commonMain.kotlinx.serialization.json.internal.Polymorphic.kt Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of kotlinx-serialization-json
Kotlin multiplatform serialization runtime library
There is a newer version: 1.7.3
/*
 * Copyright 2017-2021 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
 */
@file:OptIn(ExperimentalSerializationApi::class)

package kotlinx.serialization.json.internal

import kotlinx.serialization.*
import kotlinx.serialization.descriptors.*
import kotlinx.serialization.internal.*
import kotlinx.serialization.json.*
import kotlin.jvm.*

@Suppress("UNCHECKED_CAST")
internal inline fun  JsonEncoder.encodePolymorphically(
    serializer: SerializationStrategy,
    value: T,
    ifPolymorphic: (String) -> Unit
) {
    if (serializer !is AbstractPolymorphicSerializer<*> || json.configuration.useArrayPolymorphism) {
        serializer.serialize(this, value)
        return
    }
    val casted = serializer as AbstractPolymorphicSerializer
    val baseClassDiscriminator = serializer.descriptor.classDiscriminator(json)
    val actualSerializer = casted.findPolymorphicSerializer(this, value as Any)
    validateIfSealed(casted, actualSerializer, baseClassDiscriminator)
    checkKind(actualSerializer.descriptor.kind)
    ifPolymorphic(baseClassDiscriminator)
    actualSerializer.serialize(this, value)
}

private fun validateIfSealed(
    serializer: SerializationStrategy<*>,
    actualSerializer: SerializationStrategy,
    classDiscriminator: String
) {
    if (serializer !is SealedClassSerializer<*>) return
    @Suppress("DEPRECATION_ERROR")
    if (classDiscriminator in actualSerializer.descriptor.jsonCachedSerialNames()) {
        val baseName = serializer.descriptor.serialName
        val actualName = actualSerializer.descriptor.serialName
        error(
            "Sealed class '$actualName' cannot be serialized as base class '$baseName' because" +
                    " it has property name that conflicts with JSON class discriminator '$classDiscriminator'. " +
                    "You can either change class discriminator in JsonConfiguration, " +
                    "rename property with @SerialName annotation or fall back to array polymorphism"
        )
    }
}

internal fun checkKind(kind: SerialKind) {
    if (kind is SerialKind.ENUM) error("Enums cannot be serialized polymorphically with 'type' parameter. You can use 'JsonBuilder.useArrayPolymorphism' instead")
    if (kind is PrimitiveKind) error("Primitives cannot be serialized polymorphically with 'type' parameter. You can use 'JsonBuilder.useArrayPolymorphism' instead")
    if (kind is PolymorphicKind) error("Actual serializer for polymorphic cannot be polymorphic itself")
}

internal fun  JsonDecoder.decodeSerializableValuePolymorphic(deserializer: DeserializationStrategy): T {
    // NB: changes in this method should be reflected in StreamingJsonDecoder#decodeSerializableValue
    if (deserializer !is AbstractPolymorphicSerializer<*> || json.configuration.useArrayPolymorphism) {
        return deserializer.deserialize(this)
    }
    val discriminator = deserializer.descriptor.classDiscriminator(json)

    val jsonTree = cast(decodeJsonElement(), deserializer.descriptor)
    val type = jsonTree[discriminator]?.jsonPrimitive?.content
    val actualSerializer = deserializer.findPolymorphicSerializerOrNull(this, type)
        ?: throwSerializerNotFound(type, jsonTree)

    @Suppress("UNCHECKED_CAST")
    return json.readPolymorphicJson(discriminator, jsonTree, actualSerializer as DeserializationStrategy)
}

@JvmName("throwSerializerNotFound")
internal fun throwSerializerNotFound(type: String?, jsonTree: JsonObject): Nothing {
    val suffix =
        if (type == null) "missing class discriminator ('null')"
        else "class discriminator '$type'"
    throw JsonDecodingException(-1, "Polymorphic serializer was not found for $suffix", jsonTree.toString())
}

internal fun SerialDescriptor.classDiscriminator(json: Json): String {
    // Plain loop is faster than allocation of Sequence or ArrayList
    // We can rely on the fact that only one JsonClassDiscriminator is present —
    // compiler plugin checked that.
    for (annotation in annotations) {
        if (annotation is JsonClassDiscriminator) return annotation.discriminator
    }
    return json.configuration.classDiscriminator
}