Mongoose 6: Deep-populate with string causing errors (undocumented breaking change?)

[hansemannn]

I'm not sure if this may be documented as a breaking change somewhere, but I couldn't find it: When using a string-based populate, it fails with Mongoose 6 while it works with 5.x:

await MyModel.findById(myId).populate({ path: 'subModel', populate: 'subField' });

The same works with brackets:

await MyModel.findById(myId).populate({ path: 'subModel', populate: ['subField'] });

It's fine to migrate, but devs may not know it's an issue until they run a related query.

[IslandRhythms]

I'm reading the docs and I don't see a populate option in the populate function. What does the populate option do?
From what I'm reading on your example code, do you mean for populate to be model? so path: 'subField', model: 'subModel'?

[mjfwebb]

I believe the changes are part of this note https://mongoosejs.com/docs/migrating_to_6.html#removed-execpopulate

The note itself is poorly written. As you say there were more changes made to the way the populate method was changed than just execPopulate being removed: chaining .populate calls was replaced by an array of populate paths. The same is true for nested populate paths like what you're attempting to do.

[hansemannn]

This is possible! If helpful, I can update the docs and draft a PR for it.