Passport.js strategy with no field required - node.js

Question

I'm surprised that it's so hard to find, or maybe something wrong with me.
I need a passport.js strategy that requires no fields - to run authentication with it on simple user GET request to '/' and manipulate user session data to, for example, make a new 'guest' user.
Maybe i can do this via passport local-strategy? Or am i need to create a custom one?
I saw this Configure Passport to accept request without body? question, yet i just simply can't figure out how the suggested in answer wrapping will change anything.
Edit: here's what I'm trying to achieve
passport.use('guest', new LocalStrategy({
passReqToCallback: true
},
function (req, NOusername, NOpassword, done) {
////NO PASSWORD OR USERNAME checks here, just deciding what kind of temporary user needs to be created///
if (req.session.passport) {
///create new user with previous session data
done(null,user)
}
else {
///create clean user
done(null, user)
})
)
and then in routes.js
app.get('/', passport.authenticate('guest'), function (req, res) {
res.render('PeerRoom.ejs', req.user);
});

Answer 1

Edit: Another approach could be using req.logIn and skip dealing with the strategies altogether
app.get('/', yourCustomGuestAuthenticationMiddleware, function (req, res) {
res.render('PeerRoom.ejs', req.user);
});
function yourCustomGuestAuthenticationMiddleware(req, res, next){
// No need to do anything if a user already exists.
if(req.user) return next();
// Create a new user and login with that
var user = new User({name: 'guest'+Math.random().toString() });
user.save();
req.logIn(user, next);
}
To make a new guest user, simply do it instead of rejecting an authentication
Here's a modified example from the docs
var passport = require('passport'),
LocalStrategy = require('passport-local').Strategy;
passport.use(new LocalStrategy(
function(username, password, done) {
User.findOne({ username: username }, function(err, user) {
if (err) return done(err);
if (!user) {
/* HERE, INSTEAD OF REJECTING THE AUTHENTICATION */
// return done(null, false, { message: 'Incorrect username.' });
/* SIMPLY CREATE A NEW USER */
var user = new User({ name: 'guest'+Math.random().toString() });
user.save();
/* AND AUTHENTICATE WITH THAT */
return done(null, user);
}
if (!user.validPassword(password)) {
return done(null, false, { message: 'Incorrect password.' });
}
return done(null, user);
});
}
));