Add forceErrorText support for DropdownButtonFormField2 [Flutter core]

README.md

@@ -162,6 +162,7 @@ customize to your needs.
 | [onSaved](https://api.flutter.dev/flutter/widgets/FormField/onSaved.html)                                                     | Called with the current selected item when the form is saved       | FormFieldSetter<T>    |    No    |
 | [validator](https://api.flutter.dev/flutter/widgets/FormField/validator.html)                                                 | Called to validates if the input is invalid and display error text  | FormFieldValidator<T>         |    No    |
 | [errorBuilder](https://api.flutter.dev/flutter/widgets/FormField/errorBuilder.html)                                           | Called to display a custom error widget instead of the default error text      | Widget Function(BuildContext, String) |    No    |
+| [forceErrorText](https://api.flutter.dev/flutter/widgets/FormField/forceErrorText.html)                                       | Forces the FormFieldState into an error state and displays the given text           | String                                |    No    |
 | [autovalidateMode](https://api.flutter.dev/flutter/widgets/AutovalidateMode.html)                                             | Used to enable/disable auto validation                             | AutovalidateMode              |    No    |
 
 ## Installation

packages/dropdown_button2/CHANGELOG.md

@@ -2,6 +2,7 @@
 
 - Upgrade minimum required Flutter SDK version to 3.32.0.
 - Add `errorBuilder` support for DropdownButtonFormField2 [Flutter core].
+- Add `forceErrorText` support for DropdownButtonFormField2 [Flutter core].
 
 ## 3.0.0
 

packages/dropdown_button2/lib/src/dropdown_button2.dart

@@ -1068,6 +1068,7 @@ class DropdownButtonFormField2<T> extends FormField<T> {
     super.onSaved,
     super.validator,
     super.errorBuilder,
+    super.forceErrorText,
     AutovalidateMode? autovalidateMode,
     bool? enableFeedback,
     AlignmentGeometry alignment = AlignmentDirectional.centerStart,

packages/dropdown_button2/test/dropdown_button2_test.dart

@@ -173,7 +173,7 @@ void main() {
         return tester.widget<InputDecorator>(findInputDecorator.first);
       }
 
-      testWidgets('validator error text is displayed', (WidgetTester tester) async {
+      testWidgets('validator error text should be displayed when validation fails', (WidgetTester tester) async {
         final GlobalKey<FormState> formKey = GlobalKey<FormState>();
         const errorMessage = 'Please select a value';
 
@@ -201,7 +201,7 @@ void main() {
         expect(find.text(errorMessage), findsOneWidget);
       });
 
-      testWidgets('validator returning null shows no error', (WidgetTester tester) async {
+      testWidgets('validator should show no error when returning null', (WidgetTester tester) async {
         final GlobalKey<FormState> formKey = GlobalKey<FormState>();
 
         await tester.pumpWidget(
@@ -230,7 +230,7 @@ void main() {
         expect(inputDecorator.decoration.error, isNull);
       });
 
-      testWidgets('autovalidateMode.always validates on first build', (
+      testWidgets('autovalidateMode.always should validate on first build', (
         WidgetTester tester,
       ) async {
         int validateCalled = 0;
@@ -258,7 +258,7 @@ void main() {
         expect(find.text('Error'), findsOneWidget);
       });
 
-      testWidgets('decoration errorStyle is applied to error text', (
+      testWidgets('decoration errorStyle should be applied to error text', (
         WidgetTester tester,
       ) async {
         const errorStyle = TextStyle(color: Colors.orange, fontSize: 20);
@@ -287,7 +287,7 @@ void main() {
         expect(find.text('Styled error'), findsOneWidget);
       });
 
-      testWidgets('decoration errorMaxLines is respected', (WidgetTester tester) async {
+      testWidgets('decoration errorMaxLines should be respected', (WidgetTester tester) async {
         await tester.pumpWidget(
           MaterialApp(
             home: Scaffold(
@@ -311,7 +311,7 @@ void main() {
         expect(inputDecorator.decoration.errorMaxLines, 2);
       });
 
-      testWidgets('widget returned by errorBuilder is shown', (WidgetTester tester) async {
+      testWidgets('errorBuilder should replace default error text when provided', (WidgetTester tester) async {
         await tester.pumpWidget(
           MaterialApp(
             home: Scaffold(
@@ -337,7 +337,7 @@ void main() {
         expect(find.text('Required'), findsNothing);
       });
 
-      testWidgets('errorBuilder widget is passed to InputDecorator as error', (
+      testWidgets('errorBuilder widget should be passed to InputDecorator as error', (
         WidgetTester tester,
       ) async {
         final GlobalKey<FormState> formKey = GlobalKey<FormState>();
@@ -378,7 +378,7 @@ void main() {
         expect(find.byIcon(Icons.error), findsOneWidget);
       });
 
-      testWidgets('errorBuilder is not called when there is no error', (
+      testWidgets('errorBuilder should not be called when there is no error', (
         WidgetTester tester,
       ) async {
         bool errorBuilderCalled = false;
@@ -407,6 +407,77 @@ void main() {
 
         expect(errorBuilderCalled, isFalse);
       });
+
+      testWidgets('forceErrorText should force field to display error', (WidgetTester tester) async {
+        await tester.pumpWidget(
+          MaterialApp(
+            home: Scaffold(
+              body: Center(
+                child: DropdownButtonFormField2<int>(
+                  valueListenable: valueListenable,
+                  items: buildItems(),
+                  onChanged: (_) {},
+                  forceErrorText: 'Forced error',
+                ),
+              ),
+            ),
+          ),
+        );
+
+        await tester.pumpAndSettle();
+
+        expect(find.text('Forced error'), findsOneWidget);
+        final inputDecorator = getFormFieldInputDecorator(tester);
+        expect(inputDecorator.decoration.errorText, 'Forced error');
+      });
+
+      testWidgets('forceErrorText should make isValid return false', (WidgetTester tester) async {
+        final GlobalKey<FormFieldState<int>> fieldKey = GlobalKey<FormFieldState<int>>();
+
+        await tester.pumpWidget(
+          MaterialApp(
+            home: Scaffold(
+              body: Center(
+                child: DropdownButtonFormField2<int>(
+                  key: fieldKey,
+                  valueListenable: valueListenable,
+                  items: buildItems(),
+                  onChanged: (_) {},
+                  forceErrorText: 'Forced error',
+                ),
+              ),
+            ),
+          ),
+        );
+
+        expect(fieldKey.currentState!.isValid, isFalse);
+        expect(fieldKey.currentState!.hasError, isTrue);
+      });
+
+      testWidgets('forceErrorText should override InputDecoration.errorText when both are provided', (
+        WidgetTester tester,
+      ) async {
+        await tester.pumpWidget(
+          MaterialApp(
+            home: Scaffold(
+              body: Center(
+                child: DropdownButtonFormField2<int>(
+                  valueListenable: valueListenable,
+                  items: buildItems(),
+                  onChanged: (_) {},
+                  decoration: const InputDecoration(errorText: 'Decoration error'),
+                  forceErrorText: 'Forced error',
+                ),
+              ),
+            ),
+          ),
+        );
+
+        await tester.pumpAndSettle();
+
+        expect(find.text('Forced error'), findsOneWidget);
+        expect(find.text('Decoration error'), findsNothing);
+      });
     },
   );
 }