Child Jobs don't cancell scope in Kotlin coroutines

I'm trying to learn about cancel propagation in Jobs. I thought if a Job get's cancelled, its father too.

val cancellableScope = CoroutineScope(Dispatchers.Default + Job())
val cancellableScope2 = CoroutineScope(Dispatchers.Default + Job())

runBlocking {

    cancellableScope2.launch {

        cancellableScope.launch {
            throw Error("1")
        }.join()

        cancellableScope.launch {
            println("2")
        }.join()

    }.join()

    cancellableScope2.launch {

        delay(200)
        println("llegó 3")

    }.join()

}

I get the next output:

Exception in thread "DefaultDispatcher-worker-2" java.lang.Error: 1
	at MainKt$main$1$1$1.invokeSuspend(Main.kt:21)
	at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)
	at kotlinx.coroutines.DispatchedTask.run(DispatchedTask.kt:106)
	at kotlinx.coroutines.scheduling.CoroutineScheduler.runSafely(CoroutineScheduler.kt:584)
	at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.executeTask(CoroutineScheduler.kt:793)
	at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.runWorker(CoroutineScheduler.kt:697)
	at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.run(CoroutineScheduler.kt:684)
	Suppressed: kotlinx.coroutines.internal.DiagnosticCoroutineContextException: [StandaloneCoroutine{Cancelling}@430de60, Dispatchers.Default]

3

I expected to only get the error, but "3" get's printed too. Isn't "cancellableScope2" cancelled when first launched fails too?

I tried changing to the same context

Even though you're in cancellableScope2.launch scope you use explicit parent scope when launching here:

cancellableScope2.launch {

    cancellableScope.launch {
        throw Error("1")
    }.join()

    cancellableScope.launch {
        println("2")
    }.join()

}.join()

That means those jobs are descendant of cancellableScope only and have no relation to cancellableScope2, so they are free to collapse without affecting state of scope2.

The thing you might be confused about is that launch-ed jobs don't return any result. You do join on them but it's just a delay until they're complete. Whether they succeed, fail or get cancelled doesn't matter.

However if instead of launch + join you use async and await you'll get the behavior you expect. That creates a Deferred which does return a result so in this case await would rethrow Error(1) which will collapse scope2.