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Express middleware: res.statusCode doesn't accurately return the status code [duplicate]

This question already has answers here:
NodeJS Express = Catch the sent status code in the response
(2 answers)
Closed 2 years ago.
I have a fairly straight forward logging middleware function in an Express JS app:
app.use(function (req, res, next) {
const line = `${req.method} ${req.originalUrl} ${res.statusCode}`
console.log(line)
next()
})
And I have this route:
this.app.use('/404', function (req, res) {
res.sendStatus(404)
})
Which logs the following:
GET /404 200
With other routes it seems to always return 200.
How can I fix this so that it accurately logs status codes without changing routes?
Edit
My goal here was something quick to tell me if a route was hit and whether or not it succeeded. I don't want to have to edit all my routes to be compatible with it since I'll eventually replace it with an actual logging solution.

Depending of : https://expressjs.com/guide/error-handling.html
app.use('/404', function (req, res) {
console.error(err.stack);
res.status(404).send('not found!');
});
Also you can use http-errors module:
var createError = require('http-errors');
app.use(function(req, res, next) {
next(createError(404));
});

This still doesn't work for all routes but works for more of them:
this.app.use(async function (req, res, next) {
await next()
const line = `${req.method} ${req.originalUrl} ${res.statusCode}`
console.log(line)
})

Don't know your entire code, but this.app is not necessary. Directly use app.use.
Debug, while hitting, you request do not come within app.use('/404'), It might be serving path mentioned above it like app.use('/:variable'), so may be variable == 404.
Mention this type of static path topmost.

Does express next(err) have to have specific format?

I have an express sub app using http-errors module. When I pass new Forbidden() to the next() callback it disappears into the ether and doesn't callback. If I pass new Error() or { message: 'Forbidden' } it triggers the sub app error handler. Is this expected behaviour?
I've created my own Error objects and they all work. I see http-errors uses the inherits module, which works for me. Does the error handler check for anything on the error parameter?
I've used http-errors for years and not noticed this problem before.
const { Forbidden } = require('http-errors')
const express = require('express')
const app = express()
const subapp = express()
subapp.get((req, res, next) => {
next(new Forbidden()) // doesn't work
next(new Error()) // works
next({ message: 'Forbidden' }) // works
})
subapp.use((err, req, res, next) => {
// only called if new Error() or { message: 'Forbidden' }
})
app.use('/somepath', subapp)
app.use((err, req, res, next) => {
// not called
})
Edit:
I omitted that I was using swagger in the question above. Swagger was catching the error but not handling it appropriately; it was setting the correct headers but not sending a complete response. It was therefore missing my error middleware and passing on to the next non-error middleware.
// return response for http-errors error
subapp.use((req, res, next) => {
if (res.headersSent) {
return res.end()
}
next()
})

To answer the direct question, not it doesn't. We can test this with a simpler case shown in this code (tested).
const app = require('express')();
app.get('/test', (req, res, next) => {
const nonErrObj = {
hello: 'world'
};
return next(nonErrObj);
});
app.use((err, req, res, next) => {
console.log('Got an error');
console.table(err);
res.sendStatus(500);
});
app.listen(3000, () => {
console.log('listening on 3000');
});
By then running curl localhost:3000/test in another terminal we get the output:
listening on 3000
Got an error
┌─────────┬─────────┐
│ (index) │ Values │
├─────────┼─────────┤
│ hello │ 'world' │
└─────────┴─────────┘
This console.table is being output by our error handler, and the object we're passing to next is just a standard JS object. So the object passed to "next" can be anything and it will trigger the error handling code.
Now lets try and solve your issue. I have a hunch it's to do with your nested application which is good use of express but can get a bit confusing sometimes. I've created another test app using your code which shows the following. This code has only one global error handler.
const express = require('express');
const app = express();
const subapp = express();
// Create a top level route to test
app.get('/test', (req, res, next) => {
const nonErrObj = {
hello: 'world'
};
return next(nonErrObj);
});
// Create a sub express app to test
subapp.use('/test2', (req, res, next) => {
const nonErrObj = {
hello: 'world'
};
return next(nonErrObj);
});
// Mount the app, so we can now hit /subapp/test2
app.use('/subapp', subapp);
// A single global error handler for now
app.use((err, req, res, next) => {
console.log('Got an error');
console.table(err);
res.sendStatus(500);
});
app.listen(3000, () => {
console.log('listening on 3000');
});
If we now curl localhost:3000/subapp/test2 and curl localhost:3000/test we get the same response. Our global error handler is called with no problems. Now lets try adding an error handler to the sub app to see what happens.
In this case I just added the following under the /test2 route (not adding the full file for brevity.
subapp.use((err, req, res, next) => {
console.log('Sub app got error');
console.table(err);
res.sendStatus(500);
});
In this instance by doing the same thing, we can see that a request to localhost:3000/subapp/test2 only calls the the sub app error handler. This shows that the errors are being handled properly.
From the above we can see that there aren't any issues with random JS objects being passed through (you can dig through the Express Router code and see this as well). The only reason I can see that the http-errors wouldn't be working properly would be if they are causing a conflict with the error handling code.
Looking at the express router code we can see that it's picking up a few properties from the error object and acting based on that. I would check that your http-errors Forbidden error object isn't accidentally conflicting with one of these use cases. If that's the case, then I'd suggest finding a different error library.
I'm assuming you're also using the npm http-errors library. If that's the case, it looks like you should be providing a message on error creation. You could be getting yourself into a situation where your program is hanging or erroring in some other way because you're not providing a message.

I can't successfully chain my route handlers?

I've got a node.js/express app I'm working on and routes that look like-
app.post('/user/:who/update', isLoggedIn, userUpdate.save);
inside userUpdate.save I'm calling res.redirect or res.render (different routes but same idea). I don't like this. I'd like to keep my res.* calls in routes.js, but when I attempt this
app.post('/user/:who/update', isLoggedIn, userUpdate.save, function(req, res) {
res.redirect('/user/'+req.user.local.username);
});
with a call to next(req, res) at the end of userUpdate.save, the res.redirect function isn't called. What I think next() is, does not seem to be what it actually is. What am I missing?

The call to next() bypasses the remainder of your callbacks.
See this ref http://expressjs.com/api.html#app.post.method
Take a look at this example and alternately comment out each of the next() calls (and then both of them) and watch where the execution flows.
var express = require('express');
var app = express();
app.get('/test', function(req, res, next){
console.log('/test callback1');
next('route');
//next();
}, function(res, res, next){
console.log('/test callback2');
res.send('sent from /test/cb2')
});
app.get('/test', function(req, res){
console.log('response from /test route handler 2');
res.send('sent from /test route handler 2');
})
var server = app.listen(8911, function (s) {
console.log('Listening on port ', server.address().port);
});

undefined is not a function: unit testing passport authentication custom callback

I'm new to passport and express and trying to get a better idea of how everything works together by creating unit tests for all of my code. I have been having good success but today ran into an issue I don't quite understand...
I'm attempting to unit test the following exported function on session.js:
'use strict';
var mongoose = require('mongoose'),
passport = require('passport');
exports.login = function (req, res, next) {
passport.authenticate('local', function(err, user, info) {
var error = err || info;
if (error) return res.json(401, error);
req.logIn(user, function(err) {
if (err) return res.send(err);
res.json(req.user.userInfo);
});
})(req, res, next);
};
I seem to be having trouble with the second to last line (req, res, next) and how/when it gets called. I also have never seen this type of call in Javascript where the last line is just a set of parameters.
In order to test I'm using rewire, sinon, and mocha. In my test I'm using rewire to change the passport dependency to a mock object that I control.
My test seems to be working as expected as evidenced by where it is failing and what instanbul is telling me is covered but it alwasy throws: TypeError: undefined is not a function.
If I comment out the (req, res, next) line in session.js then my test actually runs successfully.
My test session.unit.js:
'use strict';
var rewire = require('rewire'),
should = require('should'),
sinon = require('sinon'),
sessionController = rewire('../../../../lib/controllers/session'),
passportMock = {};
describe('Session Controller', function() {
describe('#login', function(){
beforeEach(function(){
sessionController.__set__({
'passport': passportMock
});
});
it('should return 401 status and error if passport authentication returns error', function(){
//given
var res = {
json: sinon.spy(),
send: sinon.spy()
},
req = {
logIn: sinon.spy()
},
next = sinon.stub();
passportMock.authenticate = sinon.stub().callsArgWith(1, 'ERROR', null, null);
//when
sessionController.login(req, res, next);
//then
res.json.calledWith(401,'ERROR').should.be.true;
});
});
});
My questions are:
What is the last line (req, res, next) used for and when is it called? (I suspect middleware)
Is there a way I can change my test to get it to pass without the undefined error?
Thanks very much for reading and any help you can provide!!
** EDIT: **
I think I left out a critical piece of information... This session.login function is called from my routes.js file so I believe the last line is needed for middleware to continue. I'm still confused as to how to allow this to continue processing in the unit testing though.
routes.js snippet:
app.route('/api/session')
.post(session.login)
.delete(session.logout);
** EDIT2: **
Added the top part of session.js for clarity on how passport is initially declared with require. In the unit test I am replacing passport via rewire with my mock (stub) object so that I can control what passport returns.

I'm not sure if this will help, but this is generally how I stub passport.authenticate when used in the same way you have.
var stub = sinon.stub(passport, 'authenticate').returns(function() {});
stub.yields(new Error('fails here'));
// add your tests here
stub.restore();

The })(req, res, next); towards the end of your session.js is unnecessary because of how scoping rules work in JavaScript and because passport.authenticate does not return a function (it probably returns nothing which by default returns undefined), so that is the reason for the error.
Just change the })(req, res, next); from the end of session.js to just });.

Handling occasional undefined errors nicely in express

If at any point, I get an error, by trying to do something with an undefined, my entire express app crashes with a TypeError, instead of handling it nicely by redirecting to an HTTP 500 page.
Is there any way to handle these exceptions generally, or I will need to manually check in my router methods?

Have you tried this from the docs - Express Error handling?
Error-handling middleware are defined just like regular middleware, however must be defined with an arity of 4, that is the signature (err, req, res, next):
app.use(function(err, req, res, next) {
console.error(err.stack);
res.send(500, 'Something broke!');
});
Though not mandatory error-handling middleware are typically defined very last...

Maybe try { ... } catch(e) {...} is what you are looking for?
Or just checks if value is not undefined. Simple if (value) { ... will do the job

As mentioned by phenomenal you can use express error handler middle-ware to handle error at centralized place.
app.use(function(err, req, res, next) {
console.error(err.stack);
res.send(500, 'Something broke!');
});
Than to pass error from your routes you can use next to pass error to this middle-ware like this
app.get('/login',function(req,res,next){
next("your error"); // The error middle-ware handle this error.
})