refactor(AsyncObject)!: propagate cancellation error instead of swallowing (#8)

* refactor(`AsyncObject`)!: propagate cancellation error instead of swallowing

* wip: add delay to deinit tests

* wip: add delay for tests where needed

* wip: make future initializer synchrnous

* refactor: remove logic duplication for continuation management

* refactor: remove unnecessary class from test

* refactor: refactor test helper functions

* fix: manage cancelling operation before starting properly

* deps: update swift-format with Swift 5.7 support

* wip: refactor safe continuation

* style: add logging parameters to public interfaces

* style: add logging parameters to public interfaces

* wip: remove `@preconcurrency` from `Foundation` for Swift >=5.7

* wip: standardize method names

Author: soumyamahunt

AsyncObjects.xcodeproj/project.pbxproj

@@ -21,7 +21,7 @@ let package = Package(
     dependencies: [
         .package(url: "\(appleGitHub)/swift-collections.git", from: "1.0.0"),
         .package(url: "\(appleGitHub)/swift-docc-plugin", from: "1.0.0"),
-        .package(url: "\(appleGitHub)/swift-format", from: "0.50600.1"),
+        .package(url: "\(appleGitHub)/swift-format", from: "0.50700.0"),
     ],
     targets: [
         .target(
@@ -42,7 +42,7 @@ let package = Package(
     ]
 )
 
-var swiftSettings: [SwiftSetting] {
+var swiftSettings: [SwiftSetting] = {
     var swiftSettings: [SwiftSetting] = []
 
     if ProcessInfo.processInfo.environment[
@@ -77,9 +77,9 @@ var swiftSettings: [SwiftSetting] {
     }
 
     return swiftSettings
-}
+}()
 
-var testingSwiftSettings: [SwiftSetting] {
+var testingSwiftSettings: [SwiftSetting] = {
     var swiftSettings: [SwiftSetting] = []
 
     if ProcessInfo.processInfo.environment[
@@ -96,4 +96,4 @@ var testingSwiftSettings: [SwiftSetting] {
     }
 
     return swiftSettings
-}
+}()

Package.swift

@@ -3,6 +3,7 @@ import Foundation
 #else
 @preconcurrency import Foundation
 #endif
+
 import OrderedCollections
 
 /// An event object that controls access to a resource between high and low priority tasks
@@ -15,20 +16,42 @@ import OrderedCollections
 /// You can indicate high priority usage of resource by using ``increment(by:)`` method,
 /// and indicate free of resource by calling ``signal(repeat:)`` or ``signal()`` methods.
 /// For low priority resource usage or detect resource idling use ``wait()`` method
-/// or its timeout variation ``wait(forNanoseconds:)``.
+/// or its timeout variation ``wait(forNanoseconds:)``:
+///
+/// ```swift
+/// // create event with initial count and count down limit
+/// let event = AsyncCountdownEvent()
+/// // increment countdown count from high priority tasks
+/// event.increment(by: 1)
+///
+/// // wait for countdown signal from low priority tasks,
+/// // fails only if task cancelled
+/// try await event.wait()
+/// // or wait with some timeout
+/// try await event.wait(forNanoseconds: 1_000_000_000)
+///
+/// // signal countdown after completing high priority tasks
+/// event.signal()
+/// ```
 ///
 /// Use the ``limit`` parameter to indicate concurrent low priority usage, i.e. if limit set to zero,
 /// only one low priority usage allowed at one time.
-public actor AsyncCountdownEvent: AsyncObject {
+public actor AsyncCountdownEvent: AsyncObject, ContinuableCollection {
     /// The suspended tasks continuation type.
     @usableFromInline
-    typealias Continuation = SafeContinuation<GlobalContinuation<Void, Error>>
+    internal typealias Continuation = SafeContinuation<
+        GlobalContinuation<Void, Error>
+    >
     /// The platform dependent lock used to synchronize continuations tracking.
     @usableFromInline
-    let locker: Locker = .init()
+    internal let locker: Locker = .init()
     /// The continuations stored with an associated key for all the suspended task that are waiting to be resumed.
     @usableFromInline
-    private(set) var continuations: OrderedDictionary<UUID, Continuation> = [:]
+    internal private(set) var continuations:
+        OrderedDictionary<
+            UUID,
+            Continuation
+        > = [:]
     /// The limit up to which the countdown counts and triggers event.
     ///
     /// By default this is set to zero and can be changed during initialization.
@@ -42,7 +65,7 @@ public actor AsyncCountdownEvent: AsyncObject {
     ///
     /// Can be changed after initialization
     /// by using ``reset(to:)`` method.
-    public private(set) var initialCount: UInt
+    public var initialCount: UInt
     /// Indicates whether countdown event current count is within ``limit``.
     ///
     /// Queued tasks are resumed from suspension when event is set and until current count exceeds limit.
@@ -54,13 +77,13 @@ public actor AsyncCountdownEvent: AsyncObject {
     ///
     /// - Returns: Whether to wait to be resumed later.
     @inlinable
-    func _wait() -> Bool { !isSet || !continuations.isEmpty }
+    internal func shouldWait() -> Bool { !isSet || !continuations.isEmpty }
 
     /// Resume provided continuation with additional changes based on the associated flags.
     ///
     /// - Parameter continuation: The queued continuation to resume.
     @inlinable
-    func _resumeContinuation(_ continuation: Continuation) {
+    internal func resumeContinuation(_ continuation: Continuation) {
         currentCount += 1
         continuation.resume()
     }
@@ -71,12 +94,12 @@ public actor AsyncCountdownEvent: AsyncObject {
     ///   - continuation: The `continuation` to add.
     ///   - key: The key in the map.
     @inlinable
-    func _addContinuation(
+    internal func addContinuation(
         _ continuation: Continuation,
         withKey key: UUID
     ) {
         guard !continuation.resumed else { return }
-        guard _wait() else { _resumeContinuation(continuation); return }
+        guard shouldWait() else { resumeContinuation(continuation); return }
         continuations[key] = continuation
     }
 
@@ -85,49 +108,52 @@ public actor AsyncCountdownEvent: AsyncObject {
     ///
     /// - Parameter key: The key in the map.
     @inlinable
-    func _removeContinuation(withKey key: UUID) {
+    internal func removeContinuation(withKey key: UUID) {
         continuations.removeValue(forKey: key)
     }
 
     /// Decrements countdown count by the provided number.
     ///
     /// - Parameter number: The number to decrement count by.
     @inlinable
-    func _decrementCount(by number: UInt = 1) {
-        defer { _resumeContinuations() }
+    internal func decrementCount(by number: UInt = 1) {
+        defer { resumeContinuations() }
         guard currentCount > 0 else { return }
         currentCount -= number
     }
 
     /// Resume previously waiting continuations for countdown event.
     @inlinable
-    func _resumeContinuations() {
+    internal func resumeContinuations() {
         while !continuations.isEmpty && isSet {
             let (_, continuation) = continuations.removeFirst()
-            _resumeContinuation(continuation)
+            resumeContinuation(continuation)
         }
     }
 
-    /// Suspends the current task, then calls the given closure with a throwing continuation for the current task.
-    /// Continuation can be cancelled with error if current task is cancelled, by invoking `_removeContinuation`.
+    /// Increments the countdown event current count by the specified value.
     ///
-    /// Spins up a new continuation and requests to track it with key by invoking `_addContinuation`.
-    /// This operation cooperatively checks for cancellation and reacting to it by invoking `_removeContinuation`.
-    /// Continuation can be resumed with error and some cleanup code can be run here.
+    /// - Parameter count: The value by which to increase ``currentCount``.
+    @inlinable
+    internal func incrementCount(by count: UInt = 1) {
+        self.currentCount += count
+    }
+
+    /// Resets current count to initial count.
+    @inlinable
+    internal func resetCount() {
+        self.currentCount = initialCount
+        resumeContinuations()
+    }
+
+    /// Resets initial count and current count to specified value.
     ///
-    /// - Throws: If `resume(throwing:)` is called on the continuation, this function throws that error.
+    /// - Parameter count: The new initial count.
     @inlinable
-    nonisolated func _withPromisedContinuation() async throws {
-        let key = UUID()
-        try await Continuation.withCancellation(synchronizedWith: locker) {
-            Task { [weak self] in
-                await self?._removeContinuation(withKey: key)
-            }
-        } operation: { continuation in
-            Task { [weak self] in
-                await self?._addContinuation(continuation, withKey: key)
-            }
-        }
+    internal func resetCount(to count: UInt) {
+        initialCount = count
+        self.currentCount = count
+        resumeContinuations()
     }
 
     // MARK: Public
@@ -158,47 +184,97 @@ public actor AsyncCountdownEvent: AsyncObject {
     /// Use this to indicate usage of resource from high priority tasks.
     ///
     /// - Parameter count: The value by which to increase ``currentCount``.
-    public func increment(by count: UInt = 1) {
-        self.currentCount += count
+    public nonisolated func increment(
+        by count: UInt = 1,
+        file: String = #fileID,
+        function: String = #function,
+        line: UInt = #line
+    ) {
+        Task { await incrementCount(by: count) }
     }
 
     /// Resets current count to initial count.
     ///
     /// If the current count becomes less or equal to limit, multiple queued tasks
     /// are resumed from suspension until current count exceeds limit.
-    public func reset() {
-        self.currentCount = initialCount
-        _resumeContinuations()
+    ///
+    /// - Parameters:
+    ///   - file: The file reset originates from (there's usually no need to pass it
+    ///           explicitly as it defaults to `#fileID`).
+    ///   - function: The function reset originates from (there's usually no need to
+    ///               pass it explicitly as it defaults to `#function`).
+    ///   - line: The line reset originates from (there's usually no need to pass it
+    ///           explicitly as it defaults to `#line`).
+    public nonisolated func reset(
+        file: String = #fileID,
+        function: String = #function,
+        line: UInt = #line
+    ) {
+        Task { await resetCount() }
     }
 
     /// Resets initial count and current count to specified value.
     ///
     /// If the current count becomes less or equal to limit, multiple queued tasks
     /// are resumed from suspension until current count exceeds limit.
     ///
-    /// - Parameter count: The new initial count.
-    public func reset(to count: UInt) {
-        initialCount = count
-        self.currentCount = count
-        _resumeContinuations()
+    /// - Parameters:
+    ///   - count: The new initial count.
+    ///   - file: The file reset originates from (there's usually no need to pass it
+    ///           explicitly as it defaults to `#fileID`).
+    ///   - function: The function reset originates from (there's usually no need to
+    ///               pass it explicitly as it defaults to `#function`).
+    ///   - line: The line reset originates from (there's usually no need to pass it
+    ///           explicitly as it defaults to `#line`).
+    public nonisolated func reset(
+        to count: UInt,
+        file: String = #fileID,
+        function: String = #function,
+        line: UInt = #line
+    ) {
+        Task { await resetCount(to: count) }
     }
 
     /// Registers a signal (decrements) with the countdown event.
     ///
     /// Decrement the countdown. If the current count becomes less or equal to limit,
     /// one queued task is resumed from suspension.
-    public func signal() {
-        signal(repeat: 1)
+    ///
+    /// - Parameters:
+    ///   - file: The file signal originates from (there's usually no need to pass it
+    ///           explicitly as it defaults to `#fileID`).
+    ///   - function: The function signal originates from (there's usually no need to
+    ///               pass it explicitly as it defaults to `#function`).
+    ///   - line: The line signal originates from (there's usually no need to pass it
+    ///           explicitly as it defaults to `#line`).
+    public nonisolated func signal(
+        file: String = #fileID,
+        function: String = #function,
+        line: UInt = #line
+    ) {
+        Task { await decrementCount(by: 1) }
     }
 
     /// Registers multiple signals (decrements by provided count) with the countdown event.
     ///
     /// Decrement the countdown by the provided count. If the current count becomes less or equal to limit,
     /// multiple queued tasks are resumed from suspension until current count exceeds limit.
     ///
-    /// - Parameter count: The number of signals to register.
-    public func signal(repeat count: UInt) {
-        _decrementCount(by: count)
+    /// - Parameters:
+    ///   - count: The number of signals to register.
+    ///   - file: The file signal originates from (there's usually no need to pass it
+    ///           explicitly as it defaults to `#fileID`).
+    ///   - function: The function signal originates from (there's usually no need to
+    ///               pass it explicitly as it defaults to `#function`).
+    ///   - line: The line signal originates from (there's usually no need to pass it
+    ///           explicitly as it defaults to `#line`).
+    public nonisolated func signal(
+        repeat count: UInt,
+        file: String = #fileID,
+        function: String = #function,
+        line: UInt = #line
+    ) {
+        Task { await decrementCount(by: count) }
     }
 
     /// Waits for, or increments, a countdown event.
@@ -207,9 +283,23 @@ public actor AsyncCountdownEvent: AsyncObject {
     /// Otherwise, current task is suspended until either a signal occurs or event is reset.
     ///
     /// Use this to wait for high priority tasks completion to start low priority ones.
+    ///
+    /// - Parameters:
+    ///   - file: The file wait request originates from (there's usually no need to pass it
+    ///           explicitly as it defaults to `#fileID`).
+    ///   - function: The function wait request originates from (there's usually no need to
+    ///               pass it explicitly as it defaults to `#function`).
+    ///   - line: The line wait request originates from (there's usually no need to pass it
+    ///           explicitly as it defaults to `#line`).
+    ///
+    /// - Throws: `CancellationError` if cancelled.
     @Sendable
-    public func wait() async {
-        guard _wait() else { currentCount += 1; return }
-        try? await _withPromisedContinuation()
+    public func wait(
+        file: String = #fileID,
+        function: String = #function,
+        line: UInt = #line
+    ) async throws {
+        guard shouldWait() else { currentCount += 1; return }
+        try await withPromisedContinuation()
     }
 }