Add searchFieldStyle (#54674)

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

@@ -119,6 +119,7 @@ abstract class SearchDelegate<T> {
   /// {@end-tool}
   SearchDelegate({
     this.searchFieldLabel,
+    this.searchFieldStyle,
     this.keyboardType,
     this.textInputAction = TextInputAction.search,
   });
@@ -264,6 +265,11 @@ abstract class SearchDelegate<T> {
   /// If this value is set to null, the value of MaterialLocalizations.of(context).searchFieldLabel will be used instead.
   final String searchFieldLabel;
 
+  /// The style of the [searchFieldLabel].
+  ///
+  /// If this value is set to null, the value of the ambient [Theme]'s [ThemeData.inputDecorationTheme.hintStyle] will be used instead.
+  final TextStyle searchFieldStyle;
+
   /// The type of action button to use for the keyboard.
   ///
   /// Defaults to the default value specified in [TextField].
@@ -315,7 +321,6 @@ enum _SearchBody {
   results,
 }
 
-
 class _SearchPageRoute<T> extends PageRoute<T> {
   _SearchPageRoute({
     @required this.delegate,
@@ -469,6 +474,8 @@ class _SearchPageState<T> extends State<_SearchPage<T>> {
     final ThemeData theme = widget.delegate.appBarTheme(context);
     final String searchFieldLabel = widget.delegate.searchFieldLabel
       ?? MaterialLocalizations.of(context).searchFieldLabel;
+    final TextStyle searchFieldStyle = widget.delegate.searchFieldStyle
+      ?? theme.inputDecorationTheme.hintStyle;
     Widget body;
     switch(widget.delegate._currentBody) {
       case _SearchBody.suggestions:
@@ -521,7 +528,7 @@ class _SearchPageState<T> extends State<_SearchPage<T>> {
             decoration: InputDecoration(
               border: InputBorder.none,
               hintText: searchFieldLabel,
-              hintStyle: theme.inputDecorationTheme.hintStyle,
+              hintStyle: searchFieldStyle,
             ),
           ),
           actions: widget.delegate.buildActions(context),

packages/flutter/test/material/search_test.dart

@@ -509,6 +509,23 @@ void main() {
     expect(find.text(searchHint), findsOneWidget);
   });
 
+  testWidgets('Custom searchFieldStyle value', (WidgetTester tester) async {
+    const TextStyle searchStyle = TextStyle(color: Colors.red, fontSize: 3);
+
+    final _TestSearchDelegate delegate = _TestSearchDelegate(searchFieldStyle: searchStyle);
+
+    await tester.pumpWidget(
+      TestHomePage(
+      delegate: delegate,
+    ));
+    await tester.tap(find.byTooltip('Search'));
+    await tester.pumpAndSettle();
+
+    final TextField textField = tester.widget<TextField>(find.byType(TextField));
+    final TextStyle hintStyle = textField.decoration.hintStyle;
+    expect(hintStyle, delegate.searchFieldStyle);
+  });
+
   testWidgets('keyboard show search button by default', (WidgetTester tester) async {
     final _TestSearchDelegate delegate = _TestSearchDelegate();
 
@@ -697,9 +714,10 @@ class _TestSearchDelegate extends SearchDelegate<String> {
     this.suggestions = 'Suggestions',
     this.result = 'Result',
     this.actions = const <Widget>[],
+    TextStyle searchFieldStyle,
     String searchHint,
     TextInputAction textInputAction = TextInputAction.search,
-  }) : super(searchFieldLabel: searchHint, textInputAction: textInputAction);
+  }) : super(searchFieldLabel: searchHint, textInputAction: textInputAction, searchFieldStyle: searchFieldStyle);
 
   final String suggestions;
   final String result;