Allow documents to detach from sessions once they have ended

[chriskrogh]

Do you want to request a feature or report a bug?
Request a feature / Report a bug (not sure what expected behaviour is for this specific cse)

What is the current behavior?
MongoError: Use of expired sessions is not permitted is thrown when populating a document that was created in a session (See the src/index.ts in the repo below for an easy to read example).

If the current behavior is a bug, please provide the steps to reproduce.

repo for repro

• model A and model B exist such that model A has a ref to model B
• start a session & transaction
• create a document using model B, then a document using model A with the reference (ObjectId) to the B document
• commit the transaction & end the session
• try to populate the instance of B on A
• error

To avoid this, one can simply use the existing B doc when creating A instead of using B's id and a reference. However, this error is actually thrown if any of the subdocuments of B on A are populated as well (e.g if B had a C and we tried to populate C).

What is the expected behavior?
I understand that because A and B were created in a session, that subsequent writes that occur once the session has ended will still be "linked" to a dead session and that's what's throwing the error here. However, I feel like there should be an easy way to detach a document from a session (especially since the session successfully ended).

What are the versions of Node.js, Mongoose and MongoDB you are using? Note that "latest" is not a version.
Versions are visible in the repo attached.