OldViews are empty during source collection Clear()

[Serogriff]

Hey

I've been looking into your project for a few days already. And I discovered some behavior that was not obvious to me when I was investigating the leak. The main problem is SynchronizedView send me an empty array, when source collection was resetted.
I made a small code example to demonstrate the situation.

public sealed class ProfileViewModel : IDisposable
{
    private readonly R3.CompositeDisposable _disposable = new();
    private readonly int _id;

    public ProfileViewModel(int id)
    {
        _id = id;
    }

    public void Dispose()
    {
        Console.WriteLine($"Profile {_id} disposed.");
        _disposable.Dispose();
    }
}

private static void Main(string[] args)
{
    ObservableList<int> arr = new();
    using var view = arr.CreateView(x => new ProfileViewModel(x));
    view.ViewChanged += (in SynchronizedViewChangedEventArgs<int, ProfileViewModel> e) =>
    {
        switch (e.Action)
        {
            case NotifyCollectionChangedAction.Remove:
            {
                if (e.IsSingleItem)
                {
                    e.OldItem.View.Dispose();
                }
                else
                {
                    foreach (var vm in e.OldViews)
                    {
                        vm.Dispose();
                    }
                }

                break;
            }
            case NotifyCollectionChangedAction.Reset:
            {
                foreach (var vm in e.OldViews)
                {
                    vm.Dispose();
                }

                break;
            }
        }
    };

    arr.Add(1);
    arr.Add(2);
    arr.Add(3);

    arr.Clear(); // e.OldViews are empty in event handler

    return;
}

Now, to workaround this problem, I do

for (var i = arr.Count - 1; i >= 0; i--)
{
    arr.RemoveAt(i);
}

instead of arr.Clear(); and I get what I originally expected.

So, bug or by design?

[zxt385189207]

I think it's a bug

[starikcetin]

I just encountered this also. Is this a bug or is it expected from the implementation to seperately track the views and destroy them when it receives a reset event?

[slimshader]

Same for Unity, no way to destroy views after Clear()ing source List. OldViews is empty.

_tileViews.ViewChanged += (in SynchronizedViewChangedEventArgs<TileStore, TileView> eventArgs) =>
{
    Debug.Log(eventArgs.Action);

    if (eventArgs.Action == NotifyCollectionChangedAction.Remove)
    {
        Debug.Log($"Destroying view for tile {eventArgs.OldItem.Value.X}, {eventArgs.OldItem.Value.Y}");

        GameObject.Destroy(eventArgs.OldItem.View.gameObject);
    }

    if (eventArgs.Action == NotifyCollectionChangedAction.Reset)
    {
        Debug.Log($"Destroying all views");
        foreach (var item in eventArgs.OldViews)
        {
            GameObject.Destroy(item.gameObject);
        }
    }
};

[gglang]

still an issue...

[Lamonin]

Still an issue or misunderstanding

[github-actions]

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