chore(package): upgrade to eslint v9

.vscode/settings.json

@@ -1,7 +1,7 @@
 {
   "deno.enable": false,
   "editor.codeActionsOnSave": {
-    "source.fixAll.eslint": true
+    "source.fixAll.eslint": "explicit"
   },
   "markdown.extension.toc.levels": "2..3"
 }

cspell.json

@@ -46,6 +46,7 @@
     "restream",
     "snyk",
     "streamify",
+    "tseslint",
     "typicode",
     "vhosted",
     "websockets",

eslint.config.js

@@ -0,0 +1,38 @@
+const eslintPluginPrettierRecommended = require('eslint-plugin-prettier/recommended');
+const tseslint = require('typescript-eslint');
+const tseslintParser = require('@typescript-eslint/parser');
+
+/** @type {import('eslint').Linter.FlatConfig[]} */
+module.exports = [
+  eslintPluginPrettierRecommended,
+  ...tseslint.configs.recommended,
+  {
+    files: ['*.js'],
+    rules: {
+      '@typescript-eslint/no-var-requires': 'off',
+    },
+  },
+  {
+    files: ['**/*.ts'],
+    ignores: ['dist/*'],
+    languageOptions: {
+      parser: tseslintParser,
+    },
+    rules: {
+      '@typescript-eslint/no-explicit-any': 'off',
+      '@typescript-eslint/no-unused-vars': [
+        'error',
+        { vars: 'all', args: 'none', ignoreRestSiblings: false },
+      ],
+      'prettier/prettier': 'warn',
+    },
+    // overrides: [
+    //   {
+    //     files: ['src/**/*.ts'],
+    //     rules: {
+    //       'no-restricted-imports': ['error', { paths: ['express'] }],
+    //     },
+    //   },
+    // ],
+  },
+];

package.json

@@ -59,17 +59,17 @@
     "@commitlint/cli": "19.4.1",
     "@commitlint/config-conventional": "19.4.1",
     "@types/debug": "4.1.12",
+    "@types/eslint": "9.6.1",
     "@types/express": "4.17.21",
     "@types/is-glob": "4.0.4",
     "@types/jest": "29.5.12",
     "@types/micromatch": "4.0.9",
     "@types/node": "22.5.1",
     "@types/supertest": "6.0.2",
     "@types/ws": "8.5.12",
-    "@typescript-eslint/eslint-plugin": "7.16.0",
-    "@typescript-eslint/parser": "7.16.0",
+    "@typescript-eslint/parser": "8.3.0",
     "body-parser": "1.20.2",
-    "eslint": "8.57.0",
+    "eslint": "9.9.1",
     "eslint-config-prettier": "9.1.0",
     "eslint-plugin-prettier": "5.2.1",
     "express": "4.19.2",
@@ -79,11 +79,12 @@
     "lint-staged": "15.2.9",
     "mockttp": "3.15.2",
     "open": "8.4.2",
-    "prettier": "3.3.3",
-    "supertest": "7.0.0",
-    "ts-jest": "29.2.5",
-    "typescript": "5.5.4",
-    "ws": "8.18.0"
+    "prettier": "3.2.5",
+    "supertest": "6.3.4",
+    "ts-jest": "29.1.2",
+    "typescript": "5.4.4",
+    "typescript-eslint": "8.3.0",
+    "ws": "8.16.0"
   },
   "dependencies": {
     "@types/http-proxy": "^1.17.15",

src/http-proxy-middleware.ts

@@ -46,10 +46,10 @@ export class HttpProxyMiddleware<TReq, TRes> {
         debug(`proxy request to target: %O`, activeProxyOptions.target);
         this.proxy.web(req, res, activeProxyOptions);
       } catch (err) {
-        next && next(err);
+        next?.(err);
       }
     } else {
-      next && next();
+      next?.();
     }
 
     /**
@@ -79,7 +79,7 @@ export class HttpProxyMiddleware<TReq, TRes> {
   private registerPlugins(proxy: httpProxy<TReq, TRes>, options: Options<TReq, TRes>) {
     const plugins = getPlugins<TReq, TRes>(options);
     plugins.forEach((plugin) => {
-      debug(`register plugin: "${getFunctionName(plugin)}"`);
+      debug(`register plugin: "${getFunctionName(plugin as () => void)}"`);
       plugin(proxy, options);
     });
   }

src/logger.ts

@@ -1,5 +1,3 @@
-/* eslint-disable @typescript-eslint/no-empty-function */
-
 import { Logger, Options } from './types';
 
 /**

src/types.ts

@@ -3,8 +3,6 @@
  * https://github.com/DefinitelyTyped/DefinitelyTyped/blob/6f529c6c67a447190f86bfbf894d1061e41e07b7/types/http-proxy-middleware/index.d.ts
  */
 
-/* eslint-disable @typescript-eslint/no-empty-interface */
-
 import type * as http from 'http';
 import type * as httpProxy from 'http-proxy';
 import type * as net from 'net';

src/utils/function.ts

@@ -1,4 +1,4 @@
-/* eslint-disable @typescript-eslint/ban-types */
+/* eslint-disable @typescript-eslint/no-unsafe-function-type */
 
 export function getFunctionName(fn: Function): string {
   return fn.name || '[anonymous Function]';

test/types.spec.ts

@@ -1,4 +1,4 @@
-/* eslint-disable @typescript-eslint/no-empty-function */
+/* eslint-disable @typescript-eslint/no-unused-expressions */
 
 import * as express from 'express';
 import * as http from 'http';

test/unit/path-filter.spec.ts

@@ -246,7 +246,6 @@ describe('Path Filter', () => {
       });
 
       it('should not throw error with Function', () => {
-        // eslint-disable-next-line @typescript-eslint/no-empty-function
         expect(testPathFilter(() => {})).not.toThrowError(Error);
       });
     });

test/unit/path-rewriter.spec.ts

@@ -171,12 +171,10 @@ describe('Path rewriting', () => {
     });
 
     it('should not throw when function config is provided', () => {
-      // eslint-disable-next-line @typescript-eslint/no-empty-function
       expect(badFn(() => {})).not.toThrowError(Error);
     });
 
     it('should not throw when async function config is provided', () => {
-      // eslint-disable-next-line @typescript-eslint/no-empty-function
       expect(badFn(async () => {})).not.toThrowError(Error);
     });
   });

test/unit/utils/function.spec.ts

@@ -1,4 +1,3 @@
-/* eslint-disable @typescript-eslint/no-empty-function */
 import { getFunctionName } from '../../../src/utils/function';
 
 describe('getFunctionName()', () => {