fix: 133 signal builder unnecessary rebuilds (#135)

Author: nank1ro

packages/flutter_solidart/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 2.3.1
+
+- **FIX**: `SignalBuilder` rebuilded twice when a signal changed, added unit test to prevent this from happening again.
+
 ## 2.3.0
 
 ### Changes from solidart

packages/flutter_solidart/lib/src/widgets/signal_builder.dart

@@ -108,6 +108,7 @@ class SignalBuilderElement extends ComponentElement {
   Effect? _effect;
 
   SignalBuilder get _widget => widget as SignalBuilder;
+  Widget? _builtWidget;
 
   @override
   void mount(Element? parent, Object? newSlot) {
@@ -142,7 +143,7 @@ class SignalBuilderElement extends ComponentElement {
   Future<void> _invalidate() async {
     // // if the element is already dirty, we don't need to ask another rebuild
     if (dirty) return;
-    _widget.build(_parent!);
+    _builtWidget = _widget.build(_parent!);
 
     if (_shouldWaitScheduler) {
       await SchedulerBinding.instance.endOfFrame;
@@ -166,7 +167,7 @@ class SignalBuilderElement extends ComponentElement {
     reactiveSystem.activeSub = _effect?.subscriber;
 
     try {
-      return _widget.build(_parent!);
+      return _builtWidget ??= _widget.build(_parent!);
     } finally {
       reactiveSystem.activeSub = prevSub;
     }

packages/flutter_solidart/pubspec.yaml

@@ -1,6 +1,6 @@
 name: flutter_solidart
 description: A simple State Management solution for Flutter applications inspired by SolidJS
-version: 2.3.0
+version: 2.3.1
 repository: https://github.com/nank1ro/solidart
 documentation: https://solidart.mariuti.com
 topics:

packages/flutter_solidart/test/flutter_solidart_test.dart

@@ -258,11 +258,13 @@ void main() {
 
   testWidgets('SignalBuilder works properly (1 Signal)', (tester) async {
     final s = Signal(0);
+    var buildsCount = 0;
     await tester.pumpWidget(
       MaterialApp(
         home: Scaffold(
           body: SignalBuilder(
             builder: (context, child) {
+              buildsCount++;
               return Text(s.value.toString());
             },
           ),
@@ -272,9 +274,17 @@ void main() {
     Finder dataFinder(int value) => find.text('$value');
 
     expect(dataFinder(0), findsOneWidget);
+    expect(buildsCount, 1);
+
     s.value++;
     await tester.pumpAndSettle();
     expect(dataFinder(1), findsOneWidget);
+    expect(buildsCount, 2);
+
+    s.value++;
+    await tester.pumpAndSettle();
+    expect(dataFinder(2), findsOneWidget);
+    expect(buildsCount, 3);
   });
 
   testWidgets('SignalBuilder works properly (2 Signals)', (tester) async {