migrate to eslint v9 flat config

Signed-off-by: CrazyMax <1951866+crazy-max@users.noreply.github.com>

.prettierrc.json

@@ -6,6 +6,5 @@
   "singleQuote": true,
   "trailingComma": "none",
   "bracketSpacing": false,
-  "arrowParens": "avoid",
+  "arrowParens": "avoid"
-  "parser": "typescript"
 }

eslint.config.cjs

@@ -1,90 +0,0 @@
-/**
- * Copyright 2025 actions-toolkit authors
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-/* eslint-disable @typescript-eslint/no-require-imports */
-const {defineConfig, globalIgnores} = require('eslint/config');
-const {fixupConfigRules, fixupPluginRules} = require('@eslint/compat');
-const typescriptEslint = require('@typescript-eslint/eslint-plugin');
-const eslintPluginImport = require('eslint-plugin-import');
-const prettier = require('eslint-plugin-prettier');
-const vitest = require('@vitest/eslint-plugin');
-const globals = require('globals');
-const tsParser = require('@typescript-eslint/parser');
-const js = require('@eslint/js');
-const {FlatCompat} = require('@eslint/eslintrc');
-
-// __dirname and __filename exist natively in CommonJS
-const compat = new FlatCompat({
-  baseDirectory: __dirname,
-  recommendedConfig: js.configs.recommended,
-  allConfig: js.configs.all
-});
-
-module.exports = defineConfig([
-  globalIgnores([
-    // prettier-ignore
-    '.yarn/**/*',
-    'coverage/**/*',
-    'lib/**/*'
-  ]),
-  {
-    extends: fixupConfigRules(
-      compat.extends(
-        // prettier-ignore
-        'eslint:recommended',
-        'plugin:@typescript-eslint/eslint-recommended',
-        'plugin:@typescript-eslint/recommended',
-        'plugin:prettier/recommended'
-      )
-    ),
-    plugins: {
-      '@typescript-eslint': fixupPluginRules(typescriptEslint),
-      import: fixupPluginRules(eslintPluginImport),
-      prettier: fixupPluginRules(prettier)
-    },
-    languageOptions: {
-      globals: {
-        ...globals.node
-      },
-      parser: tsParser,
-      ecmaVersion: 2023,
-      sourceType: 'module'
-    },
-    rules: {
-      '@typescript-eslint/no-require-imports': [
-        'error',
-        {
-          allowAsImport: true
-        }
-      ],
-      'import/no-unresolved': [
-        'error',
-        {
-          ignore: ['\\.js$', 'csv-parse/sync', '@octokit/openapi-types', '@octokit/core', '@octokit/plugin-rest-endpoint-methods', 'vitest/config']
-        }
-      ]
-    }
-  },
-  {
-    files: ['__tests__/**'],
-    ...vitest.configs.recommended,
-    rules: {
-      ...vitest.configs.recommended.rules,
-      'vitest/no-conditional-expect': 'error',
-      'vitest/no-disabled-tests': 0
-    }
-  }
-]);

eslint.config.mjs

@@ -0,0 +1,68 @@
+/**
+ * Copyright 2025 actions-toolkit authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import {defineConfig} from 'eslint/config';
+import js from '@eslint/js';
+import tseslint from '@typescript-eslint/eslint-plugin';
+import vitest from '@vitest/eslint-plugin';
+import globals from 'globals';
+import eslintConfigPrettier from 'eslint-config-prettier/flat';
+import eslintPluginPrettier from 'eslint-plugin-prettier';
+
+export default defineConfig([
+  {
+    ignores: ['.yarn/**/*', 'coverage/**/*', 'lib/**/*']
+  },
+  js.configs.recommended,
+  ...tseslint.configs['flat/recommended'],
+  eslintConfigPrettier,
+  {
+    languageOptions: {
+      globals: {
+        ...globals.node
+      }
+    }
+  },
+  {
+    files: ['__tests__/**'],
+    ...vitest.configs.recommended,
+    languageOptions: {
+      globals: {
+        ...globals.node,
+        ...vitest.environments.env.globals
+      }
+    },
+    rules: {
+      ...vitest.configs.recommended.rules,
+      'vitest/no-conditional-expect': 'error',
+      'vitest/no-disabled-tests': 0
+    }
+  },
+  {
+    plugins: {
+      prettier: eslintPluginPrettier
+    },
+    rules: {
+      'prettier/prettier': 'error',
+      '@typescript-eslint/no-require-imports': [
+        'error',
+        {
+          allowAsImport: true
+        }
+      ]
+    }
+  }
+]);

package.json

@@ -5,12 +5,8 @@
   "type": "module",
   "scripts": {
     "build": "tsc",
-    "lint": "yarn run prettier && yarn run eslint",
+    "lint": "eslint --max-warnings=0 .",
-    "format": "yarn run prettier:fix && yarn run eslint:fix",
+    "format": "eslint --fix .",
-    "eslint": "eslint --max-warnings=0 .",
-    "eslint:fix": "eslint --fix .",
-    "prettier": "prettier --check \"./**/*.ts\"",
-    "prettier:fix": "prettier --write \"./**/*.ts\"",
     "test": "vitest run -c vitest.config.ts",
     "test:coverage": "vitest run -c vitest.config.ts --coverage",
     "test:itg": "vitest run -c vitest.config.itg.ts --maxWorkers=1",
@@ -70,8 +66,6 @@
     "tmp": "^0.2.5"
   },
   "devDependencies": {
-    "@eslint/compat": "^2.0.0",
-    "@eslint/eslintrc": "^3.3.3",
     "@eslint/js": "^9.39.2",
     "@types/gunzip-maybe": "^1.4.3",
     "@types/he": "^1.2.3",
@@ -86,8 +80,8 @@
     "@vitest/eslint-plugin": "^1.6.9",
     "eslint": "^9.39.2",
     "eslint-config-prettier": "^10.1.8",
-    "eslint-plugin-import": "^2.32.0",
     "eslint-plugin-prettier": "^5.5.4",
+    "globals": "^14.0.0",
     "prettier": "^3.7.4",
     "rimraf": "^6.1.2",
     "typescript": "^5.9.3",