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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,59 @@ | ||
| /// An asynchronous sequence that only emits the provided value once. | ||
| /// | ||
| /// ```swift | ||
| /// Empty<Int>().sink( | ||
| /// receiveValue: { print($0) }, | ||
| /// receiveCompletion: { completion in | ||
| /// switch completion { | ||
| /// case .finished: | ||
| /// print("Finished") | ||
| /// case .failure: | ||
| /// print("Failed") | ||
| /// } | ||
| /// } | ||
| /// ) | ||
| /// | ||
| /// // Prints: | ||
| /// // Finished | ||
| /// ``` | ||
| public struct Empty<Element>: AsyncSequence { | ||
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| // Private | ||
| private let completeImmediately: Bool | ||
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| // MARK: Initialization | ||
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| /// Creates an empty async sequence. | ||
| /// | ||
| /// - Parameter completeImmediately: A Boolean value that indicates whether | ||
| /// the async sequence should immediately finish. | ||
| public init(completeImmediately: Bool = true) { | ||
| self.completeImmediately = completeImmediately | ||
| } | ||
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| // MARK: AsyncSequence | ||
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| /// Creates an async iterator that emits elements of this async sequence. | ||
| /// - Returns: An instance that conforms to `AsyncIteratorProtocol`. | ||
| public func makeAsyncIterator() -> Self { | ||
| .init(completeImmediately: self.completeImmediately) | ||
| } | ||
| } | ||
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| // MARK: AsyncIteratorProtocol | ||
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| extension Empty: AsyncIteratorProtocol { | ||
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| /// Produces the next element in the sequence. | ||
| /// | ||
| /// Because this is an empty sequence, this will always be nil. | ||
| /// | ||
| /// - Returns: `nil` as this is an empty sequence. | ||
| public mutating func next() async -> Element? { | ||
| if !self.completeImmediately { | ||
| try? await Task.sleep(seconds: 999_999_999) | ||
| } | ||
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| return nil | ||
| } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,45 @@ | ||
| import XCTest | ||
| @testable import Asynchrone | ||
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| final class EmptyTests: XCTestCase { | ||
| func testNothingEmitted() async { | ||
| let values = await Empty<Int>().collect() | ||
| XCTAssertEqual(values, []) | ||
| } | ||
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| func testSequenceDoesntComplete() async { | ||
| do { | ||
| try await withThrowingTaskGroup(of: Void.self) { group in | ||
| let timeout: TimeInterval = 1 | ||
| let deadline = Date(timeIntervalSinceNow: timeout) | ||
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| group.addTask { | ||
| _ = await Empty<Int>(completeImmediately: false).collect() | ||
| throw TaskCompletedError() | ||
| } | ||
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| group.addTask { | ||
| if deadline.timeIntervalSinceNow > 0 { | ||
| try await Task.sleep(seconds: timeout) | ||
| } | ||
| } | ||
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| try await group.next() | ||
| group.cancelAll() | ||
| } | ||
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| // All good! | ||
| } catch _ as TaskCompletedError { | ||
| XCTFail("Task incorrectly finished") | ||
| } catch { | ||
| XCTFail("Unknown error thrown \(error)") | ||
| } | ||
| } | ||
| } | ||
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| // MARK: TaskCompletedError | ||
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| fileprivate struct TaskCompletedError: Error { } |
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