Response built by express is broken if res and req don't extend node's http.IncomingMessage and http.ServerResponse

[Tofandel]

To reproduce

import createApp from 'express';

const app = createApp();
console.log(app.response);

console.log(app.response.getHeader('vary'));

import createApp from 'express';
import {IncomingMessage} from 'unenv/runtime/node/http/_request'
import {ServerResponse} from 'unenv/runtime/node/http/_response'

const req = new IncomingMessage();
const res = new ServerResponse(req);

// Taken from express init middleware implementation
const app = createApp();
Object.setPrototypeOf(res, app.response);

res.setHeader('vary', 'test'); // TypeError: Cannot set properties of undefined (setting 'vary')

node:_http_outgoing:747
  const entry = headers[name.toLowerCase()];
                       ^

TypeError: Cannot read properties of undefined (reading 'vary')
    at ServerResponse.getHeader (node:_http_outgoing:747:24)

Because the non native response methods are being overwritten with the native methods

Solution:

var request = require('./request');

/**
 * Response prototype.
 * @public
 */

var res = new http.ServerResponse(request)

[Tofandel]

See also https://github.com/expressjs/express/issues/2548 and https://github.com/unjs/node-mock-http/issues/5