Remove direct qs dependency

- As suggested here: #5783 (comment)
- See also #6647, #5723, #6374, #3230, #3272, https://github.com/expressjs/express/pulls?q=is%3Apr+qs+is%3Aclosed
- This doesn't remove `qs` from `body-parser`

Author: lukaselmer

History.md

@@ -1,3 +1,10 @@
+unreleased
+==========
+
+* Remove `app.set('query parser', 'extended')` option; users should pass a custom parser function instead
+  - To replicate old `'extended'` behavior: `app.set('query parser', str => require('qs').parse(str))`
+  - This allows removing `qs` from the dependencies for users who don't configure it explicitly
+
 5.1.0 / 2025-03-31
 ========================
 

lib/utils.js

@@ -17,7 +17,6 @@ var contentType = require('content-type');
 var etag = require('etag');
 var mime = require('mime-types')
 var proxyaddr = require('proxy-addr');
-var qs = require('qs');
 var querystring = require('node:querystring');
 const { Buffer } = require('node:buffer');
 
@@ -154,7 +153,7 @@ exports.compileETag = function(val) {
 /**
  * Compile "query parser" value to function.
  *
- * @param  {String|Function} val
+ * @param  {String|Function|Boolean} val
  * @return {Function}
  * @api private
  */
@@ -174,8 +173,7 @@ exports.compileQueryParser = function compileQueryParser(val) {
     case false:
       break;
     case 'extended':
-      fn = parseExtendedQueryString;
-      break;
+      throw new TypeError("query parser 'extended' is no longer supported; use: `app.set('query parser', str => qs.parse(str, { allowPrototypes: true }))` to replicate the old behavior");
     default:
       throw new TypeError('unknown value for query parser function: ' + val);
   }
@@ -255,17 +253,3 @@ function createETagGenerator (options) {
     return etag(buf, options)
   }
 }
-
-/**
- * Parse an extended query string with qs.
- *
- * @param {String} str
- * @return {Object}
- * @private
- */
-
-function parseExtendedQueryString(str) {
-  return qs.parse(str, {
-    allowPrototypes: true
-  });
-}

package.json

@@ -52,7 +52,6 @@
     "once": "^1.4.0",
     "parseurl": "^1.3.3",
     "proxy-addr": "^2.0.7",
-    "qs": "^6.14.0",
     "range-parser": "^1.2.1",
     "router": "^2.2.0",
     "send": "^1.1.0",
@@ -76,6 +75,7 @@
     "morgan": "1.10.1",
     "nyc": "^17.1.0",
     "pbkdf2-password": "1.2.1",
+    "qs": "^6.14.0",
     "supertest": "^6.3.0",
     "vhost": "~3.0.2"
   },

test/req.query.js

@@ -1,6 +1,7 @@
 'use strict'
 
 var assert = require('node:assert')
+var qs = require('qs');
 var express = require('../')
   , request = require('supertest');
 
@@ -22,24 +23,32 @@ describe('req', function(){
       .expect(200, '{"user[name]":"tj"}', done);
     });
 
-    describe('when "query parser" is extended', function () {
+    describe('when "query parser" is set to qs (formerly "extended")', function () {
       it('should parse complex keys', function (done) {
-        var app = createApp('extended');
+        var app = createApp(qs.parse);
 
         request(app)
         .get('/?foo[0][bar]=baz&foo[0][fizz]=buzz&foo[]=done!')
         .expect(200, '{"foo":[{"bar":"baz","fizz":"buzz"},"done!"]}', done);
       });
 
       it('should parse parameters with dots', function (done) {
-        var app = createApp('extended');
+        var app = createApp(qs.parse);
 
         request(app)
         .get('/?user.name=tj')
         .expect(200, '{"user.name":"tj"}', done);
       });
     });
 
+    describe('when "query parser" is set to extended', function () {
+      it('should throw with a helpful error message', function () {
+        assert.throws(() => createApp('extended'),
+          new TypeError("query parser 'extended' is no longer supported; use: `app.set('query parser', str => qs.parse(str, { allowPrototypes: true }))` to replicate the old behavior")
+        );
+      });
+    });
+
     describe('when "query parser" is simple', function () {
       it('should not parse complex keys', function (done) {
         var app = createApp('simple');