Hello, I have an annotation that takes a KClass, I...

# ksp

[Christopher Porto]

Hello, I have an annotation that takes a KClass, I wanted to access information of that class in processor but it's not in class path, was wondering if theres a way to work around this? Do I have no choice but to provide the class information I need in annotation instead

[jw]

How does the code compile if it's not on the compilation unit's classpath?

[Christopher Porto]

It passes the KClass annotation class Foo(val clazz: KClass<...> the KSP processor works fine until I try accessing the KClass since its not in class path which I get exception in runtime

[Christopher Porto]

I'm trying to reference that KClass in code that I'm generating but seems I have no choice but to have the fully qualified name passed instead of KClass and generate import and calls based on that :(

[jw]

I'm on mobile so I can show code. I'll have to find a reference to doing this later.

[Christopher Porto]

No rush, appreciate any help

[Jake Woods]

I believe you can cast these KClass definitions to a KClassDeclaration using as if they have come from an annotation value

[David Rawson]

Something similar has come up a few times before in this Slack, maybe we need a PR to put it in the docs as it is quite a common use case?

We have found that obtaining the concrete instance of the annotation with the KClass arguments is premature. Maintaining the KSP view of the annotation is easier, and KSP will see the KClass args as KSType , from which you can get the declaration:

val ksType = ksAnnotated.getAnnotationsByType(Foo::class).single().arguments.single { it.name.asString() == "clazz" }.value as KSType
val declaration = ksType.declaration
val simpleName = declaration.simpleName.asString() // Bar etc.

[Christopher Porto]

Interesting, I'll try it out later but does look good, thanks blob smile Definitely would be nice to be mentioned somewhere in docs, not entirely intuitive imo

[Jake Woods]

Not sure if it’s useful anymore but here’s a little extension method I’ve been using to make the syntax for this slightly nicer:

inline fun <reified A : Annotation> KSAnnotation.getKClassArgument(
  property: KProperty1<A, *>
): KSType {
  val argument = this.arguments.find { it.name?.asString() == property.name } ?: run {
    val validNames = this.arguments.mapNotNull { it.name?.asString() }.joinToString(", ")
    error("Could not find annotation argument ${property.name}. (Valid names: $validNames)")
  }
  
  return (argument.value as? KSType) ?: error("${property.name} is not a valid KSType")
}

Assuming we have an annotation like this:

annotation class MyAnnotation(val klass: KClass<*>)

Then we can use the extension like so:

myAnnotationReference.getKClassArgument(MyAnnotation::klass)

[Christopher Porto]

Ah that helped me realize what I was missing, thank you, was using getAnnotationsByType which returns the instance of the annotation and not the KSAnnotation 😛