empty objects are being saved as null

[matanDevalore]

Prerequisites

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

Mongoose version

8.2.4

Node.js version

20.12.0

MongoDB server version

6.0.2 Community

Typescript version (if applicable)

5.4.3

Description

I have a schema which accepts an Object property.

On mongoose version 8+, when updating the document in DB, with an empty object ( {} ), the value that is actually being saved is null.

when querying the DB and fetching the relevant document, variables: null is being returned, which makes other validations in the system to throw the following error:

On older versions (tested on 7.6.3), it doesn't happen and it behave as expected (the object is being saved as an empty object):

I can ofc changing the validators in the system, but it seems like the wrong solution. empty object doesn't equal to null.

Steps to Reproduce

1. create a mongoose model with an object field. for example:

const TestSchema = new Schema({
  data: {
    type: Object,
  },
});

export const TestModel = mongoose.model('Test', TestSchema);

2. create a new document in DB (with empty object: data: {}). (the object will be saved without data property - which is fine)
3. load this document using findOne.
4. reset the data field again to empty object: document.data = {}
5. save this document using document.save()

Expected Behavior

after update, the data field should be an empty object {}. as can see using mongoDB Compass in old mongoose versions:

another good solution for me, is if you will add a new parameter that will allow me to choose the way it should behave. (allowNullable: false)

[vkarpov15]

This was fixed in v8.3.1 with #14504, looks like the same issue as #14445. Please upgrade to v8.3.1 for the fix.