chore: upgrade to eslint v9

Author: bmish

eslint-remote-tester.config.js

@@ -1,7 +1,7 @@
 "use strict";
 
 const fs = require("node:fs");
-const { basename, extname } = require("node:path");
+const path = require("node:path");
 
 /** @type {import('eslint-remote-tester').Config} */
 module.exports = {
@@ -42,7 +42,7 @@ module.exports = {
                 .readdirSync(`${__dirname}/lib/rules`)
                 .map(
                     (filename) =>
-                        `qunit/${basename(filename, extname(filename))}`,
+                        `qunit/${path.basename(filename, path.extname(filename))}`,
                 )
                 .map((ruleName) => [ruleName, "error"]),
         ),

eslint.config.js

@@ -4,6 +4,10 @@ const js = require("@eslint/js");
 const { FlatCompat } = require("@eslint/eslintrc");
 const eslintPluginEslintPluginAll = require("eslint-plugin-eslint-plugin/configs/all");
 const eslintPluginMarkdown = require("eslint-plugin-markdown");
+const eslintPluginMocha = require("eslint-plugin-mocha");
+const eslintPluginN = require("eslint-plugin-n");
+const eslintPluginPrettierRecommended = require("eslint-plugin-prettier/recommended");
+const eslintPluginUnicorn = require("eslint-plugin-unicorn");
 const globals = require("globals");
 
 const compat = new FlatCompat({
@@ -12,19 +16,17 @@ const compat = new FlatCompat({
 });
 
 module.exports = [
-    ...compat.extends(
-        "plugin:eslint-comments/recommended",
-        "plugin:node/recommended",
-        "plugin:prettier/recommended",
-        "plugin:unicorn/recommended",
-    ),
+    ...compat.extends("plugin:eslint-comments/recommended"),
 
     eslintPluginEslintPluginAll,
+    eslintPluginN.configs["flat/recommended"],
+    eslintPluginPrettierRecommended,
+    eslintPluginUnicorn.configs["flat/recommended"],
 
-    // Apply mocha config only to tests.
-    ...compat
-        .extends("plugin:mocha/recommended")
-        .map((config) => ({ ...config, files: ["tests/**/*.js"] })),
+    {
+        ...eslintPluginMocha.configs.flat.recommended,
+        files: ["tests/**/*.js"],
+    },
 
     {
         languageOptions: {
@@ -136,14 +138,6 @@ module.exports = [
             "spaced-comment": ["error", "always", { exceptions: ["-"] }],
             strict: ["error", "global"],
             "use-isnan": "error",
-            "valid-jsdoc": [
-                "error",
-                {
-                    prefer: {
-                        return: "returns",
-                    },
-                },
-            ],
             "valid-typeof": "error",
             yoda: ["error", "never"],
 
@@ -172,8 +166,8 @@ module.exports = [
             ],
             "eslint-plugin/require-meta-schema-description": "off", // TODO: enable this.
 
-            // eslint-plugin-node
-            "node/no-missing-require": [
+            // eslint-plugin-n
+            "n/no-missing-require": [
                 "error",
                 {
                     allowModules: ["@typescript-eslint/parser"],