Add semantics label property to Text widget (#18518)

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

@@ -211,6 +211,7 @@ class Text extends StatelessWidget {
     this.overflow,
     this.textScaleFactor,
     this.maxLines,
+    this.semanticsLabel,
   }) : assert(data != null),
        textSpan = null,
        super(key: key);
@@ -226,6 +227,7 @@ class Text extends StatelessWidget {
     this.overflow,
     this.textScaleFactor,
     this.maxLines,
+    this.semanticsLabel,
   }): assert(textSpan != null),
       data = null,
       super(key: key);
@@ -305,13 +307,27 @@ class Text extends StatelessWidget {
   /// widget directly to entirely override the [DefaultTextStyle].
   final int maxLines;
 
+  /// An alternative semantics label for this text.
+  ///
+  /// If present, the semantics of this widget will contain this value instead
+  /// of the actual text.
+  ///
+  /// This is useful for replacing abbreviations or shorthands will the full
+  /// text value:
+  ///
+  /// ```dart
+  /// new Text(r'$$', semanticsLabel: 'Double dollars')
+  ///
+  /// ```
+  final String semanticsLabel;
+
   @override
   Widget build(BuildContext context) {
     final DefaultTextStyle defaultTextStyle = DefaultTextStyle.of(context);
     TextStyle effectiveTextStyle = style;
     if (style == null || style.inherit)
       effectiveTextStyle = defaultTextStyle.style.merge(style);
-    return new RichText(
+    Widget result = new RichText(
       textAlign: textAlign ?? defaultTextStyle.textAlign ?? TextAlign.start,
       textDirection: textDirection, // RichText uses Directionality.of to obtain a default if this is null.
       locale: locale, // RichText uses Localizations.localeOf to obtain a default if this is null
@@ -325,6 +341,16 @@ class Text extends StatelessWidget {
         children: textSpan != null ? <TextSpan>[textSpan] : null,
       ),
     );
+    if (semanticsLabel != null) {
+      result = new Semantics(
+        textDirection: textDirection,
+        label: semanticsLabel,
+        child: new ExcludeSemantics(
+          child: result,
+        )
+      );
+    }
+    return result;
   }
 
   @override
@@ -342,5 +368,8 @@ class Text extends StatelessWidget {
     properties.add(new EnumProperty<TextOverflow>('overflow', overflow, defaultValue: null));
     properties.add(new DoubleProperty('textScaleFactor', textScaleFactor, defaultValue: null));
     properties.add(new IntProperty('maxLines', maxLines, defaultValue: null));
+    if (semanticsLabel != null) {
+      properties.add(new StringProperty('semanticsLabel', semanticsLabel));
+    }
   }
 }

packages/flutter/test/widgets/text_test.dart

@@ -5,6 +5,8 @@
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 
+import 'semantics_tester.dart';
+
 void main() {
   testWidgets('Text respects media query', (WidgetTester tester) async {
     await tester.pumpWidget(const MediaQuery(
@@ -109,4 +111,29 @@ void main() {
     expect(text, isNotNull);
     expect(text.text.style.fontSize, 20.0);
   });
+
+  testWidgets('semanticsLabel can override text label', (WidgetTester tester) async {
+    final SemanticsTester semantics = new SemanticsTester(tester);
+    await tester.pumpWidget(
+      const Text('\$\$', semanticsLabel: 'Double dollars', textDirection: TextDirection.ltr)
+    );
+    final TestSemantics expectedSemantics = new TestSemantics.root(
+      children: <TestSemantics>[
+        new TestSemantics.rootChild(
+          label: 'Double dollars',
+          textDirection: TextDirection.ltr,
+        ),
+      ],
+    );
+    expect(semantics, hasSemantics(expectedSemantics, ignoreTransform: true, ignoreId: true, ignoreRect: true));
+
+    await tester.pumpWidget(
+      const Directionality(
+        textDirection: TextDirection.ltr,
+        child: const Text('\$\$', semanticsLabel: 'Double dollars')),
+    );
+
+    expect(semantics, hasSemantics(expectedSemantics, ignoreTransform: true, ignoreId: true, ignoreRect: true));
+    semantics.dispose();
+  });
 }