KT-46872

Test.kt

import java.io.*
import java.lang.NullPointerException

data class A(val s: String?) : Serializable {
    fun add(b: B) {
        bs.add(b)
    }
    // we'll add B(this) to 'bs'
    private val bs = mutableSetOf<B>()
    // check is B(this) is in 'bs'
    fun isValid() = bs.contains(B(this))
}
data class B(val a: A) : Serializable

fun main() {
    try {
        val expected = A("A")
        expected.add(B(expected))
        val baos = ByteArrayOutputStream()
        ObjectOutputStream(baos).use {
            with(it) {
                writeObject(expected)
                flush()
            }
        }
        val bais = ByteArrayInputStream(baos.toByteArray())
        val actual = ObjectInputStream(bais).use {
            it.readObject()
        } as A
        println(if (expected == actual) "pass" else "fail")
        // BUT DID IT REALLY PASS? IS THE DESERIALIZED OBJECT VALID?
        println("Is 'expected' valid? ${expected.isValid()}")
        println("is 'actual'   valid? ${actual.isValid()}")
    } catch (npe: NullPointerException) {
        println("fail")
        npe.printStackTrace()
    }
}