async_taskgroup_next_on_pending.swift

// RUN: %target-run-simple-swift( -Xfrontend -disable-availability-checking %import-libdispatch -parse-as-library) | %FileCheck %s --dump-input=always

// REQUIRES: executable_test
// REQUIRES: concurrency
// REQUIRES: libdispatch

// rdar://113915243 - flaky test on watchos
// UNSUPPORTED: OS=watchos

// REQUIRES: concurrency_runtime

import Dispatch

func completeSlowly(n:Int)async->Int{
try?awaitTask.sleep(for:.milliseconds(n *300))
return n
}

/// Tasks complete AFTER they are next() polled.
func test_sum_nextOnPending()async{
letnumbers=[1,2,3]
letexpected=6

letsum=try!awaitwithTaskGroup(of:Int.self){(group)async->Intin
fornin numbers {
 group.addTask{
awaitcompleteSlowly(n: n)
}
}

varsum=0
print("before group.next(), sum: \(sum)")
whilelet n =try!await group.next(){
assert(numbers.contains(n),"Unexpected value: \(n)! Expected any of \(numbers)")
print("next: \(n)")
 sum += n
print("before group.next(), sum: \(sum)")
}

 print("task group returning: \(sum)")
return sum
}

 // The completions are set apart by n seconds, so we expect them to arrive
 // in the order as the numbers (and delays) would suggest:

 // CHECK: task group returning: 6

 // CHECK: result: 6
print("result: \(sum)")
assert(sum == expected,"Expected: \(expected), got: \(sum)")
}

@mainstructMain{
staticfunc main()async{
awaittest_sum_nextOnPending()
}
}