Hi, I've made a 'KSerializer to TypeScript generator'. It will take an

@Serializer

annotated class and generate some TypeScript interfaces - so they can generate compatible JSON. The basics are in, and it needs more work to finish up some of the tricky bits. Please take a look! https://github.com/adamko-dev/kotlinx-serialization-typescript-generator/ It's available from JitPack. There's code examples in the docs directory

Can I use kotlinx.serialization to decode/encode Swift Model(with Encodable/Decodable Protocal) to/from json string?

What do you do when kotlinx.serialization tries to decode everything as the wrong model?

Hi all! Given the following JSONs:

{ "nav": { "watch:" {...} } }
{ "nav": { "browse:" {...} } }

How can I deserialize

Nav

based on its key (

"watch" | "browse"

)? This is what I tried:

@Serializable
data class Nav(
  val action: Action
)

@Serializable
sealed class Action {
  @Serializable
  @SerialName("watch")
  data class Watch(...) : Action()

  @Serializable
  @SerialName("browse")
  data class Browse(...) : Action()
}

But it doesn't work -

Field 'action' is required for type with serial name Nav

; what am I missing?

I've just updated to Kotlin 1.6.10 (was 1.4.32) and Serialization 1.3.2 (was 1.1.0) I'm getting a runtime error in my tests when trying to serialize a sealed class:

java.lang.NoSuchMethodError: 'void kotlinx.serialization.internal.ObjectSerializer.<init>(java.lang.String, java.lang.Object, java.lang.annotation.Annotation[])'

Inside`kotlinx.serialization.internal.ObjectSerializer`, I see the constructor. (It's scoped

internal

, not sure how scoping rules apply here, given the code is generated)

@PublishedApi
@OptIn(ExperimentalSerializationApi::class)
internal class ObjectSerializer<T : Any>(serialName: String, private val objectInstance: T) : KSerializer<T> {

    @PublishedApi // See comment in SealedClassSerializer
    internal constructor(
        serialName: String,
        objectInstance: T,
        classAnnotations: Array<Annotation>
    ) : this(serialName, objectInstance) {
        _annotations = classAnnotations.asList()
    }

is it possible to make idea issue a warning if a data class with enums that have no

@SerialId

is serialized to protobuf? (protobuf serializes enums as ints and when they have no serialId the order matters. In json thats not a problem because enums are serialized as string.

I’m following along with https://github.com/Kotlin/kotlinx.serialization/blob/master/docs/polymorphism.md#objects and I found that the list of multiple objects caused the type to show up, but if I only had EmptyResponse, then the output would just be [{}]. Is there a way to force it to give the type when there’s only one object?

Hi, basically i have two Map<String,Market> and Map<String,Station>, they are used for deserializing get calls.

json {
serializersModule = SerializersModule {
    contextual(Map::class) { MarketMapSerializer }
    contextual(Map::class) { StationMapSerializer }}
}

 object MarketMapSerializer :
        JsonTransformingSerializer<Map<String, Market>>(MapSerializer(String.serializer(), Market.serializer())) {
        override fun transformDeserialize(element: JsonElement): JsonElement {
            return JsonObject(element.jsonObject.filterNot { (k, _) ->
                k == "token"
            })
        }
    }

    object StationMapSerializer :
        JsonTransformingSerializer<Map<String, Station>>(MapSerializer(String.serializer(), Station.serializer())) {
        override fun transformDeserialize(element: JsonElement): JsonElement {
            return JsonObject(element.jsonObject.filterNot { (k, _) ->
                k == "token"
            })
        }
    }

and i'm getting this exception. Exception in thread "main" kotlinx.serialization.modules.SerializerAlreadyRegisteredException: Contextual serializer or serializer provider for class kotlin.collections.Map already registered in this module. Is it possible to specify types in contextual mapping?

Hi, how can I write a serialiazer for a class where it has two properties

client

&

environment

, and if only

client

is set, it's saved as a String, else as an object containing both ?

Hi, I'm trying to use a JsonTransformingSerializer to transform an array of strings into one string if there is only one and keep as array else I'm using this

override fun transformSerialize(element: JsonElement): JsonElement {
    require(element is JsonArray) // this serializer is used only with lists
    return element.singleOrNull() ?: element
}

Which is the exact code from the documentation but I'm getting nothing when there's one string and an array if multiple, what I'm doing wrong 🤔

Hi. I am trying to merge a serialized data class into a json object which may have values not included in the data class. I am doing something similar to this.

@Serializable
data class Xxx(...) {
    fun merge(apiSnapshot: String): JSONObject {
        val merged = JSONObject(apiSnapshot)
        Json.encodeToJsonElement(this).jsonObject.entries.forEach { (key, value) ->
            if (value == null) {
                merged.remove(key)
            } else {
                merged.put(key, value)
            }
        }
        return merged
    }
}

However, the values are from the serialized

JsonObject

are all strings, including nulls. Is there a way to do this that preserves the type? I also tried

encodeToString

and parsing with

JSONObject

, which does preserve the types, but I lost nulls when I did this. I could combine the two approaches but I’m hoping there is a more elegant approach.

is better error messages for json parsing errors on the roadmap? it would be cool have a list of problems.

listOf(MissingField("surname"), WrongType("age", was=INT, expected=STRING))

, and also a path to field names when something is missing in a nested object.

Hi, how can I create a serialiazer for an Enum where it would serialize as an int (from the

value

field, using an interface to ensure that field exists), and deserialize as the enum value For now I have the serializer working and it was pretty easy, but what should be the deserializer ?

Hello, I have a JSON where the keys are the ids.

{
  "0": {"name": "John"},
  "1": {"name": "Jane"},
  "2": {"name": "Pete"},
  ...
}

I'm super new to the Serialization library, and I can't find which will be the best approach to deserialize it and have the id as part of the object? Something like this:

Person (id: Int, name: String)

Thank you🙂

Hello, in case the serializer throws for various reasons, which is the optimal way to handle the throwing and return a bad response? im using this but i do not like it much because i try-catch. im looking for a way to avoid that.

Hey Guys, I am using sealed class to handle api response. I am trying some code but getting some error. Can somone suggest me? Please see in the thread.

Hi guys, can you please help me understand where I am wrong? Hi, all. Maybe someone can help me understand what is the problem with my code for class serialization? Not to polute the channel posted question on stackoverflow. Thanks in advance! https://stackoverflow.com/questions/71988144/serializer-for-class-is-not-found-mark-the-class-as-serializable-or-prov thanks

I'm using

kotlinx-serialization

in my MPP library, and all the tests run successfully on the JVM target. However when running

iosX64Test

I'm getting a segmentation fault. I've stripped the code right back and I'm not sure what's causing it. Can someone help me understand how to debug this please?

I receive requests like:

[2,"6bd18013-b33f-43bb-bf91-7745e5517dd2","StatusNotification",{"connectorId":1,"errorCode":"NoError","status":"Available"}]

and

[2,"5a3a42a2-212d-4815-9581-f64ce55fd6cc","Heartbeat",{}]

over websockets to which I then answer:

[3,"6bd18013-b33f-43bb-bf91-7745e5517dd2",{}]

and

[3,"5a3a42a2-212d-4815-9581-f64ce55fd6cc",{"currentTime":"2022-04-27T11:29:38.179938700"}]

. What is the most elegant way to deserialize, serialize and answer them?

I’m trying to do something where: any time one of a subset of fields are changed in a class, I want to write a serialized version of that class to some store. I was looking at something like this:

@Serializable
class Foo {
   var id: String by Delegates.observable("initialId", ::onChange)

   private fun onChange() {
      keyStore.set("foo", Json.encodeToString(this))
   }
}

but this won’t work because delegates don’t get serialized. Is there a good way to accomplish something like this?

My question started out about how to rewrite a JsonTransformingSerializer as a KSerializer. I think that is now resolved. My remaining question is whether a new serializer can be made to be the default for a type so it doesn’t need to be annotated every time.

I'm trying to write a custom serializer for

Enum

, the "common base class of all enum classes", but I'm struggling with the syntax for the generic type parameter. Has some done this successfully?

I’m using polymorphic serialization in an app, and I get a serialization error when I run in release mode, but not debug mode.

I saw it’s possible to customize the value of the

type

field when serializing polymorphic classes…I’m curious if it’s possible to customize the name of that field (

type

) via an annotation? Or would that require a custom serializer?

Hey, I wan to use a custom annotation class during encoding. So I marked my annotation class with @SerialInfo and I use

descriptor.getElementAnnotations(index)

, but the annotation for this property is not found. Did I miss something?

Anybody interested in ordered CSV and Fixed Length Formats? https://github.com/hfhbd/kotlinx-serialization-csv

Cross-posting from #opensource: https://kotlinlang.slack.com/archives/C2YH04E3S/p1651966101700999

Are json lists deserialized in order? If so, does the yaml plugin make kotlinx serialization lose that order? And is there any way to make sure the order is kept? Our source files are in yaml and need to be deserialized to kotlin data classes in a very specific order...

I’m trying to set up Ktor with exposed and I can’t figure out how to serialize my model. I have

object Cars: IntIdTable() {
    val name = varchar("name", 128)
    val year = integer("year")
}

class Car(id: EntityID<Int>): IntEntity(id) {
    companion object : IntEntityClass<Car>(Cars)
    var name by Cars.name
    var year by Cars.year
}

//@Serializable
class SerializedCar(id: EntityID<Int>, name: String, year: Int): IntEntity(id)

then :

class CarDAO {
    private fun resultRowToCar(row: ResultRow) = SerializedCar(
        id = row[Cars.id],
        name = row[Cars.name],
        year = row[Cars.year]
    )

    suspend fun show(id: Int): SerializedCar? = transaction {
        Cars
            .select { Cars.id eq id }
            .map(::resultRowToCar)
            .singleOrNull()
    }
}

and my route is :

get("/cars/{id}") {
            val id = call.parameters.getOrFail<Int>("id").toInt()
            call.respond(mapOf("car" to carDAO.show(id)))
        }

but I get this error :

500: kotlinx.serialization.SerializationException: Serializer for class 'SerializedCar' is not found.
Mark the class as @Serializable or provide the serializer explicitly.

You can see the project here for more info:

<https://github.com/danygiguere/ktor-kotlin-example>

And if I uncomment

//@Serializable

, my IDE tells me :

Impossible to make this class serializable because its parent is not serializable and does not have exactly one constructor without parameters