realm-java: BUG: Inserted sub-objects not being linked to parent object

We have a simple scenario that we cannot seem to get working despite trying every approach we’ve seen in the docs/issue list.

We have two objects (Chat/Message), with chat having a list of messages: NOTE: We use Kotlin

@RealmClass
class Chat, RealmModel {
    ....
    var messages = RealmList<Message>()
    ....
}

@RealmClass
class Message : RealmModel {
    @PrimaryKey
    lateinit var id:String
    ....
}

When we insert new Messages into the Chat the Message object is being inserted in the database correctly but the Chat object is not linked to it – despite the Message being inserted THROUGH the Chat object (definitely a bug)

We’ve verified in the Realm Browser and there are indeed no linked messages (ie: it’s a persitence issue not a querying one)

Insertion code:

val chatService:ChatService = ....
val chatID:String = ...

// insertion code
val database:Realm = Realm.getDefaultInstance()
var message:Message = Message.fromJSON( dataJSON )
database.beginTransaction()
// message = database.copyToRealmOrUpdate( message ) // tried this too, makes no difference
val chat:Chat = chatService.getChatWithID( chatID )
// database.copyToRealmOrUpdate( chat ) // tried this too, makes no difference
chat.messages.add( message )
database.commitTransaction()

NOTE: We’ve also tried manually patching the object with JSON and we get the exact same effect (messages are updated, but chat does not have them linked)

val chatData:Map<String, Any?> = mapOf(
    "id" to chatID,
    "messages" to chat.messages.map{ ... conversion to JSON ... }
)
database.createOrUpdateObjectFromJson( Chat::class.java, JSONObject( chatData ))
database.commitTransaction()