Fix crash on state reset when preferences are queried

marcprux · marcprux · commit 23cf094ecec5 · 2026-05-08T19:06:52.000-04:00
diff --git a/Sources/SkipUI/SkipUI/Containers/Navigation.swift b/Sources/SkipUI/SkipUI/Containers/Navigation.swift
@@ -134,14 +134,10 @@ public struct NavigationStack : View, Renderable {
 
     #if SKIP
     @Composable public override func Render(context: ComposeContext) {
-        // Have to use rememberSaveable for e.g. a nav stack in each tab
-        let destinations = rememberSaveable(stateSaver: context.stateSaver as! Saver<Preference<NavigationDestinations>, Any>) { mutableStateOf(Preference<NavigationDestinations>(key: NavigationDestinationsPreferenceKey.self))
-        }
-        // Make this collector non-erasable so that destinations defined at e.g. the root nav stack layer don't disappear when you push
-        let destinationsCollector = PreferenceCollector<NavigationDestinations>(key: NavigationDestinationsPreferenceKey.self, state: destinations, isErasable: false)
-        let destinationLayoutHints = rememberSaveable(stateSaver: context.stateSaver as! Saver<Preference<NavigationDestinationLayoutHintsMap>, Any>) { mutableStateOf(Preference<NavigationDestinationLayoutHintsMap>(key: NavigationDestinationLayoutHintsPreferenceKey.self))
-        }
-        let destinationLayoutHintsCollector = PreferenceCollector<NavigationDestinationLayoutHintsMap>(key: NavigationDestinationLayoutHintsPreferenceKey.self, state: destinationLayoutHints, isErasable: false)
+        // Have to use rememberSaveable for e.g. a nav stack in each tab. Make the collectors non-erasable so that
+        // destinations defined at e.g. the root nav stack layer don't disappear when you push.
+        let (destinations, destinationsCollector) = rememberSaveablePreferenceCollector(key: NavigationDestinationsPreferenceKey.self, stateSaver: context.stateSaver as! Saver<Preference<NavigationDestinations>, Any>, isErasable: false)
+        let (destinationLayoutHints, destinationLayoutHintsCollector) = rememberSaveablePreferenceCollector(key: NavigationDestinationLayoutHintsPreferenceKey.self, stateSaver: context.stateSaver as! Saver<Preference<NavigationDestinationLayoutHintsMap>, Any>, isErasable: false)
         let reducedDestinations = destinations.value.reduced
         let reducedDestinationLayoutHints = destinationLayoutHints.value.reduced
         let mergedDestinations = mergeNavigationDestinationsWithLayoutHints(reducedDestinations, layoutHints: reducedDestinationLayoutHints)
@@ -166,12 +162,9 @@ public struct NavigationStack : View, Renderable {
                             }
                             // These preferences are per-entry, but if we put them in RenderEntry then their initial values don't show
                             // during the navigation animation. We have to collect them here
-                            let title = rememberSaveable(stateSaver: state.stateSaver as! Saver<Preference<Text>, Any>) { mutableStateOf(Preference<Text>(key: NavigationTitlePreferenceKey.self)) }
-                            let titleCollector = PreferenceCollector<Text>(key: NavigationTitlePreferenceKey.self, state: title)
-                            let toolbarPreferences = rememberSaveable(stateSaver: state.stateSaver as! Saver<Preference<ToolbarPreferences>, Any>) { mutableStateOf(Preference<ToolbarPreferences>(key: ToolbarPreferenceKey.self)) }
-                            let toolbarPreferencesCollector = PreferenceCollector<ToolbarPreferences>(key: ToolbarPreferenceKey.self, state: toolbarPreferences)
-                            let toolbarContentPreferences = rememberSaveable(stateSaver: state.stateSaver as! Saver<Preference<ToolbarContentPreferences>, Any>) { mutableStateOf(Preference<ToolbarContentPreferences>(key: ToolbarContentPreferenceKey.self)) }
-                            let toolbarContentPreferencesCollector = PreferenceCollector<ToolbarContentPreferences>(key: ToolbarContentPreferenceKey.self, state: toolbarContentPreferences)
+                            let (title, titleCollector) = rememberSaveablePreferenceCollector(key: NavigationTitlePreferenceKey.self, stateSaver: state.stateSaver as! Saver<Preference<Text>, Any>)
+                            let (toolbarPreferences, toolbarPreferencesCollector) = rememberSaveablePreferenceCollector(key: ToolbarPreferenceKey.self, stateSaver: state.stateSaver as! Saver<Preference<ToolbarPreferences>, Any>)
+                            let (toolbarContentPreferences, toolbarContentPreferencesCollector) = rememberSaveablePreferenceCollector(key: ToolbarContentPreferenceKey.self, stateSaver: state.stateSaver as! Saver<Preference<ToolbarContentPreferences>, Any>)
                             let arguments = NavigationEntryArguments(isRoot: true, state: state, safeArea: safeArea, ignoresSafeAreaEdges: ignoresSafeAreaEdges, title: title.value.reduced, toolbarPreferences: toolbarPreferences.value.reduced)
                             PreferenceValues.shared.collectPreferences([titleCollector, toolbarPreferencesCollector, toolbarContentPreferencesCollector, destinationsCollector, destinationLayoutHintsCollector]) {
                                 RenderEntry(navigator: navigator, toolbarContent: toolbarContentPreferences, arguments: arguments, context: context) { context in
@@ -185,12 +178,9 @@ public struct NavigationStack : View, Renderable {
                             }
                             // These preferences are per-entry, but if we put them in RenderEntry then their initial values don't show
                             // during the navigation animation. We have to collect them here
-                            let title = rememberSaveable(stateSaver: state.stateSaver as! Saver<Preference<Text>, Any>) { mutableStateOf(Preference<Text>(key: NavigationTitlePreferenceKey.self)) }
-                            let titleCollector = PreferenceCollector<Text>(key: NavigationTitlePreferenceKey.self, state: title)
-                            let toolbarPreferences = rememberSaveable(stateSaver: state.stateSaver as! Saver<Preference<ToolbarPreferences>, Any>) { mutableStateOf(Preference<ToolbarPreferences>(key: ToolbarPreferenceKey.self)) }
-                            let toolbarPreferencesCollector = PreferenceCollector<ToolbarPreferences>(key: ToolbarPreferenceKey.self, state: toolbarPreferences)
-                            let toolbarContentPreferences = rememberSaveable(stateSaver: state.stateSaver as! Saver<Preference<ToolbarContentPreferences>, Any>) { mutableStateOf(Preference<ToolbarContentPreferences>(key: ToolbarContentPreferenceKey.self)) }
-                            let toolbarContentPreferencesCollector = PreferenceCollector<ToolbarContentPreferences>(key: ToolbarContentPreferenceKey.self, state: toolbarContentPreferences)
+                            let (title, titleCollector) = rememberSaveablePreferenceCollector(key: NavigationTitlePreferenceKey.self, stateSaver: state.stateSaver as! Saver<Preference<Text>, Any>)
+                            let (toolbarPreferences, toolbarPreferencesCollector) = rememberSaveablePreferenceCollector(key: ToolbarPreferenceKey.self, stateSaver: state.stateSaver as! Saver<Preference<ToolbarPreferences>, Any>)
+                            let (toolbarContentPreferences, toolbarContentPreferencesCollector) = rememberSaveablePreferenceCollector(key: ToolbarContentPreferenceKey.self, stateSaver: state.stateSaver as! Saver<Preference<ToolbarContentPreferences>, Any>)
                             EnvironmentValues.shared.setValues {
                                 $0.setdismiss(DismissAction(action: { navigator.value.navigateBack() }))
                                 return ComposeResult.ok
@@ -266,11 +256,9 @@ public struct NavigationStack : View, Renderable {
         let searchFieldOffsetPx = rememberSaveable(stateSaver: context.stateSaver as! Saver<Float, Any>) { mutableStateOf(Float(0.0)) }
         let searchFieldScrollConnection = remember { SearchFieldScrollConnection(heightPx: searchFieldHeightPx, offsetPx: searchFieldOffsetPx) }
 
-        let searchableStatePreference = rememberSaveable(stateSaver: context.stateSaver as! Saver<Preference<SearchableState?>, Any>) { mutableStateOf(Preference<SearchableState?>(key: SearchableStatePreferenceKey.self)) }
-        let searchableStateCollector = PreferenceCollector<SearchableState?>(key: SearchableStatePreferenceKey.self, state: searchableStatePreference)
+        let (searchableStatePreference, searchableStateCollector) = rememberSaveablePreferenceCollector(key: SearchableStatePreferenceKey.self, stateSaver: context.stateSaver as! Saver<Preference<SearchableState?>, Any>)
 
-        let scrollToTop = rememberSaveable(stateSaver: context.stateSaver as! Saver<Preference<ScrollToTopAction>, Any>) { mutableStateOf(Preference<ScrollToTopAction>(key: ScrollToTopPreferenceKey.self)) }
-        let scrollToTopCollector = PreferenceCollector<ScrollToTopAction>(key: ScrollToTopPreferenceKey.self, state: scrollToTop)
+        let (scrollToTop, scrollToTopCollector) = rememberSaveablePreferenceCollector(key: ScrollToTopPreferenceKey.self, stateSaver: context.stateSaver as! Saver<Preference<ScrollToTopAction>, Any>)
 
         let initialScrollBehavior = isInlineTitleDisplayMode ? TopAppBarDefaults.pinnedScrollBehavior() : TopAppBarDefaults.exitUntilCollapsedScrollBehavior()
         // Determine the final scrollBehavior early by checking if the environment value would modify it
diff --git a/Sources/SkipUI/SkipUI/Containers/PresentationRoot.swift b/Sources/SkipUI/SkipUI/Containers/PresentationRoot.swift
@@ -32,8 +32,7 @@ import androidx.compose.ui.platform.LocalLayoutDirection
 @Composable public func PresentationRoot(defaultColorScheme: ColorScheme? = nil, absoluteSystemBarEdges systemBarEdges: Edge.Set = .all, context: ComposeContext, content: @Composable (ComposeContext) -> Void) {
     launchUIApplicationActivity()
 
-    let preferredColorScheme = rememberSaveable(stateSaver: context.stateSaver as! Saver<Preference<PreferredColorScheme>, Any>) { mutableStateOf(Preference<PreferredColorScheme>(key: PreferredColorSchemePreferenceKey.self)) }
-    let preferredColorSchemeCollector = PreferenceCollector<PreferredColorScheme>(key: PreferredColorSchemePreferenceKey.self, state: preferredColorScheme)
+    let (preferredColorScheme, preferredColorSchemeCollector) = rememberSaveablePreferenceCollector(key: PreferredColorSchemePreferenceKey.self, stateSaver: context.stateSaver as! Saver<Preference<PreferredColorScheme>, Any>)
     PreferenceValues.shared.collectPreferences([preferredColorSchemeCollector]) {
         let materialColorScheme = preferredColorScheme.value.reduced.colorScheme?.asMaterialTheme() ?? defaultColorScheme?.asMaterialTheme() ?? MaterialTheme.colorScheme
         MaterialTheme(colorScheme: materialColorScheme) {
diff --git a/Sources/SkipUI/SkipUI/Containers/ScrollView.swift b/Sources/SkipUI/SkipUI/Containers/ScrollView.swift
@@ -52,8 +52,7 @@ public struct ScrollView : View, Renderable {
     // SKIP INSERT: @OptIn(ExperimentalMaterialApi::class)
     @Composable override func Render(context: ComposeContext) {
         // Some components in Compose have their own scrolling built in
-        let builtinScrollAxisSet = rememberSaveable(stateSaver: context.stateSaver as! Saver<Preference<Axis.Set>, Any>) { mutableStateOf(Preference<Axis.Set>(key: BuiltinScrollAxisSetPreferenceKey.self)) }
-        let builtinScrollAxisSetCollector = PreferenceCollector<Axis.Set>(key: BuiltinScrollAxisSetPreferenceKey.self, state: builtinScrollAxisSet)
+        let (builtinScrollAxisSet, builtinScrollAxisSetCollector) = rememberSaveablePreferenceCollector(key: BuiltinScrollAxisSetPreferenceKey.self, stateSaver: context.stateSaver as! Saver<Preference<Axis.Set>, Any>)
 
         let scrollState = rememberScrollState()
         let coroutineScope = rememberCoroutineScope()
diff --git a/Sources/SkipUI/SkipUI/Containers/TabView.swift b/Sources/SkipUI/SkipUI/Containers/TabView.swift
@@ -242,8 +242,7 @@ public struct TabView : View, Renderable {
         // Isolate access to current route within child Composable so route nav does not force us to recompose
         navigateToCurrentRoute(tabBackStacks: tabBackStacks, selectedTabIndex: selectedTabIndex, tabRenderables: tabRenderables)
 
-        let tabBarPreferences = rememberSaveable(stateSaver: context.stateSaver as! Saver<Preference<ToolbarBarPreferences>, Any>) { mutableStateOf(Preference<ToolbarBarPreferences>(key: TabBarPreferenceKey.self)) }
-        let tabBarPreferencesCollector = PreferenceCollector<ToolbarBarPreferences>(key: TabBarPreferenceKey.self, state: tabBarPreferences)
+        let (tabBarPreferences, tabBarPreferencesCollector) = rememberSaveablePreferenceCollector(key: TabBarPreferenceKey.self, stateSaver: context.stateSaver as! Saver<Preference<ToolbarBarPreferences>, Any>)
 
         let safeArea = EnvironmentValues.shared._safeArea
         /// Latest TabView-scope safe area; use inside long-lived nav entry closures so inset updates (e.g. status bar hide) propagate without relying on lexical capture of `safeArea`.
diff --git a/Sources/SkipUI/SkipUI/Environment/PreferenceKey.swift b/Sources/SkipUI/SkipUI/Environment/PreferenceKey.swift
@@ -166,6 +166,30 @@ struct PreferenceCollector<Value> {
     }
 }
 
+/// Wraps `rememberSaveable` for a `Preference<V>` with defensive null handling.
+///
+/// After certain Android configuration changes (e.g. a system font scale change) the activity is recreated and the
+/// in-memory map backing our `ComposeStateSaver` is lost, so saved keys no longer resolve to their values and the
+/// restored `MutableState` ends up holding null. Reading `.reduced` on a null `Preference` then crashes. Reset to
+/// the value produced by `initial` whenever the state value is null. See https://github.com/skiptools/skip-ui/issues/300.
+@Composable func rememberSaveablePreference<V>(stateSaver: Saver<Preference<V>, Any>, initial: () -> Preference<V>) -> MutableState<Preference<V>> {
+    let state = rememberSaveable(stateSaver: stateSaver) { mutableStateOf(initial()) }
+    if (state.value as Any?) == nil {
+        state.value = initial()
+    }
+    return state
+}
+
+/// Combines `rememberSaveablePreference` with the matching `PreferenceCollector` so callers don't have to repeat
+/// the value type or the key. The generic `V` is supplied once on the `stateSaver` cast and inferred elsewhere.
+/// Pass `collectorKey` for cases where producers contribute under a different key than the `PreferenceKey` companion
+/// (e.g. when the producer keys on the value type itself rather than the `PreferenceKey` type).
+@Composable func rememberSaveablePreferenceCollector<V>(key: Any.Type, stateSaver: Saver<Preference<V>, Any>, collectorKey: Any? = nil, isErasable: Bool = true) -> (state: MutableState<Preference<V>>, collector: PreferenceCollector<V>) {
+    let state = rememberSaveablePreference(stateSaver: stateSaver) { Preference<V>(key: key) }
+    let collector = PreferenceCollector<V>(key: collectorKey ?? key, state: state, isErasable: isErasable)
+    return (state: state, collector: collector)
+}
+
 struct PreferenceNode<Value>: Equatable {
     let id: Int
     let value: Value
@@ -218,8 +242,8 @@ extension View {
     public func onPreferenceChange(key: Any, defaultValue: Any?, reducer: @escaping (Any?, Any?) -> Any?, action: @escaping (Any?) -> Void) -> any View {
         #if SKIP
         return ModifiedContent(content: self, modifier: RenderModifier { renderable, context in
-            let preference = rememberSaveable(stateSaver: context.stateSaver as! Saver<Preference<Any?>, Any>) {
-                mutableStateOf(Preference<Any?>(key: key, initialValue: defaultValue, reducer: reducer))
+            let preference = rememberSaveablePreference(stateSaver: context.stateSaver as! Saver<Preference<Any?>, Any>) {
+                Preference<Any?>(key: key, initialValue: defaultValue, reducer: reducer)
             }
             let preferenceCollector = PreferenceCollector<Any?>(key: key, state: preference)
             let currentAction = rememberUpdatedState(action)
diff --git a/Sources/SkipUI/SkipUI/Layout/Presentation.swift b/Sources/SkipUI/SkipUI/Layout/Presentation.swift
@@ -92,8 +92,7 @@ private let AlertDialogMaxWidth: Dp = 560.dp
 
 // SKIP INSERT: @OptIn(ExperimentalMaterial3Api::class)
 @Composable func SheetPresentation(isPresented: Binding<Bool>, isFullScreen: Bool, context: ComposeContext, content: () -> any View, onDismiss: (() -> Void)?) {
-    let interactiveDismissDisabledPreference = rememberSaveable(stateSaver: context.stateSaver as! Saver<Preference<Bool>, Any>) { mutableStateOf(Preference<Bool>(key: InteractiveDismissDisabledPreferenceKey.self)) }
-    let interactiveDismissDisabledCollector = PreferenceCollector<Bool>(key: InteractiveDismissDisabledPreferenceKey.self, state: interactiveDismissDisabledPreference)
+    let (interactiveDismissDisabledPreference, interactiveDismissDisabledCollector) = rememberSaveablePreferenceCollector(key: InteractiveDismissDisabledPreferenceKey.self, stateSaver: context.stateSaver as! Saver<Preference<Bool>, Any>)
 
     let sheetState = rememberModalBottomSheetState(skipPartiallyExpanded: true)
     let isPresentedValue = isPresented.get()
@@ -130,8 +129,8 @@ private let AlertDialogMaxWidth: Dp = 560.dp
             let sheetDepth = EnvironmentValues.shared._sheetDepth
             var systemBarEdges: Edge.Set = isFullScreen ? .all : [.top, .bottom]
 
-            let detentPreferences = rememberSaveable(stateSaver: context.stateSaver as! Saver<Preference<PresentationDetentPreferences>, Any>) { mutableStateOf(Preference<PresentationDetentPreferences>(key: PresentationDetentPreferenceKey.self)) }
-            let detentPreferencesCollector = PreferenceCollector<PresentationDetentPreferences>(key: PresentationDetentPreferences.self, state: detentPreferences)
+            // Producers contribute under the value type rather than the `PreferenceKey` type, so override `collectorKey`.
+            let (detentPreferences, detentPreferencesCollector) = rememberSaveablePreferenceCollector(key: PresentationDetentPreferenceKey.self, stateSaver: context.stateSaver as! Saver<Preference<PresentationDetentPreferences>, Any>, collectorKey: PresentationDetentPreferences.self)
             let reducedDetentPreferences = detentPreferences.value.reduced
 
             if !isFullScreen && verticalSizeClass != .compact {
