`UIViewController.present` doesn't set state to `nil` when dismissed

[myihsan]

Description

if the child state is Identifiable, the dismiss action is not be sent when dismissed. I think #3309 introduced this issue.

Checklist

• [X] I have determined whether this bug is also reproducible in a vanilla SwiftUI project.
• [X] If possible, I've reproduced the issue using the main branch of this package.
• [X] This issue hasn't been addressed in an existing GitHub issue or discussion.

Expected behavior

Send dismiss action when dismissed whatever the child state is Identifiable.

Actual behavior

https://github.com/pointfreeco/swift-composable-architecture/blob/fc5cbeec88114ff987f6c3cad3a7f3a3713fdb56/Sources/ComposableArchitecture/Observation/Store%2BObservation.swift#L395-L398 The id that determines whether or not to send the dismiss action is set by the following. https://github.com/pointfreeco/swift-composable-architecture/blob/fc5cbeec88114ff987f6c3cad3a7f3a3713fdb56/Sources/ComposableArchitecture/Observation/Store%2BObservation.swift#L338-L348 However, when scoping for present, if the child state is nil which is the most of the time, the id will also be nil, but _identifiableID(childState) will not be. So the dismiss action will not be sent.

This issue doesn't affect SwiftUI implementations because the scoped Binding is created every time when body is called, including the time the child state becomes non-nil.

I can work around this by mimicking SwiftUI's behavior, but it's so weird.

observe { [weak self] in
  guard let self, store.alert != nil else { return }
  var token: ObserveToken!
  token = present(
    item: $store.scope(state: \.alert, action: \.alert),
    onDismiss: { token.cancel() }
  ) { store in
    return UIAlertController(store: store)
  }
}

Reproducing project

TicTacToe https://github.com/pointfreeco/swift-composable-architecture/blob/fc5cbeec88114ff987f6c3cad3a7f3a3713fdb56/Examples/TicTacToe/tic-tac-toe/Sources/LoginUIKit/LoginViewController.swift#L94-L96 The alert is an AlertState which is Identifiable.

The Composable Architecture version information

1.14.0

[jshier]

This is the issue I reported in a discussion where the presentation tools didn't work in UIKit when scoping stores. Nice to have a true root cause and a reduction.

[stephencelis]

Thanks for the repro! We'll look into this soon.