Documentation

OptionOrNull

Represents either a value, a missing field, or a null field Normally you would only need Option but this type exists for use with APIs that make a distinction between a json field being null and being missing altogether

Ensure you set nullAsUndefined and emptyEncodeAsNull to false in your jsonOptions eg: core.jsonwithoptions { emptyencodeasnull: bool.false, nullasundefined: bool.false }