SerializationException: can't locate argument-less serializer

Question

I'm creating a Kotlin Multiplatform library; actually I got 3 modules ( common, jvm and js ),

In the classpath I got: classpath "org.jetbrains.kotlin:kotlin-serialization:${versions.kotlin}"

And in my modules I got:

• common: "org.jetbrains.kotlinx:kotlinx-serialization-runtime-common:${versions.kotlinSerialization}"
• jdk: "org.jetbrains.kotlinx:kotlinx-serialization-runtime:${versions.kotlinSerialization}"
• js: "org.jetbrains.kotlinx:kotlinx-serialization-runtime-js:${versions.kotlinSerialization}"

and apply plugin: 'kotlinx-serialization' ofc.

​

But when I run this simple test:

@Serializable
data class ASimpleClass( val a: Int )

.

@Test  
fun testingMultiplatformCode_canSerialize() {
    JSON.stringify( ASimpleClass( 1 ) )
}

I got this error:

kotlinx.serialization.SerializationException: Can't locate argument-less serializer for class studio.forface.ktmdb.ASimpleClass. For generic classes, such as lists, please provide serializer explicitly.

    at kotlinx.serialization.PlatformUtilsKt.serializer(PlatformUtils.kt:28)
    at studio.forface.ktmdb.ProjectTests.testingMultiplatformCode_canSerialize(ProjectTests.kt:33)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
    at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
    at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
    at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
    at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
    at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)

I have same result annotating the property "a" ( @SerialName ), which shouldn't require an annotation anyway.

Am I missing something? :/ thanks

Answer 1

The error indicates that serialization plugin was not actually applied.

In your config classpath line:

classpath "org.jetbrains.kotlin:kotlin-serialization:${versions.kotlin}"

has not applied plugin because it can't infer version from property versions.kotlin. You need to define this value in buildscript block or try inline kotlin version like that

classpath "org.jetbrains.kotlin:kotlin-serialization:1.3.10"

or use Plugins API. Replace buildscript block in root build.gradle with:

plugins {
    id "kotlinx-serialization" version "1.3.10" apply false
    // ... another plugins
}

And add following to root settings.gradle:

pluginManagement {
    resolutionStrategy {
        eachPlugin {
            if (requested.id.id == "kotlinx-serialization") {
                useModule("org.jetbrains.kotlin:kotlin-serialization:${requested.version}")
            }
        }
    }
}

Also, if you are configuring multiplatform project, you likely need to add 'multiplatform' plugin as described in Kotlin docs