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Make ThrowingTaskGroup.nextResult() non-throwing. #38771

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Merged
merged 1 commit into from
Aug 6, 2021
Merged

Make ThrowingTaskGroup.nextResult() non-throwing. #38771

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11 changes: 9 additions & 2 deletions stdlib/public/Concurrency/TaskGroup.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -577,8 +577,9 @@ public struct ThrowingTaskGroup<ChildTaskResult, Failure: Error> {
return try await _taskGroupWaitNext(group: _group)
}

/// - SeeAlso: `next()`
public mutating func nextResult() async throws -> Result<ChildTaskResult, Failure>? {
@_silgen_name("$sScg10nextResults0B0Oyxq_GSgyYaKF")
@usableFromInline
mutating func nextResultForABI() async throws -> Result<ChildTaskResult, Failure>? {
do {
guard let success: ChildTaskResult = try await _taskGroupWaitNext(group: _group) else {
return nil
Expand All @@ -590,6 +591,12 @@ public struct ThrowingTaskGroup<ChildTaskResult, Failure: Error> {
}
}

/// - SeeAlso: `next()`
@_alwaysEmitIntoClient
public mutating func nextResult() async -> Result<ChildTaskResult, Failure>? {
return try! await nextResultForABI()
}

/// Query whether the group has any remaining tasks.
///
/// Task groups are always empty upon entry to the `withTaskGroup` body, and
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17 changes: 11 additions & 6 deletions test/Concurrency/Runtime/async_taskgroup_throw_recover.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -21,7 +21,7 @@ func boom() async throws -> Int {
@available(SwiftStdlib 5.5, *)
func test_taskGroup_throws() async {
let got: Int = try await withThrowingTaskGroup(of: Int.self) { group in
group.spawn { try await boom() }
group.addTask { try await boom() }

do {
while let r = try await group.next() {
Expand All @@ -33,19 +33,24 @@ func test_taskGroup_throws() async {
let gc = group.isCancelled
print("group cancelled: \(gc)")

group.spawn { () async -> Int in
group.addTask { () async -> Int in
let c = Task.isCancelled
print("task 3 (cancelled: \(c))")
return 3
}

guard let third = try! await group.next() else {
switch await group.nextResult() {
case .success(let third):
print("task group returning normally: \(third)")
return third

case .failure(let error):
fatalError("got an erroneous third result")

case .none:
print("task group failed to get 3")
return 0
}

print("task group returning normally: \(third)")
return third
}

fatalError("Should have thrown and handled inside the catch block")
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