Fix set-state-error on TimeInputWidget

The widget is read-only, so we don't need to use a controller, it is simply rebuilt when the
user selects a new time

Author: rolandgeider

lib/widgets/core/datetime_input.dart

@@ -58,7 +58,6 @@ class TimeInputWidget extends StatefulWidget {
 }
 
 class _TimeInputWidgetState extends State<TimeInputWidget> {
-  final _controller = TextEditingController();
   TimeOfDay? _value;
 
   @override
@@ -75,20 +74,14 @@ class _TimeInputWidgetState extends State<TimeInputWidget> {
     }
   }
 
-  @override
-  void dispose() {
-    _controller.dispose();
-    super.dispose();
-  }
-
   @override
   Widget build(BuildContext context) {
-    // The field is read-only, so rewriting the display text every build is safe.
-    _controller.text = _value?.format(context) ?? '';
-
+    // Keyed initialValue, not a controller: a controller notifies the enclosing
+    // Form on assignment, which crashes if that happens during a build.
     return TextFormField(
+      key: ValueKey(_value),
       readOnly: true,
-      controller: _controller,
+      initialValue: _value?.format(context) ?? '',
       validator: widget.validator,
       decoration: InputDecoration(
         labelText: widget.labelText,
@@ -170,7 +163,6 @@ class DateInputWidget extends StatefulWidget {
 }
 
 class _DateInputWidgetState extends State<DateInputWidget> {
-  final _controller = TextEditingController();
   DateTime? _value;
 
   @override
@@ -187,21 +179,15 @@ class _DateInputWidgetState extends State<DateInputWidget> {
     }
   }
 
-  @override
-  void dispose() {
-    _controller.dispose();
-    super.dispose();
-  }
-
   @override
   Widget build(BuildContext context) {
     final dateFormat = DateFormat.yMd(Localizations.localeOf(context).languageCode);
-    // The field is read-only, so rewriting the display text every build is safe.
-    _controller.text = _value != null ? dateFormat.format(_value!) : '';
-
+    // Keyed initialValue, not a controller: a controller notifies the enclosing
+    // Form on assignment, which crashes if that happens during a build.
     return TextFormField(
+      key: ValueKey(_value),
       readOnly: true,
-      controller: _controller,
+      initialValue: _value != null ? dateFormat.format(_value!) : '',
       validator: widget.validator,
       decoration: InputDecoration(
         labelText: widget.labelText,

test/core/datetime_input_test.dart

@@ -95,6 +95,29 @@ void main() {
       expect(cleared, isTrue);
       expect(find.text('3:30 PM'), findsNothing);
     });
+
+    testWidgets('does not rebuild the enclosing Form during build when the value '
+        'changes from the parent (regression: issue #2401)', (WidgetTester tester) async {
+      final notifier = ValueNotifier<TimeOfDay?>(null);
+      await tester.pumpWidget(
+        wrap(
+          Form(
+            child: ValueListenableBuilder<TimeOfDay?>(
+              valueListenable: notifier,
+              builder: (context, value, _) =>
+                  TimeInputWidget(value: value, labelText: 'Time', onChanged: (_) {}),
+            ),
+          ),
+        ),
+      );
+      await tester.pumpAndSettle();
+
+      notifier.value = const TimeOfDay(hour: 15, minute: 30);
+      await tester.pumpAndSettle();
+
+      expect(tester.takeException(), isNull);
+      expect(find.text('3:30 PM'), findsOneWidget);
+    });
   });
 
   group('DateInputWidget', () {
@@ -130,5 +153,28 @@ void main() {
 
       expect(find.text('5.1.2021'), findsOneWidget);
     });
+
+    testWidgets('does not rebuild the enclosing Form during build when the value '
+        'changes from the parent (regression: issue #2401)', (WidgetTester tester) async {
+      final notifier = ValueNotifier<DateTime?>(null);
+      await tester.pumpWidget(
+        wrap(
+          Form(
+            child: ValueListenableBuilder<DateTime?>(
+              valueListenable: notifier,
+              builder: (context, value, _) =>
+                  DateInputWidget(value: value, labelText: 'Date', onChanged: (_) {}),
+            ),
+          ),
+        ),
+      );
+      await tester.pumpAndSettle();
+
+      notifier.value = DateTime(2021, 1, 5);
+      await tester.pumpAndSettle();
+
+      expect(tester.takeException(), isNull);
+      expect(find.text('1/5/2021'), findsOneWidget);
+    });
   });
 }