I'm migrating from

Moshi

@Serializable
data class User(
    val id: String,
    val name: String,
    val age: Int? = null <-----------
)

Is there a way to configure this, so I don't have to provide default value of null (just have the

age

be optional? It's very error prone

What is error prone about it? It's no less error prone than needing to specify the type or the name of each property.

well optionality in language is express by adding

?

to the type, not

? = null

Why the default value should be null and not anything else? It should be the same as setting an empty string for

String

. It would be doing assumptions.

The type dictates what's allowed in the serialized form. In this case, it's an integer or a null literal. The default indicates what value to use should the property be absent from the serialized form. They serve different purposes.

Anyway you can config this behavior to avoid being explicit. https://github.com/Kotlin/kotlinx.serialization/blob/master/docs/json.md#explicit-nulls

Hmm okay that does make sense, but not really expected coming from other parsers & ios Decodable as well

explicitNulls = false

works, thanks!