refactor: extract shared ESLint config and add lint scripts

config/eslint/base.cjs

@@ -0,0 +1,31 @@
+module.exports = {
+    'parser': '@typescript-eslint/parser',
+    'parserOptions': {
+        'ecmaVersion': 2022,
+        'sourceType': 'module'
+    },
+    'plugins': ['@typescript-eslint'],
+    'extends': [
+        'eslint:recommended'
+    ],
+    'env': {
+        'browser': true,
+        'node': true,
+        'mocha': true
+    },
+    'rules': {
+        'indent': ['error', 4, { 'SwitchCase': 1 }],
+        'no-empty': ['error', { 'allowEmptyCatch': true }],
+        'quotes': ['error', 'single', { 'avoidEscape': true }],
+        /**
+         * The codebase uses some while(true) statements.
+         * Refactor to remove this rule.
+         */
+        'no-constant-condition': 0,
+        /**
+         * Less combines assignments with conditionals sometimes
+         */
+        'no-cond-assign': 0,
+        'no-multiple-empty-lines': 'error'
+    }
+};

package.json

@@ -5,6 +5,8 @@
 	"description": "Less monorepo",
 	"homepage": "http://lesscss.org",
 	"scripts": {
+		"lint": "eslint packages/less --ext .js,.ts",
+		"lint:fix": "eslint packages/less --ext .js,.ts --fix",
 		"publish": "node scripts/bump-and-publish.js",
 		"publish:dry-run": "DRY_RUN=true node scripts/bump-and-publish.js",
 		"publish:beta": "node scripts/publish-beta.js",
@@ -28,7 +30,10 @@
 		"url": "https://github.com/less/less.js.git"
 	},
 	"devDependencies": {
+		"@typescript-eslint/eslint-plugin": "^4.28.0",
+		"@typescript-eslint/parser": "^4.28.0",
 		"all-contributors-cli": "~6.26.1",
+		"eslint": "^7.29.0",
 		"github-changes": "^1.1.2",
 		"husky": "~9.1.7",
 		"npm-run-all": "^4.1.5",

packages/less/.eslintrc.cjs

@@ -1,63 +1,37 @@
 module.exports = {
-    'parser': '@typescript-eslint/parser',
-    'extends': 'eslint:recommended',
-    'parserOptions': {
-        'ecmaVersion': 2018,
-        'sourceType': 'module'
-    },
-    'plugins': ['@typescript-eslint'],
-    'env': {
-        'browser': true,
-        'node': true,
-        'mocha': true
-    },
-    'globals': {},
-    'rules': {
-        indent: ['error', 4, {
-            SwitchCase: 1
-        }],
-        'no-empty': ['error', { 'allowEmptyCatch': true }],
-        quotes: ['error', 'single', {
-            avoidEscape: true
-        }],
-        /**
-         * The codebase uses some while(true) statements.
-         * Refactor to remove this rule.
-         */
-        'no-constant-condition': 0,
-        /**
-         * Less combines assignments with conditionals sometimes
-         */
-        'no-cond-assign': 0,
-        /**
-         * @todo - remove when some kind of code style (XO?) is added
-         */
-        'no-multiple-empty-lines': 'error'
-    },
+    'extends': ['../../config/eslint/base.cjs'],
     'overrides': [
         {
             files: ['*.ts'],
-            extends: ['plugin:@typescript-eslint/recommended'],
+            'extends': ['plugin:@typescript-eslint/recommended'],
             rules: {
-                /**
-                 * Suppress until Less has better-defined types
-                 * @see https://github.com/less/less.js/discussions/3786
-                 */
                 '@typescript-eslint/no-explicit-any': 0
             }
         },
+        {
+            files: ['lib/**/*.{js,ts}'],
+            rules: {
+                'no-unused-vars': 0,
+                'no-redeclare': 0
+            }
+        },
+        {
+            files: ['benchmark/**/*.{js,ts}', 'build/**/*.{js,ts}', 'scripts/**/*.{js,ts}'],
+            rules: {
+                'no-unused-vars': 0,
+                'no-redeclare': 0,
+                'no-undef': 0
+            }
+        },
         {
             files: ['test/**/*.{js,ts}', 'benchmark/index.js'],
-            /**
-             * @todo - fix later
-             */
             rules: {
                 'no-undef': 0,
                 'no-useless-escape': 0,
                 'no-unused-vars': 0,
                 'no-redeclare': 0,
                 '@typescript-eslint/no-unused-vars': 0
             }
-        },
+        }
     ]
-}
+};