Warning: Unable to register kotlin.Lazy for reflection using Quarkus

Question

I have the following data class in my Kotlin code that uses Quarkus as a server side framework.

data class Location(
    val id: String,
    val serviceTimeInMinutes: Long,
    val openingTimes: List<OpeningTime>,
) {
    val sortedOpeningTimes: List<OpeningTime> by lazy {
        openingTimes.sortedWith { o1, o2 ->
            if (o1.weekday == o2.weekday) {
                o1.from.compareTo(o2.from)
            } else {
                o1.weekday.compareTo(o2.weekday)
            }
        }
    }
}

When I now run ./gradlew quarkusDev, I get the following warning:

2023-08-22 15:13:28,401 WARN  [io.qua.dep.ste.ReflectiveHierarchyStep] (build-4) Unable to properly register the hierarchy of the following classes for reflection as they are not in the Jandex index:
    - kotlin.Lazy (source: <unknown>)
    - kotlin.jvm.functions.Function1 (source: <unknown>)
Consider adding them to the index either by creating a Jandex index for your dependency via the Maven plugin, an empty META-INF/beans.xml or quarkus.index-dependency properties.

When I change the property to an ordinary property by removing the by lazy-block, the line with the kotlin.Lazy disappears as expected.

However, if I wanted to lazily execute that block, is there a way to get rid of that warning? And is there a way to get rid of the warning for kotlin.jvm.functions.Function1?

Note

I am aware of the configuration properties quarkus.index-dependency.<...>, which I already used to get rid of that warning for the threeten library like this:

quarkus.index-dependency.threeten.group-id=org.threeten
quarkus.index-dependency.threeten.artifact-id=threeten-extra

I suppose if I knew group-id and artifact-id of Kotlin (if they exist), adding extra lines in the application.properties might be worth a try.

Answer 1

Just stumbled upon the solution myself: Lazy and Function1 both are implemented in the kotlin stdlib.

Adding the stdlib to the Quarkus index dependencies with

quarkus.index-dependency.kotlin.group-id=org.jetbrains.kotlin
quarkus.index-dependency.kotlin.artifact-id=kotlin-stdlib

is sufficient to remove the warning.

Probably it would be a nice feature for the Quarkus Kotlin extension to allow devs omitting that additional configuration - so I think I'll raise an issue there I've raised this issue on GitHub.