Update to ESLint 9's "flat" configuration file format, convert deprecated eslint-plugin-node to eslint-plugin-n.

.eslintrc.json

@@ -1,71 +0,0 @@
-{
-  "parserOptions": {
-    "ecmaVersion": 2019,
-    "sourceType": "script"
-  },
-  "env": {
-    "node": true,
-    "es6": true
-  },
-  "plugins": [
-    "node",
-    "unicorn"
-  ],
-  "extends": [
-    "eslint:all",
-    "plugin:unicorn/all"
-  ],
-  "reportUnusedDisableDirectives": true,
-  "rules": {
-    "max-statements": "off",
-    "multiline-ternary": "off",
-    "no-magic-numbers": "off",
-    "no-ternary": "off",
-    "one-var": "off",
-    "sort-keys": "off",
-
-    "node/handle-callback-err": "error",
-    "node/no-callback-literal": "error",
-    "node/no-exports-assign": "error",
-    "node/no-extraneous-import": "error",
-    "node/no-extraneous-require": "error",
-    "node/no-missing-import": "error",
-    "node/no-missing-require": "error",
-    "node/no-new-require": "error",
-    "node/no-path-concat": "error",
-    "node/no-process-exit": "error",
-    "node/no-unpublished-bin": "error",
-    "node/no-unpublished-import": "error",
-    "node/no-unpublished-require": "error",
-    "node/no-unsupported-features/es-builtins": "error",
-    "node/no-unsupported-features/es-syntax": "error",
-    "node/no-unsupported-features/node-builtins": "error",
-    "node/process-exit-as-throw": "error",
-    "node/shebang": "error",
-    "node/no-deprecated-api": "error",
-    "node/callback-return": "error",
-    "node/exports-style": "error",
-    "node/file-extension-in-import": "error",
-    "node/global-require": "error",
-    "node/no-mixed-requires": "error",
-    "node/no-process-env": "error",
-    "node/no-restricted-import": "error",
-    "node/no-restricted-require": "error",
-    "node/no-sync": "error",
-    "node/prefer-global/buffer": "error",
-    "node/prefer-global/console": "error",
-    "node/prefer-global/process": "error",
-    "node/prefer-global/text-decoder": "error",
-    "node/prefer-global/text-encoder": "error",
-    "node/prefer-global/url-search-params": "error",
-    "node/prefer-global/url": "error",
-    "node/prefer-promises/dns": "error",
-    "node/prefer-promises/fs": "error",
-
-    "unicorn/no-array-callback-reference": "off",
-    "unicorn/no-unsafe-regex": "off",
-    "unicorn/prefer-module": "off",
-    "unicorn/prefer-top-level-await": "off",
-    "unicorn/switch-case-braces": ["error", "avoid"]
-  }
-}

eslint.config.mjs

@@ -0,0 +1,39 @@
+/* eslint-disable n/no-unpublished-import */
+
+import js from "@eslint/js";
+import eslintPluginNode from "eslint-plugin-n";
+import eslintPluginUnicorn from "eslint-plugin-unicorn";
+
+export default [
+  js.configs.all,
+  eslintPluginNode.configs["flat/recommended"],
+  eslintPluginUnicorn.configs["flat/all"],
+  {
+    "languageOptions": {
+      "sourceType": "commonjs"
+    },
+    "linterOptions": {
+      "reportUnusedDisableDirectives": true
+    },
+    "rules": {
+      "max-statements": "off",
+      "no-magic-numbers": "off",
+      "no-ternary": "off",
+      "one-var": "off",
+      "sort-imports": "off",
+      "sort-keys": "off",
+  
+      "unicorn/no-array-callback-reference": "off",
+      "unicorn/prefer-module": "off",
+      "unicorn/prefer-top-level-await": "off"
+    }
+  },
+  {
+    "files": [
+      "eslint.config.mjs"
+    ],
+    "languageOptions": {
+      "sourceType": "module"
+    }
+  }
+];

package.json

@@ -19,7 +19,7 @@
     "build": "ncc build markdownlint-cli2-action.js",
     "docker-npm-install": "docker run --rm --tty --name npm-install --volume $PWD:/home/workdir --workdir /home/workdir --user node node:16 npm install",
     "docker-npm-run-upgrade": "docker run --rm --tty --name npm-run-upgrade --volume $PWD:/home/workdir --workdir /home/workdir --user node node:16 npm run upgrade",
-    "lint": "eslint *.js && markdownlint-cli2 *.md",
+    "lint": "eslint *.js eslint.config.mjs && markdownlint-cli2 *.md",
     "test": "npm run lint && npm run build && git diff --exit-code",
     "upgrade": "npx --yes npm-check-updates --upgrade"
   },
@@ -28,9 +28,10 @@
     "markdownlint-cli2": "0.13.0"
   },
   "devDependencies": {
+    "@eslint/js": "9.0.0",
     "@vercel/ncc": "0.38.1",
     "eslint": "9.0.0",
-    "eslint-plugin-node": "11.1.0",
+    "eslint-plugin-n": "17.2.1",
     "eslint-plugin-unicorn": "52.0.0"
   }
 }