popRoot() behavioral question for Android rememberCircuitNavigator (with BackHandler)

[dfrancis-clear]

Hello! Huge shout out to Zac and all the maintainers on the library. Absolutely love working with Circuit 💯

Now for my question 😅

I'm running into some (potentially) unexpected behavior with calling popRoot() within a nested Circuit (NavigableCircuitContent using the Android version of rememberCircuitNavigator() that contains a BackHandler - here).

For example, not all of the app is in Circuit (yet) and we navigate into a Circuit via Fragment navigation, setting up the NavigableCircuitContent and Navigator within the Fragment (important to note, the OnBackPressedDispatcher.onBackPressed() behavior of this screen will pop / dismiss the Fragment to go back to wherever it came from).

From the Circuit in this fragment, it starts on ScreenA, calls navigator.goTo(ScreenB), which then has a "Close" button that invokes navigator.popRoot() (here) and with this, popRoot() resets the root to ScreenB, then pop() is called, triggering the onRootPop set up in the Android version of rememberCircuitNavigator (with a BackHandler). With this, the backStack size is 1, so I'd expect this inner BackHandler to be disabled (one of the enabled conditions is backStack.size > 1) and for the OnBackPressedDispatcher.onBackPressed() callback that is invoked to be the one on the next level up (the Fragment's). What I see happening is that recomposition within rememberCircuitNavigator hasn't happened yet, so the inner OnBackHandler is what gets invoked, falling into onBack() where the backStack.size is 1.

After tapping the "Close" button again, invoking navigator.popRoot() again, it works as expected (recomposition has happened at this point, the inner BackHandler is not enabled), invoking the OnBackPressedDispatcher.onBackPressed() of the next level up (the Fragment).

Am I misunderstanding what's expected to happen with popRoot() in this case?

Messed around in the Star sample and was able to reproduce the issue: added a BackHandler Toast within MainActivity, changed its NavigableCircuitContent root to PetListScreen, then changed the "Full bio on Petfinder" action on PetDetailScreen to invoke navigator.popRoot().

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EDIT: If this should be opened or transferred to being an "Issue", let me know, happy to do it.

Screen_recording_20250430_114243.mp4

[stagg]

Ya that this is a problem with how BackHandler needs an extra composition to be disabled. I suppose we can modify rememberCircuitNavigator() to delay a composition, disable the back handler, and then trigger the onRootPop.
Fair to say we should handle this case in rememberCircuitNavigator(), so lets transfer this to an issue 🙇🏻

[dfrancis-clear]

Issue created: #2065 - thanks for the quick reply @stagg ! Will see if we have capacity for maybe throwing together a quick contribution for this 🙏