[iOS] [Animated] Fix Animated-driven transform state when deleting views from view hierarchy

[gavrix]

This is an implementation of proposal #17475.
I haven't been using ReactNative since original evaluation about a year ago, upon revisiting I see this issue is still around.

Issue:

When deleting a view which UI state (like transform) has been connected to AnimatedProps, said state is reset to defaults before running deleting animation (fade to transparent using opacity, by default). This makes it impossible to implement nice swipe-to-delete experience (when swipe is driven by native driver)

Proposal

To iterate what I described in #17475: instead of disconnected animated component from native view when component is unmounted, keep that connection at native side around until native view is fully purged from the hierarchy.

Concerns:

I'm not 100% sure this is a correct approach. May there be legitimate use cases when AnimatedProps has to be disconnected from native view while latter has to remain in the hierarchy? If anyone has broader context around this mechanism I'd like to discuss.

Changelog:

[iOS] [Changed] - AnimatedProps isn't disconnected from native view (by calling __disconnectAnimatedView) when component is unmounted on js side. Instead, runtime on native side is keeping track of such connections and disconnects when native view is fully removed from hierarchy.

Test Plan:

As a proof-of-concept please see gif provided in #17475.
I wanted to provide a proper integration test but couldn't wrap my head around how to best do it. Any help or hint on direction would much appreciated.

[matthargett]

@hramos it looks like this is dependent on the iOS snapshot test fix PR by @grabbou #22861, if we want CI to be green before merge.

@gavrix does Android not have this problem as well?

[gavrix]

I came to my attention that Reanimated implements the same functionality as Animated and somehow doesn't have this issue. I am going to close this issue and consider Reanimated preferred animation framework.

[matthargett]

That solution works for you, but should this PR still be merged to fix the underlying issue in RN? It seems so to me :)

[gavrix]

It was an experiment and only supported on iOS and I was mainly asking for feedback and I found that issue is not reproducible with Reanimated (which is basically an Animated replacement)