_id getter for ObjectIds

[vkarpov15]

Re: #6115, make it much easier to get an id regardless of whether a path is populated or not

[djanowski]

👏

[vkarpov15]

@djanowski I'd love to hear more about why you're so excited for this change if you care to share 👍

[djanowski]

When dealing with populated or non-populated paths, when you need just the ID, we have a bunch of (foo.bar._id || foo.bar).toString().

[freezy]

This breaks a lot of code for me.

I have serializers that need to determine if a field is populated. I used to do that with doc.populated(field), but some queries are aggregations where that doesn't work (because there is no Mongoose document).

I used to fall back to return doc.field && doc.field._id, but that returns now true also for unpopulated fields. Is there a way to know if an object comes from an aggregation so I can do the check accordingly?

[vkarpov15]

@freezy sorry about the inconvenience. Can you explain what you mean by "some queries are aggregations"? You can't use populate() with aggregate, so I'm not sure why you would need to check if a field is populated if the document came out of an aggregate()