async_task_priority_current.swift

// RUN: %target-run-simple-swift( -target %target-swift-5.1-abi-triple %import-libdispatch -parse-as-library) | %FileCheck --dump-input=always %s

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

// rdar://76038845
// REQUIRES: concurrency_runtime
// UNSUPPORTED: back_deployment_runtime

import Dispatch

@available(SwiftStdlib 5.1,*)
@mainstructMain{
staticfunc main()async{
print("main priority: \(Task.currentPriority)") // CHECK: main priority: TaskPriority.medium
awaittest_detach()
awaittest_multiple_lo_indirectly_escalated()
}
}

@available(SwiftStdlib 5.1,*)
func test_detach()async{
leta1=Task.currentPriority
print("a1: \(a1)") // CHECK: a1: TaskPriority.medium

 // Note: remember to detach using a higher priority, otherwise a lower one
 // might be escalated by the get() and we could see `default` in the detached
 // task.
awaitdetach(priority:.userInitiated){
leta2=Task.currentPriority
print("a2: \(a2)") // CHECK: a2: TaskPriority.high
}.get()

leta3=Task.currentPriority
print("a3: \(a3)") // CHECK: a3: TaskPriority.medium
}

@available(SwiftStdlib 5.1,*)
func test_multiple_lo_indirectly_escalated()async{
@Sendable
func loopUntil(priority:TaskPriority)async{
while(Task.currentPriority != priority){
awaitTask.sleep(1_000_000_000)
}
}

letz=detach(priority:.background){
awaitloopUntil(priority:.userInitiated)
}
letx=detach(priority:.background){
 _ =await z // waiting on `z`, but it won't complete since we're also background
awaitloopUntil(priority:.userInitiated)
}

 // detach, don't wait
detach(priority:.userInitiated){
await x // escalates x, which waits on z, so z also escalates
}

 // since `_` awaited from userInitiated on `x` we:
 // - boost `x` to `userInitiated`
 // and then since `x` waits on `z`
 // - `z` also gets boosted to `userInitiated`
 // which "unlocks" it, allowing the 'default' `await z` to complete:
await x
await z
print("default done") // CHECK: default done
}