Mongoose populate - node.js

Question

Here is my test code which I can not figure out why it isn't working, as it is very similar to test 'populating multiple children of a sub-array at a time'.
var mongoose = require('mongoose'),
Schema = mongoose.Schema,
ObjectId = Schema.ObjectId;
mongoose.connect('mongodb://localhost/testy');
var UserSchema = new Schema({
name: String
});
var MovieSchema = new Schema({
title: String,
tags: [OwnedTagSchema]
});
var TagSchema = new Schema({
name: String
});
var OwnedTagSchema = new Schema({
_name: {type: Schema.ObjectId, ref: 'Tag'},
_owner: {type: Schema.ObjectId, ref: 'User'}
});
var Tag = mongoose.model('Tag', TagSchema),
User = mongoose.model('User', UserSchema),
Movie = mongoose.model('Movie', MovieSchema);
OwnedTag = mongoose.model('OwnedTag', OwnedTagSchema);
User.create({name: 'Johnny'}, function(err, johnny) {
Tag.create({name: 'drama'}, function(err, drama) {
Movie.create({'title': 'Dracula', tags:[{_name: drama._id, _owner: johnny._id}]}, function(movie) {
// runs fine without 'populate'
Movie.find({}).populate('tags._owner').run(function(err, movies) {
console.log(movies);
});
});
})
});
Produced error is
node.js:201
throw e; // process.nextTick error, or 'error' event on first tick
^
TypeError: Cannot call method 'path' of undefined
at /Users/tema/nok/node_modules/mongoose/lib/model.js:234:44
Update
Got rid from OwnedTag and rewrote MovieSchema like this
var MovieSchema = new Schema({
title: String,
tags: [new Schema({
_name: {type: Schema.ObjectId, ref: 'Tag'},
_owner: {type: Schema.ObjectId, ref: 'User'}
})]
});
Working code https://gist.github.com/1541219

Answer 1

Your variable OwnedTagSchema must be defined before you use it or you'll end up doing basically this:
var MovieSchema = new Schema({
title: String,
tags: [undefined]
});
Move it above MovieSchema definition.

Answer 2

I would expect your code to work, too. Does it work if you put the OwnedTag right in MovieSchema, like so?
var MovieSchema = new Schema({
title: String,
tags: [{
_name: {type: Schema.ObjectId, ref: 'Tag'},
_owner: {type: Schema.ObjectId, ref: 'User'}
}]
});
edit:
var MovieSchema = new Schema({
title: String,
tags: [{ type: Schema.ObjectId, ref: 'OwnedTag' }]
});