Can we mount express app into koa?

Can we have something like

koaApp.use(expressToKoaMount('/prefix', expressAppOrHttpServer))

Tried implement that with on-finished(https://github.com/jshttp/on-finished) But got many header is set error

[ericfong]

Finally, it works by: (mounting kue-ui into koa app)

// kue-ui
const expressApp = express()
const prefix = '/kue-ui/'
expressApp.use(prefix, kueUiExpressApp)
koaApp.use(function*(next) {
  // do routing by simple matching, koa-route may also work
  if (this.path.startsWith(prefix)) {
    // direct to express
    if (this.status === 404 || this.status === '404') {
      delete this.res.statusCode
    }
    // stop koa future processing (NOTE not sure it is un-doc feature or not?)
    this.respond = false
    // pass req and res to express
    expressApp(this.req, this.res)
  } else {
    // go to next middleware
    yield next
  }
})

A bit hacky, hope kue-ui can have a koa / promise version

[adipascu]

I used this snippet to use express 4 inside koa 2

  const Koa = require('koa');
  const app = new Koa();
  app.use(async ctx => {
    ctx.status = 200;  // this is required to prevent incorrect codes returned after express runs
    ctx.respond = false;
    express_app(ctx.req, ctx.res);
  });

  app.listen(3000);