Cannot update MongoDB using mongoose - node.js

Question

I am trying to update a collection from my database using de node module mongoose. The problem is with $set updates. Here is my code:
// Update a user
app.patch('/user/:user_id', passport.authenticate('bearer', { session: false }),
function (req, res) {
var conditions = { _id: new ObjectId(req.params.user_id)},
updateObj = { $set: req.body }; // {email : "bob#example.com", username: "bob"}
User.update(conditions, updateObj, function callback (err, numAffected, rawResponse) {
if (err) {
res.send(err);
return;
}
// numAffected is the number of updated documents
if (numAffected == 0) {
res.json({ message: 'No user affected'});
return;
}
res.json({ message: 'User updated'});
});
});
If I update an existing key like email, it is updated. But if I want to add a new key, numAffected is always 0 and the rawResponse is undefined.
Any idea of what happens?
Edit
Here is my Schema:
var userSchema = mongoose.Schema({
email : String,
username : String,
password : String
});

Answer 1

In order to set multiple fields in a document, you must set the Multi option in your config, otherwise Mongoose will ignore the continuation, and only update the first doc.
From the docs:
var conditions = { name: 'borne' }
, update = { $inc: { visits: 1 }}
, options = { multi: true };
Model.update(conditions, update, options, callback);
function callback (err, numAffected) {
// numAffected is the number of updated documents
});
Another note here: The numAffected should return as expected, but I can't find any documentation on their site about the raw response, but it should return as expected as well. Do you know of any documentation for this?

Answer 2

I think this is what you really want to do with mongoose to update email and username of a user.
app.patch('/user/:user_id', passport.authenticate('bearer', { session: false }),
function (req, res) {
User.findOneAndUpdate({_id: req.params.user_id},
{
$set: {
username: req.body.username,
email: req.body.email
}
}, function(err, user) {
if (err)
res.send(err);
if (user) {
res.json({message: 'User updated'});
} else {
res.json({message: 'User does not exist'});
}
});
});