Understanding done function in PassportJS - node.js

Question

I am trying to implement a normal login and signup module and I am facing difficulty in understanding the done function.here is the line I feel is responsible for the done function. Now what I wanted to do was return the corresponding messages like if there was some server error.
app.post('/user/auth/login', passport.authenticate('local-login'), function(req, res) {
console.log("Login Request Successful");
if(req.user){
res.status(200).send(JSON.stringify({
'msg' : "Successfully logged in"
}));
}
else{
res.status(400)
}
//console.log(req.user);
});
This is for the case when after logging in Passport attaches a user object to the request module.
But how do I differentiate between a server error and authentication failed error
Here is my authenticate middleware.
passport.use('local-login', new LocalStrategy({
passReqToCallback: true
}, function(req, username, password, done) {
Users.findOne({
'emailId': username
}, function(err, user) {
if (err)
return done(err);
if (!user)
return done(null, false);
else if (passwordHash.verify(password, user.password)) {
console.log("User is verified");
req.session.save();
return done(null, user);
} else
return done(null, false);
});
}));
Basically, I need to access the messages in done() function. How do I do that?
How does function, like if I type the wrong password, the message I get in my browser in Unauthorized. It means somewhere it is setting the response.data field to Unauthorized. Instead of that I want to know when there is an error and want to send my custom message.

Answer 1

I don't know what do you mean by
access the messages in done() function
, however You can very well do with supplying addition object with message in done callback
if (!user) {
return done(null, false, {
message: 'Unknown user or invalid password'
});
}
if (!user.authenticate(password)) {
return done(null, false, {
message: 'Unknown user or invalid password'
});
}

Answer 2

Another method.
I don't know how I missed it. There is an option of custom callbacks in the docs. Here is the implementation of the same.
app.post('/user/auth/login', function(req, res) {
passport.authenticate('local-login', function(err, user, info) {
if (err) {
res.status(500).send(JSON.stringify({
'msg': "Internal Server Error"
}));
}
if (!user) {
res.status(401).send(JSON.stringify({
'msg': "Username or Password is incorrect"
}));
}
if (user) {
res.status(200).send(JSON.stringify({
'msg': "Successfully logged in"
}));
}
})(req, res, next);
});
The only issue with this solution is that you will have to manually login and create session and all that.
An optional callback can be supplied to allow the application to overrride the default manner in which authentication attempts are
handled. The callback has the following signature, where user
will be set to the authenticated user on a successful
authentication attempt, or false otherwise. An optional info
argument will be passed, containing additional details provided by
the strategy's verify callback.
app.get('/protected', function(req, res, next) {
passport.authenticate ('local',function(err, user, info) {
if (err) { return next(err) }
if (!user) { return res.redirect('/signin') }
res. redirect('/account');
})(req, res, next);
});
Note that if a callback is supplied, it becomes the application's responsibility to log-in the user, establish a session, and otherwise
perform the desired operations.