Mongoose/MongoDB not saving objects

Question

In my last commit, I have my POST route working perfectly, but after starting implementing PassportJS I'm not able to save new users anymore. I have been deleting the db and the collections in a couple of occasions mainly because I've been changing the structure of the schema, so I want to ask if any kind of corruption is possible, knowing that I always have been manipulating Mongo through MongoDB Compass.

//DB setup
    mongoose.set('useFindAndModify', true);
    this.connection = mongoose.createConnection(process.env.MONGODB_URL || MONGO_URI, {
        useNewUrlParser: true,
        useCreateIndex: true
    });
    this.connection.once('open', args => console.log('DB is connected'));
    this.connection.once('error', err => console.log(err));

This is the method executed by the route and the route itself.

private async postUser(req: Request, res: Response) {
    const {username, password, email} = req.body;
    console.log(username + " " + password + " " + email);
    const {salt, hash} = this.genPass(password);
    console.log(salt + " " + hash);
    const newUser = new User({ username: username, password: hash, salt: salt, email: email });
    console.log(newUser);
    await newUser.save((err, newUser) => {
        console.log('smth');
        if (err) {
            res.json('username or email already exist');
            return console.error(err);
        }
        else {
            console.log(newUser.get('username') + ' created');
            res.json({data: newUser});
        }
    });
}

this.router.post('/sign', (req: Request, res:Response) => {
        this.postUser(req, res)
            .then(x => console.log (x));
    });

The schema

const userSchema = new Schema ({
    username: { type: String, required: true, unique: true},
    password: { type: String, required: true},
    salt: {type: String, required: true},
    email: { type: String, required: true, unique:true, lowercase: true}
},
{
  timestamps: true,
});

export default model('user', userSchema);

Console output

(node:19004) DeprecationWarning: current Server Discovery and Monitoring engine is deprecated, and 
will be removed in a future version. To use the new Server Discover
and Monitoring engine, pass option { useUnifiedTopology: true } to the MongoClient constructor.

Server on port 3000
DB is connected
admin passw email
cf0bcf9bd942010fba7bfd1bcde96ae93b2e1a55f078a70b1cb48f000551c4e1 
e73a50fb837a55abd9bcc5da1e635cb0c825663aaaf2b3318f8f9bc38ea89e50af2c70f4ee247256a282709b9a6abee0d9ba5
a574d6dec19d519692683027135
{
  _id: 5ef6b7111668ca4a3c0e8332,
  username: 'admin',
  password: 
  'e73a50fb837a55abd9bcc5da1e635cb0c825663aaaf2b3318f8f9bc38ea89e50af2c
   70f4ee247256a282709b9a6abee0d9ba5a574d6dec19d519692683027135',
  salt: 'cf0bcf9bd942010fba7bfd1bcde96ae93b2e1a55f078a70b1cb48f000551c4e1',
  email: 'email'
 }
 undefined
 POST /sign - - ms - -

(Also would like to ask about that deprecation warning but I don't think it's related to the main topic of this post)

Answer 1

It seems like you user is saved to the database, save won't return the inserted document

await newUser.save((err) => {
        if (err) { 
     ///.... 
    }

also you have to check if the user exist in the database before hand

User.find({ email: email, (err, user) =>{
     if (err) throw err 
      if(user) return console.log("user already exist")
       //... your code 
    const newUser = new User({ username: username, password: hash, salt: salt, // construct a document
     email: email });
     
     newUser.save()
      
});

to make mongoose deprecated errors disappear add this lines

mongoose.set('useUnifiedTopology', true)
mongoose.set('useNewUrlParser', true)
mongoose.set('useFindAndModify', false)

Answer 2

Fixed it. Instead of using createConnection() I used mongoose.connect() and when I needed the object Connection I used mongoose.connection . Weird af I think and I would love to know the reason but if it works it works.