Repro for mongoose Model.populate throwing uncaught synchronous MissingSchemaError.

bar.js

const mongoose = require('mongoose');

module.exports = mongoose.model('Bar', new mongoose.Schema({
  baz: String,
}));

foo.js

const mongoose = require('mongoose');

module.exports = mongoose.model('Foo', new mongoose.Schema({
  bar: {
    type: mongoose.Schema.ObjectId,
    ref: 'Bar',
  },
}));

index.js

const mongoose = require('mongoose');
mongoose.Promise = Promise;

const Foo = require('./foo');
// Uncomment to "fix":
// const Bar = require('./foo');

process.on('uncaughtException', function (err) {
  console.log('Uncaught exception!', err);
  process.exit(1);
});

mongoose.connect('mongodb://localhost/test_mongoose_populate_uncaught')
.then(repro)
.then(() => console.log('resolved'))
.catch((err) => console.log('rejected with', err))
.then(() => mongoose.disconnect());

function repro () {
  try {
    return Foo.find().populate('bar').exec();
  } catch (err) {
    console.log('I can catch it!');
  }
}

setup.js

const mongoose = require('mongoose');
mongoose.Promise = Promise;

const Foo = require('./foo');
const Bar = require('./bar');

mongoose.connect('mongodb://localhost/test_mongoose_populate_uncaught')
.then(setup)
.then(() => mongoose.disconnect());

function setup () {
  return Bar.create({baz: 'abc'})
  .then((bar) => Foo.create({bar}));
}