Sooo… generics are supported in Protobuf with kotlinx.serialization? I wrote a test case using this, I was surprised and delighted to see it pass!

@OptIn(ExperimentalSerializationApi::class)
@Serializable
data class GenericWrapper<T>(
    @ProtoNumber(1) val name: String,
    @ProtoNumber(2) val content: T,
)

I have a class

@kotlinx.serialization.Serializable
data class Geolocation(
    val latitude: Double,
    val longitude: Double
)

that I'm using to get responses from rest calls. Unfortunately the rest api is not consistent and so in some places I need to use

lat

and

lng

instead of

latitude

and

longitude

. What is the best way to handle this? A custom serializer or extend the class and add

@SerialName

if that's possible? I'd like to really just have one

Geolocation

so I'm leaning towards the custom serializer...

Is there some way to remove the names for these inner private fields? They're never mean't to be accessed and are only there so they get added to the serialized output. Its just saying unused variable, which isnt a huge issue but it could be better

@Serializable
data class ReplyParams(
    @ProtoNumber(2) val videoId: String,
    @ProtoNumber(4) val commentId: String
) {
    @ProtoNumber(5)
    private val unknownParams: UnknownParams = UnknownParams()

    @ProtoNumber(10)
    private val unknownNumber: Int = 0

    @Serializable
    private class UnknownParams {
        @ProtoNumber(1)
        private val unknownNumber: Int = 7
    }
}

Re: closed-polymorphic type serialisation, are we able to change the key

type

field to something else? to achieve something like

{
  "typeKey": "owned",
  "status": "open",
  "name": "kotlinx.coroutines",
  "owner": "kotlin"
}

Hello API is returning data in the following format

{
  "album": {
    "artist": "Michael Jackson",
    "tags": {
      "tag": [
        {
          "url": "https://www.last.fm/tag/pop",
          "name": "pop"
        },
        {
          "url": "https://www.last.fm/tag/soul",
          "name": "soul"
        }
      ]
    }
  }
}

The

tags

attribute contains a single child

tag

, so some kind of container (

TrackContainer

) class is required to parse this JSON:

@Serializable
internal data class AlbumApiModel(
    @SerialName("artist") val artist: String,
    @SerialName("tracks") val tracks: TrackContainer? = null,
)

@Serializable
internal data class TrackContainer(
    @SerialName("track") val track: List<AlbumTrackApiModel>,
)

Since creation of this class is a bit verbose I wonder if there is a way to parse nested attributes without a need to define

TrackContainer

class- something like

@SerialName("tracks.track")

@Serializable
internal data class AlbumApiModel(
    @SerialName("artist") val artist: String,
    @SerialName("tracks.track") val tracks: List<Track>? = null,
)

I'm having some trouble making sense of class inheritance and serialization I have this data structure, which can vary deeper down in the json object The easy way which I've gone is just creating the same data class for each one but then I end up with having the same structure multiple times The ideal way I believe for this case would be to use generics and then that way it could simplify my code a lot (I assume) heres two examples of the data i'm working with

{
  "contents": {
    "singleColumnBrowseResultsRenderer": {
      "tabs": [
        {
          "tabRenderer": {
            "content": {
              "sectionListRenderer": {
                "contents": [
                  {
                    "playlistVideoListRenderer": { ... }
                  }
                ]
              }
            }
          }
        }
      ]
    }
  }
}

{
  "contents": {
    "singleColumnBrowseResultsRenderer": {
      "tabs": [
        {
          "tabRenderer": {
            "content": {
              "sectionListRenderer": {
                "contents": [
                  {
                    "itemSectionRenderer": { ... }
                  }
                ]
              }
            }
          }
        }
      ]
    }
  }
}

Let's assume I have the following data class

@Serializable
 data class Accounts(
     val data: List<Account>
 ) {

        @Serializable
        data class Account(
            @SerialName("name")
            val name: String,
            @SerialName("lastname")
            val lastname: String,
        ) 
}

The

Json.encodeToString()

and

decodeToString

returns a JsonObject

{
  "data": [
    {
      "name": "Mike",
      "lastname": "Ekim"
    },
    {
      "name": "John",
      "lastname": "Nhoj"
    },
...

How can encode the data class to return a JsonArray? Like the following:

data: [{
      "name": "Mike",
      "lastname": "Ekim"
    }, {
      "name": "John",
      "lastname": "Nhoj"
    },
...]

1.4.1 artifacts already published, but no master merge nor GitHub released published. Is it an intentional release?

Hello 👋 I'm wondering why these two compile:

private inline fun <reified K, reified V> JsonElement.decodeOne(key: String): Map<K, V> {
    return jsonObject[key]
        ?.let { Json.decodeFromJsonElement<Map<K, V>>(it) }
        .orEmpty()
}

private fun <K, V> JsonElement.decodeOne(key: String): Map<K, V> {
    return jsonObject[key]
        ?.let { Json.decodeFromJsonElement<Map<K, V>>(it) }
        .orEmpty()
}

but only the first one works at runtime. Wouldn't it be possible to check this at compile time. The same way it's done (screenshot) for

Json.decodeFromJsonElement<K>(smth)

when

K

is generic, but not reified. Or is type-erasure still a problem here?

👋 Any clue why the

PLUGIN_IS_NOT_ENABLED

warning is only shown on IDE and doesn’t log (or fail when

allWarningsAsErrors

) ?

The value in

encoder.encodeSerializableValue(serializers[0]!!(), value)

will error with type mismatch. Expected

CapturedType(out X*>)

but X`<*>`. How to pass the value?

// An external class from lib
class X<T>

object XSerializer : KSerializer<X<Int>> {
    override val descriptor: SerialDescriptor
        get() = TODO("Not yet implemented")

    override fun deserialize(decoder: Decoder): X<Int> {
        TODO("Not yet implemented")
    }

    override fun serialize(encoder: Encoder, value: X<Int>) {
        TODO("Not yet implemented")
    }
}

// A map to take correct serializer by arg
val serializers: Map<Int, () ->  KSerializer<out X<*>>> = mapOf(0 to { XSerializer })

object GenericSerializer : KSerializer<X<*>> {
    override val descriptor: SerialDescriptor
        get() = TODO("Not yet implemented")

    override fun deserialize(decoder: Decoder): X<*> {
        TODO("Not yet implemented")
    }

    override fun serialize(encoder: Encoder, value: X<*>) {
        encoder.encodeSerializableValue(serializers[0]!!(), value)
    }
}

There is a link testable. https://pl.kotl.in/VVNMv8Zso

Hi, i have this json file: https://meta.fabricmc.net/v2/versions/loader/1.19.2/0.14.9 and i want to deserialize it. My current approach for this is this: https://pastes.dev/UAKFSC4YQo. The problem is, that it throws this error. https://pastes.dev/tIKiMmCyDQ

How to create a serializer for a recursive map? Just like

class A : Map<String, A>

. The map is guava multimap that not implement the map interface. But can be converted to a map. Below is what I tried. Will throw

StackOverflowError

from

SetSerializer

object Serializer : KSerializer<A> {
    private val serializer by lazy { MapSerializer(String.serializer(), SetSerializer(this)) }
    override val descriptor by lazy {
        SerialDescriptor(
            "A",
            serializer.descriptor
        )
    }
    override fun deserialize(decoder: Decoder) =
        A(Multimaps.newMultimap(serializer.deserialize(decoder)) { setOf() })
    override fun serialize(encoder: Encoder, value: A) =
        serializer.serialize(encoder, value.asMap().mapValues { it.value.toSet() })
}

is there an official short name for kotlinx-serialization, one that is valid as a package name?

kxser

seems to be used by some libs but imo thats not very catchy.

kotlinxserialization

is hard to read. can anyone think of something nicer?

Hi all! I'm trying to build a project in my kotlinx.serialization fork, branch dev and I get an error when run

gradlew clean build

:

\projects\kotlinx.serialization\core\jvmMainModule\src\module-info.java:4: error: package is empty or does not exist: kotlinx.serialization
    exports kotlinx.serialization;
                   ^

JDK liberica 11.0.16, language level 11. When rebuild project, the error does not reproduce. Has anyone encountered this problem and knows the solution?

Any headup on how fix this issue ?

Caused by: kotlinx.serialization.json.internal.JsonDecodingException: Polymorphic serializer was not found for missing class discriminator ('null')
2022-10-25 20:31:56.910 4548-4548/com.socialpillars.ngo E/AndroidRuntime: JSON input: .....te_time":"2022-03-30T06:43:29.433318+05:30","type":"post"}]}

data class Posts(
    @SerialName("uuid") val postId: String,
    @SerialName("description") val description: String,
    @SerialName("likes_count") var likesCount: Int,
    @SerialName("images") private val _images: List<Image>,
    @SerialName("user") val user: User,
    @SerialName("is_liked") var isLiked: Boolean,
    @SerialName("create_time") private val _eventStartTime: String,
    var isMyPost: Boolean = false
)

data class FeedItem(
    @SerialName("post") var posts: Posts?,
    @SerialName("event") var events: Events?,
    @SerialName("type") var type: FeedType
)

Is there any way to implement a class like this, without having to override its parameters and still getting them serialized?

@Serializable
open class Test<T>(
    val test: T
)

@Serializable
class TestImpl : Test<String>()
// This doesn't work cause it needs the parameter

I want to Serialize and Deserialize a Map<String, *>: i.e. value can be any type (known at compile time), I would like to enforce that the types added to the Map have a serializer. How do you recommend to do it?

I’m receiving a JSON with several arrays: foo1, foo2, foo3, etc. with different numbers in the name. I’d like to have a single foo array that contains all of these. Is there an easy way to do this? Right now, I just have a class that contains optional foo1: Array, foo2: Array, etc and a method to convert it to another class with foo: Array, but I’d like to skip the conversion if possible.

I've started working a bit on a set of standard serializers for KotlinX Serialization together with aSemy. Project is currently super early in its lifecycle, but it would be fun to have some input and feature requests from people who'd consider using it 🙂 Feel free to raise an issue, watch or ⭐ it here Currently we have support for various jdk-specific types such as

LocalDateTime

,

Instant

,

UUID

,

URL

, but also have multiplatform support for serializing enums by their ordinal value.

Quick question about JSON serialziation. I receive this beautiful JSON

{"actual":"","target":null}

but both values are supposed to be

Float?

. I already use

coerceInputValues

to allow string values to be parsed but the

""

doesn’t get translated to

null

or something. Is there a way I can tell Kotlin to use the default value if it can’t deserialize something?

I'm using the code below to serialize the responses from the API into proper strings but I'm getting an error like this

Expected JsonPrimitive at text, found {"runs":[{"text":"All"}]}

I'm not sure what I'm doing wrong here

internal typealias ApiText = @Serializable(ApiTextSerializer::class) String

private class ApiTextSerializer : KSerializer<String> {
    override val descriptor: SerialDescriptor = buildClassSerialDescriptor("ApiText")

    override fun deserialize(decoder: Decoder): String {
        val input = decoder as JsonDecoder

        return input.decodeJsonElement().jsonObject["runs"]!!.jsonArray.joinToString(separator = "") {
            it.jsonObject["text"]!!.jsonPrimitive.content
        }
    }

    override fun serialize(encoder: Encoder, value: String) {
        throw RuntimeException("Serialization is not needed")
    }
}

I want to serialize BigInteger as a class but, I fail to get some none primitive value: here's my code:

object BigIntegerSerializerForMeta :
    KSerializer<BigInteger> {

    override val descriptor: SerialDescriptor = buildClassSerialDescriptor("BigIntSerializer") {
        element("value", PolymorphicPrimitiveSerializer(String.serializer()).descriptor)
    }
    const val radix = 16
    override fun deserialize(decoder: Decoder): BigInteger {
        return BigInteger(decoder.decodeSerializableValue(String.serializer()), radix)

    }
    override fun serialize(encoder: Encoder, value: BigInteger) =
        encoder.encodeSerializableValue(String.serializer(), value.toString(radix))
}

I get {"1234567890"} instead of {"type":BigIntSerializer,"value":"1234567890"}

Why is `allowStructuredMapKeys` (docs)

false

by default? Is it because serializing a map to an array is non-standard behaviour? And throwing an exception (if

false

) is standard behaviour?

Hi guys, with kotlinx serialization i am facing following error in kmm project

Caused by: kotlinx.serialization.json.internal.JsonDecodingException: Polymorphic serializer was not found for missing class discriminator ('null')

Not able to find any solution for that. Can anyone help me with that. Tried some solutions from google and stackoverflow, but didnt worked.

Polymorphic serializing a Pair inside polymorphic serialization of Any

val module = SerializersModule {
    polymorphic(Any::class) {
        subclass(Int::class, PolymorphicPrimitiveSerializer(Int.serializer()))
        subclass(String::class, PolymorphicPrimitiveSerializer(String.serializer()))
        subclass(Pair::class, PolymorphicSerializer(Pair::class))
    }
    polymorphic(Pair::class) {
        PairSerializer(Int.serializer(), String.serializer())
    }

}

val format = Json { serializersModule = module }
val mm = mapOf<String, Any>()
        .plus("intString pair" to 5 to "FIVE")

How to declare the Serialization for the Pair?

I'm a bit confused by the

PrimitiveSerialDescriptor

. The docs state:

For primitive serialization, the PrimitiveSerialDescriptor function must be used with a unique name of the type that is being serialized.

But this KDoc example sets the name to

kotlinx.serialization.LongAsStringSerializer

, which is the name of the serializer, not the type being serialized. Which one is correct?

sorry for the newbie question, I need to parse an xml into a (data) class and I'm using xmlutil

<?xml version="1.0" encoding="UTF-8"?>
<registry>
    <comment>
Copyright 2015-2022 The Khronos Group Inc.

SPDX-License-Identifier: Apache-2.0 OR MIT
    </comment>

I started with

fun parse(text: String) {
    val format = XML {}
    val registry = format.decodeFromString<Registry>(text)
}

@Serializable
data class Registry(
    val comment: String,)

but I get:

Execution failed for task ':generateCode'.

> Could not find a field for name (vkk.Registry) Registry/comment (Element)

candidates: Comment at position Line number = 3

What am I missing?

Hello folks, question can someone help/point to docs me understand why this does not work? Thanks in advance for any answers !

@file:UseSerializers(UrlSerializer::class)

// using serializer explicitly works
val url = URL("<https://test>")
val protobytes = ProtoBuf.encodeToByteArray(UrlSerializer, url)
val result = ProtoBuf.decodeFromByteArray(UrlSerializer, protobytes)

// use file serializer, this fails
shouldThrow<SerializationException> {
    val protobytes2 = ProtoBuf.encodeToByteArray(url)
    val result2: URL = ProtoBuf.decodeFromByteArray(protobytes)
    println(result2)
}

// use typealias serializer, this also fails
shouldThrow<SerializationException> {
    val url2: UrlAsString = url
    val protobytes2 = ProtoBuf.encodeToByteArray(url)
    val result2: UrlAsString = ProtoBuf.decodeFromByteArray(protobytes)
    println(result2)
}

// using inside data class works (like in the guide)
@Serializable
data class TestUrl(val value: URL)

val testUrl = TestUrl(url)
val proto = ProtoBuf.encodeToByteArray(testUrl)
val resultUrl: TestUrl = ProtoBuf.decodeFromByteArray(proto)
println(resultUrl)

In case, when using file serializer or global how come it throws: cannot find serializer for URL ?