Use Case

Using the nodejs driver, I'm calling

collection.updateOne({_id: ObjectId("...")}, {$addToSet: undefined, $inc: undefined})

This seems dumb, but it is because I have code that omits the various terms if there are no corresponding updates.  When calling MongoClient.connect, I am including ignoreUndefined=true.  

My expectation is that this would either throw an error – because there are no actions to take (they are both undefined) – or there would be no change to the record at all.  In fact, what happens is that all fields in the record other than _id are gone after this update.  Obviously, that's a disaster.

I have code that avoids these updates that would do nothing.  But in one particular case I failed to detect this situation and certain critical records were essentially lost.

I note that if I had called replaceOne() that would be different.  But surely updateOne shouldn't work like this.

User Experience

• What is the desired/expected outcome for the user once this ticket is implemented?
• If bug: What is the number of impacted customers? How severe is the impact? Is anyone blocked or broken?

Dependencies

• upstream and/or downstream requirements and timelines to bear in mind

Risks/Unknowns

• What could go wrong while implementing this change? (e.g., performance, inadvertent behavioral changes in adjacent functionality, existing tech debt, etc)
• Is there an opportunity for better cross-driver alignment or testing in this area?
• Is there an opportunity to improve existing documentation on this subject?

Acceptance Criteria

Implementation Requirements

• The check for "atomic" (dollar prefix keys) operators should take into account the ignoreUndefined setting when determining if those keys will be included in the server command.
• Throw an error from the driver if all atomic operators are undefined.

Testing Requirements

• unit test, spec test sync, etc

Documentation Requirements

• DOCSP ticket, API docs, etc

Follow Up Requirements

• additional tickets to file, required releases, etc
• if node behavior differs/will differ from other drivers, confirm with dbx devs what standard to aim for and what plan, if any, exists to reconcile the diverging behavior moving forward