I am using this validator:

{{{}}
  $jsonSchema: {
    bsonType: 'object',
    additionalProperties: true,
    properties: {
      r: {
        bsonType: 'string',
      },
    },
  },
}

This validator should allow me to insert a document that doesn't have the property "r", but when I try to insert a document without this property it fails.

However, if I change the "r" field to "ref", then I can insert documents without the "ref" field.