Merge pull request #424 from jinyus/nav-bug-fix

fix: use identityHashCode for context

Author: rodydavis

packages/signals_flutter/lib/src/watch/extension.dart

@@ -16,12 +16,12 @@ T watchSignal<T>(
     }
   }
   if (ctx is Element) {
-    final key = ctx.hashCode;
+    final key = identityHashCode(ctx);
     if (_elementRefs[key] == null) {
       final label = [
         'widget',
         ctx.widget.runtimeType.toString(),
-        ctx.widget.hashCode.toString(),
+        identityHashCode(ctx.widget).toString(),
       ].join('=');
       final watcher = ElementWatcher(
         key,
@@ -47,6 +47,6 @@ void unwatchSignal<T>(BuildContext context, core.ReadonlySignal<T> signal) {
       return state.unwatchSignal(signal);
     }
   }
-  final key = ctx.hashCode;
+  final key = identityHashCode(ctx);
   _elementRefs.remove(key)?.unwatch(signal);
 }

packages/signals_flutter/test/navigation_bug.dart

@@ -0,0 +1,96 @@
+// ignore_for_file: hash_and_equals
+
+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:signals_flutter/signals_flutter.dart';
+
+void main() {
+  testWidgets(
+    'watch with forced hashCode collision demonstrates bug',
+    (WidgetTester tester) async {
+      final counter = signal(0);
+      const collisionHash = 999999;
+
+      await tester.pumpWidget(
+        MaterialApp(
+          home: _CollisionWidget(
+            counter: counter,
+            forcedHash: collisionHash,
+          ),
+        ),
+      );
+
+      await tester.pumpAndSettle();
+      expect(find.text('Count: 0'), findsOneWidget);
+
+      counter.value = 1;
+      await tester.pumpAndSettle();
+      expect(find.text('Count: 1'), findsOneWidget);
+
+      await tester.pumpWidget(
+        const MaterialApp(
+          home: Scaffold(body: Text('Away')),
+        ),
+      );
+
+      await tester.pumpAndSettle();
+      expect(find.text('Away'), findsOneWidget);
+
+      await tester.pumpWidget(
+        MaterialApp(
+          home: _CollisionWidget(
+            counter: counter,
+            forcedHash: collisionHash,
+          ),
+        ),
+      );
+
+      await tester.pumpAndSettle();
+      expect(find.text('Count: 1'), findsOneWidget);
+
+      counter.value = 2;
+      await tester.pumpAndSettle();
+
+      expect(
+        find.text('Count: 2'),
+        findsOneWidget,
+        reason: 'Widget should rebuild when signal changes after re-navigation',
+      );
+    },
+  );
+}
+
+class _CollisionWidget extends StatefulWidget {
+  const _CollisionWidget({
+    required this.counter,
+    required this.forcedHash,
+  });
+
+  final Signal<int> counter;
+  final int forcedHash;
+
+  @override
+  State<_CollisionWidget> createState() => _CollisionWidgetStateWithHash();
+
+  @override
+  StatefulElement createElement() => _CollisionElement(this);
+}
+
+class _CollisionElement extends StatefulElement {
+  _CollisionElement(super.widget);
+
+  @override
+  int get hashCode => (widget as _CollisionWidget).forcedHash;
+}
+
+class _CollisionWidgetStateWithHash extends State<_CollisionWidget> {
+  @override
+  Widget build(BuildContext context) {
+    final count = widget.counter.watch(context);
+    return Scaffold(
+      body: Center(
+        child: Text('Count: $count'),
+      ),
+    );
+  }
+}