Trigger fullDocumentBeforeChange doesn’t contain all fields

Hi,

I’m facing an issue when updating a document from a Realm/Atlas Device Sync and getting the complete fullDocumentBeforeChange data.

The problem:
I have a trigger with a config that looks like this:

{
  "name": "MyTrigger",
  "type": "DATABASE",
  "config": {
    "operation_types": ["UPDATE"],
    ...
    "match": {
          "operationType": "update",
          "updateDescription.updatedFields.myField": {
            "$exists": true
          }
    },
    "project": {
      "operationType": 1,
      "fullDocumentBeforeChange": {
        "myField": 1
      }
    },
    "full_document": false,
    "full_document_before_change": true,
    "unordered": false
  },
  "disabled": false,
  "event_processors": {
    "FUNCTION": {
      "config": {
        "function_name": "myFunctionName"
      }
    }
  }
}

I’ve also tried changing the project config to fullDocumentBeforeChange: 1 , but the result was that other fields were there, but not myField .

I’ve tested by manually changing the value from myField in the database, and in that case it works fine, but if I do it from Atlas Device Sync, it doesn’t.

Change event output example:

With Atlas Device Sync { ..., "fullDocumentBeforeChange": {} }
With MongoDB Compass { ..., "fullDocumentBeforeChange": { "myField": "my field value before change" } }