Regression when serialize wrapped Any type property annotated with @Contextual

Describe the bug Kotlin version: 1.4.0 + kotlinx-serialization-core:1.0.0-RC) + @Contextual val data: Any? reports:

Exception in thread “main” kotlinx.serialization.SerializationException: Serializer for class ‘Any’ is not found.

But when (Kotlin version: 1.3.70 + kotlinx-serialization-runtime:0.20.0), @ContextualSerialization val data: Any? works fine.

To Reproduce

@Serializable
abstract class Box(
        var code: String,
        var msg: String?
){
    constructor(): this(OK, null)
    companion object{
        const val OK = "OK"
    }
}

@Serializable
//data class DataBox(@ContextualSerialization val data: Any?) : Box(OK,null)  //kotlin 1.3.70
data class DataBox(@Contextual val data: Any?) : Box(OK,null) //kotlin 1.4.0
{
    constructor(): this(null)
}

fun test3(){
    val json = Json{}
    //val str = json.stringify(DataBox.serializer(),DataBox(data = Person("Tom"))) //kotlin 1.3.70, ouput: {"code":"OK","msg":null,"data":{"name":"Tom"}}
    val str = json.encodeToString(DataBox.serializer(),DataBox(data = Person("Tom")))// kotlin 1.4.0: Execption!!! 
    println(str)
}

reports error:

Exception in thread “main” kotlinx.serialization.SerializationException: Serializer for class ‘Any’ is not found. Mark the class as @Serializable or provide the serializer explicitly. at kotlinx.serialization.internal.Platform_commonKt.serializerNotRegistered(Platform.common.kt:127) at kotlinx.serialization.ContextualSerializer.serialize(ContextualSerializer.kt:52) at kotlinx.serialization.json.internal.StreamingJsonEncoder.encodeSerializableValue(StreamingJsonEncoder.kt:223) at kotlinx.serialization.encoding.Encoder$DefaultImpls.encodeNullableSerializableValue(Encoding.kt:296) at kotlinx.serialization.json.JsonEncoder$DefaultImpls.encodeNullableSerializableValue(JsonEncoder.kt) at kotlinx.serialization.json.internal.StreamingJsonEncoder.encodeNullableSerializableValue(StreamingJsonEncoder.kt:15) at kotlinx.serialization.encoding.AbstractEncoder.encodeNullableSerializableElement(AbstractEncoder.kt:94) at DataBox.write$Self(main.kt) at DataBox$$serializer.serialize(main.kt) at DataBox$$serializer.serialize(main.kt:32) at kotlinx.serialization.json.internal.StreamingJsonEncoder.encodeSerializableValue(StreamingJsonEncoder.kt:223) at kotlinx.serialization.json.Json.encodeToString(Json.kt:73) at MainKt.test3(main.kt:138)

Expected behavior Expect the behavior of 1.4.0 + 1.0.0-RC same as one of 1.3.70 + 0.20.0

Environment

• Kotlin version: 1.4.0
• Library version: 1.0.0-RC
• Kotlin platforms: JVM
• Gradle version: 6.3
• IDE version: IntellijIDEA 2020.2.1 Other relevant context : MacOS 10.12.6, JDK 1.8.0_261

[kikothemaster]

I’m using Map<String, Any> for the feedback purposes where attributes could be any. But in the new version, I cannot use that anymore 👎

[VincentJoshuaET]

How do I use either Contextual or Polymorphic for Map<String, Any?>?