Thread frozen on ALPHA-15 and Combine

[leandrofavarin]

I believe there's a regression from https://github.com/rickclephas/KMP-NativeCoroutines/pull/126. In my case I'm creating a Publisher from a SwiftUI View initialiser, like so:

struct PresentView<Content: View, ModelT>: View {
  @State var model: ModelT
  @State private var models: AnyPublisher<Any, Never> // https://github.com/rickclephas/KMP-NativeCoroutines/issues/90
  private let content: (ModelT) -> Content

  init(presenter: Presenter<ModelT>, content: @escaping (ModelT) -> Content) {
    ...
    self.models = createPublisher(for: presenter.__modelsFlow)
      .assertNoFailure()
      .eraseToAnyPublisher()
    self.content = content
  }

  var body: some View {
    content(model)
      .onReceive(models) { self.model = $0 as! ModelT }
  }
}

This didn't happen on ALPHA-14.

[rickclephas]

Thanks for reporting this, unfortunately I wasn't able to reproduce this. The following seems to work:

struct ClockView: View {

    @State var state: KotlinLong = 0
    @State var publisher: AnyPublisher<KotlinLong, Never>
    private let content: (KotlinLong) -> Text

    init() {
        publisher = createPublisher(for: Clock().time).assertNoFailure().eraseToAnyPublisher()
        content = { Text("\($0)") }
    }

    var body: some View {
        content(state)
            .onReceive(publisher) { self.state = $0 }
    }
}

Could you possible share a reproducer? Feel free to use the sample project.

[leandrofavarin]

I should have added one yesterday, sorry! You can find a repro here. 🙏

[rickclephas]

No problem! It seems only the following combination results in a thread freeze:

• Collecting a StateFlow (from the main thread)
• Using a CoroutineScope with Dispatchers.Main.immediate

The reason being that there is always an initial value that is immediately send to the Swift callback. Fixed by making sure the Flow collection is started after the lock has been released.

[rickclephas]

FYI this has been fixed in v1.0.0-ALPHA-17.