Upgrade to latest eslint 9 (#4393)

Use eslint.config.mjs
Update some of the eslint packages in package.json

eslint.config.mjs

@@ -0,0 +1,57 @@
+import globals from "globals";
+import babelParser from "@babel/eslint-parser";
+import path from "node:path";
+import { fileURLToPath } from "node:url";
+import js from "@eslint/js";
+import { FlatCompat } from "@eslint/eslintrc";
+
+const __filename = fileURLToPath(import.meta.url);
+const __dirname = path.dirname(__filename);
+const compat = new FlatCompat({
+    baseDirectory: __dirname,
+    recommendedConfig: js.configs.recommended,
+    allConfig: js.configs.all
+});
+
+export default [{
+    ignores: [
+        "**/node_modules",
+        "**/.gitignore",
+        "**/tmp",
+        "**/vendor",
+        "**/public",
+        "**/docs",
+        "**/solr",
+    ],
+}, ...compat.extends("plugin:prettier/recommended"), {
+    languageOptions: {
+        globals: {
+            ...globals.browser,
+            ...globals.node,
+            ...globals.jquery,
+        },
+
+        parser: babelParser,
+    },
+
+    rules: {
+        "prefer-const": "error",
+
+        "no-trailing-spaces": ["error", {
+            skipBlankLines: true,
+            ignoreComments: true,
+        }],
+
+        "arrow-body-style": "off",
+        "prefer-arrow-callback": "off",
+        "no-unused-vars": "warn",
+    },
+}, {
+    files: ["**/*.spec.js", "**/*.spec.jsx"],
+
+    languageOptions: {
+        globals: {
+            ...globals.jest,
+        },
+    },
+}];

package.json

@@ -18,13 +18,16 @@
     "@babel/eslint-plugin": "^7.22.10",
     "@babel/plugin-transform-runtime": "^7.18.10",
     "@babel/preset-env": "^7.18.10",
+    "@eslint/eslintrc": "^3.1.0",
+    "@eslint/js": "^9.11.1",
     "@vue/test-utils": "2.4.6",
     "@vue/vue3-jest": "29.2.6",
     "babel-jest": "^29.4.0",
     "babel-plugin-macros": "^3.1.0",
-    "eslint": "^8.54.0",
-    "eslint-config-prettier": "^9.0.0",
-    "eslint-plugin-prettier": "^5.0.1",
+    "eslint": "^9.11.1",
+    "eslint-config-prettier": "^9.1.0",
+    "eslint-plugin-prettier": "^5.2.1",
+    "globals": "^15.9.0",
     "jest": "^29.4.0",
     "jquery": "^3.7.0",
     "lint-staged": "^15.1.0",
@@ -45,15 +48,18 @@
   "scripts": {
     "test": "jest",
     "test:debug": "node --inspect node_modules/.bin/jest --runInBand",
-    "lint": "eslint --fix --ext .js",
+    "lint": "eslint -c eslint.config.mjs",
     "format": "prettier . --write",
     "prepare": "simple-git-hooks"
   },
   "jest": {
     "verbose": true,
     "testEnvironmentOptions": {
       "url": "http://localhost/",
-      "customExportConditions": ["node", "node-addons"]
+      "customExportConditions": [
+        "node",
+        "node-addons"
+      ]
     },
     "roots": [
       "spec/javascript"