Do not copy the old selection when applying localization to dates in InputDatePickerFormField (#107268)

Fixes flutter/flutter#107155

Author: jason-simmons

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

@@ -179,7 +179,7 @@ class _InputDatePickerFormFieldState extends State<InputDatePickerFormField> {
     if (_selectedDate != null) {
       final MaterialLocalizations localizations = MaterialLocalizations.of(context);
       _inputText = localizations.formatCompactDate(_selectedDate!);
-      TextEditingValue textEditingValue = _controller.value.copyWith(text: _inputText);
+      TextEditingValue textEditingValue = TextEditingValue(text: _inputText!);
       // Select the new text if we are auto focused and haven't selected the text before.
       if (widget.autofocus && !_autoSelected) {
         textEditingValue = textEditingValue.copyWith(selection: TextSelection(
@@ -191,7 +191,7 @@ class _InputDatePickerFormFieldState extends State<InputDatePickerFormField> {
       _controller.value = textEditingValue;
     } else {
       _inputText = '';
-      _controller.value = _controller.value.copyWith(text: _inputText);
+      _controller.value = TextEditingValue(text: _inputText!);
     }
   }
 

packages/flutter/test/material/input_date_picker_form_field_test.dart

@@ -2,12 +2,33 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter_test/flutter_test.dart';
 
 import '../widgets/clipboard_utils.dart';
 
+class TestMaterialLocalizations extends DefaultMaterialLocalizations {
+  @override
+  String formatCompactDate(DateTime date) {
+    return '${date.month}/${date.day}/${date.year}';
+  }
+}
+
+class TestMaterialLocalizationsDelegate extends LocalizationsDelegate<MaterialLocalizations> {
+  @override
+  bool isSupported(Locale locale) => true;
+
+  @override
+  Future<MaterialLocalizations> load(Locale locale) {
+    return SynchronousFuture<MaterialLocalizations>(TestMaterialLocalizations());
+  }
+
+  @override
+  bool shouldReload(TestMaterialLocalizationsDelegate old) => false;
+}
+
 void main() {
   TestWidgetsFlutterBinding.ensureInitialized();
   final MockClipboard mockClipboard = MockClipboard();
@@ -27,9 +48,11 @@ void main() {
     bool autofocus = false,
     Key? formKey,
     ThemeData? theme,
+    Iterable<LocalizationsDelegate<dynamic>>? localizationsDelegates,
   }) {
     return MaterialApp(
       theme: theme ?? ThemeData.from(colorScheme: const ColorScheme.light()),
+      localizationsDelegates: localizationsDelegates,
       home: Material(
         child: Form(
           key: formKey,
@@ -300,5 +323,27 @@ void main() {
       expect(containerColor, equals(Colors.transparent));
     });
 
+    testWidgets('Date text localization', (WidgetTester tester) async {
+      final Iterable<LocalizationsDelegate<dynamic>> delegates = <LocalizationsDelegate<dynamic>>[
+        TestMaterialLocalizationsDelegate(),
+        DefaultWidgetsLocalizations.delegate,
+      ];
+      await tester.pumpWidget(
+        inputDatePickerField(
+          localizationsDelegates: delegates,
+        )
+      );
+      await tester.enterText(find.byType(TextField), '01/01/2022');
+      await tester.pumpAndSettle();
+
+      // Verify that the widget can be updated to a new value after the
+      // entered text was transformed by the localization formatter.
+      await tester.pumpWidget(
+        inputDatePickerField(
+          initialDate: DateTime(2017),
+          localizationsDelegates: delegates,
+        )
+      );
+    });
   });
 }