.eslintrc.js

/* eslint-env node */
module.exports = {
	root: true,
	env: {
		browser: true,
		greasemonkey: true,
		es2021: true,
	},
	parserOptions: {
		ecmaVersion: "latest",
	},
	extends: [
		"eslint:recommended",
		"plugin:@cspell/recommended",
		"plugin:security/recommended-legacy",

		// Display Prettier errors as ESLint errors.
		// Enables eslint-plugin-prettier and eslint-config-prettier.
		"plugin:prettier/recommended",

		//! Prettier should always be the last configuration in the extends array.
	],
	rules: {
		"no-unused-vars": ["error", { argsIgnorePattern: "^_" }], // Ignore variables whose names begin with an underscore.
	},
	overrides: [
		/*
		 * Userscript files.
		 */
		{
			files: ["*.user.js"],
			extends: ["plugin:userscripts/recommended"],
			rules: {
				"userscripts/better-use-match": "off", // Disable this warning for now.
			},
			settings: {
				userscriptVersions: {
					tampermonkey: ">=4",
					violentmonkey: ">=2",
					greasemonkey: "*",
				},
			},
		},

		/*
		 * JSON files.
		 */
		{
			files: ["*.json"],
			extends: [
				"plugin:json/recommended-with-comments",

				// Display Prettier errors as ESLint errors.
				// Enables eslint-plugin-prettier and eslint-config-prettier.
				"plugin:prettier/recommended",

				//! Prettier should always be the last configuration in the extends array.
			],
		},

		/*
		 * `package.json` file.
		 * This needs it's own configuration, because it doesn't work together with `plugin:json`.
		 * See https://github.com/kellyselden/eslint-plugin-json-files/issues/40
		 * Must be after `*.json`.
		 */
		{
			files: ["package.json"],
			plugins: ["json-files"],
			extends: [
				// Display Prettier errors as ESLint errors.
				// Enables eslint-plugin-prettier and eslint-config-prettier.
				"plugin:prettier/recommended",

				//! Prettier should always be the last configuration in the extends array.
			],
			rules: {
				"json-files/ensure-repository-directory": "error",
				"json-files/no-branch-in-dependencies": "error",
				"json-files/require-engines": "error",
				"json-files/require-license": "error",
				"json-files/require-unique-dependency-names": "error",
				"json-files/sort-package-json": "error",
			},
		},

		/*
		 * Markdown files.
		 */
		{
			files: ["*.md"],
			parser: "eslint-plugin-markdownlint/parser",
			extends: [
				"plugin:markdownlint/recommended",

				// Display Prettier errors as ESLint errors.
				// Enables eslint-plugin-prettier and eslint-config-prettier.
				"plugin:prettier/recommended",

				//! Prettier should always be the last configuration in the extends array.
			],
			rules: {
				"markdownlint/md007": [
					"error",
					{
						indent: 4,
					},
				], // For compatibility with Prettier. See https://github.com/DavidAnson/markdownlint/blob/main/doc/Prettier.md
				"markdownlint/md030": [
					"error",
					{
						ol_multi: 3,
						ol_single: 3,
						ul_multi: 3,
						ul_single: 3,
					},
				], // For compatibility with Prettier. See https://github.com/DavidAnson/markdownlint/blob/main/doc/Prettier.md
				"markdownlint/md013": "off", // Disable line length.
				"markdownlint/md033": [
					"error",
					{ allowed_elements: ["br", "sup", "kbd"] },
				],
				"prettier/prettier": ["error", { parser: "markdown" }],
			},
		},
	],
};