Can not cope with Optional.empty() arguments in @JsonbCreator method/constructor

[misl]

Just like in #237, I also like to stick to immutable pojos. However I tried a different approach using Optional<> fields. In comparisons like this on with other Json serialization frameworks (Jackson and/or Gson) it is stated that JSON-B has improved handling of Optional<> fields.

However the examples mostly show only serialization works. How about deserialization optional fields. Especially when using immutable pojos. In the following example I used a contructor with Optional<> arguments:

import javax.json.bind.Jsonb;
import javax.json.bind.JsonbBuilder;
import javax.json.bind.annotation.JsonbCreator;
import javax.json.bind.annotation.JsonbProperty;
import java.util.Optional;

public class OptionalInConstructor {

  public static class MyModel {
    private final String mandatory;
    private final Optional<String> optional;

    @JsonbCreator
    public MyModel( @JsonbProperty("mandatory") String mandatory, @JsonbProperty("optional") Optional<String> optional ) {
      this.mandatory = mandatory;
      this.optional = optional;
    }

    @JsonbProperty("mandatory")
    public String getMandatory() {
      return mandatory;
    }

    @JsonbProperty("optional")
    public Optional<String> getOptional() {
      return optional;
    }
  }

  public static void main( String[] args ) {
    MyModel model = new MyModel( "mandatory", Optional.empty() );

    // From Object -->Json
    Jsonb jsonb = JsonbBuilder.create();
    String serializedModel = jsonb.toJson( model );
    System.out.println( "Json: " + serializedModel );

    // From Json --> Object
    MyModel deserialized = jsonb.fromJson( serializedModel, MyModel.class );
  }
}

Unfortunately this lead to the following error:

Json: {"mandatory":"mandatory"}
Jun 24, 2019 11:29:14 PM org.eclipse.yasson.internal.Unmarshaller deserializeItem
SEVERE: JsonbCreator parameter optional is missing in json document.
Exception in thread "main" javax.json.bind.JsonbException: JsonbCreator parameter optional is missing in json document.
	at org.eclipse.yasson.internal.serializer.ObjectDeserializer.createInstance(ObjectDeserializer.java:120)
	at org.eclipse.yasson.internal.serializer.ObjectDeserializer.getInstance(ObjectDeserializer.java:93)
	at org.eclipse.yasson.internal.serializer.AbstractContainerDeserializer.deserialize(AbstractContainerDeserializer.java:61)
	at org.eclipse.yasson.internal.Unmarshaller.deserializeItem(Unmarshaller.java:70)
	at org.eclipse.yasson.internal.Unmarshaller.deserialize(Unmarshaller.java:56)
	at org.eclipse.yasson.internal.JsonBinding.deserialize(JsonBinding.java:53)
	at org.eclipse.yasson.internal.JsonBinding.fromJson(JsonBinding.java:60)
	at OptionalInConstructor.main(OptionalInConstructor.java:39)

When the Optional<> argument is present it works correctly.

Should this be possible? Or is there another way (without making my pojo mutable) to achieve this?

[Degubi]

It seems the given example code is working on master, printing out deserialized.getOptional() correctly prints Optional.empty