Manually revert #102

cookbook/lib/issue/issue151.dart

@@ -0,0 +1,81 @@
+import 'package:flutter/material.dart';
+import 'package:smooth_sheets/smooth_sheets.dart';
+
+/// Issue [#151](https://github.com/fujidaiti/smooth_sheets/issues/151):
+/// Attaching SheetController to NavigationSheet causes
+/// "Null check operator used on a null value"
+void main() {
+  runApp(const Issue151());
+}
+
+class Issue151 extends StatelessWidget {
+  const Issue151({super.key});
+
+  @override
+  Widget build(BuildContext context) {
+    return const MaterialApp(
+      home: Stack(
+        children: [
+          Scaffold(),
+          _Sheet(),
+        ],
+      ),
+    );
+  }
+}
+
+class _Sheet extends StatefulWidget {
+  const _Sheet();
+
+  @override
+  State<_Sheet> createState() => _SheetState();
+}
+
+class _SheetState extends State<_Sheet> {
+  NavigationSheetTransitionObserver? _transitionObserver;
+  late final SheetController _sheetController;
+
+  @override
+  void initState() {
+    super.initState();
+    _transitionObserver = NavigationSheetTransitionObserver();
+    _sheetController = SheetController()
+      ..addListener(() {
+        debugPrint('extent: ${_sheetController.value.maybePixels}');
+      });
+  }
+
+  @override
+  void dispose() {
+    _transitionObserver = null;
+    _sheetController.dispose();
+    super.dispose();
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final nestedNavigator = Navigator(
+      observers: [_transitionObserver!],
+      onGenerateInitialRoutes: (navigator, initialRoute) {
+        return [
+          DraggableNavigationSheetRoute(
+            builder: (context) => Container(
+              color: Colors.indigoAccent,
+              height: 500,
+              width: double.infinity,
+            ),
+          ),
+        ];
+      },
+    );
+
+    return NavigationSheet(
+      controller: _sheetController,
+      transitionObserver: _transitionObserver!,
+      child: Material(
+        color: Colors.indigo,
+        child: nestedNavigator,
+      ),
+    );
+  }
+}

package/lib/src/draggable/draggable_sheet.dart

@@ -73,30 +73,25 @@ class DraggableSheet extends StatelessWidget {
         this.keyboardDismissBehavior ?? theme?.keyboardDismissBehavior;
     final gestureTamper = TamperSheetGesture.maybeOf(context);
 
-    Widget result = ImplicitSheetControllerScope(
+    Widget result = SheetExtentScope(
       controller: controller,
-      builder: (context, controller) {
-        return SheetExtentScope(
-          controller: controller,
-          factory: const DraggableSheetExtentFactory(),
-          config: DraggableSheetExtentConfig(
-            initialExtent: initialExtent,
-            minExtent: minExtent,
-            maxExtent: maxExtent,
-            physics: physics,
-            gestureTamperer: gestureTamper,
-            debugLabel: 'DraggableSheet',
+      factory: const DraggableSheetExtentFactory(),
+      config: DraggableSheetExtentConfig(
+        initialExtent: initialExtent,
+        minExtent: minExtent,
+        maxExtent: maxExtent,
+        physics: physics,
+        gestureTamperer: gestureTamper,
+        debugLabel: 'DraggableSheet',
+      ),
+      child: SheetViewport(
+        child: SheetContentViewport(
+          child: SheetDraggable(
+            behavior: hitTestBehavior,
+            child: child,
           ),
-          child: SheetViewport(
-            child: SheetContentViewport(
-              child: SheetDraggable(
-                behavior: hitTestBehavior,
-                child: child,
-              ),
-            ),
-          ),
-        );
-      },
+        ),
+      ),
     );
 
     if (keyboardDismissBehavior != null) {

package/lib/src/foundation/sheet_controller.dart

@@ -105,7 +105,21 @@ class SheetControllerScope extends InheritedWidget {
   }
 
   static SheetController of(BuildContext context) {
-    return maybeOf(context)!;
+    final controller = maybeOf(context);
+
+    assert((() {
+      if (controller == null) {
+        throw FlutterError(
+          'No $SheetControllerScope ancestor could be found starting '
+          'from the context that was passed to $SheetControllerScope.of(). '
+          'The context used was:\n'
+          '$context',
+        );
+      }
+      return true;
+    })());
+
+    return controller!;
   }
 
   @override
@@ -114,41 +128,6 @@ class SheetControllerScope extends InheritedWidget {
   }
 }
 
-/// A widget that ensures that a [SheetController] is available in the subtree.
-///
-/// The [builder] callback will be called with the [controller] if it is
-/// explicitly provided and is not null, or a [SheetController] that is hosted
-/// in the nearest ancestor [SheetControllerScope]. If neither is found, a newly
-/// created [SheetController] hosted in a [DefaultSheetController] will be
-/// used as a fallback.
-@internal
-// TODO: Remove this.
-class ImplicitSheetControllerScope extends StatelessWidget {
-  const ImplicitSheetControllerScope({
-    super.key,
-    this.controller,
-    required this.builder,
-  });
-
-  final SheetController? controller;
-  final Widget Function(BuildContext, SheetController) builder;
-
-  @override
-  Widget build(BuildContext context) {
-    return switch (controller ?? DefaultSheetController.maybeOf(context)) {
-      final controller? => builder(context, controller),
-      null => DefaultSheetController(
-          child: Builder(
-            builder: (context) {
-              final controller = DefaultSheetController.of(context);
-              return builder(context, controller);
-            },
-          ),
-        ),
-    };
-  }
-}
-
 class DefaultSheetController extends StatefulWidget {
   const DefaultSheetController({
     super.key,

package/lib/src/foundation/sheet_extent.dart

@@ -855,15 +855,15 @@ class SheetExtentScope<C extends SheetExtentConfig, E extends SheetExtent<C>>
   /// Creates a widget that hosts a [SheetExtent].
   const SheetExtentScope({
     super.key,
-    required this.controller,
+    this.controller,
     required this.config,
     required this.factory,
     this.isPrimary = true,
     required this.child,
   });
 
-  /// The [SheetController] that will be attached to the created [SheetExtent].
-  final SheetController controller;
+  /// The [SheetController] attached to the [SheetExtent].
+  final SheetController? controller;
 
   final C config;
 
@@ -921,6 +921,7 @@ class _SheetExtentScopeState<C extends SheetExtentConfig,
     with TickerProviderStateMixin
     implements SheetContext {
   late E _extent;
+  SheetController? _controller;
 
   @override
   TickerProvider get vsync => this;
@@ -942,28 +943,31 @@ class _SheetExtentScopeState<C extends SheetExtentConfig,
 
   @override
   void dispose() {
-    _discard(_extent);
+    _disposeExtent(_extent);
+    _controller = null;
     super.dispose();
   }
 
   @override
   void didChangeDependencies() {
     super.didChangeDependencies();
-    _invalidateExtentOwnership();
+    _rewireControllerAndScope();
+    _rewireControllerAndExtent();
   }
 
   @override
   void didUpdateWidget(SheetExtentScope<C, E> oldWidget) {
     super.didUpdateWidget(oldWidget);
+    _rewireControllerAndScope();
     final oldExtent = _extent;
     if (widget.factory != oldWidget.factory) {
       _extent = _createExtent()..takeOver(oldExtent);
       _scopeKey?._notifySheetExtentCreation();
-      _discard(oldExtent);
+      _disposeExtent(oldExtent);
+      _rewireControllerAndExtent();
     } else if (widget.config != oldWidget.config) {
       _extent.applyNewConfig(widget.config);
     }
-    _invalidateExtentOwnership();
   }
 
   E _createExtent() {
@@ -973,22 +977,30 @@ class _SheetExtentScopeState<C extends SheetExtentConfig,
     );
   }
 
-  void _discard(E extent) {
-    widget.controller.detach(extent);
+  void _disposeExtent(E extent) {
+    _controller?.detach(extent);
     extent.dispose();
   }
 
-  void _invalidateExtentOwnership() {
-    assert(_debugAssertExtentOwnership());
+  void _rewireControllerAndScope() {
+    final newController =
+        widget.controller ?? SheetControllerScope.maybeOf(context);
+    if (_controller != newController) {
+      _controller?.detach(_extent);
+      _controller = newController?..attach(_extent);
+    }
+  }
 
+  void _rewireControllerAndExtent() {
+    assert(_debugAssertPrimaryScopeNotNested());
     if (widget.isPrimary) {
-      widget.controller.attach(_extent);
+      _controller?.attach(_extent);
     } else {
-      widget.controller.detach(_extent);
+      _controller?.detach(_extent);
     }
   }
 
-  bool _debugAssertExtentOwnership() {
+  bool _debugAssertPrimaryScopeNotNested() {
     assert(
       () {
         final parentScope = context
@@ -1000,7 +1012,7 @@ class _SheetExtentScopeState<C extends SheetExtentConfig,
         }
 
         throw FlutterError(
-          'Nesting SheetExtentScope widgets that are marked as primary '
+          'Nesting $SheetExtentScope widgets that are marked as primary '
           'is not allowed. Typically, this error occurs when you try to nest '
           'sheet widgets such as DraggableSheet or ScrollableSheet.',
         );

package/lib/src/navigation/navigation_route.dart

@@ -1,6 +1,5 @@
 import 'package:flutter/material.dart';
 
-import '../foundation/sheet_controller.dart';
 import '../foundation/sheet_extent.dart';
 import '../foundation/sheet_viewport.dart';
 import 'navigation_sheet.dart';
@@ -136,7 +135,6 @@ class NavigationSheetRouteContent extends StatelessWidget {
       isPrimary: false,
       factory: factory,
       config: config,
-      controller: SheetControllerScope.of(context),
       child: NavigationSheetRouteViewport(
         child: SheetContentViewport(child: child),
       ),

package/lib/src/navigation/navigation_sheet.dart

@@ -65,27 +65,22 @@ class _NavigationSheetState extends State<NavigationSheet>
         widget.keyboardDismissBehavior ?? theme?.keyboardDismissBehavior;
     final gestureTamper = TamperSheetGesture.maybeOf(context);
 
-    Widget result = ImplicitSheetControllerScope(
+    Widget result = SheetExtentScope(
+      key: _scopeKey,
       controller: widget.controller,
-      builder: (context, controller) {
-        return SheetExtentScope(
-          key: _scopeKey,
-          controller: controller,
-          factory: this,
-          isPrimary: true,
-          config: SheetExtentConfig(
-            minExtent: const Extent.pixels(0),
-            maxExtent: const Extent.proportional(1),
-            // TODO: Use more appropriate physics.
-            physics: const ClampingSheetPhysics(),
-            gestureTamperer: gestureTamper,
-            debugLabel: kDebugMode ? 'NavigationSheet' : null,
-          ),
-          child: NavigationSheetViewport(
-            child: SheetContentViewport(child: widget.child),
-          ),
-        );
-      },
+      factory: this,
+      isPrimary: true,
+      config: SheetExtentConfig(
+        minExtent: const Extent.pixels(0),
+        maxExtent: const Extent.proportional(1),
+        // TODO: Use more appropriate physics.
+        physics: const ClampingSheetPhysics(),
+        gestureTamperer: gestureTamper,
+        debugLabel: kDebugMode ? 'NavigationSheet' : null,
+      ),
+      child: NavigationSheetViewport(
+        child: SheetContentViewport(child: widget.child),
+      ),
     );
 
     if (keyboardDismissBehavior != null) {