Using NavigationLink programmatically fails on iPadOS when using @StateObject in detail view

Question

The following code works perfectly fine on iOS, but not on iPadOS. When I tap on one of the items in the list, the corresponding detail view is shown, but it will not change if I tap on another item. When I change the model in the LanguageDetail view to @ObservedObject, it works. To be clear, this is only an example to illustrate the problem. In my actual project, I'm not able to make this change though. The code below demonstrates this problem.

struct ContentView: View {
    let languages: [String] = ["Objective-C", "Java", "Python", "Swift", "Rust"]
    
    @State var selectedLanguage: String?
    
    var body: some View {
        NavigationView {
            List(languages, id: \.self) { language in
                Button(action: {selectedLanguage = language}) {
                    Text(language)
                        .bold()
                        .padding()
                }
            }
            .background {
                NavigationLink(isActive: $selectedLanguage.isPresent()) {
                    if let lang = selectedLanguage {
                        LanguageDetail(model: LanguageDetailModel(languageName: lang))
                    } else {
                        EmptyView()
                    }
                } label: {
                    EmptyView()
                }
            }
        }
    }
}

struct LanguageDetail: View {
    @StateObject var model: LanguageDetailModel
    var body: some View {
        VStack {
            Text(model.languageName)
                .font(.headline)
            Text("to rule them all...")
        }
    }
}

class LanguageDetailModel: ObservableObject {
    @Published var languageName: String
    
    init(languageName: String) {
        self.languageName = languageName
    }
}

This extension is needed:

/// This extension is from the [SwiftUI Navigation Project on Github](https://github.com/pointfreeco/swiftui-navigation)
extension Binding {
    /// Creates a binding by projecting the current optional value to a boolean describing if it's
    /// non-`nil`.
    ///
    /// Writing `false` to the binding will `nil` out the base value. Writing `true` does nothing.
    ///
    /// - Returns: A binding to a boolean. Returns `true` if non-`nil`, otherwise `false`.
    public func isPresent<Wrapped>() -> Binding<Bool>
    where Value == Wrapped? {
        .init(
            get: { self.wrappedValue != nil },
            set: { isPresent, transaction in
                if !isPresent {
                    self.transaction(transaction).wrappedValue = nil
                }
            }
        )
    }
}

Answer 1

import SwiftUI

enum Language: Int, Identifiable, CaseIterable {

    case objc
    case java
    case python
    case swift
    case rust
    
    var id: Self { self }
    
    var localizedDescription: LocalizedStringKey {
        switch self {
            case .objc: return "Objective-C"
            case .java: return "Java"
            case .python: return "Python"
            case .swift: return "Swift"
            case .rust: return "Rust"
        }
    }
}

struct LanguagesTest: View {

    @State private var selection: Language?
    
    var body: some View {
        NavigationSplitView {
            List(Language.allCases, selection: $selection) { language in
                NavigationLink(value: language) {
                    Text(language.localizedDescription)
                }
            }
        } detail: {
            if let language = selection {
                LanguageDetail(language: language)
            }
            else {
                Text("Select Language")
            }
        }
    }
}


struct LanguageDetail: View {

    let language: Language

    var body: some View {
        VStack {
            Text(language.localizedDescription)
                .font(.headline)
            Text("to rule them all...")
        }
    }
}