SearchBar should listen to changes to the SearchController and update suggestions on change (#134337)

This PR is adding a listener to the `SearchController`, so that the `suggestionBuilder` can be updated when the `SearchController` changes. 

Another method we can possibly do is  have an update method on `SearchController`, so that the user can manually update the suggestions instead of us doing it automatically.

Fixes #132161

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

@@ -673,11 +673,19 @@ class _ViewContentState extends State<_ViewContent> {
     super.initState();
     _viewRect = widget.viewRect;
     _controller = widget.searchController;
+    _controller.addListener(updateSuggestions);
+
     if (!_focusNode.hasFocus) {
       _focusNode.requestFocus();
     }
   }
 
+  @override
+  void dispose(){
+    _controller.removeListener(updateSuggestions);
+    super.dispose();
+  }
+
   @override
   void didUpdateWidget(covariant _ViewContent oldWidget) {
     super.didUpdateWidget(oldWidget);
@@ -737,7 +745,6 @@ class _ViewContentState extends State<_ViewContent> {
         icon: const Icon(Icons.close),
         onPressed: () {
           _controller.clear();
-          updateSuggestions();
         },
       ),
     ];

packages/flutter/test/material/search_anchor_test.dart

@@ -1490,6 +1490,95 @@ void main() {
     expect(controller.value.text, suggestion);
   });
 
+  testWidgets('SearchAnchor should update suggestions on changes to search controller', (WidgetTester tester) async {
+    final SearchController controller = SearchController();
+    const List<String> suggestions = <String>['foo','far','bim'];
+    addTearDown(controller.dispose);
+
+    await tester.pumpWidget(MaterialApp(
+      home: StatefulBuilder(
+        builder: (BuildContext context, StateSetter setState) {
+          return Material(
+            child: Align(
+              alignment: Alignment.topCenter,
+              child: SearchAnchor(
+                searchController: controller,
+                builder: (BuildContext context, SearchController controller) {
+                  return const Icon(Icons.search);
+                },
+                suggestionsBuilder: (BuildContext context, SearchController controller) {
+                  final String searchText = controller.text.toLowerCase();
+                  if (searchText.isEmpty) {
+                    return const <Widget>[
+                      Center(
+                        child: Text('No Search'),
+                      ),
+                    ];
+                  }
+                  final Iterable<String> filterSuggestions = suggestions.where(
+                    (String suggestion) => suggestion.toLowerCase().contains(searchText),
+                  );
+                  return filterSuggestions.map((String suggestion) {
+                    return ListTile(
+                      title: Text(suggestion),
+                      trailing: IconButton(
+                        icon: const Icon(Icons.call_missed),
+                        onPressed: () {
+                          controller.text = suggestion;
+                        },
+                      ),
+                      onTap: () {
+                        controller.closeView(suggestion);
+                      },
+                    );
+                  }).toList();
+                },
+              ),
+            ),
+          );
+        }
+      ),
+    ));
+
+    await tester.tap(find.byIcon(Icons.search));
+    await tester.pumpAndSettle();
+
+    final Finder listTile1 = find.widgetWithText(ListTile, 'foo');
+    final Finder listTile2 = find.widgetWithText(ListTile, 'far');
+    final Finder listTile3 = find.widgetWithText(ListTile, 'bim');
+    final Finder textWidget = find.widgetWithText(Center, 'No Search');
+    final Finder iconInListTile1 = find.descendant(of: listTile1, matching: find.byIcon(Icons.call_missed));
+
+    expect(textWidget,findsOneWidget);
+    expect(listTile1, findsNothing);
+    expect(listTile2, findsNothing);
+    expect(listTile3, findsNothing);
+
+    await tester.enterText(find.byType(SearchBar), 'f');
+    await tester.pumpAndSettle();
+    expect(textWidget,findsNothing);
+    expect(listTile1, findsOneWidget);
+    expect(listTile2, findsOneWidget);
+    expect(listTile3, findsNothing);
+
+    await tester.tap(iconInListTile1);
+    await tester.pumpAndSettle();
+    expect(controller.value.text, 'foo');
+    expect(textWidget,findsNothing);
+    expect(listTile1, findsOneWidget);
+    expect(listTile2, findsNothing);
+    expect(listTile3, findsNothing);
+
+    await tester.tap(listTile1);
+    await tester.pumpAndSettle();
+    expect(controller.isOpen, false);
+    expect(controller.value.text, 'foo');
+    expect(textWidget,findsNothing);
+    expect(listTile1, findsNothing);
+    expect(listTile2, findsNothing);
+    expect(listTile3, findsNothing);
+  });
+
   testWidgets('SearchAnchor suggestionsBuilder property could be async', (WidgetTester tester) async {
     final SearchController controller = SearchController();
     const String suggestion = 'suggestion text';