Fix OpenURL crash on macOS Sequoia

[beetee17]

Refer to the discussion at #301 for details.

[stephencelis]

Suggested change

	static let liveValue = OpenURLEffect { @MainActor url in
	// NB: This must be annotated '@MainActor' to avoid a Swift bug:
	// https://github.com/pointfreeco/swift-dependencies/discussions/301
	static let liveValue = OpenURLEffect { @MainActor url in

[stephencelis]

@beetee17 Thanks, and sorry for the delay! This time of year has been busy.

Do you think it's possible to get a unit test in place that demonstrates the problem? Ideally we would have CI catch any regressions if someone were to refactor away that @MainActor annotation. I've at the very least added a suggestion to comment on the inclusion of it.

[beetee17]

@stephencelis, sorry for the delay as well. I was finally able to gain access to macOS Sequoia 15.0 on an M1 Mac Mini for testing. I was able to verify the root cause of the crash, however, the fix comes with a drawback.

The following is copy-pasted from the latest commit message, let me know if more details are required:

Further testing has revealed that the crash stems from the completion handler for openURL. This may be a bummer for use-cases that require it to check whether an app was available to handle a URL scheme.

An attempt was made to have the best of both worlds by returning .systemAction in the OpenURLAction handler, however this causes the completion handler to never return.

Therefore, the only real fix is to always return .handled, which makes it equivalent to the watchOS implementation that always yields true.

Overall, it may be cleaner to use the watchOS implementation instead, I only left the implementation as it is to document my initial attempt to work around the crash. Feel free to change it or let me know and I will change it as well.

The unit test to catch regressions is simple, it simply runs the live value and ensures that the function returns without crashing. However, since the live implementation was hidden behind the private enum OpenURLKey, I changed the access modifier to internal for the purpose of testing.

EDIT: I actually am unsure why the earlier @MainActor fix worked for my users, as that still causes a crash when running the test. Regardless, it is invalid and I will also update the app with these most recent findings.