Populate does not work with cursor(), but works with exec()

I’m running Mongoose 4.4.20 with Mongo 3.0.12.

These are the relevant parts of my schema:

var ObjectId = mongoose.Schema.Types.ObjectId
var campaignSchema = mongoose.Schema({
  // ...
  summary: { type: ObjectId, ref: 'summaries' },
  // ...
}

var summarySchema = mongoose.Schema({
  // ...
}

var Campaign = mongoose.model('Campaign', campaignSchema, 'campaigns')
var Summary = mongoose.model('Summary', summarySchema, 'summaries')

If I use regular exec, it works just fine:

Campaign.find({
   ...
})
  .populate('summary')
  .exec()
  .then(function (data) {
    console.log(data)
  })

However, if I try the same with cursor, it does not work: the summary field is not populated:

var cursor = Campaign.find({
   ...
})
  .populate('summary')
  .cursor()

cursor.next().then(function (data) {
  console.log(data)
})

The code above only shows the refs’ ObjectId instead of the full document.

Edit

I’m really sorry, there might be an error when I copy-pasted the code. That extra .exec does not exist.

[vkarpov15]

@zoellner opened up a new issue #5334 to track, keeping this issue closed ☝️

[zoellner]

I am seeing the same issue. code to reproduce below. There are a few options to populate and I’m not seeing a difference. It seems that the model option is ignored

link1 is populated as expected (there is no difference when changing the model options, no error when using the model: 'asdf' option) link2 is always null after the population when using cursor

code to reproduce:

'use strict';

const mongoose = require('mongoose');
const _h = require('highland');

mongoose.Promise = global.Promise;
mongoose.connect('mongodb://localhost/mongoose-gh-4559');

const LinkedSchema = new mongoose.Schema({
  name: {type: String}
});

const Linked = mongoose.model('Linked', LinkedSchema);

const MainSchema = new mongoose.Schema({
  link1: {type: mongoose.Schema.Types.ObjectId, ref: 'Linked'},
  link2: {type: mongoose.Schema.Types.ObjectId}
});

const Main = mongoose.model('Main', MainSchema);

Linked.remove({}, () => {
  Main.remove({}, () => {
    Linked.create({name: 'link1'}, (err, link1) => {
      Linked.create({name: 'link2'}, (err, link2) => {
        Main.create({link1: link1._id, link2: link2._id}, () => {
          console.log('cursor');
          _h(Main.find({})
            //use string for Model
            .populate({path: 'link1', model: 'Linked'})
            .populate({path: 'link2', model: 'Linked'})

            //use reference to Model
            // .populate({path: 'link1', model: Linked})
            // .populate({path: 'link2', model: Linked})

            //use invalid model
            // .populate({path: 'link1', model: 'asdf'})
            // .populate({path: 'link2', model: 'asdf'})
            .lean()
            .cursor()
          )
          .tap(_h.log)
          .done(() => {
            console.log('no cursor');
            Main.find({})
            .populate({path: 'link1', model: 'Linked'}) //also works with model: Linked
            .populate({path: 'link2', model: 'Linked'}) //also works with model: Linked
            .lean()
            .exec((err, docs) => {
              console.log(docs);
              process.exit();
            });
          });
        });
      });
    });
  });
});

code output:

cursor
{ _id: 593064f0ee054b339b8a5165,
  link1: { _id: 593064f0ee054b339b8a5163, name: 'link1', __v: 0 },
  link2: null,
  __v: 0 }
no cursor
[ { _id: 593064f0ee054b339b8a5165,
    link1: { _id: 593064f0ee054b339b8a5163, name: 'link1', __v: 0 },
    link2: { _id: 593064f0ee054b339b8a5164, name: 'link2', __v: 0 },
    __v: 0 } ]