Crash FocusState with two TextFields

[fpcornelis]

If you use focus state with two Textfields, app crashes.

If you replace VStack with Form/List it works, but I dont want use a Form.

import SwiftUI
import SwiftUIBackports

struct FocusState: View {
    var body: some View {
        NavigationLink {
            Demo()
                .backport.navigationTitle("Sign In")
        } label: {
            Text("Focus State")
        }
    }
}

private struct Demo: View {
    enum Field: Hashable {
        case username
        case password
    }

    @State private var username = ""
    @State private var password = ""
    @Backport.FocusState private var focusedField: Field?

    var body: some View {
        VStack {
            TextField("Username", text: $username)
                .backport.focused($focusedField, equals: .username)
                .backport.submitLabel(.next)
                .backport.onSubmit {
                    if !username.isEmpty {
                        focusedField = .password
                    }
                }

            TextField("Password", text: $password)
                .backport.focused($focusedField, equals: .password)
                .backport.submitLabel(.done)
                .backport.onSubmit {
                    signIn()
                }

            Button("Sign In") {
                signIn()

            }
        }
        .padding()

        .onAppear {
            focusedField = .username
        }
    }

    private func signIn() {
        if username.isEmpty {
            focusedField = .username
        } else if password.isEmpty {
            focusedField = .password
        } else {
            focusedField = nil
            print(username, password)
        }
    }
}

[shaps80]

You'll need to provide more details on the crash, stack trace, etc. I have previously used a similar setup without issue.

Ideally a sample project demonstrating the issue, otherwise it could take me a long time to investigate sorry.

[elbelga]

Stacktrace

Thread 0 Crashed:: Dispatch queue: com.apple.main-thread 0 libobjc.A.dylib 0x105b1ee3c bool objc::DenseMapBase<objc::DenseMap<DisguisedPtr, unsigned long, (anonymous namespace)::RefcountMapValuePurgeable, objc::DenseMapInfo<DisguisedPtr>, objc::detail::DenseMapPair<DisguisedPtr, unsigned long>>, DisguisedPtr, unsigned long, (anonymous namespace)::RefcountMapValuePurgeable, objc::DenseMapInfo<DisguisedPtr>, objc::detail::DenseMapPair<DisguisedPtr, unsigned long>>::LookupBucketFor<DisguisedPtr>(DisguisedPtr const&, objc::detail::DenseMapPair<DisguisedPtr, unsigned long>*&) + 4 1 libobjc.A.dylib 0x105b1f9c7 objc::DenseMapBase<objc::DenseMap<DisguisedPtr, unsigned long, (anonymous namespace)::RefcountMapValuePurgeable, objc::DenseMapInfo<DisguisedPtr>, objc::detail::DenseMapPair<DisguisedPtr, unsigned long>>, DisguisedPtr, unsigned long, (anonymous namespace)::RefcountMapValuePurgeable, objc::DenseMapInfo<DisguisedPtr>, objc::detail::DenseMapPair<DisguisedPtr, unsigned long>>::operator[](DisguisedPtr&&) + 35 2 libobjc.A.dylib 0x105b1f97d objc_object::sidetable_retain(bool) + 89 3 BackportsDemo 0x10500b164 Coordinator.responds(to:) + 84 4 BackportsDemo 0x10500b2c7 @objc Coordinator.responds(to:) + 39 5 BackportsDemo 0x10500b221 Coordinator.responds(to:) + 273 6 BackportsDemo 0x10500b2c7 @objc Coordinator.responds(to:) + 39 7 BackportsDemo 0x10500b221 Coordinator.responds(to:) + 273 8 BackportsDemo 0x10500b2c7 @objc Coordinator.responds(to:) + 39 9 BackportsDemo 0x10500b221 Coordinator.responds(to:) + 273 10 BackportsDemo 0x10500b2c7 @objc Coordinator.responds(to:) + 39 11 BackportsDemo 0x10500b221 Coordinator.responds(to:) + 273 12 BackportsDemo 0x10500b2c7 @objc Coordinator.responds(to:) + 39 13 BackportsDemo 0x10500b221 Coordinator.responds(to:) + 273 ....

SwiftUIBackportsDemo-main.zip

[shaps80]

Interesting, I think this indicates an underlying issue (similar to #62) because they have almost identical configurations for the delegate-dance in order to prevent introducing issues into native SwiftUI code, as well as allow multiple modifiers to co-exist.

@roland-schmitz-ocu worth you taking a look at this as well, I think its related and perhaps even proves my points I made on the other issue.

I'm fairly confident this all worked previously, so I wonder if something was introduced since iOS 16 that just wasn't uncovered until now since a lot of users of this library are here for "backports" therefore not iOS the latest iOS versions.

[roland-schmitz-ocu]

Thanks @shaps80 for the pointer to this issue. I could reproduce it on iOS 15, 16 and 17 and yes you are right, the issue is very similar to #62. Also here the delegate dance happened multiple times which created a cycle in the delegate chain. I could fix it in the same way as in the other two cases by not touching the delegate when it has already been setup. I added a third commit to my PR #63 which 100% fixes also this issue on iOS 15, iOS 16 and iOS 17.

[elbelga]

I believe it solves the crash, but focusstate doesnt work properly, doesnt focus in the correct field.

In the example above, when screen appears focus on password and it's not correct.

[shaps80]

Thanks @shaps80 for the pointer to this issue. I could reproduce it on iOS 15, 16 and 17 and yes you are right, the issue is very similar to #62. Also here the delegate dance happened multiple times which created a cycle in the delegate chain. I could fix it in the same way as in the other two cases by not touching the delegate when it has already been setup. I added a third commit to my PR #63 which 100% fixes also this issue on iOS 15, iOS 16 and iOS 17.

Perfect, I merged already :)