Is it normal that `Job.cancel()` throws a `Cancel...

# ktor

[Marc Knaup]

Is it normal that Job.cancel() throws a CancellationException itself?
Or is this a bug in Ktor?

java.util.concurrent.CancellationException: Job was cancelled
    at io.ktor.client.engine.UtilsKt$attachToUserJob$cleanupHandler$1.invoke(Utils.kt:77)
    at io.ktor.client.engine.UtilsKt$attachToUserJob$cleanupHandler$1.invoke(Unknown Source:2)
    …
    at kotlinx.coroutines.JobSupport.cancel(JobSupport.kt:614)
    at kotlinx.coroutines.Job$DefaultImpls.cancel$default(Job.kt:164)

[elizarov]

Looks like a bug.

[luke]

This is expected behaviour. https://kotlinlang.org/docs/reference/coroutines/cancellation-and-timeouts.html#cancellation-is-cooperative

[Marc Knaup]

@luke yes, but the call that's canceled should throw the exception, not the code that initiates the cancelation.

[luke]

Does this not indicate that an instance of Job can throw a CancellationException when calling cancel()? https://kotlin.github.io/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines/-job/cancel.html

[Marc Knaup]

No, it doesn't

[luke]

Nope, you're right, sorry. I have no idea then.

[olegivo]

It must be a
kotlin.coroutines.cancellation.CancellationException
but was java.util.concurrent.CancellationException

Something went wrong. I have this bug now

[olegivo]

I searched for that exception and here some old but not fixed bugs:
• https://youtrack.jetbrains.com/issue/KTOR-2628
• https://youtrack.jetbrains.com/issue/KTOR-1054/Occasional-Channel-has-been-cancelled-errors-when-using-OkHttp
• https://github.com/ktorio/ktor/issues/1946

[olegivo]

to work around this behavior I use this construction in HttpResponseValidator block:

handleResponseExceptionWithRequest { exception, _ ->
    when (exception) {
        is java.util.concurrent.CancellationException -> throw kotlin.coroutines.cancellation.CancellationException(exception)
        else -> throw exception
    }
}

[olegivo]

Maybe, the problem is in linking wrong exception type