ForEachReducer can't get idsBefore for enum State

[Otbivnoe]

As I understand the problem it tries to get idsBefore, but since the initial state is empty (TripsChild.State.empty) and key path refers to TripsChild.State.trips, it returns nil - that causes a crash after a force unwrap.

I wrote a simplified version of my code for a faster reproduce.

Pay attention it's important to pass empty as an initial state.

---

Starting point of the app:

TripsChildView(
    store: .init(initialState: .empty) {
        TripsChild()
    }
)

Content is the following:

struct TripsChild: Reducer {

    @ObservableState
    @CasePathable
    @dynamicMemberLookup
    enum State: Equatable {
        case empty
        case trips(IdentifiedArrayOf<TripChildListItem.State>)
    }

    @CasePathable
    enum Action {
        case onAppear
        case trips(IdentifiedActionOf<TripChildListItem>)
    }

    var body: some Reducer<State, Action> {
        Reduce { state, action in
            return .none
        }
        .forEach(\.trips, action: \.trips) {
            TripChildListItem()
        }
    }
}

struct TripsChildView: View {

    let store: StoreOf<TripsChild>

    var body: some View {
        VStack {
            switch store.state {
            case .empty:
                EmptyView()
            case .trips:
                List {
                    ForEach(store.scope(state: \.trips, action: \.trips)) { store in
                        TripChildItemView(store: store)
                    }
                }
            }
        }
        .onAppear {
            store.send(.onAppear)
        }
    }
}

and a list item:

struct TripChildListItem: Reducer {

    @ObservableState
    struct State: Identifiable, Equatable {
        let id = UUID()
    }

    @CasePathable
    enum Action {}

    var body: some Reducer<State, Action> {
        EmptyReducer()
    }
}

struct TripChildItemView: View {

    let store: StoreOf<TripChildListItem>

    var body: some View {
        Text(store.state.id.uuidString)
    }
}

Xcode 15.4
Library version: 1.11.2

p.s. I asked the similar question yesterday (#3245), but seems like it's another problem.

[mbrandonw]

Hi @Otbivnoe, this is the same problem as #3245. The getters you are using are unavailable, and it was a bug in Swift that this code was allowed. It has been fixed in Swift 6.

[Otbivnoe]

Answer in this thread: #3245