Pass-Through `inputFormatters` in `DropdownMenu` (#143250)

Pass-Through `inputFormatters` in `DropdownMenu`.

Fixes: #142374

packages/flutter/lib/src/material/dropdown_menu.dart

@@ -164,6 +164,7 @@ class DropdownMenu<T> extends StatefulWidget {
     this.expandedInsets,
     this.searchCallback,
     required this.dropdownMenuEntries,
+    this.inputFormatters,
   });
 
   /// Determine if the [DropdownMenu] is enabled.
@@ -389,6 +390,20 @@ class DropdownMenu<T> extends StatefulWidget {
   /// which contains the contents of the text input field.
   final SearchCallback<T>? searchCallback;
 
+  /// Optional input validation and formatting overrides.
+  ///
+  /// Formatters are run in the provided order when the user changes the text
+  /// this widget contains. When this parameter changes, the new formatters will
+  /// not be applied until the next time the user inserts or deletes text.
+  /// Formatters don't run when the text is changed
+  /// programmatically via [controller].
+  ///
+  /// See also:
+  ///
+  ///  * [TextEditingController], which implements the [Listenable] interface
+  ///    and notifies its listeners on [TextEditingValue] changes.
+  final List<TextInputFormatter>? inputFormatters;
+
   @override
   State<DropdownMenu<T>> createState() => _DropdownMenuState<T>();
 }
@@ -755,6 +770,7 @@ class _DropdownMenuState<T> extends State<DropdownMenu<T>> {
                 _enableFilter = widget.enableFilter;
               });
             },
+            inputFormatters: widget.inputFormatters,
             decoration: InputDecoration(
               enabled: widget.enabled,
               label: widget.label,

packages/flutter/test/material/dropdown_menu_test.dart

@@ -1972,6 +1972,54 @@ void main() {
     // Test input border when focused.
     expect(box, paints..rrect(color: theme.colorScheme.primary));
   });
+
+  testWidgets('DropdownMenu honors inputFormatters', (WidgetTester tester) async {
+    int called = 0;
+    final TextInputFormatter formatter = TextInputFormatter.withFunction(
+      (TextEditingValue oldValue, TextEditingValue newValue) {
+        called += 1;
+        return newValue;
+      },
+    );
+    final TextEditingController controller = TextEditingController();
+
+    await tester.pumpWidget(
+      MaterialApp(
+        home: Scaffold(
+          body: DropdownMenu<String>(
+            controller: controller,
+            dropdownMenuEntries: const <DropdownMenuEntry<String>>[
+              DropdownMenuEntry<String>(
+                value: 'Blue',
+                label: 'Blue',
+              ),
+              DropdownMenuEntry<String>(
+                value: 'Green',
+                label: 'Green',
+              ),
+            ],
+            inputFormatters: <TextInputFormatter>[
+              formatter,
+              FilteringTextInputFormatter.deny(RegExp('[0-9]'))
+            ],
+          ),
+        ),
+      ),
+    );
+
+    final EditableTextState state = tester.firstState(find.byType(EditableText));
+    state.updateEditingValue(const TextEditingValue(text: 'Blue'));
+    expect(called, 1);
+    expect(controller.text, 'Blue');
+
+    state.updateEditingValue(const TextEditingValue(text: 'Green'));
+    expect(called, 2);
+    expect(controller.text, 'Green');
+
+    state.updateEditingValue(const TextEditingValue(text: 'Green2'));
+    expect(called, 3);
+    expect(controller.text, 'Green');
+  });
 }
 
 enum TestMenu {