Is it possible to make the parser ignore some field when encoding them? I would like a class like this:

data class MyDataClass(@IgnoreThisKey val privateKey: String, val value: String)

And when serializing any data(not only

MyDataClass

) and there's a property with

IgnoreThisKey

annotation, it should not be included.

@Transient

is probably what you're looking for

And make sure it's

@kotlinx.serialization.Transient

not

@kotlin.jvm.Transient

just in case you're not using IntelliJ, which will give this warning:

@kotlin.jvm.Transient

does not affect

@Serializable

classes. Please use

@kotlinx.serialization.Transient

instead.

And I should be able to add this annotation onto my own annotation?

this should work

@Serializable
data class MyDataClass(
  @Transient
  val privateKey: String? = null,
  val value: String,
)

It's mostly the encoding part I'm interesting in. So it's important that when I call

json.encodeToString(MyDataClass("private", "Value"))

it results in

{"value": "Value"}

no that's not possible,

@Transient

goes on properties

I'm currently working with a library and I want to change the backend from Gson to Serialization and we already have a annotation class. So would be great if I could update without the users of my library needing to update their code. Gson has ExclusionStrategy, where we are just checking if the field contains our own annotation class. So was wondering if I could do something alike in Serialization. So would be nice if I could do it inside of the JsonBuilder somehow, and without specifing the specific class directly, but only do the filter by the annotation class on the properties.

hmmm... I don't think there's a direct equivalent. Trying to come up with something could be quite difficult. You could try creating your own KSerializer that always encodes to null, and specifying it as the serializer

@Serializable(with = TransientSerializer::class)
data class MyDataClass(
  val privateKey: String? = null,
  val value: String,
)

object TransientSerializer : KSerializer<Any> {
  override fun encode(...) {}
  override fun decode(...) {}
}

Think I will just upgrade my major version, then I would go with the simple solution, of getting the users of this library to write in the @Transient themselves 😛

haha I totally agree