Mongoose: Binary buffer saved incorrectly

[ValYouW]

This is a reopen of #5497 (as I couldn't get a response there).
Reproduction was on Mongoose v4.11.7

Calling findOneAndUpdate and updating a binary field saves the binary data incorrectly.
As mentioned in #5497 this is a breaking change that apparently introduced in version 4.11.2 (I suspect this commit: 1613ef5).

Please see the reproduction script below (which include runSettersOnQuery: true):

var mongoose = require('mongoose'),
    uuid = require('uuid'),
    uuidParse = require('uuid-parse');

mongoose.Promise = Promise;

function generateUUID() {
    var buffer = uuid.v4(null, new Buffer(16));
    return new mongoose.Types.Buffer(buffer).toObject(0x04);
}

function toUUID(string) {
    if (!string) {return null;}
    if (Buffer.isBuffer(string) || Buffer.isBuffer(string.buffer)) { return string; }
    var buffer = uuidParse.parse(string);
    return new mongoose.Types.Buffer(buffer).toObject(0x04);
}

function fromUUID(buffer) {
    if (!buffer || buffer.length !== 16) {return null;}
    return uuidParse.unparse(buffer);
}

var UserSchema = new mongoose.Schema({
    name: String,
    foo: {
        type: mongoose.Schema.Types.Buffer,
        get: fromUUID,
        set: toUUID
    }
}, {collection: 'users'});

var UserModel = mongoose.model('User', UserSchema);

var connStr = 'mongodb://test:[email protected]/test';
mongoose.connect(connStr);

var user = {name: 'insert', foo: uuid.v4()};
console.log('Inserting user, my foo will be OK:', user);
var dalUser = new UserModel(user);
dalUser.save().then(() => {
    console.log('User inserted successfully');
}).catch(console.error);


user = {name: 'upsert', foo: uuid.v4()};
console.log('Upserting user, my foo will be wrong:', user);
var opts = {upsert: true, setDefaultsOnInsert: true, runSettersOnQuery: true };
UserModel.findOneAndUpdate({foo: user.foo}, user, opts).exec().then(() => {
    console.log('User upserted successfully');
}).catch(console.error);

And the result in the DB is:

Thanks!

[vkarpov15]

Will double check why this changed, thanks for your patience.

[vkarpov15]

Thanks for your patience @ValYouW and thanks for the very detailed bug report. We didn't notice it because the mongoose logs showed that we were saving with sub_type = 4, but underneath the logs it ended up becoming sub_type = 0. Fix will be in 4.11.9 tomorrow :+1: :beers: