Is there a way to catch exceptions thrown within flattenMerge()? - kotlin

Question

Playground sample
Given this code, the exception thrown in getRecords() is not caught in testFlattenMerge() - should it not be catchable though? Also, in getPeople(), the exception can be caught which causes flattenMerge() to work as expected, but it prints out "Caught in people" before any numbers are printed, and not after 64, as I expected. Is this the correct behavior? I can't quite fit my mental model of flattenMerge() around this.
import kotlin.reflect.KProperty
import kotlin.system.measureTimeMillis
import kotlinx.coroutines.flow.*
import kotlinx.coroutines.*
fun getRecords(id: Int) = flow {
repeat(5) { emit("A record for $id") }
if (id == 6) throw RuntimeException("Anything but #6!")
repeat(5) { emit("A record for $id") }
}
fun getPeople() = flow {
repeat(10) { emit(getRecords(it)) }
// repeat(10) { emit(getRecords(it).catch{ println("Caught in getPeople()")}) } // This works, but it prints /before/ any cnt lines...?
}
suspend fun testFlattenMerge() {
println ("Merge with flattenMerge()")
var cnt = 0
val flowOfFlows = getPeople()
flowOfFlows.catch{ println("Caught before flattenMerge")}
.flattenMerge()
.catch{ println("Caught after flattenMerge")}
.collect {
println("${cnt++}") // Without catching inside getPeople() this stops at 64
}
}
suspend fun testManualMerge() {
println("Merge manually")
var cnt = 0
repeat(10) {
getRecords(it).catch{ println("Caught in manual merge") }
.collect {
println("${cnt++}") // This goes up to 94, as expected
}
}
}
fun main() = runBlocking {
testFlattenMerge()
testManualMerge()
}