I have a serializable data class that I am using with ktor c

Question

I have a serializable data class that I am using with ktor client ``` Serializable data class Job val information JobInformation = JobInformation val additional AdditionalInformation = AdditionalInformation val bom PersistentList lt BOM gt = persistentListOf Serializable data class BOM SerialName comp item val compItem String = val sequence String = SerialName comp qty val compQty String = SerialName comp uom val compUom String = val operation String = val type String = ``` but when ktor client tries to decode the data from the request response I get this error ```kotlinx serialization json internal JsonDecodingException Expected class kotlinx serialization json JsonObject Kotlin reflection is not available as the serialized body of kotlinx serialization Polymorphic lt PersistentList gt but had class kotlinx serialization json JsonArray Kotlin reflection is not available ``` I understand what the error is saying but I don t know how to fix it

Adam S · Answer

is `PersistentList` from kotlinx collections Have you set up custom serializers <https github com Kotlin kotlinx collections immutable issues 63>

Chad Gregory · Answer

First I would like to know how a first party package is missing serialization support for 3 years but I m just going to table that for now I created this ``` Serializer forClass = PersistentList class class PersistentListSerializer lt T gt private val dataSerializer KSerializer lt T gt KSerializer lt PersistentList lt T gt gt private class PersistentListDescriptor lt T gt SerialDescriptor by serialDescriptor lt List lt T gt gt ExperimentalSerializationApi override val serialName String = kotlinx serialization immutable persistentList override val descriptor SerialDescriptor = PersistentListDescriptor lt T gt override fun serialize encoder Encoder value PersistentList lt T gt return ListSerializer dataSerializer serialize encoder value toList override fun deserialize decoder Decoder PersistentList lt T gt return ListSerializer dataSerializer deserialize decoder toPersistentList ``` Switched with Kapt to KSP because of this stupid error <https github com Kotlin kotlinx serialization issues 1908 issuecomment 1105187175> but now I am getting a new error ``` E FATAL EXCEPTION main Process com example testapp PID 22633 java lang IllegalStateException Only KClass supported as classifier got T at kotlinx serialization internal Platform commonKt kclass Platform common kt 102 at kotlinx serialization SerializersKt SerializersKt serializerByKTypeImpl$SerializersKt SerializersKt Serializers kt 78 at kotlinx serialization SerializersKt SerializersKt serializer Serializers kt 59 at kotlinx serialization SerializersKt serializer Unknown Source 1 at kotlinx serialization SerializersKt SerializersKt builtinSerializer$SerializersKt SerializersKt Serializers kt 96 at kotlinx serialization SerializersKt SerializersKt serializerByKTypeImpl$SerializersKt SerializersKt Serializers kt 84 at kotlinx serialization SerializersKt SerializersKt serializer Serializers kt 59 at kotlinx serialization SerializersKt serializer Unknown Source 1 at kotlinx serialization SerializersKt SerializersKt serializer Serializers kt 41 at kotlinx serialization SerializersKt serializer Unknown Source 1 at ca on listech imm util PersistentListSerializer$PersistentListDescriptor lt init gt PersistentListSerializer kt 31 at ca on listech imm util PersistentListSerializer lt init gt PersistentListSerializer kt 22 at ca on listech imm domain models Job$$serializer childSerializers Job kt 10 at kotlinx serialization internal PluginGeneratedSerialDescriptor$childSerializers$2 invoke PluginGeneratedSerialDescriptor kt 36 at kotlinx serialization internal PluginGeneratedSerialDescriptor$childSerializers$2 invoke PluginGeneratedSerialDescriptor kt 36 at kotlin SafePublicationLazyImpl getValue LazyJVM kt 107 at kotlinx serialization internal PluginGeneratedSerialDescriptor getChildSerializers PluginGeneratedSerialDescriptor kt 36 at kotlinx serialization internal PluginGeneratedSerialDescriptor getElementDescriptor PluginGeneratedSerialDescriptor kt 76 at kotlinx serialization descriptors SerialDescriptorKt$elementDescriptors$1$1 next SerialDescriptor kt 284 at kotlinx serialization descriptors SerialDescriptorKt$elementDescriptors$1$1 next SerialDescriptor kt 279 at kotlinx serialization internal PluginGeneratedSerialDescriptorKt hashCodeImpl PluginGeneratedSerialDescriptor kt 137 at kotlinx serialization internal PluginGeneratedSerialDescriptor$ hashCode$2 invoke PluginGeneratedSerialDescriptor kt 44 at kotlinx serialization internal PluginGeneratedSerialDescriptor$ hashCode$2 invoke PluginGeneratedSerialDescriptor kt 44 at kotlin SafePublicationLazyImpl getValue LazyJVM kt 107 at kotlinx serialization internal PluginGeneratedSerialDescriptor get hashCode PluginGeneratedSerialDescriptor kt 44 at kotlinx serialization internal PluginGeneratedSerialDescriptor hashCode PluginGeneratedSerialDescriptor kt 97 at java util concurrent ConcurrentHashMap get ConcurrentHashMap java 936 at kotlinx serialization json internal DescriptorSchemaCache get SchemaCache kt 35 at kotlinx serialization json internal DescriptorSchemaCache getOrPut SchemaCache kt 27 at kotlinx serialization json internal JsonNamesMapKt getJsonNameIndex JsonNamesMap kt 52 at kotlinx serialization json internal StreamingJsonDecoder decodeObjectIndex StreamingJsonDecoder kt 139 at kotlinx serialization json internal StreamingJsonDecoder decodeElementIndex StreamingJsonDecoder kt 92 at ca on listech imm domain models Job$$serializer deserialize Job kt 10 at ca on listech imm domain models Job$$serializer deserialize Job kt 10 at kotlinx serialization json internal PolymorphicKt decodeSerializableValuePolymorphic Polymorphic kt 59 at kotlinx serialization json internal StreamingJsonDecoder decodeSerializableValue StreamingJsonDecoder kt 36 at kotlinx serialization encoding AbstractDecoder decodeSerializableValue AbstractDecoder kt 43 at kotlinx serialization encoding AbstractDecoder decodeSerializableElement AbstractDecoder kt 70 ```

Adam S · Answer

``` Serializer forClass = PersistentList class class PersistentListSerializer lt T gt private val dataSerializer KSerializer lt T gt ``` annotating it with ` Serializer` probably isn t right

Adam S · Answer

normally ` Serializer forClass ` is used on independent objects

Adam S · Answer

are you sure you need to serialize directly to from `PersistentList` What if you used a regular list and then converted it via a property ``` Serializable data class X private val boms List lt BOM gt val bomsPersistent = boms toPersistentList ``` tweak it to make it more accurate a bit prettier

Chad Gregory · Answer

that might be the a better idea this is getting kind of ridiculous lol

Adam S · Answer

yeah KxS can be complicated it s usually easier to have a little bit of extra Kotlin code because it s easier to understand and debug

Chad Gregory · Answer

I am using this with Datastore would there be any issue with retrieving bom from a DataStore as a Flow lt Job gt ```val getJob Flow lt Job gt = cxt job data suspend fun updateActiveJob info JobInformation additional AdditionalInformation bom List lt BOM gt cxt job updateData job gt job copy information = info additional = additional bom = job bomList mutate for item in bom it add item ```

Adam S · Answer

sorry I don t really understand the context Are you asking if you can use KxS to encode decode data on the fly Because that s fine

Chad Gregory · Answer

my question is since I made this change ``` Serializable data class X private val bom List lt BOM gt val bomList = bom toPersistentList ``` will there be an issue with getting the data out of the datastore via a Flow when the serializable data class does not have a PersistentList property

Adam S · Answer

that depends on a lot of things All KxS cares about is that 1 everything has a KSerializer and SerialDescriptor and 2 the property `bom` is structured like a list

Adam S · Answer

for example if it s JSON data then KxS doesn t care if it s deserializing to a List or an Array or ArrayList or MutableList

Chad Gregory · Answer

Well the DataStore contains a PersistentList lt BOM gt which then needs to become a List lt BOM gt so my guess is that would be an issue since I had issues going from List lt BOM gt to PersistentList lt BOM gt

Chad Gregory · Answer

if so there basically no point to even use PersistentList at all and just store it as json data for something

Adam S · Answer

that could well be I ve never used the kotlinx collections so I wouldn t know

Chad Gregory · Answer

well with the context of this thread that would be true