swift-composable-architecture-mirror/Tests/ComposableArchitectureTests/Reducers/IfLetReducerTests.swift

import ComposableArchitecture
import XCTest

@available(*, deprecated, message: "TODO: Update to use case pathable syntax with Swift 5.9")
final class IfLetReducerTests: BaseTCATestCase {
  func testNilChild() async {
    let store = await TestStore(initialState: Int?.none) {
      EmptyReducer<Int?, Void>()
        .ifLet(\.self, action: \.self) {}
    }

    XCTExpectFailure {
      $0.compactDescription == """
        failed - An "ifLet" at "\(#fileID):\(#line - 5)" received a child action when child state \
        was "nil". …

          Action:
            ()

        This is generally considered an application logic error, and can happen for a few \
        reasons:

        • A parent reducer set child state to "nil" before this reducer ran. This reducer must \
        run before any other reducer sets child state to "nil". This ensures that child \
        reducers can handle their actions while their state is still available.

        • An in-flight effect emitted this action when child state was "nil". While it may be \
        perfectly reasonable to ignore this action, consider canceling the associated effect \
        before child state becomes "nil", especially if it is a long-living effect.

        • This action was sent to the store while state was "nil". Make sure that actions for \
        this reducer can only be sent from a store when state is non-"nil". In SwiftUI \
        applications, use "IfLetStore".
        """
    }

    await store.send(())
  }

  func testEffectCancellation() async {
    if #available(iOS 16, macOS 13, tvOS 16, watchOS 9, *) {
      struct Child: Reducer {
        struct State: Equatable {
          var count = 0
        }
        enum Action: Equatable {
          case timerButtonTapped
          case timerTick
        }
        @Dependency(\.continuousClock) var clock
        var body: some Reducer<State, Action> {
          Reduce { state, action in
            switch action {
            case .timerButtonTapped:
              return .run { send in
                for await _ in self.clock.timer(interval: .seconds(1)) {
                  await send(.timerTick)
                }
              }
            case .timerTick:
              state.count += 1
              return .none
            }
          }
        }
      }
      struct Parent: Reducer {
        struct State: Equatable {
          var child: Child.State?
        }
        enum Action: Equatable {
          case child(Child.Action)
          case childButtonTapped
        }
        var body: some ReducerOf<Self> {
          Reduce { state, action in
            switch action {
            case .child:
              return .none
            case .childButtonTapped:
              state.child = state.child == nil ? Child.State() : nil
              return .none
            }
          }
          .ifLet(\.child, action: /Action.child) {
            Child()
          }
        }
      }
      let clock = TestClock()
      let store = await TestStore(initialState: Parent.State()) {
        Parent()
      } withDependencies: {
        $0.continuousClock = clock
      }
      await store.send(.childButtonTapped) {
        $0.child = Child.State()
      }
      await store.send(.child(.timerButtonTapped))
      await clock.advance(by: .seconds(2))
      await store.receive(.child(.timerTick)) {
        XCTModify(&$0.child) {
          $0.count = 1
        }
      }
      await store.receive(.child(.timerTick)) {
        XCTModify(&$0.child) {
          $0.count = 2
        }
      }
      await store.send(.childButtonTapped) {
        $0.child = nil
      }
    }
  }

  func testGrandchildEffectCancellation() async {
    if #available(iOS 16, macOS 13, tvOS 16, watchOS 9, *) {
      struct GrandChild: Reducer {
        struct State: Equatable {
          var count = 0
        }
        enum Action: Equatable {
          case timerButtonTapped
          case timerTick
        }
        @Dependency(\.continuousClock) var clock
        var body: some Reducer<State, Action> {
          Reduce { state, action in
            switch action {
            case .timerButtonTapped:
              return .run { send in
                for await _ in self.clock.timer(interval: .seconds(1)) {
                  await send(.timerTick)
                }
              }
            case .timerTick:
              state.count += 1
              return .none
            }
          }
        }
      }
      struct Child: Reducer {
        struct State: Equatable {
          var grandChild: GrandChild.State?
        }
        enum Action: Equatable {
          case grandChild(GrandChild.Action)
        }
        var body: some Reducer<State, Action> {
          EmptyReducer()
            .ifLet(\.grandChild, action: /Action.grandChild) {
              GrandChild()
            }
        }
      }
      struct Parent: Reducer {
        struct State: Equatable {
          var child: Child.State?
        }
        enum Action: Equatable {
          case child(Child.Action)
          case exitButtonTapped
          case startButtonTapped
        }
        var body: some Reducer<State, Action> {
          Reduce { state, action in
            switch action {
            case .child:
              return .none
            case .exitButtonTapped:
              state.child = nil
              return .none
            case .startButtonTapped:
              state.child = Child.State(grandChild: GrandChild.State())
              return .none
            }
          }
          .ifLet(\.child, action: /Action.child) {
            Child()
          }
        }
      }
      let clock = TestClock()
      let store = await TestStore(initialState: Parent.State()) {
        Parent()
      } withDependencies: {
        $0.continuousClock = clock
      }
      await store.send(.startButtonTapped) {
        $0.child = Child.State(grandChild: GrandChild.State())
      }
      await store.send(.child(.grandChild(.timerButtonTapped)))
      await clock.advance(by: .seconds(1))
      await store.receive(.child(.grandChild(.timerTick))) {
        XCTModify(&$0.child) {
          XCTModify(&$0.grandChild) {
            $0.count = 1
          }
        }
      }
      await store.send(.exitButtonTapped) {
        $0.child = nil
      }
    }
  }

  func testEphemeralState() async {
    if #available(iOS 16, macOS 13, tvOS 16, watchOS 9, *) {
      struct Parent: Reducer {
        struct State: Equatable {
          var alert: AlertState<AlertAction>?
        }
        enum Action: Equatable {
          case alert(AlertAction)
          case tap
        }
        enum AlertAction { case ok }
        var body: some Reducer<State, Action> {
          Reduce { state, action in
            switch action {
            case .alert:
              return .none
            case .tap:
              state.alert = AlertState { TextState("Hi!") }
              return .none
            }
          }
          .ifLet(\.alert, action: /Action.alert) {
          }
        }
      }
      let store = await TestStore(initialState: Parent.State()) {
        Parent()
      }
      await store.send(.tap) {
        $0.alert = AlertState { TextState("Hi!") }
      }
      await store.send(.alert(.ok)) {
        $0.alert = nil
      }
    }
  }

  func testIdentifiableChild() async {
    struct Feature: Reducer {
      struct State: Equatable {
        var child: Child.State?
      }
      enum Action: Equatable {
        case child(Child.Action)
        case newChild
      }
      var body: some Reducer<State, Action> {
        Reduce { state, action in
          switch action {
          case .child:
            return .none
          case .newChild:
            guard let childState = state.child
            else { return .none }
            state.child = Child.State(id: childState.id + 1)
            return .none
          }
        }
        .ifLet(\.child, action: /Action.child) { Child() }
      }
    }
    struct Child: Reducer {
      struct State: Equatable, Identifiable {
        let id: Int
        var value = 0
      }
      enum Action: Equatable {
        case tap
        case response(Int)
      }
      @Dependency(\.mainQueue) var mainQueue
      var body: some Reducer<State, Action> {
        Reduce { state, action in
          switch action {
          case .tap:
            return .run { [id = state.id] send in
              try await mainQueue.sleep(for: .seconds(0))
              await send(.response(id))
            }
          case let .response(value):
            state.value = value
            return .none
          }
        }
      }
    }

    let mainQueue = DispatchQueue.test
    let store = await TestStore(initialState: Feature.State(child: Child.State(id: 1))) {
      Feature()
    } withDependencies: {
      $0.mainQueue = mainQueue.eraseToAnyScheduler()
    }

    await store.send(.child(.tap))
    await store.send(.newChild) {
      $0.child = Child.State(id: 2)
    }
    await store.send(.child(.tap))
    await mainQueue.advance()
    await store.receive(.child(.response(2))) {
      $0.child = Child.State(id: 2, value: 2)
    }
  }

  func testEphemeralDismissal() async {
    struct Feature: Reducer {
      struct State: Equatable {
        var alert: AlertState<AlertAction>?
      }
      enum Action: Equatable {
        case alert(AlertAction)
        case tap
      }
      enum AlertAction: Equatable {
        case again
        case ok
      }
      var body: some ReducerOf<Self> {
        Reduce { state, action in
          switch action {
          case .alert(.ok):
            return .none
          case .alert(.again), .tap:
            state.alert = AlertState { TextState("Hello") }
            return .none
          }
        }
        .ifLet(\.alert, action: /Action.alert)
      }
    }

    let store = await TestStore(initialState: Feature.State()) { Feature() }

    await store.send(.tap) {
      $0.alert = AlertState { TextState("Hello") }
    }
    await store.send(.alert(.again))
    await store.send(.alert(.ok)) {
      $0.alert = nil
    }
  }
}