-matching: 'off'
+  func-names: 'off'
+  func-style: 'off'
+  function-call-argument-newline: 'off'
+  function-paren-newline: 'off'
+  generator-star-spacing: error
+  global-require: 'off'
+  grouped-accessor-pairs: error
+  guard-for-in: 'off'
+  handle-callback-err: 'off'
+  id-blacklist: error
+  id-denylist: error
+  id-length: 'off'
+  id-match: error
+  implicit-arrow-linebreak: error
+  indent: 'off'
+  indent-legacy: 'off'
+  init-declarations: 'off'
+  jsx-quotes: error
+  key-spacing: 'off'
+  keyword-spacing: 'off'
+  line-comment-position: 'off'
+  linebreak-style: 'off'
+  lines-around-comment: 'off'
+  lines-around-directive: 'off'
+  lines-between-class-members: error
+  max-classes-per-file: error
+  max-depth: 'off'
+  max-len: 'off'
+  max-lines: 'off'
+  max-lines-per-function: 'off'
+  max-nested-callbacks: error
+  max-params: 'off'
+  max-statements: 'off'
+  max-statements-per-line: 'off'
+  multiline-comment-style: 'off'
+  multiline-ternary: 'off'
+  new-parens: 'off'
+  newline-after-var: 'off'
+  newline-before-return: 'off'
+  newline-per-chained-call: 'off'
+  no-alert: 'off'
+  no-array-constructor: 'off'
+  no-await-in-loop: error
+  no-bitwise: 'off'
+  no-buffer-constructor: 'off'
+  no-caller: error
+  no-catch-shadow: 'off'
+  no-confusing-arrow: error
+  no-console: 'off'
+  no-constant-condition:
+    - error
+    - checkLoops: false
+  no-constructor-return: error
+  no-continue: 'off'
+  no-div-regex: 'off'
+  no-duplicate-imports: error
+  no-else-return: 'off'
+  no-empty-function: 'off'
+  no-eq-null: 'off'
+  no-eval: 'off'
+  no-extend-native: 'off'
+  no-extra-bind: 'off'
+  no-extra-label: 'off'
+  no-extra-parens: 'off'
+  no-floating-decimal: 'off'
+  no-implicit-coercion:
+    - error
+    - boolean: false
+      number: false
+      string: false
+  no-implicit-globals: 'off'
+  no-implied-eval: error
+  no-inline-comments: 'off'
+  no-invalid-this: 'off'
+  no-iterator: error
+  no-label-var: 'off'
+  no-labels: 'off'
+  no-lone-blocks: 'off'
+  no-lonely-if: 'off'
+  no-loop-func: 'off'
+  no-loss-of-precision: error
+  no-magic-numbers: 'off'
+  no-mixed-operators: 'off'
+  no-mixed-requires: 'off'
+  no-multi-assign: 'off'
+  no-multi-spaces: 'off'
+  no-multi-str: error
+  no-multiple-empty-lines: 'off'
+  no-native-reassign: 'off'
+  no-negated-condition: 'off'
+  no-negated-in-lhs: error
+  no-nested-ternary: 'off'
+  no-new: 'off'
+  no-new-func: 'off'
+  no-new-object: 'off'
+  no-new-require: error
+  no-new-wrappers: error
+  no-octal-escape: error
+  no-param-reassign: 'off'
+  no-path-concat: error
+  no-plusplus: 'off'
+  no-process-env: 'off'
+  no-process-exit: 'off'
+  no-promise-executor-return: error
+  no-proto: 'off'
+  no-restricted-exports: error
+  no-restricted-globals: error
+  no-restricted-imports: error
+  no-restricted-modules: error
+  no-restricted-properties: error
+  no-restricted-syntax: error
+  no-return-assign: 'off'
+  no-return-await: error
+  no-script-url: 'off'
+  no-self-compare: 'off'
+  no-sequences: 'off'
+  no-shadow: 'off'
+  no-spaced-func: 'off'
+  no-sync: 'off'
+  no-tabs: 'off'
+  no-template-curly-in-string: error
+  no-ternary: 'off'
+  no-throw-literal: 'off'
+  no-trailing-spaces: 'off'
+  no-undef-init: 'off'
+  no-undefined: 'off'
+  no-underscore-dangle: 'off'
+  no-unmodified-loop-condition: 'off'
+  no-unneeded-ternary: 'off'
+  no-unreachable-loop: error
+  no-unused-expressions: 'off'
+  no-use-before-define: 'off'
+  no-useless-backreference: error
+  no-useless-call: 'off'
+  no-useless-computed-key: error
+  no-useless-concat: 'off'
+  no-useless-constructor: error
+  no-useless-rename: error
+  no-useless-return: 'off'
+  no-var: 'off'
+  no-void: 'off'
+  no-warning-comments: 'off'
+  no-whitespace-before-property: error
+  nonblock-statement-body-position:
+    - error
+    - any
+  object-curly-newline: 'off'
+  object-curly-spacing: 'off'
+  object-property-newline: 'off'
+  object-shorthand: 'off'
+  one-var: 'off'
+  one-var-declaration-per-line: 'off'
+  operator-assignment: 'off'
+  operator-linebreak: 'off'
+  padded-blocks: 'off'
+  padding-line-between-statements: error
+  prefer-arrow-callback: 'off'
+  prefer-const: 'off'
+  prefer-destructuring: 'off'
+  prefer-exponentiation-operator: 'off'
+  prefer-named-capture-group: 'off'
+  prefer-numeric-literals: error
+  prefer-object-spread: 'off'
+  prefer-promise-reject-errors: error
+  prefer-reflect: 'off'
+  prefer-regex-literals: 'off'
+  prefer-rest-params: 'off'
+  prefer-spread: 'off'
+  prefer-template: 'off'
+  quote-props: 'off'
+  quotes: 'off'
+  radix: 'off'
+  require-atomic-updates: error
+  require-await: error
+  require-jsdoc: 'off'
+  require-unicode-regexp: 'off'
+  rest-spread-spacing: error
+  semi: 'off'
+  semi-spacing: 'off'
+  semi-style: 'off'
+  sort-imports: error
+  sort-keys: 'off'
+  sort-vars: 'off'
+  space-before-blocks: 'off'
+  space-before-function-paren: 'off'
+  space-in-parens: 'off'
+  space-infix-ops: 'off'
+  space-unary-ops: 'off'
+  spaced-comment: 'off'
+  strict: 'off'
+  switch-colon-spacing: 'off'
+  symbol-description: error
+  template-curly-spacing: error
+  template-tag-spacing: error
+  unicode-bom:
+    - error
+    - never
+  valid-jsdoc: 'off'
+  valid-typeof:
+    - error
+    - requireStringLiterals: false
+  vars-on-top: 'off'
+  wrap-iife: 'off'
+  wrap-regex: 'off'
+  yield-star-spacing: error
+  yoda: 'off'
+
+  # temporary rules
+  no-useless-escape: 'off'
+  no-unused-vars: 'off'
+  no-empty: 'off'
+  no-extra-semi: 'off'
+  no-redeclare: 'off'
+  no-control-regex: "off"
+  no-mixed-spaces-and-tabs: "off"
+  no-extra-boolean-cast: "off"
+  no-prototype-builtins: "off"
+  no-undef: "off"
+  no-unreachable: "off"
+  no-self-assign: "off"

package.json

@@ -24,7 +24,9 @@
     "wiki"
   ],
   "dependencies": {},
-  "devDependencies": {},
+  "devDependencies": {
+    "eslint": "^7.10.0"
+  },
   "bundleDependencies": [],
   "license": "BSD",
   "engines": {