Auto remove empty object in condition

[adostal]

Prerequisites

• I have written a descriptive issue title
• I have searched existing issues to ensure the bug has not already been reported

Mongoose version

6.9.2

Node.js version

19.0.1

MongoDB server version

6

Typescript version (if applicable)

4.9.5

Description

I use casl.js in my project.
The conditions themselves are generated automatically from the @casl/mongoose library
The problem is that newer versions of mongoose remove the empty object that is sometimes part of the condition.
After updating mongoose from 6.7.5 to 6.9.2, the empty object started to be removed.

If it would be possible to set this behavior in the mongoose configuration, that would be great.

Steps to Reproduce

// query for all people (conditions are from casl.js - sometimes with empty object)
const people = PeopleModel.find({$or: [
  {},
  {type: "xxx"},
  .... other conditions
]})

Expected Behavior

In version 6.9.2 is finally condition without empty object {}:

condition: $or: [{"type": "xxx", ... other conditions}]

In version 6.7.5 is finally condition with empty object {}:

condition: $or: [{}, {"type": "xxx", ... other conditions}]

[vkarpov15]

This looks like it is caused by #12898 . We merged this issue because we thought that $or: [{}] is likely indicative of a potential bug where strictQuery removed some fields. However, you're right, there are some valid use cases for this behavior. We'll revert #12898 in 6.10.1.