[Reactive] Entity tracking on modification

[dr1rrb]

Current behavior

We didn't provided public API to properly track multiple versions of a same entity (a.k.a. IKeyEquatable), so when we edit an entity (i.e. we replace it as entities are expected to be immutable), the entity tracking raises a remove and a add.

This can causes issues with animations in ListView.

Expected behavior

We should be able to get a replace for shuch updates.

How to reproduce it (as minimally and precisely as possible)

public record MyObject(int Id, int Version);

public ListState<MyObject> Items => ListState<MyObject>.Value(this, () => Enumerable.Range(0, 10).Select(i => new MyObject(i, 0)).ToImmutableList());

public async ValueTask Update()
    => await Items.Update(list => list.SetItem(2, new MyObject(2, list[2].Version + 1)));

Data-bind to a ListView and observe that invoking the Update will cause some animations.

Environment

Nuget Package: Uno.Extensions.Reactive.[Win]UI
Package Version(s): latest
Affected platform(s):

• iOS
• Android
• WebAssembly
• WebAssembly renders for Xamarin.Forms
• Windows

Workaround

To hide the issue you can just disable entrance and exit animations on the ListView.

On Android and iOS you also have to disable the native animations:

• For Android, this is done globally in the app by setting feature flag: FeatureConfiguration.NativeListViewBase.RemoveItemAnimator = true; (note: this is the default value).
• On iOS: you have to the uno only flag on directly on your ListView: ios:UseCollectionAnimations="False" (You can set it globally in the app by creating an implciti style for your the ListView).