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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

4face
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  • The error message says: `Can't locate argument-less serializer for class studio.forface.ktmdb.ASimpleClass.` So, perhaps you need to provide an argumentless constructor to the class? Just a guess... – Thomas Cook Oct 27 '18 at 14:23
  • It's probably because you need to annotate the property `a` with something from the `kotlinx.serialization` library... My guess would be that becuase `a` is not annotated, the serializer is looking for an arg-less constructor and there isn't one so it bonks out... – Thomas Cook Oct 27 '18 at 14:25
  • Hmmm, looking at the official docs, it does appear your example code should work. – Thomas Cook Oct 27 '18 at 14:30
  • Sadly is not about that. I re-update the post :) – 4face Oct 27 '18 at 14:30
  • Try annotating `a` with `@SerialName("a")` – Thomas Cook Oct 27 '18 at 14:30
  • I tried, but same result. As you said, an annotation should not be required on properties, but it was worth a try – 4face Oct 27 '18 at 14:33
  • I had same problem on an Android project, using inheritance, maybe I could be something similar since it is a multiplatform project and maybe the Java class "inherit" in some way from the Common class? But that would be weird, since Kotlin.serialization is made up on the multiplaform base :/ – 4face Oct 27 '18 at 14:37
  • Maybe you've used the wrong import? You said you had 3 seperate dependancies on different kotlinx.serialization packages. Maybe you just imported the wrong one in the file containing your class and the one containing the test? – Thomas Cook Oct 27 '18 at 16:02
  • sources and tests are in the same modules ( common with common test etc ) – 4face Oct 27 '18 at 16:17

2 Answers2

5

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

Max Elkin
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1

According to that stacktrace, you've launched tests from the IDEA? Try to delegate them to gradle: Settings - Build, Execution, Deployment - Build Tools - Gradle - Runner - tick Delegate IDE build/run actions to gradle. Serialization compiler plugin does not have support yet for running tests via IDEA.

sandwwraith
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