add onReset callback to FormField (#167060)

This PR adds onReset callback to FormField

fixes #167057


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packages/flutter/lib/src/widgets/form.dart

@@ -466,6 +466,7 @@ class FormField<T> extends StatefulWidget {
     super.key,
     required this.builder,
     this.onSaved,
+    this.onReset,
     this.forceErrorText,
     this.validator,
     this.errorBuilder,
@@ -485,6 +486,10 @@ class FormField<T> extends StatefulWidget {
   /// [FormState.save].
   final FormFieldSetter<T>? onSaved;
 
+  /// An optional method to call when the form field is reset via
+  /// [FormFieldState.reset].
+  final VoidCallback? onReset;
+
   /// An optional property that forces the [FormFieldState] into an error state
   /// by directly setting the [FormFieldState.errorText] property without
   /// running the validator function.
@@ -631,6 +636,7 @@ class FormFieldState<T> extends State<FormField<T>> with RestorationMixin {
       _hasInteractedByUser.value = false;
       _errorText.value = null;
     });
+    widget.onReset?.call();
     Form.maybeOf(context)?._fieldDidChange();
   }
 

packages/flutter/test/widgets/form_test.dart

@@ -89,6 +89,32 @@ void main() {
     await checkText('');
   });
 
+  testWidgets('onReset callback is called', (WidgetTester tester) async {
+    final GlobalKey<FormState> formKey = GlobalKey<FormState>();
+    bool resetCalled = false;
+
+    await tester.pumpWidget(
+      MaterialApp(
+        home: Form(
+          key: formKey,
+          child: FormField<String>(
+            builder: (_) => const SizedBox.shrink(),
+            onReset: () {
+              resetCalled = true;
+            },
+          ),
+        ),
+      ),
+    );
+
+    expect(resetCalled, isFalse);
+
+    formKey.currentState!.reset();
+    await tester.pump();
+
+    expect(resetCalled, isTrue);
+  });
+
   testWidgets('Validator sets the error text only when validate is called', (
     WidgetTester tester,
   ) async {