Cannot read property '0' of undefined

[muka]

Hi
I have a snippet like this (also using express-promise-router from master)

const router = require('express-promise-router')()
router.get(function(req, res) {
  return foo(req.body).then(bar => res.json(bar))
})
app.use(authstuff())
app.use(`/foo`, router)

Running tests I get

     TypeError: Cannot read property '0' of undefined
      at Route.instanceToWrap.(anonymous function) [as get] (node_modules/express-promise-router/lib/express-promise-router.js:80:87)
      at Function.proto.(anonymous function) (node_modules/express/lib/router/index.js:510:19)
      at Function.instanceToWrap.(anonymous function) [as get] (node_modules/express-promise-router/lib/express-promise-router.js:95:45)
      at Object.module.exports.router (routes/token.js:39:12)
      at Object.<anonymous> (app.js:143:18)
      at require (internal/module.js:11:18)
      at require.connect.then.then (index.js:21:25)
      at tryCatcher (node_modules/bluebird/js/release/util.js:16:23)
      at Promise._settlePromiseFromHandler (node_modules/bluebird/js/release/promise.js:512:31)
      at Promise._settlePromise (node_modules/bluebird/js/release/promise.js:569:18)
      at Promise._settlePromise0 (node_modules/bluebird/js/release/promise.js:614:10)
      at Promise._settlePromises (node_modules/bluebird/js/release/promise.js:693:18)
      at Async._drainQueue (node_modules/bluebird/js/release/async.js:133:16)
      at Async._drainQueues (node_modules/bluebird/js/release/async.js:143:10)
      at Immediate.Async.drainQueues (node_modules/bluebird/js/release/async.js:17:14)

Maybe I am not using properly or should it be a managed case?

Thanks

[mormahr]

Hi, thanks for reporting this issue.

The express.Router documentation defines router.get like this: router.METHOD(path, [callback, ...] callback), so i'd say that calling it without a path is not allowed.
express.Router won't crash on this but won't work as you want it to either. (see snippet below).

const express = require("express")
const app = express()

const router = express.Router()
router.get(function (req, res) {
	res.send("test")
})

app.use("/", router)
app.listen(3000)

(Opening http://localhost:3000/ won't show "test")

Use router.get("/", ...) instead, like this:

const express = require("express")
const app = express()

const router = express.Router()
router.get("/", function (req, res) { // <- you can't omit the path when calling .METHOD
	res.send("test")
})

app.use(router) // <- you can omit the path when calling .use
app.listen(3000)

We try to act as a drop-in replacement and try to stay as close to the original behavior as possible, therefor i might provide a "fix" so we don't crash.

Documentation:
http://expressjs.com/en/4x/api.html#router.METHOD
http://expressjs.com/en/4x/api.html#router.use

If anything is still unclear don't hesitate to ask ☺️

[muka]

Hi,
thank you for clarifying! I fixed the wrong call on my code and works now.

So the bug is not really a bug :)

The crash is useful to detect the wrong usage , eventually the user may get warned of the wrong usage, but is really an edge case

Thanks

[neonexus22]

const router = require('express-promise-router')()
router.get('some-route', function(req, res) { // add the path to which you want to route as first argument
return foo(req.body).then(bar => res.json(bar))
})
app.use(authstuff())
app.use(/foo, router)

// We get that error typically not because of 'express-promise-router', but others errors like invalid function, spelling mistakes.... etc

[megamit]

I have encountered this error when trying the documented and valid router.route() usage as shown here
https://expressjs.com/en/4x/api.html#router.route
The following code gives the same error as above:

router.route('campaigns/:id')
    .get(async (req, res, next) => {
       /*   ...    */
    })

if you try to give it a sub route so that promise router doesnt error i.e. .get('/',/async (req, res, next) express throws instead:
Error: Route.get() requires a callback function but got a [object String]
Ideally this should be supported. Could this issue be reopened

[mormahr]

@megamit could you open a new issue? I'm not sure if this is related to the current one.