Screens are not cleared when calling navigator.replaceAll

[shpasha]

Suppose our rootNavigator is configured with the following disposeBehavior field:

NavigatorDisposeBehavior(
   disposeNestedNavigators = false,
   disposeSteps = true,
)

And it contains the navigation stack: A -> B -> C

Screen B also contains a nested navigator (for example, this could be a TabScreen) with the stack B1 -> B2 -> B3.
In turn, within screens B1, B2, B3, there are some view models.

From screen C, we perform a rootNavigator.replaceAll action to screen D.

Current Behavior:

• View models on screens B1, B2, B3 are not cleared (because StepDisposableEffect does not perform recursive clearing of screens).

Expected Behavior:

• View models on screens B1, B2, B3 are cleared.

It seems logical to me if ViewModels were cleared as soon as the screen they were attached to disappeared from the navigation stack.
This is a critical issue for building hierarchical navigation. Are there any plans to fix this?

[shpasha]

My current workaround is:

• Pass navigator to NavigatorDisposer class, which inherits ScreenDisposable
• When Screen is disposed NavigatorDisposer also disposes navigator

Sample code:

private class NavigatorDisposer : ScreenDisposable {

    var navigator: Navigator? = null

    override fun onDispose(screen: Screen) {
        navigator?.let { disposeNavigator(it) }
        navigator = null
    }
}

@Composable
private fun Screen.DisposeNavigatorOnScreenDisposeEffect(navigator: Navigator) {
    val screen = this
    LaunchedEffect(navigator) {
        val disposer = ScreenLifecycleStore.get(screen) {
            NavigatorDisposer()
        }
        disposer.navigator = navigator
    }
}

@Composable
public fun Screen.Navigator(
    screen: Screen,
    disposeBehavior: NavigatorDisposeBehavior = NavigatorDisposeBehavior(),
    onBackPressed: OnBackPressed = { true },
    key: String = compositionUniqueId(),
    content: NavigatorContent = { CurrentScreen() }
) {
    Navigator(
        screen = screen,
        disposeBehavior = disposeBehavior,
        onBackPressed = onBackPressed,
        key = key,
        content = { navigator ->
            DisposeNavigatorOnScreenDisposeEffect(navigator)
            content(navigator)
        }
    )
}

But I don't think this is the best way

[hristogochev]

What would the disposeNavigator function be in your workaround? @shpasha

[hristogochev]

I believe the solution I've come up with for #402 may also help this issue.

[shpasha]

What would the disposeNavigator function be in your workaround? @shpasha

@hristogochev you can find disposeNavigator function implementation in voyager source codes