NikolaiRuhe

import XCTest

final class BarrierTests: XCTestCase {
    func test() async {
        let subsystem = Subsystem()
        await withTaskGroup(of: Void.self) { group in
            for index in 0 ..< 100 {
                group.addTask { subsystem.performWork(id: index) }
            }

NikolaiRuhe

actor A {
    var iterator: AsyncStream<Void>.Iterator
    init() {
        iterator = AsyncStream<Void> { _ in }.makeAsyncIterator()
    }

    func f() async {
        await iterator.next() // Cannot call mutating async function 'next()' on actor-isolated property 'iterator'
    }
}

NikolaiRuhe

extension Binding where Value: MutableCollection, Value.Element: Identifiable {
    subscript(_ id: Value.Element.ID) -> Binding<Value.Element> {
        let index = wrappedValue.firstIndex { $0.id == id }
        guard let index else {
            fatalError("id not found: \(id)")
        }
        return self[index]
    }
}

NikolaiRuhe

import XCTest
import SwiftUI

final class CaptureListTests: XCTestCase {

    func testCaptureList() throws {
        withBound("foo") { $boundValue in
            print("value: \(boundValue), binding type: \(type(of: $boundValue))")
        }
    }

NikolaiRuhe

func testRequestCancellation() async throws {

    // Used to synchronize unit test with request task.
    let meeting = TaskMeeting()

    // This request just waits for the unit test in its handler.
    let sut = Request(responseHandler: { _ in
        try? await meeting.rendezvous {}
    })

NikolaiRuhe

// TaskMeeting
// (c) 2022, Nikolai Ruhe

/// A type that synchronizes progress of two tasks.
public final actor TaskMeeting: Sendable {
    private var completion: CheckedContinuation<Void, Error>? = nil

    /// This method synchronizes two tasks so that both perform the closure at
    /// the same time. Both tasks need to call `rendezvous`.
    ///

NikolaiRuhe

/// A type that synchronizes progress of two tasks.
///
/// After setup, two tasks should eventually call the `join` function. The
/// first task will suspend until the second task arrives and calls `join` as
/// well. Both tasks resume normally after that.
public final actor TaskRendezvous: Sendable {
    private var completion: CheckedContinuation<Void, Error>? = nil

    /// Suspends until a second task calls `join()` on this instance.
    public func join() async throws {

NikolaiRuhe

// example unit test:

func testAscii() async throws {
    locate {
        "Celcius"
        "Farenheit"
        "Kelvin"
        "yes?"
        "no?"
        "yes;no;cancel"

NikolaiRuhe

    func testCSV() throws {
        let plainField = Prefix { $0 != .init(ascii: ",") && $0 != .init(ascii: "|") && $0 != .init(ascii: "\n") }

        let quotedField = Parse {
            "|".utf8
            Many {
                OneOf {
                    Parse { "||".utf8 }.map { Substring("").utf8 }
                    Prefix { $0 != .init(ascii: "|") }
                }

NikolaiRuhe

    func testQuotedField() throws {
        let quotedField = Parse {
            "|".utf8
            Many(into: "") { result, element in
                result += String(element)!
            } element: {
                OneOf {
                    Parse { "||".utf8 }.map { Substring("|").utf8 }
                    Prefix(1...) { $0 != .init(ascii: "|") }
                }