.eslintrc.json

{
  "root": true,
  "ignorePatterns": ["node_modules/*", "_locales/*", ".github/*", "addons-l10n/*", "libraries/thirdparty/*"],
  "parserOptions": {
    "sourceType": "module"
  },
  "env": {
    "es2020": true,
    "browser": true
  },
  "globals": {
    // Scratch Addons-defined
    "scratchAddons": "writable",
    "__scratchAddonsTraps": "writable",
    "__scratchAddonsRedux": "writable",
    "_realConsole": "writable",
    "__scratchAddonsTextColor": "writable",

    // Third Party-defined
    "Vue": "readonly",
    "SparkMD5": "readonly",
    "scratchblocks": "readonly",
    "tinycolor": "readonly",
    "Chart": "readonly",
    "Comlink": "readonly",
    "idb": "readonly",

    // Scratch-defined
    "Scratch": "readonly",
    "Blockly": "readonly",

    // Non-standard API
    "Clipboard": "readonly",
    "ClipboardItem": "readonly"
  },
  "extends": "eslint:recommended",
  "rules": {
    "no-prototype-builtins": 1,
    "no-template-curly-in-string": 2,
    "array-callback-return": 2,
    "default-case-last": 2,
    "eqeqeq": 2,
    "guard-for-in": 2,
    "no-empty": [2, { "allowEmptyCatch": true }],
    "no-caller": 2,
    "no-implied-eval": 2,
    "no-new-wrappers": 2,
    "no-proto": 2,
    "no-loss-of-precision": 2,
    "no-nonoctal-decimal-escape": 2,
    "no-unsafe-optional-chaining": 2,
    "no-useless-backreference": 2,
    "no-unused-vars": 0,
    "no-useless-escape": 0,
    "no-inner-declarations": 0,
    "no-constant-condition": [2, { "checkLoops": false }],
    "no-restricted-syntax": [
      2,
      {
        "selector": "MemberExpression[property.type=Identifier][property.name=path]:matches([object.name=e],[object.name=ev],[object.name=event])",
        "message": "Event.path is incompatible with Firefox, use Event.composedPath()"
      }
    ],
    "no-constant-binary-expression": 2
  },
  "overrides": [
    {
      "files": [
        "addon-api/background/*.js",
        "addon-api/popup/*.js",
        "addons/*/background.js",
        "background/**/*.js",
        "content-scripts/*.js",
        "libraries/common/*.js",
        "libraries/thirdparty/*.js",
        "popups/**/*.js",
        "webpages/**/*.js"
      ],
      "env": {
        "webextensions": true
      },
      "rules": {
        "no-eval": 2
      }
    },
    {
      "files": ["content-scripts/*.js"],
      "rules": {
        "no-restricted-syntax": [
          "error",
          {
            "selector": "ImportExpression",
            "message": "import() in content script is unsupported in Firefox, declare directly in manifest.json"
          },
          {
            "selector": "MemberExpression[property.type=Identifier][property.name=path]:matches([object.name=e],[object.name=ev],[object.name=event])",
            "message": "Event.path does not exist in Firefox, use Event.composedPath()"
          }
        ]
      }
    }
  ]
}