Arghhh. Another #SwiftUI regression in 16.4: NavigationSplitView won’t animate the first push of the detail column if the content column goes from List, to no List. Again, this worked just fine in prior releases!

NavigationSplitViewBug.swift

import SwiftUI

enum FruitSuggestion: String, Identifiable, CaseIterable {
    case apple, banana, orange
    var id: Self { self }
}

struct AppView: View {
    
    @State private var selection: FruitSuggestion?
    @State private var contentSelection = Set<Int>()
    
    var body: some View {
        NavigationSplitView {
            SidebarView(selection: $selection)
        } content: {
            if let content = selection {
                switch content {
                case .apple:
                    Text("Apple View")
                case .banana:
                    Text("Banana View")
                case .orange:
                    ContentView(fruit: content, rowSelection: $contentSelection)
                }
            } else {
                Text("Nothing selected")
            }
        } detail: {
            if let row = contentSelection.first {
                DetailView(row: row)
            } else {
                Text("No Item Selected")
            }
        }
    }
}

struct SidebarView: View {
    
    @Binding var selection: FruitSuggestion?
    
    var body: some View {
        List(selection: $selection) {
            ForEach(FruitSuggestion.allCases) {
                NavigationLink($0.rawValue, value: $0)
            }
        }
        .navigationTitle("Sidebar")
    }
}

struct ContentView: View {
    
    let fruit: FruitSuggestion?
    @Binding var rowSelection: Set<Int>
    
    var body: some View {
        List(selection: $rowSelection) {
            ForEach(0...20, id: \.self) { id in
                NavigationLink(value: id) {
                    Text("Row \(id)")
                }
            }
        }
        .navigationTitle(fruit?.rawValue ?? "")
    }
}

struct DetailView: View {
    
    let row: Int
    
    var body: some View {
        Text("Detail View \(row)")
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        AppView()
    }
}