Deserializing an Option as None when field is missing

[petejodo]

I'm not sure this is actually possible so asking as a question here but given the following:

@Serializable
data class PatchData(
  val required: Int,
  val someNullableProperty: Option<Int?>,
)

Is it possible to have someNullableProperty to only be None if the field is missing from the json but Some(null) if the field is set to null? E.g.

• { "required": 1 } becomes PatchData(required: 1, someNullableProperty: None)
• { "required": 1, "someNullableProperty": null } becomes PatchData(required: 1, someNullableProperty: Some(null))

This is to deal with PATCH requests where the field missing represents something different than when the field is null.

I know this is probably counter to the ideal of arrow but figured I'd ask. Also would be interesting to hear how others may represent/handle this. Thanks

[kyay10]

It suffices to use a default value:

@Serializable
data class PatchData(
  val required: Int,
  val someNullableProperty: Option<Int?> = None,
)