given a `Job`, how can I fail it with an exception? I want to cancel it abnormally so its parent fai...

# coroutines

[zak.taccardi]

given a Job, how can I fail it with an exception? I want to cancel it abnormally so its parent fails

[Zach Klippenstein (he/him) [MOD]]

“fail without an exception” is basically the definition of “cancellation”. Cancellation is failure without an exception, or failure with a CancellationException, and cancellation is just failure with an exception. They all use the same mechanism, just different words to describe different special cases.

[zak.taccardi]

yeah, that’s the problem. trying to have it fail, not just cancel

[zak.taccardi]

basically just trying to implement this:

private fun Job.fail() {
    TODO("make this job fail with an exception")
}

[Zach Klippenstein (he/him) [MOD]]

job.cancel(RuntimeException("fail"))?

[zak.taccardi]

that doesn’t actually compile anymore

[zak.taccardi]

only non-deprecated/hidden API for cancellation is

fun cancel(cause: CancellationException? = null)

[Zach Klippenstein (he/him) [MOD]]

ugh, right, i always forget that. So job.cancel(CancellationException(RuntimeException("fail")))

[zak.taccardi]

I don’t think that works unless these implementations are wrong

https://kotlinlang.slack.com/archives/C1CFAFJSK/p1599770812224000?thread_ts=1599768358.219600&cid=C1CFAFJSK

[zak.taccardi]

this seemed to do the trick, lol

private fun CoroutineScope.fail() {
     try {
         runBlocking(this.coroutineContext) {
             @Suppress("RedundantAsync", "IMPLICIT_NOTHING_TYPE_ARGUMENT_IN_RETURN_POSITION")
             async([e-mail]) {
                 error("bad things!!")
             }
                 .await()
         }
     } catch (exception: IllegalStateException) {
     }
 }

[Zach Klippenstein (he/him) [MOD]]

I mean, if you really just want to cancel the parent, just get the parent job and cancel it

[Zach Klippenstein (he/him) [MOD]]

I have no idea what that code does haha

[Zach Klippenstein (he/him) [MOD]]

if you have to try that hard, i feel like it’s a sign something else is wrong

[zak.taccardi]

writing tests lol

[zak.taccardi]

not production code haha

[Zach Klippenstein (he/him) [MOD]]

I mean, tests are production code in that they are committed, they will probably outlast you, and other people have to maintain them – “it’s just tests” is no reason to write over-complicated code

[zak.taccardi]

I don’t feel this is too complicated. Just trying to write tests for the code I wrote, which requires a job.fail() function rather than job.cancel()

tests.kt

[zak.taccardi]

non-test-code.kt