kotlinx.serialization: Android, Gradle, Serialization plugin is incompatible with Kotlin Android plugin 1.9.20

Apparently, the issue is caused by a bug in the Kotlin 1.9.10 IDE plugin (not the Gradle plugin). It is described here: https://youtrack.jetbrains.com/issue/KTIJ-10755

To fix this problem, you need to update the Kotlin IDE plugin. Unfortunately, 1.9.20 IDE plugin version is not available for Hedgehog 2023.1.1 yet. There are two ways to fix it:

1. Go to Settings -> Languages & Frameworks -> Kotlin or invoke action Configure Kotlin plugin updates. Select EAP channel in the window and update to 1.9.20-RC2 (per https://youtrack.jetbrains.com/issue/KTIJ-10755/HMPP-IDE-False-PLUGINISNOTENABLED-in-IDE-for-kotlinx-serialization-plugin-however-project-builds-correctly#focus=Comments-27-8389206.0-0)
2. Update to Android Studio Iguana 2023.2.1 Canary or Intellij IDEA 2023.3 that have Kotlin 1.9.20 pre-installed.

using 1.9.20 in Android Studio Hedgehog 2023.1.1 not work as well.

I can add it’s not only about annotation warning. Generated serializers are not resolved by the IDE (but code compiles).

@pdvrieze In my example I apply plugin like that

build.gradle.kts (project level)
plugins {
    id("org.jetbrains.kotlin.plugin.serialization") version "1.9.20" apply false
}
 
build.gradle.kts (module level)
plugin {
    kotlin("plugin.serialization")
}

I think that’s the correct way to apply plugin when you want to share version across modules.

I’ve faced with the same problem, is there any solution?

There is no problem with code compilation or running the application. This issue is about IDE not resolving serializers and displaying warning for the annotation. I kindly ask @mcmouse88 and @lifestreamy to check if you can reproduce the issue in my sample project.

@pdvrieze my IDE specs:

Android Studio Giraffe | 2022.3.1 Patch 4
Build #AI-223.8836.35.2231.11090377, built on November 13, 2023
Runtime version: 17.0.6+0-17.0.6b829.9-10027231 aarch64
VM: OpenJDK 64-Bit Server VM by JetBrains s.r.o.
macOS 13.4.1

My friends can reproduce it on their systems, leading me to believe that a cache-related problem can be ruled out.

@linean I’ve just tried you project. It does compile.

The annotation is still highlighted, the .serializer() is unresolved.

Running main gives an error

Error: Could not find or load main class com.serialization.issue.MainKt
Caused by: java.lang.ClassNotFoundException: com.serialization.issue.MainKt

Process finished with exit code 1

But a unit test with it has passed:

EDIT: after having launched the unit test the main function runs successfully for some reason.

Trying to open the project on Giraffe (2022.3.1 Patch 4) it indeed fails (LInux, so OS doesn’t seem to matter). I suspect this is a bug/incompatibility with older Intellij versions (the 2022.3.1 part of the Android Studio version). Note that the compiler plugin (and the corresponding IDE plugin) are managed through YouTrack.

Using 1.9.20-RC2 IDE Plugin in Android Studio Hedgehog breaks Jetpack Compose Live Edit feature

@linean it has been reproduced )

Android Studio Giraffe | 2022.3.1 Patch 1
Build #AI-223.8836.35.2231.10671973, built on August 17, 2023
Runtime version: 17.0.6+0-17.0.6b829.9-10027231 amd64
VM: OpenJDK 64-Bit Server VM by JetBrains s.r.o.
Linux 5.15.0-88-generic
Cores: 8

Current Desktop: X-Cinnamon

For me, using setting kotlin serialization to “1.6.2” fixed it after having enabled 1.9.20 EAP within Android Studio Hedgehog 2023.1.1

For me, Fixed when removed Retrofit converter API. Guess Retrofit Gson library was conflicted with kotlinxSerialization plugins

@lifestreamy Thank you! kotlin.android as 1.9.10 then removing `kotlin(“jvm”) did indeed work.

Regarding

Better always declare all the plugins with their versions in the project-level gradle file (strictly with apply false), then just add the individual plugins in plugins{} blocks of each module where they are needed. That way you will have a consistent plugin version across all the modules that apply it.

Just want to be 100% sure I understand your suggestion. Is it to add kotlin("plugin.serialization") version "1.9.10" apply false to the build.gradle.kts project then in the build.gradle.kts module add only kotlin("plugin.serialization")? That does seem to work and appears much cleaner… Thank You!

It’s Working on the below Environment:- Kotlin version: [1.9.0] Plugin version: [1.9.0] Kotlin platforms: [JVM] Gradle version: [8.2] IDE: Android Studio Giraffe | 2022.3.1 Patch 4

it’s not the latest version but for now, we can use it.

@Jdbarad 1.9.10 versions of both plugins work correctly together without giving any warnings. You, of course, can downgrade to 1.9.0 or 1.3.0 or whatever though, it is your choice.

Maybe the new releases with plugin versions 2.0.0+ will work as expected.

The current latest version for both plugins is 2.0.0-Beta1, I’ve not tested it.

Not sure if this issue is awaiting more info, but even I started getting

kotlinx.serialization compiler plugin is not applied to the module, so this annotation would not be processed. Make sure that you've setup your buildscript correctly and re-import project.

warning for all @Serializable annotations since upgrading kotlinx.serialization to 1.6.1 and kotlin to 1.9.20.

Although serialization does seem to work without problems.

You can find my project at https://github.com/ammargitham/WallFlow/, the dependency update commit is https://github.com/ammargitham/WallFlow/commit/8cbbe35c02f7afa6aeb23c417b814e14b14f54de.

Edit: I have tried out a bit more and I am also getting this with 1.9.0 and 1.9.10, so I guess this is not related to the original issue. My colleague pointed me to https://github.com/Kotlin/kotlinx.serialization/issues/2385#issuecomment-1764839583.

We are also facing this issue. AS Hedgehog 2023.1.1 RC 3, Kotlin/Serialization 1.9.20. The IDE is saying: kotlinx.serialization compiler plugin is not applied to the module, so this annotation would not be processed. Make sure that you've setup your buildscript correctly and re-import project.

At runtime it only is a problem when using minification/proguard/r8 (setting: android.enableR8.fullMode = false). When trying to use

@Serializable
data class OtpCodeRequestDto(
    @SerialName("phoneNumber")
    val phoneNumber: String,
)

as request body in a Retrofit call, with r8 minification on, we are getting these exceptions:

Failed to request OTP code: java.lang.IllegalArgumentException: Unable to create converter for class java.lang.Object
    for method IMfaApi.requestOtpCode
java.lang.IllegalArgumentException: Unable to create converter for class java.lang.Object
    for method IMfaApi.requestOtpCode
	at retrofit2.Utils.methodError(Utils.java:54)
	at retrofit2.HttpServiceMethod.createResponseConverter(HttpServiceMethod.java:126)
	at retrofit2.HttpServiceMethod.parseAnnotations(HttpServiceMethod.java:85)
	at retrofit2.ServiceMethod.parseAnnotations(ServiceMethod.java:39)
	at retrofit2.Retrofit.loadServiceMethod(Retrofit.java:202)
	at retrofit2.Retrofit$1.invoke(Retrofit.java:160)
	at java.lang.reflect.Proxy.invoke(Proxy.java:1006)
	at $Proxy5.requestOtpCode(Unknown Source)
	at com.bmw.chargenow.data.auth.OtpRepository.requestOtp(OtpRepository.kt:39)