Add accessibility identifier to SemanticsProperties (#138331)

This PR adds `String? identifier` to `Semantics` and `SemanticsProperties`. The `identifier` will be exposed on Android as `resource-id` and on iOS as `accessibilityIdentifier`.

Mainly targeted at #17988

Initial Engine PR with Android support: https://github.com/flutter/engine/pull/47961
iOS Engine PR: https://github.com/flutter/engine/pull/48858

### Migration

This change breaks the SemanticsUpdateBuilder API which is on the Framework<-->Engine border. For more details see [engine PR](https://github.com/flutter/engine/pull/47961).

Steps:
part 1: [engine] add `SemanticsUpdateBuilderNew` https://github.com/flutter/engine/pull/47961
**part 2: [flutter] use `SemanticsUpdateBuilderNew`**  <-- we are here
part 3: [engine] update `SemanticsUpdateBuilder` to be the same as `SemanticsUpdateBuilderNew`*
part 4: [flutter] use (now updated) `SemanticsUpdateBuilder` again.
part 5: [engine] remove `SemanticsBuilderNew`

packages/flutter/lib/src/rendering/proxy_box.dart

@@ -4356,6 +4356,9 @@ class RenderSemanticsAnnotations extends RenderProxyBox {
     if (_properties.image != null) {
       config.isImage = _properties.image!;
     }
+    if (_properties.identifier != null) {
+      config.identifier = _properties.identifier!;
+    }
     if (_attributedLabel != null) {
       config.attributedLabel = _attributedLabel!;
     }

packages/flutter/lib/src/semantics/binding.dart

@@ -2,14 +2,16 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-import 'dart:ui' as ui show AccessibilityFeatures, SemanticsActionEvent, SemanticsUpdateBuilder;
+// ignore: deprecated_member_use
+import 'dart:ui' as ui show AccessibilityFeatures, SemanticsActionEvent, SemanticsUpdateBuilderNew;
 
 import 'package:flutter/foundation.dart';
 import 'package:flutter/services.dart';
 
 import 'debug.dart';
 
-export 'dart:ui' show AccessibilityFeatures, SemanticsActionEvent, SemanticsUpdateBuilder;
+// ignore: deprecated_member_use
+export 'dart:ui' show AccessibilityFeatures, SemanticsActionEvent, SemanticsUpdateBuilderNew;
 
 /// The glue between the semantics layer and the Flutter engine.
 mixin SemanticsBinding on BindingBase {
@@ -160,8 +162,10 @@ mixin SemanticsBinding on BindingBase {
   ///
   /// This method is used by the [SemanticsOwner] to create builder for all its
   /// semantics updates.
-  ui.SemanticsUpdateBuilder createSemanticsUpdateBuilder() {
+  // ignore: deprecated_member_use
-    return ui.SemanticsUpdateBuilder();
+  ui.SemanticsUpdateBuilderNew createSemanticsUpdateBuilder() {
+    // ignore: deprecated_member_use
+    return ui.SemanticsUpdateBuilderNew();
   }
 
   /// The platform is requesting that animations be disabled or simplified.

packages/flutter/lib/src/semantics/semantics.dart

@@ -3,7 +3,8 @@
 // found in the LICENSE file.
 
 import 'dart:math' as math;
-import 'dart:ui' show Offset, Rect, SemanticsAction, SemanticsFlag, SemanticsUpdate, SemanticsUpdateBuilder, StringAttribute, TextDirection;
+// ignore: deprecated_member_use
+import 'dart:ui' show Offset, Rect, SemanticsAction, SemanticsFlag, SemanticsUpdate, SemanticsUpdateBuilderNew, StringAttribute, TextDirection;
 
 import 'package:collection/collection.dart';
 import 'package:flutter/foundation.dart';
@@ -426,6 +427,7 @@ class SemanticsData with Diagnosticable {
   SemanticsData({
     required this.flags,
     required this.actions,
+    required this.identifier,
     required this.attributedLabel,
     required this.attributedValue,
     required this.attributedIncreasedValue,
@@ -461,6 +463,9 @@ class SemanticsData with Diagnosticable {
   /// A bit field of [SemanticsAction]s that apply to this node.
   final int actions;
 
+  /// {@macro flutter.semantics.SemanticsProperties.identifier}
+  final String identifier;
+
   /// A textual description for the current label of the node.
   ///
   /// The reading direction is given by [textDirection].
@@ -696,6 +701,7 @@ class SemanticsData with Diagnosticable {
           flag.name,
     ];
     properties.add(IterableProperty<String>('flags', flagSummary, ifEmpty: null));
+    properties.add(StringProperty('identifier', identifier, defaultValue: ''));
     properties.add(AttributedStringProperty('label', attributedLabel));
     properties.add(AttributedStringProperty('value', attributedValue));
     properties.add(AttributedStringProperty('increasedValue', attributedIncreasedValue));
@@ -721,6 +727,7 @@ class SemanticsData with Diagnosticable {
     return other is SemanticsData
         && other.flags == flags
         && other.actions == actions
+        && other.identifier == identifier
         && other.attributedLabel == attributedLabel
         && other.attributedValue == attributedValue
         && other.attributedIncreasedValue == attributedIncreasedValue
@@ -749,6 +756,7 @@ class SemanticsData with Diagnosticable {
   int get hashCode => Object.hash(
     flags,
     actions,
+    identifier,
     attributedLabel,
     attributedValue,
     attributedIncreasedValue,
@@ -765,8 +773,8 @@ class SemanticsData with Diagnosticable {
     scrollExtentMax,
     scrollExtentMin,
     platformViewId,
-    maxValueLength,
     Object.hash(
+      maxValueLength,
       currentValueLength,
       transform,
       elevation,
@@ -901,6 +909,7 @@ class SemanticsProperties extends DiagnosticableTree {
     this.liveRegion,
     this.maxValueLength,
     this.currentValueLength,
+    this.identifier,
     this.label,
     this.attributedLabel,
     this.value,
@@ -1165,6 +1174,21 @@ class SemanticsProperties extends DiagnosticableTree {
   /// [maxValueLength] is set.
   final int? currentValueLength;
 
+  /// {@template flutter.semantics.SemanticsProperties.identifier}
+  /// Provides an identifier for the semantics node in native accessibility hierarchy.
+  ///
+  /// This value is not exposed to the users of the app.
+  ///
+  /// It's usually used for UI testing with tools that work by querying the
+  /// native accessibility, like UIAutomator, XCUITest, or Appium.
+  ///
+  /// On Android, this is used for `AccessibilityNodeInfo.setViewIdResourceName`.
+  /// It'll be appear in accessibility hierarchy as `resource-id`.
+  ///
+  /// On iOS, this will set `UIAccessibilityElement.accessibilityIdentifier`.
+  /// {@endtemplate}
+  final String? identifier;
+
   /// Provides a textual description of the widget.
   ///
   /// If a label is provided, there must either by an ambient [Directionality]
@@ -1632,6 +1656,7 @@ class SemanticsProperties extends DiagnosticableTree {
     properties.add(DiagnosticsProperty<bool>('mixed', mixed, defaultValue: null));
     properties.add(DiagnosticsProperty<bool>('expanded', expanded, defaultValue: null));
     properties.add(DiagnosticsProperty<bool>('selected', selected, defaultValue: null));
+    properties.add(StringProperty('identifier', identifier));
     properties.add(StringProperty('label', label, defaultValue: null));
     properties.add(AttributedStringProperty('attributedLabel', attributedLabel, defaultValue: null));
     properties.add(StringProperty('value', value, defaultValue: null));
@@ -2210,6 +2235,10 @@ class SemanticsNode with DiagnosticableTreeMixin {
   /// Whether this node currently has a given [SemanticsFlag].
   bool hasFlag(SemanticsFlag flag) => _flags & flag.index != 0;
 
+  /// {@macro flutter.semantics.SemanticsProperties.identifier}
+  String get identifier => _identifier;
+  String _identifier = _kEmptyConfig.identifier;
+
   /// A textual description of this node.
   ///
   /// The reading direction is given by [textDirection].
@@ -2514,6 +2543,7 @@ class SemanticsNode with DiagnosticableTreeMixin {
 
     final bool mergeAllDescendantsIntoThisNodeValueChanged = _mergeAllDescendantsIntoThisNode != config.isMergingSemanticsOfDescendants;
 
+    _identifier = config.identifier;
     _attributedLabel = config.attributedLabel;
     _attributedValue = config.attributedValue;
     _attributedIncreasedValue = config.attributedIncreasedValue;
@@ -2569,6 +2599,7 @@ class SemanticsNode with DiagnosticableTreeMixin {
     // Can't use _effectiveActionsAsBits here. The filtering of action bits
     // must be done after the merging the its descendants.
     int actions = _actionsAsBits;
+    String identifier = _identifier;
     AttributedString attributedLabel = _attributedLabel;
     AttributedString attributedValue = _attributedValue;
     AttributedString attributedIncreasedValue = _attributedIncreasedValue;
@@ -2625,6 +2656,9 @@ class SemanticsNode with DiagnosticableTreeMixin {
         platformViewId ??= node._platformViewId;
         maxValueLength ??= node._maxValueLength;
         currentValueLength ??= node._currentValueLength;
+        if (identifier == '') {
+          identifier = node._identifier;
+        }
         if (attributedValue.string == '') {
           attributedValue = node._attributedValue;
         }
@@ -2682,6 +2716,7 @@ class SemanticsNode with DiagnosticableTreeMixin {
     return SemanticsData(
       flags: flags,
       actions: _areUserActionsBlocked ? actions & _kUnblockedUserActions : actions,
+      identifier: identifier,
       attributedLabel: attributedLabel,
       attributedValue: attributedValue,
       attributedIncreasedValue: attributedIncreasedValue,
@@ -2715,7 +2750,8 @@ class SemanticsNode with DiagnosticableTreeMixin {
   static final Int32List _kEmptyCustomSemanticsActionsList = Int32List(0);
   static final Float64List _kIdentityTransform = _initIdentityTransform();
 
-  void _addToUpdate(SemanticsUpdateBuilder builder, Set<int> customSemanticsActionIdsUpdate) {
+  // ignore: deprecated_member_use
+  void _addToUpdate(SemanticsUpdateBuilderNew builder, Set<int> customSemanticsActionIdsUpdate) {
     assert(_dirty);
     final SemanticsData data = getSemanticsData();
     final Int32List childrenInTraversalOrder;
@@ -2750,6 +2786,7 @@ class SemanticsNode with DiagnosticableTreeMixin {
       flags: data.flags,
       actions: data.actions,
       rect: data.rect,
+      identifier: data.identifier,
       label: data.attributedLabel.string,
       labelAttributes: data.attributedLabel.attributes,
       value: data.attributedValue.string,
@@ -2904,6 +2941,7 @@ class SemanticsNode with DiagnosticableTreeMixin {
     properties.add(IterableProperty<String>('flags', flags, ifEmpty: null));
     properties.add(FlagProperty('isInvisible', value: isInvisible, ifTrue: 'invisible'));
     properties.add(FlagProperty('isHidden', value: hasFlag(SemanticsFlag.isHidden), ifTrue: 'HIDDEN'));
+    properties.add(StringProperty('identifier', _identifier, defaultValue: ''));
     properties.add(AttributedStringProperty('label', _attributedLabel));
     properties.add(AttributedStringProperty('value', _attributedValue));
     properties.add(AttributedStringProperty('increasedValue', _attributedIncreasedValue));
@@ -3406,7 +3444,8 @@ class SemanticsOwner extends ChangeNotifier {
       }
     }
     visitedNodes.sort((SemanticsNode a, SemanticsNode b) => a.depth - b.depth);
-    final SemanticsUpdateBuilder builder = SemanticsBinding.instance.createSemanticsUpdateBuilder();
+    // ignore: deprecated_member_use
+    final SemanticsUpdateBuilderNew builder = SemanticsBinding.instance.createSemanticsUpdateBuilder();
     for (final SemanticsNode node in visitedNodes) {
       assert(node.parent?._dirty != true); // could be null (no parent) or false (not dirty)
       // The _serialize() method marks the node as not dirty, and
@@ -4201,6 +4240,14 @@ class SemanticsConfiguration {
     }
   }
 
+  /// {@macro flutter.semantics.SemanticsProperties.identifier}
+  String get identifier => _identifier;
+  String _identifier = '';
+  set identifier(String identifier) {
+    _identifier = identifier;
+    _hasBeenAnnotated = true;
+  }
+
   /// A textual description of the owning [RenderObject].
   ///
   /// Setting this attribute will override the [attributedLabel].
@@ -4898,6 +4945,9 @@ class SemanticsConfiguration {
 
     textDirection ??= child.textDirection;
     _sortKey ??= child._sortKey;
+    if (_identifier == '') {
+      _identifier = child._identifier;
+    }
     _attributedLabel = _concatAttributedString(
       thisAttributedString: _attributedLabel,
       thisTextDirection: textDirection,
@@ -4938,6 +4988,7 @@ class SemanticsConfiguration {
       .._isMergingSemanticsOfDescendants = _isMergingSemanticsOfDescendants
       .._textDirection = _textDirection
       .._sortKey = _sortKey
+      .._identifier = _identifier
       .._attributedLabel = _attributedLabel
       .._attributedIncreasedValue = _attributedIncreasedValue
       .._attributedValue = _attributedValue

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

@@ -7123,6 +7123,7 @@ class Semantics extends SingleChildRenderObjectWidget {
     bool? expanded,
     int? maxValueLength,
     int? currentValueLength,
+    String? identifier,
     String? label,
     AttributedString? attributedLabel,
     String? value,
@@ -7191,6 +7192,7 @@ class Semantics extends SingleChildRenderObjectWidget {
       liveRegion: liveRegion,
       maxValueLength: maxValueLength,
       currentValueLength: currentValueLength,
+      identifier: identifier,
       label: label,
       attributedLabel: attributedLabel,
       value: value,

packages/flutter/test/semantics/semantics_test.dart

@@ -682,6 +682,7 @@ void main() {
       '   flags: []\n'
       '   invisible\n'
       '   isHidden: false\n'
+      '   identifier: ""\n'
       '   label: ""\n'
       '   value: ""\n'
       '   increasedValue: ""\n'
@@ -805,6 +806,7 @@ void main() {
       '   flags: []\n'
       '   invisible\n'
       '   isHidden: false\n'
+      '   identifier: ""\n'
       '   label: ""\n'
       '   value: ""\n'
       '   increasedValue: ""\n'

packages/flutter/test/semantics/semantics_update_test.dart

@@ -157,6 +157,7 @@ void main() {
       'Semantics('
         'container: false, '
         'properties: SemanticsProperties, '
+        'identifier: null, '// ignore: missing_whitespace_between_adjacent_strings
         'attributedLabel: "label" [SpellOutStringAttribute(TextRange(start: 0, end: 5))], '
         'attributedValue: "value" [LocaleStringAttribute(TextRange(start: 0, end: 5), en-MX)], '
         'attributedHint: "hint" [SpellOutStringAttribute(TextRange(start: 1, end: 2))], '
@@ -171,13 +172,16 @@ void main() {
 
 class SemanticsUpdateTestBinding extends AutomatedTestWidgetsFlutterBinding {
   @override
-  ui.SemanticsUpdateBuilder createSemanticsUpdateBuilder() {
+  // ignore: deprecated_member_use
+  ui.SemanticsUpdateBuilderNew createSemanticsUpdateBuilder() {
     return SemanticsUpdateBuilderSpy();
   }
 }
 
-class SemanticsUpdateBuilderSpy extends Fake implements ui.SemanticsUpdateBuilder {
+// ignore: deprecated_member_use
-  final SemanticsUpdateBuilder _builder = ui.SemanticsUpdateBuilder();
+class SemanticsUpdateBuilderSpy extends Fake implements ui.SemanticsUpdateBuilderNew {
+  // ignore: deprecated_member_use
+  final SemanticsUpdateBuilderNew _builder = ui.SemanticsUpdateBuilderNew();
 
   static Map<int, SemanticsNodeUpdateObservation> observations = <int, SemanticsNodeUpdateObservation>{};
 
@@ -199,6 +203,7 @@ class SemanticsUpdateBuilderSpy extends Fake implements ui.SemanticsUpdateBuilde
     required double elevation,
     required double thickness,
     required Rect rect,
+    required String identifier,
     required String label,
     List<StringAttribute>? labelAttributes,
     required String value,

packages/flutter_test/lib/src/matchers.dart

@@ -624,6 +624,7 @@ AsyncMatcher matchesReferenceImage(ui.Image image) {
 ///   * [SemanticsController.find] under [WidgetTester.semantics], the tester method which retrieves semantics.
 ///   * [containsSemantics], a similar matcher without default values for flags or actions.
 Matcher matchesSemantics({
+  String? identifier,
   String? label,
   AttributedString? attributedLabel,
   String? hint,
@@ -701,6 +702,7 @@ Matcher matchesSemantics({
   List<Matcher>? children,
 }) {
   return _MatchesSemanticsData(
+    identifier: identifier,
     label: label,
     attributedLabel: attributedLabel,
     hint: hint,
@@ -808,6 +810,7 @@ Matcher matchesSemantics({
 ///   * [SemanticsController.find] under [WidgetTester.semantics], the tester method which retrieves semantics.
 ///   * [matchesSemantics], a similar matcher with default values for flags and actions.
 Matcher containsSemantics({
+  String? identifier,
   String? label,
   AttributedString? attributedLabel,
   String? hint,
@@ -885,6 +888,7 @@ Matcher containsSemantics({
   List<Matcher>? children,
 }) {
   return _MatchesSemanticsData(
+    identifier: identifier,
     label: label,
     attributedLabel: attributedLabel,
     hint: hint,
@@ -2207,6 +2211,7 @@ class _MatchesReferenceImage extends AsyncMatcher {
 
 class _MatchesSemanticsData extends Matcher {
   _MatchesSemanticsData({
+    required this.identifier,
     required this.label,
     required this.attributedLabel,
     required this.hint,
@@ -2344,6 +2349,7 @@ class _MatchesSemanticsData extends Matcher {
                 onLongPressHint: onLongPressHint,
               );
 
+  final String? identifier;
   final String? label;
   final AttributedString? attributedLabel;
   final String? hint;

packages/flutter_test/test/matchers_test.dart

@@ -663,6 +663,7 @@ void main() {
       final SemanticsData data = SemanticsData(
         flags: flags,
         actions: actions,
+        identifier: 'i',
         attributedLabel: AttributedString('a'),
         attributedIncreasedValue: AttributedString('b'),
         attributedValue: AttributedString('c'),
@@ -790,6 +791,7 @@ void main() {
         link: true,
         onTap: () { },
         onLongPress: () { },
+        identifier: 'ident',
         label: 'foo',
         hint: 'bar',
         value: 'baz',
@@ -947,6 +949,7 @@ void main() {
       final SemanticsData data = SemanticsData(
         flags: flags,
         actions: actions,
+        identifier: 'i',
         attributedLabel: AttributedString('a'),
         attributedIncreasedValue: AttributedString('b'),
         attributedValue: AttributedString('c'),
@@ -1039,6 +1042,7 @@ void main() {
       final SemanticsData data = SemanticsData(
         flags: 0,
         actions: 0,
+        identifier: 'i',
         attributedLabel: AttributedString('a'),
         attributedIncreasedValue: AttributedString('b'),
         attributedValue: AttributedString('c'),
@@ -1137,6 +1141,7 @@ void main() {
       final SemanticsData emptyData = SemanticsData(
         flags: 0,
         actions: 0,
+        identifier: 'i',
         attributedLabel: AttributedString('a'),
         attributedIncreasedValue: AttributedString('b'),
         attributedValue: AttributedString('c'),
@@ -1163,6 +1168,7 @@ void main() {
       final SemanticsData fullData = SemanticsData(
         flags: allFlags,
         actions: allActions,
+        identifier: 'i',
         attributedLabel: AttributedString('a'),
         attributedIncreasedValue: AttributedString('b'),
         attributedValue: AttributedString('c'),
@@ -1252,6 +1258,7 @@ void main() {
       final SemanticsData data = SemanticsData(
         flags: 0,
         actions: SemanticsAction.customAction.index,
+        identifier: 'i',
         attributedLabel: AttributedString('a'),
         attributedIncreasedValue: AttributedString('b'),
         attributedValue: AttributedString('c'),

packages/flutter_test/test/view_test.dart

@@ -313,7 +313,8 @@ void main() {
     });
 
     testWidgets('updateSemantics is passed through to backing FlutterView', (WidgetTester tester) async {
-      final SemanticsUpdate expectedUpdate = SemanticsUpdateBuilder().build();
+      // ignore: deprecated_member_use
+      final SemanticsUpdate expectedUpdate = SemanticsUpdateBuilderNew().build();
       final _FakeFlutterView backingView = _FakeFlutterView();
       final TestFlutterView view = TestFlutterView(
         view: backingView,