ScrollViewReader does not update correctly with @Perceptible on iOS 16

[maja0270558]

Description

When using @Perceptible for state tracking inside a ViewModel, views that rely on ScrollViewReader do not update correctly on iOS 16.4 .

The same code works as expected if switch to using an ObservableObject with @Published.

struct ContentView: View {
//   let viewModel: ViewModel = .init()
    @ObservedObject var viewModel: ObservableObjectViewModel = .init()

    var body: some View {
        WithPerceptionTracking {
            ScrollViewReader { proxy in
                VStack {
                    ScrollView {
                        VStack(spacing: 0) {
                            ForEach(viewModel.data, id: \.self) { item in
                                Text("\(item)")
                            }
                            
                            // Example bottom spacer
                            Color.clear
                                .frame(height: 1)
                                .id("bottom_id")
                        }
                    }
                }
                .task {
                    viewModel.onAppear()
                    
                    try? await Task.sleep(nanoseconds: 2_500_000_000)
                    withAnimation {
                        proxy.scrollTo("bottom_id", anchor: .bottom)
                    }
                }
            }
        }
    }
}

@Perceptible
class ViewModel {
    var data: [Int] = []
    
    func onAppear() {
        Task {
            try? await Task.sleep(nanoseconds: 2 * 1_000_000_000)
            data = fake
        }
    }
    
    let fake: [Int] = {
        Array(0...100)
    }()
}


class ObservableObjectViewModel: ObservableObject {
    @Published var data: [Int] = []
    
    func onAppear() {
        Task {
            try? await Task.sleep(nanoseconds: 2 * 1_000_000_000)
            data = fake
        }
    }
    
    let fake: [Int] = {
        Array(0...100)
    }()
}

#Preview {
    ContentView()
}

Thank you for your great work on Perception! ❤️

Checklist

• I have determined that this bug is not reproducible using Swift's observation tools. If the bug is reproducible using the @Observable macro or another tool from the Observation framework, please file it directly with Apple.
• If possible, I've reproduced the issue using the main branch of this package.
• This issue hasn't been addressed in an existing GitHub issue or discussion.

Expected behavior

No response

Actual behavior

No response

Steps to reproduce

No response

Perception version information

1.6.0

Destination operating system

iOS 16.4

Xcode version information

16.2

Swift Compiler version information

swift-driver version: 1.115.1 Apple Swift version 6.0.3 (swiftlang-6.0.3.1.10 clang-1600.0.30.1)
Target: arm64-apple-macosx15.0

[mbrandonw]

Hi @maja0270558, it's mentioned int he docs, but anytime there is an escaping trailing closure in a SwiftUI view (such as ScrollViewReader, GeometryReader, etc.) you need to put an additional WithPerceptionTracking in since it:

ScrollViewReader { proxy in
  WithPerceptionTracking {
    …
  }
}

Since this isn't an issue with the library I am going to convert it to a discussion. Please feel free to continue the conversation over there!