Migrate to ESLint v9

eslint.config.mjs

@@ -0,0 +1,54 @@
+// @ts-check
+
+import eslint from '@eslint/js';
+import pluginVitest from '@vitest/eslint-plugin';
+import { defineConfig } from 'eslint/config';
+import gitignore from 'eslint-config-flat-gitignore';
+import pluginImportLite from 'eslint-plugin-import-lite';
+import pluginPrettierRecommended from 'eslint-plugin-prettier/recommended';
+import pluginSimpleImportSort from 'eslint-plugin-simple-import-sort';
+import globals from 'globals';
+import tseslint from 'typescript-eslint';
+
+export default defineConfig(
+    gitignore(),
+    {
+        languageOptions: {
+            globals: {
+                ...globals.node,
+            },
+            ecmaVersion: 2022,
+            sourceType: 'commonjs',
+        },
+    },
+    eslint.configs.recommended,
+    tseslint.configs.recommended,
+    {
+        rules: {
+            curly: 'error',
+            eqeqeq: ['error', 'always', { null: 'ignore' }],
+            'no-var': 'error',
+            'no-console': 'error',
+            'prefer-const': 'error',
+            'prefer-object-spread': 'error',
+        },
+    },
+    {
+        plugins: {
+            'simple-import-sort': pluginSimpleImportSort,
+            import: pluginImportLite,
+        },
+        rules: {
+            'simple-import-sort/imports': 'error',
+            'simple-import-sort/exports': 'error',
+            'import/first': 'error',
+            'import/newline-after-import': 'error',
+            'import/no-duplicates': 'error',
+        },
+    },
+    {
+        files: ['**/*.spec.ts'],
+        ...pluginVitest.configs.recommended,
+    },
+    pluginPrettierRecommended,
+);

index.js

@@ -2,7 +2,7 @@
  * While in local development, make sure you've run `pnpm run build` first.
  */
 
-// eslint-disable-next-line @typescript-eslint/no-var-requires
+// eslint-disable-next-line @typescript-eslint/no-require-imports
 const concurrently = require('./dist/src/index.js');
 
 // For require()

package.json

@@ -2,7 +2,7 @@
   "name": "concurrently",
   "version": "9.2.0",
   "description": "Run commands concurrently",
-  "packageManager": "pnpm@10.14.0+sha512.ad27a79641b49c3e481a16a805baa71817a04bbe06a38d17e60e2eaee83f6a146c6a688125f5792e48dd5ba30e7da52a5cda4c3992b9ccf333f9ce223af84748",
+  "packageManager": "pnpm@10.15.0+sha512.486ebc259d3e999a4e8691ce03b5cac4a71cbeca39372a9b762cb500cfdf0873e2cb16abe3d951b1ee2cf012503f027b98b6584e4df22524e0c7450d9ec7aa7b",
   "main": "index.js",
   "types": "index.d.ts",
   "type": "commonjs",
@@ -32,7 +32,7 @@
     "clean": "tsc --build --clean",
     "format": "prettier --check '**/*.{json,y?(a)ml,md}'",
     "format:fix": "pnpm run format --write",
-    "lint": "eslint --ignore-path .gitignore --ext mjs,js,ts .",
+    "lint": "eslint",
     "lint:fix": "pnpm run lint --fix",
     "prepublishOnly": "safe-publish-latest && pnpm run build",
     "report-coverage": "cat coverage/lcov.info | coveralls",
@@ -64,29 +64,31 @@
     "yargs": "17.7.2"
   },
   "devDependencies": {
+    "@eslint/js": "9.33.0",
     "@hirez_io/observer-spy": "^2.2.0",
     "@types/node": "^18.19.123",
     "@types/shell-quote": "^1.7.5",
     "@types/supports-color": "^8.1.3",
     "@types/yargs": "^17.0.33",
-    "@typescript-eslint/eslint-plugin": "^7.18.0",
-    "@typescript-eslint/parser": "^7.18.0",
     "@vitest/coverage-v8": "^3.2.4",
-    "@vitest/eslint-plugin": "^1.3.4",
+    "@vitest/eslint-plugin": "1.3.4",
     "coveralls-next": "^5.0.0",
     "ctrlc-wrapper": "^0.0.5",
     "esbuild": "~0.25.9",
-    "eslint": "^8.57.1",
+    "eslint": "^9.33.0",
+    "eslint-config-flat-gitignore": "2.1.0",
     "eslint-config-prettier": "^10.1.8",
-    "eslint-plugin-import": "^2.32.0",
+    "eslint-plugin-import-lite": "0.3.0",
     "eslint-plugin-prettier": "^5.5.4",
     "eslint-plugin-simple-import-sort": "^12.1.1",
+    "globals": "16.3.0",
     "husky": "^9.1.7",
     "lint-staged": "^15.5.2",
     "prettier": "^3.6.2",
     "safe-publish-latest": "^2.0.0",
     "string-argv": "^0.3.2",
-    "typescript": "~5.8.3",
+    "typescript": "~5.9.2",
+    "typescript-eslint": "8.40.0",
     "vitest": "^3.2.4"
   },
   "files": [