TestReflection.kt

package io.github.config4k

import io.kotlintest.specs.WordSpec
import sun.reflect.generics.reflectiveObjects.ParameterizedTypeImpl
import sun.reflect.generics.reflectiveObjects.WildcardTypeImpl
import java.lang.reflect.ParameterizedType
import java.lang.reflect.WildcardType
import kotlin.reflect.KClass
import kotlin.reflect.jvm.javaType
import kotlin.reflect.primaryConstructor


class TestReflection : WordSpec() {
    init {
        "Company.names's type" should {
            "be String::class" {
                val clazz = Company::class
                val type = clazz.primaryConstructor!!
                        .parameters.find { it.name == "names" }!!.type
                val list = getGenericList(type.javaType as ParameterizedType)
                list shouldBe listOf(String::class)
            }
        }

        "Company.names2's type" should {
            "be List::class, String::class" {
                val clazz = Company::class
                val type = clazz.primaryConstructor!!
                        .parameters.find { it.name == "names2" }!!.type
                val list = getGenericList(type.javaType as ParameterizedType)
                list shouldBe listOf(List::class, String::class)
            }
        }
    }
}

fun getGenericList(type: ParameterizedType): List<KClass<*>> {
    val impl =
            if (type.actualTypeArguments.size > 1) type.actualTypeArguments[1]
            else type.actualTypeArguments[0]
    val list = listOf((when (impl) {
        is ParameterizedTypeImpl -> impl.rawType
        is WildcardTypeImpl -> {
            val r = impl.upperBounds[0]
            if (r is ParameterizedTypeImpl) r.rawType else r as Class<*>
        }
        else -> impl as Class<*>
    }).kotlin)

    return if (impl is WildcardTypeImpl) list + getGenericList(impl.upperBounds[0] as ParameterizedType)
    else list
}

class Company(names: List<String>, names2: List<List<String>>)