would like it to return `{"mandatory":3}` instead

# serialization

[Rainer Schlonvoigt]

would like it to return {"mandatory":3} instead

[turansky]

Default value for optionalField required. null in your case.
And then you can use Json.encodeDefaults flag

[ribesg]

The correct answer is no, it’s not possible. You can define a default value and then use the Json.encodeDefaults flag as a hack.