Hi folks, just wondering why this code throws `NoS...

# coroutines

[George]

Hi folks, just wondering why this code throws NoSuchElementException. Does not null count as a produced value?

suspend fun main(args: Array<String>) {
    val someThingNullable: Any? = null
    val result = mono { someThingNullable }.awaitSingle()
    println(result)
}

Thanks in advance for any answer !

[Dmitry Khalanskiy [JB]]

https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-reactor/kotlinx.coroutines.reactor/mono.html null does not count as a value. Also, reactive streams in general don't permit passing null values through them.

[George]

Oh mb i missed that part in docs. Thanks for the help !!

[Riccardo Lippolis]

you can use .awaitSingleOrNull() if you want to handle an empty mono as well. Keep in mind that there's a functional difference between a Mono that succeeds without emitting a value, and a Mono emitting a null value. But in this case you're using the mono function, which does not emit a value if the code block produces a null value, but succeeds directly.