$set doesn't update subdocument

[jeffwhelpley]

When I do this in mongoose 4.1.2:

user.findOneAndUpdate({ _id: someid }, { $set: { field1: 'val1', field2: { subfield1: 'sub1', subfield2: 'sub2' }}});

field1 is updated, but field2 is not. When I downgrade to mongoose 4.0.6 this works fine.

[vkarpov15]

What does your schema look like?

[jeffwhelpley]

The code example I gave is fake. Here is a real example:

var postSchema = {
  title: String,
  answers: [{
    details: String,
    stats: {
      votes: Number,
      count: Number
    }
  }]
};

// later on in code
post.findOneAndUpdate(
  { _id: somePostId, answers._id: someAnswerId }, 
  { $set: { 'answers.$': { details: 'blah', stats: { votes: 1, count: 3 }}}}
);

So, in this example in 4.1.2 details is correctly updated to blah, but the stats field is completely removed from the answer. Even if there was a value in there before, its like stats was $unset or something. In 4.0.6, the details and stats are set correctly.