Unknown authentication strategy "google"

Question

I get the message Unknown authentication strategy "google" in the browser when I try to login with Google using passport.JS in my node.js and express app. I can't seem to figure out what I'm doing wrong. Here is my code. I've also read other posts but didn't find a working fix yet.

config\passport.js

const passport = require('passport');
const mongoose = require('mongoose')
const User = require('../Models/User')
const GoogleStrategy = require('passport-google-oauth20').Strategy

module.exports = function (passport) {
  passport.use(
    new GoogleStrategy(
      {
        clientID: process.env.GOOGLE_CLIENT_ID,
        clientSecret: process.env.GOOGLE_CLIENT_SECRET,
        callbackURL: '/auth/google/callback',
      },
      async (accessToken, refreshToken, profile, done) => {
        const newUser = {
          googleId: profile.id,
          displayName: profile.displayName,
          firstName: profile.name.givenName,
          lastName: profile.name.familyName,
          image: profile.photos[0].value,
        }

        try {
          let user = await User.findOne({ googleId: profile.id })

          if (user) {
            done(null, user)
          } else {
            user = await User.create(newUser)
            done(null, user)
          }
        } catch (err) {
          console.error(err)
        }
      }
    )
  )

  passport.serializeUser((user, done) => {
    done(null, user.id)
  })

  passport.deserializeUser((id, done) => {
    User.findById(id, (err, user) => done(err, user))
  })
}

Routes\auth.js

const express = require('express')
const passport = require('passport')
const router = express.Router()

// @desc    Auth with Google
// @route   GET /auth/google
router.get('/google', passport.authenticate('google', { scope: ['profile'] }))

// @desc    Google auth callback
// @route   GET /auth/google/callback
router.get(
  '/google/callback',
  passport.authenticate('google', { failureRedirect: '/login' }),
  (req, res) => {
    res.redirect('/')
  }
)

// @desc    Logout user
// @route   /auth/logout
router.get('/logout', (req, res) => {
  req.logout()
  res.redirect('/')
})

module.exports = router

App.js

var createError = require('http-errors');
var express = require('express');
const dotenv = require('dotenv');
var path = require('path');
const passport = require("passport")
var cookieParser = require('cookie-parser');
var logger = require('morgan');
const connectDB = require('./config/db')
const mongoose = require('mongoose');
const session = require("express-session")
const MongoStore = require('connect-mongo')(session)
const expressLayouts = require("express-ejs-layouts")
const port = 3000

// Load config
dotenv.config({ path: './config/config.env' })

//Connect to MongoDB
connectDB();

// passport config
require('./config/passport');

const app = express();

// view engine and EJS layout setup
app.use(expressLayouts)
app.set('layout', './layouts/layout')
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'ejs');

app.use(logger('dev'));
app.use(express.json());
app.use(express.urlencoded({ extended: false }));
app.use(cookieParser());
app.use(express.static(path.join(__dirname, 'public')))

//Passport middleware - Express Session
  session({
    secret: process.env.SESSION_SECRET,
    resave: false,
    saveUninitialized: false,
    store: new MongoStore({ mongooseConnection: mongoose.connection, collection: 'sessions' }),
  })

app.use(passport.initialize());
app.use(passport.session());

// routes
app.use('/', require('./routes/homepage'))
app.use('/login', require('./routes/login'))
app.use('/users', require('./routes/users'))
app.use('/project', require('./routes/project'));
app.use('/about', require('./routes/about'));
app.use('/auth', require('./routes/auth'));

// catch 404 and forward to error handler
app.use(function(req, res, next) {
  next(createError(404));
});

// error handler
app.use(function(err, req, res, next) {
  // set locals, only providing error in development
  res.locals.message = err.message;
  res.locals.error = req.app.get('env') === 'development' ? err : {};

  // render the error page
  res.status(err.status || 500);
  res.render('error');
});
app.listen(port, () => {
  console.log(`Example app listening at http://localhost:${port}`)
})

module.exports = app;

Answer 1

I found my answer. I had to get rid of the module.exports = function (passport) in my passport.js file since I'm calling it through ``require('./config/passport')instead ofrequire('./config/passport')(passport)```