add Json configuration not serialize all null properties

If a property is null, usually it is not necessary for client(at least javascript web app), only consumes network traffic of remote server such as ktor.

Hope add a Json configuration not serialize all null properties:

val format = Json { ignoreNull = true } //default can be false

then

@Serializable
class Project(val name: String, val renamedTo: String?)

fun main() {
    val data = Project("kotlinx.serialization", null)
    println(Json.encodeToString(data))
}

output:

{“name”:“kotlinx.serialization”}

[rwsbillyang]

You can set null as a default value of your nullable property and use encodeDefaults = false as shown with an example here: https://github.com/Kotlin/kotlinx.serialization/blob/master/docs/json.md#encoding-defaults

Does it work for you?

encodeDefaults = false remove all keys which have default value include non-null, as following:

@Serializable
class Project2(val name: String, val renamedTo: String? = null, val level: Int = 100)
fun test2(){
    val json = Json{ encodeDefaults = false }
    val data = Project2("kotlinx.serialization")

   //output: {"name":"kotlinx.serialization"}, remove the key: level
    println(json.stringify(Project2.serializer(), data)) 
}

The feature of Include.NON_NULL in Jackson is expected.

[sandwwraith]

@ArtemMikhaylov This issue is about serialization, not deserialization of some rest API result call. For your use-case, check out coerceInputValues property in json builder: https://github.com/Kotlin/kotlinx.serialization/blob/master/docs/json.md#coercing-input-values