test: add discarded middleware test (#5819)

Author: ctcpip

test/app.router.js

@@ -1156,6 +1156,56 @@ describe('app.router', function(){
  var app = express();
  assert.strictEqual(app.get('/', function () {}), app)
  })
+
+ it('should should not use disposed router/middleware', function(done){
+ // more context: https://github.com/expressjs/express/issues/5743#issuecomment-2277148412
+
+ var app = express();
+ var router = new express.Router();
+
+ router.use(function(req, res, next){
+ res.setHeader('old', 'foo');
+ next();
+ });
+
+ app.use(function (req, res, next) {
+ return router.handle(req, res, next);
+ });
+
+ app.get('/', function(req, res, next){
+ res.send('yee');
+ next();
+ });
+
+ request(app)
+ .get('/')
+ .expect('old', 'foo')
+ .expect(function(res) {
+ if (typeof res.headers['new'] !== 'undefined') {
+ throw new Error('`new` header should not be present');
+ }
+ })
+ .expect(200, 'yee', function(err, res) {
+ if (err) return done(err);
+
+ router = new express.Router();
+
+ router.use(function(req, res, next){
+ res.setHeader('new', 'bar');
+ next();
+ });
+
+ request(app)
+ .get('/')
+ .expect('new', 'bar')
+ .expect(function(res) {
+ if (typeof res.headers['old'] !== 'undefined') {
+ throw new Error('`old` header should not be present');
+ }
+ })
+ .expect(200, 'yee', done);
+ });
+ })
 })
 
 function supportsRegexp(source) {