FindByIdAndUpdate creates an _id inside a nested object

Issue

I'm developing an endpoint that accepts a basic invitation, I need to get a notification by an id provided in the parameters (suing express), and then update his result field. The interface/schema is like this:

const NotiticationSchema = new Schema<Notitication>({
    title: { type: String, required: true },
    description: { type: String, default: null },
    date: { type: Date, default: Date.now() },
    type: { type: String, required: true },
    navigation: {
        type: String,
        enum: NotificationNav,
        required: true
    },
    navigationId: {
        type: String,
        enum: NotificationIds,
        required: true
    },
    teamId: { type: String, required: true },
    result: {
        type: {
            accepted: { type: Boolean, required: true },
            motivation: { type: String, required: true }
        },
        default: null
    }
});

This is the code that I'm currently using:

const notification = await NotiticationModel.findByIdAndUpdate(req.params["id"]!, { $set: { result: { accepted: true, motivation: null } } });

The expected output should be:

{
  ...
  "result": {
    "accepted": true,
    "motivation": null
  }
}

What NotiticationModel.findByIdAndUpdate() does:

{
  ...
  "result": {
    "accepted": true,
    "motivation": null,
    "_id": {
      "$oid": "65b23b495a60bda2c6e67996"
    }
  }
}

I've never encountered this behaviour, anyone can help?

P.S. I've already asked AI, it didn't give any useful advice.

Solution

This is expected behaviour. When you add an object to MongoDB then mongoose will automatically assign an _id property of type ObjectId to it.

To remove this feature pass the _id: false property into your schema for the relevant object like so:

const NotiticationSchema = new Schema<Notitication>({
    //...
    teamId: { type: String, required: true },
    result: {
        type: {
            accepted: { type: Boolean, required: true },
            motivation: { type: String, required: true }
        },
        default: null,
        _id: false //< here
    }
});

Answered By - jQueeny