Add link support in web accessibility (flutter/engine#46117)

fixes https://github.com/flutter/flutter/issues/134795

## Pre-launch Checklist

- [ ] I read the [Contributor Guide] and followed the process outlined
there for submitting PRs.
- [ ] I read the [Tree Hygiene] wiki page, which explains my
responsibilities.
- [ ] I read and followed the [Flutter Style Guide] and the [C++,
Objective-C, Java style guides].
- [ ] I listed at least one issue that this PR fixes in the description
above.
- [ ] I added new tests to check the change I am making or feature I am
adding, or the PR is [test-exempt]. See [testing the engine] for
instructions on writing and running engine tests.
- [ ] I updated/added relevant documentation (doc comments with `///`).
- [ ] I signed the [CLA].
- [ ] All existing and new tests are passing.

If you need help, consider asking for advice on the #hackers-new channel
on [Discord].

<!-- Links -->
[Contributor Guide]:
https://github.com/flutter/flutter/wiki/Tree-hygiene#overview
[Tree Hygiene]: https://github.com/flutter/flutter/wiki/Tree-hygiene
[test-exempt]:
https://github.com/flutter/flutter/wiki/Tree-hygiene#tests
[Flutter Style Guide]:
https://github.com/flutter/flutter/wiki/Style-guide-for-Flutter-repo
[C++, Objective-C, Java style guides]:
https://github.com/flutter/engine/blob/main/CONTRIBUTING.md#style
[testing the engine]:
https://github.com/flutter/flutter/wiki/Testing-the-engine
[CLA]: https://cla.developers.google.com/
[flutter/tests]: https://github.com/flutter/tests
[breaking change policy]:
https://github.com/flutter/flutter/wiki/Tree-hygiene#handling-breaking-changes
[Discord]: https://github.com/flutter/flutter/wiki/Chat

engine/src/flutter/ci/licenses_golden/licenses_flutter

@@ -2720,6 +2720,7 @@ ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/semantics/focusable.dart + ..
 ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/semantics/image.dart + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/semantics/incrementable.dart + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/semantics/label_and_value.dart + ../../../flutter/LICENSE
+ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/semantics/link.dart + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/semantics/live_region.dart + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/semantics/platform_view.dart + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/semantics/scrollable.dart + ../../../flutter/LICENSE
@@ -5496,6 +5497,7 @@ FILE: ../../../flutter/lib/web_ui/lib/src/engine/semantics/focusable.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/semantics/image.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/semantics/incrementable.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/semantics/label_and_value.dart
+FILE: ../../../flutter/lib/web_ui/lib/src/engine/semantics/link.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/semantics/live_region.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/semantics/platform_view.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/semantics/scrollable.dart

engine/src/flutter/lib/web_ui/lib/src/engine.dart

@@ -143,6 +143,7 @@ export 'engine/semantics/focusable.dart';
 export 'engine/semantics/image.dart';
 export 'engine/semantics/incrementable.dart';
 export 'engine/semantics/label_and_value.dart';
+export 'engine/semantics/link.dart';
 export 'engine/semantics/live_region.dart';
 export 'engine/semantics/platform_view.dart';
 export 'engine/semantics/scrollable.dart';

engine/src/flutter/lib/web_ui/lib/src/engine/semantics.dart

@@ -8,6 +8,7 @@ export 'semantics/focusable.dart';
 export 'semantics/image.dart';
 export 'semantics/incrementable.dart';
 export 'semantics/label_and_value.dart';
+export 'semantics/link.dart';
 export 'semantics/live_region.dart';
 export 'semantics/platform_view.dart';
 export 'semantics/scrollable.dart';

engine/src/flutter/lib/web_ui/lib/src/engine/semantics/checkable.dart

@@ -13,7 +13,6 @@
 
 import 'package:ui/ui.dart' as ui;
 
-import '../dom.dart';
 import 'semantics.dart';
 
 /// The specific type of checkable control.
@@ -63,18 +62,18 @@ class Checkable extends PrimaryRoleManager {
     if (semanticsObject.isFlagsDirty) {
       switch (_kind) {
         case _CheckableKind.checkbox:
-          semanticsObject.setAriaRole('checkbox');
+          setAriaRole('checkbox');
         case _CheckableKind.radio:
-          semanticsObject.setAriaRole('radio');
+          setAriaRole('radio');
         case _CheckableKind.toggle:
-          semanticsObject.setAriaRole('switch');
+          setAriaRole('switch');
       }
 
       /// Adding disabled and aria-disabled attribute to notify the assistive
       /// technologies of disabled elements.
       _updateDisabledAttribute();
 
-      semanticsObject.element.setAttribute(
+      setAttribute(
         'aria-checked',
         (semanticsObject.hasFlag(ui.SemanticsFlag.isChecked) ||
                 semanticsObject.hasFlag(ui.SemanticsFlag.isToggled))
@@ -92,17 +91,15 @@ class Checkable extends PrimaryRoleManager {
 
   void _updateDisabledAttribute() {
     if (semanticsObject.enabledState() == EnabledState.disabled) {
-      final DomElement element = semanticsObject.element;
-      element
-        ..setAttribute('aria-disabled', 'true')
-        ..setAttribute('disabled', 'true');
+      setAttribute('aria-disabled', 'true');
+      setAttribute('disabled', 'true');
     } else {
       _removeDisabledAttribute();
     }
   }
 
   void _removeDisabledAttribute() {
-    final DomElement element = semanticsObject.element;
-    element..removeAttribute('aria-disabled')..removeAttribute('disabled');
+    removeAttribute('aria-disabled');
+    removeAttribute('disabled');
   }
 }

engine/src/flutter/lib/web_ui/lib/src/engine/semantics/dialog.dart

@@ -38,8 +38,8 @@ class Dialog extends PrimaryRoleManager {
         }
         return true;
       }());
-      semanticsObject.element.setAttribute('aria-label', label ?? '');
-      semanticsObject.setAriaRole('dialog');
+      setAttribute('aria-label', label ?? '');
+      setAriaRole('dialog');
     }
   }
 
@@ -51,8 +51,8 @@ class Dialog extends PrimaryRoleManager {
       return;
     }
 
-    semanticsObject.setAriaRole('dialog');
-    semanticsObject.element.setAttribute(
+    setAriaRole('dialog');
+    setAttribute(
       'aria-describedby',
       routeName.semanticsObject.element.id,
     );
@@ -61,7 +61,10 @@ class Dialog extends PrimaryRoleManager {
 
 /// Supplies a description for the nearest ancestor [Dialog].
 class RouteName extends RoleManager {
-  RouteName(SemanticsObject semanticsObject) : super(Role.routeName, semanticsObject);
+  RouteName(
+    SemanticsObject semanticsObject,
+    PrimaryRoleManager owner,
+  ) : super(Role.routeName, semanticsObject, owner);
 
   Dialog? _dialog;
 

engine/src/flutter/lib/web_ui/lib/src/engine/semantics/focusable.dart

@@ -28,9 +28,9 @@ import 'semantics.dart';
 ///
 ///   * https://developer.mozilla.org/en-US/docs/Web/Accessibility/Keyboard-navigable_JavaScript_widgets
 class Focusable extends RoleManager {
-  Focusable(SemanticsObject semanticsObject)
+  Focusable(SemanticsObject semanticsObject, PrimaryRoleManager owner)
       : _focusManager = AccessibilityFocusManager(semanticsObject.owner),
-        super(Role.focusable, semanticsObject);
+        super(Role.focusable, semanticsObject, owner);
 
   final AccessibilityFocusManager _focusManager;
 
@@ -38,7 +38,7 @@ class Focusable extends RoleManager {
   void update() {
     if (semanticsObject.isFocusable) {
       if (!_focusManager.isManaging) {
-        _focusManager.manage(semanticsObject.id, semanticsObject.element);
+        _focusManager.manage(semanticsObject.id, owner.element);
       }
       _focusManager.changeFocus(semanticsObject.hasFocus && (!semanticsObject.hasEnabledState || semanticsObject.isEnabled));
     } else {

engine/src/flutter/lib/web_ui/lib/src/engine/semantics/image.dart

@@ -49,14 +49,14 @@ class ImageRoleManager extends PrimaryRoleManager {
             ..height = '${semanticsObject.rect!.height}px';
         }
         _auxiliaryImageElement!.style.fontSize = '6px';
-        semanticsObject.element.append(_auxiliaryImageElement!);
+        append(_auxiliaryImageElement!);
       }
 
       _auxiliaryImageElement!.setAttribute('role', 'img');
       _setLabel(_auxiliaryImageElement);
     } else if (semanticsObject.isVisualOnly) {
-      semanticsObject.setAriaRole('img');
-      _setLabel(semanticsObject.element);
+      setAriaRole('img');
+      _setLabel(element);
       _cleanUpAuxiliaryElement();
     } else {
       _cleanUpAuxiliaryElement();
@@ -78,7 +78,7 @@ class ImageRoleManager extends PrimaryRoleManager {
   }
 
   void _cleanupElement() {
-    semanticsObject.element.removeAttribute('aria-label');
+    removeAttribute('aria-label');
   }
 
   @override

engine/src/flutter/lib/web_ui/lib/src/engine/semantics/incrementable.dart

@@ -29,7 +29,7 @@ class Incrementable extends PrimaryRoleManager {
     addRouteName();
     addLabelAndValue();
 
-    semanticsObject.element.append(_element);
+    append(_element);
     _element.type = 'range';
     _element.setAttribute('role', 'slider');
 

engine/src/flutter/lib/web_ui/lib/src/engine/semantics/label_and_value.dart

@@ -2,7 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-import '../dom.dart';
 import 'semantics.dart';
 
 /// Renders [SemanticsObject.label] and/or [SemanticsObject.value] to the semantics DOM.
@@ -26,8 +25,8 @@ import 'semantics.dart';
 /// This role manager does not manage images and text fields. See
 /// [ImageRoleManager] and [TextField].
 class LabelAndValue extends RoleManager {
-  LabelAndValue(SemanticsObject semanticsObject)
-      : super(Role.labelAndValue, semanticsObject);
+  LabelAndValue(SemanticsObject semanticsObject, PrimaryRoleManager owner)
+      : super(Role.labelAndValue, semanticsObject, owner);
 
   @override
   void update() {
@@ -62,12 +61,11 @@ class LabelAndValue extends RoleManager {
       combinedValue.write(semanticsObject.value);
     }
 
-    semanticsObject.element
-        .setAttribute('aria-label', combinedValue.toString());
+    owner.setAttribute('aria-label', combinedValue.toString());
   }
 
   void _cleanUpDom() {
-    semanticsObject.element.removeAttribute('aria-label');
+    owner.removeAttribute('aria-label');
   }
 
   @override

engine/src/flutter/lib/web_ui/lib/src/engine/semantics/link.dart

@@ -0,0 +1,21 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import '../dom.dart';
+import '../semantics.dart';
+
+/// Provides accessibility for links.
+class Link extends PrimaryRoleManager {
+  Link(SemanticsObject semanticsObject) : super.withBasics(PrimaryRole.link, semanticsObject);
+
+  @override
+  DomElement createElement() {
+    final DomElement element = domDocument.createElement('a');
+    // TODO(chunhtai): Fill in the real link once the framework sends entire uri.
+    // https://github.com/flutter/flutter/issues/102535.
+    element.setAttribute('href', '#');
+    element.style.display = 'block';
+    return element;
+  }
+}

engine/src/flutter/lib/web_ui/lib/src/engine/semantics/live_region.dart

@@ -15,8 +15,8 @@ import 'semantics.dart';
 /// label of the element. See [LabelAndValue]. If there is no label provided
 /// no content will be read.
 class LiveRegion extends RoleManager {
-  LiveRegion(SemanticsObject semanticsObject)
-      : super(Role.liveRegion, semanticsObject);
+  LiveRegion(SemanticsObject semanticsObject, PrimaryRoleManager owner)
+      : super(Role.liveRegion, semanticsObject, owner);
 
   String? _lastAnnouncement;
 

engine/src/flutter/lib/web_ui/lib/src/engine/semantics/platform_view.dart

@@ -2,7 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-import '../dom.dart';
 import '../platform_views/slots.dart';
 import 'semantics.dart';
 
@@ -30,13 +29,13 @@ class PlatformViewRoleManager extends PrimaryRoleManager {
 
     if (semanticsObject.isPlatformView) {
       if (semanticsObject.isPlatformViewIdDirty) {
-        semanticsObject.element.setAttribute(
+        setAttribute(
           'aria-owns',
           getPlatformViewDomId(semanticsObject.platformViewId),
         );
       }
     } else {
-      semanticsObject.element.removeAttribute('aria-owns');
+      removeAttribute('aria-owns');
     }
   }
 }

engine/src/flutter/lib/web_ui/lib/src/engine/semantics/scrollable.dart

@@ -30,7 +30,7 @@ class Scrollable extends PrimaryRoleManager {
       ..transformOrigin = '0 0 0'
       // Ignore pointer events since this is a dummy element.
       ..pointerEvents = 'none';
-    semanticsObject.element.append(_scrollOverflowElement);
+    append(_scrollOverflowElement);
   }
 
   /// Disables browser-driven scrolling in the presence of pointer events.
@@ -112,7 +112,7 @@ class Scrollable extends PrimaryRoleManager {
       // This is effective only in Chrome. Safari does not implement this
       // CSS property. In Safari the `PointerBinding` uses `preventDefault`
       // to prevent browser scrolling.
-      semanticsObject.element.style.touchAction = 'none';
+      element.style.touchAction = 'none';
       _gestureModeDidChange();
 
       // Memoize the tear-off because Dart does not guarantee that two
@@ -126,17 +126,17 @@ class Scrollable extends PrimaryRoleManager {
       _scrollListener = createDomEventListener((_) {
         _recomputeScrollPosition();
       });
-      semanticsObject.element.addEventListener('scroll', _scrollListener);
+      addEventListener('scroll', _scrollListener);
     }
   }
 
   /// The value of "scrollTop" or "scrollLeft", depending on the scroll axis.
   int get _domScrollPosition {
     if (semanticsObject.isVerticalScrollContainer) {
-      return semanticsObject.element.scrollTop.toInt();
+      return element.scrollTop.toInt();
     } else {
       assert(semanticsObject.isHorizontalScrollContainer);
-      return semanticsObject.element.scrollLeft.toInt();
+      return element.scrollLeft.toInt();
     }
   }
 
@@ -153,7 +153,6 @@ class Scrollable extends PrimaryRoleManager {
   void _neutralizeDomScrollPosition() {
     // This value is arbitrary.
     const int canonicalNeutralScrollPosition = 10;
-    final DomElement element = semanticsObject.element;
     final ui.Rect? rect = semanticsObject.rect;
     if (rect == null) {
       printWarning('Warning! the rect attribute of semanticsObject is null');
@@ -197,7 +196,6 @@ class Scrollable extends PrimaryRoleManager {
   }
 
   void _gestureModeDidChange() {
-    final DomElement element = semanticsObject.element;
     switch (semanticsObject.owner.gestureMode) {
       case GestureMode.browserGestures:
         // overflow:scroll will cause the browser report "scroll" events when
@@ -227,13 +225,13 @@ class Scrollable extends PrimaryRoleManager {
   @override
   void dispose() {
     super.dispose();
-    final DomCSSStyleDeclaration style = semanticsObject.element.style;
+    final DomCSSStyleDeclaration style = element.style;
     assert(_gestureModeListener != null);
     style.removeProperty('overflowY');
     style.removeProperty('overflowX');
     style.removeProperty('touch-action');
     if (_scrollListener != null) {
-      semanticsObject.element.removeEventListener('scroll', _scrollListener);
+      removeEventListener('scroll', _scrollListener);
     }
     semanticsObject.owner.removeGestureModeListener(_gestureModeListener);
     _gestureModeListener = null;

engine/src/flutter/lib/web_ui/lib/src/engine/semantics/semantics.dart

@@ -24,6 +24,7 @@ import 'focusable.dart';
 import 'image.dart';
 import 'incrementable.dart';
 import 'label_and_value.dart';
+import 'link.dart';
 import 'live_region.dart';
 import 'platform_view.dart';
 import 'scrollable.dart';
@@ -382,6 +383,9 @@ enum PrimaryRole {
   ///
   /// Provides a label or a value.
   generic,
+
+  /// Contains a link.
+  link,
 }
 
 /// Identifies one of the secondary [RoleManager]s of a [PrimaryRoleManager].
@@ -437,6 +441,8 @@ abstract class PrimaryRoleManager {
   /// management intereferes with the widget's functionality.
   PrimaryRoleManager.blank(this.role, this.semanticsObject);
 
+  late final DomElement element = _initElement(createElement(), semanticsObject);
+
   /// The primary role identifier.
   final PrimaryRole role;
 
@@ -453,29 +459,82 @@ abstract class PrimaryRoleManager {
   @visibleForTesting
   List<Role> get debugSecondaryRoles => _secondaryRoleManagers?.map((RoleManager manager) => manager.role).toList() ?? const <Role>[];
 
+  @protected
+  DomElement createElement() => domDocument.createElement('flt-semantics');
+
+  static DomElement _initElement(DomElement element, SemanticsObject semanticsObject) {
+    // DOM nodes created for semantics objects are positioned absolutely using
+    // transforms.
+    element.style.position = 'absolute';
+    element.setAttribute('id', 'flt-semantic-node-${semanticsObject.id}');
+
+    // The root node has some properties that other nodes do not.
+    if (semanticsObject.id == 0 && !configuration.debugShowSemanticsNodes) {
+      // Make all semantics transparent. Use `filter` instead of `opacity`
+      // attribute because `filter` is stronger. `opacity` does not apply to
+      // some elements, particularly on iOS, such as the slider thumb and track.
+      //
+      // Use transparency instead of "visibility:hidden" or "display:none"
+      // so that a screen reader does not ignore these elements.
+      element.style.filter = 'opacity(0%)';
+
+      // Make text explicitly transparent to signal to the browser that no
+      // rasterization needs to be done.
+      element.style.color = 'rgba(0,0,0,0)';
+    }
+
+    // Make semantic elements visible for debugging by outlining them using a
+    // green border. Do not use `border` attribute because it affects layout
+    // (`outline` does not).
+    if (configuration.debugShowSemanticsNodes) {
+      element.style.outline = '1px solid green';
+    }
+    return element;
+  }
+
+  /// Sets the `role` ARIA attribute.
+  void setAriaRole(String ariaRoleName) {
+    setAttribute('role', ariaRoleName);
+  }
+
+  /// Sets the `role` ARIA attribute.
+  void setAttribute(String name, Object value) {
+    element.setAttribute(name, value);
+  }
+
+  void append(DomElement child) {
+    element.append(child);
+  }
+
+  void removeAttribute(String name) => element.removeAttribute(name);
+
+  void addEventListener(String type, DomEventListener? listener, [bool? useCapture]) => element.addEventListener(type, listener, useCapture);
+
+  void removeEventListener(String type, DomEventListener? listener, [bool? useCapture]) => element.removeEventListener(type, listener, useCapture);
+
   /// Adds generic focus management features.
   void addFocusManagement() {
-    addSecondaryRole(Focusable(semanticsObject));
+    addSecondaryRole(Focusable(semanticsObject, this));
   }
 
   /// Adds generic live region features.
   void addLiveRegion() {
-    addSecondaryRole(LiveRegion(semanticsObject));
+    addSecondaryRole(LiveRegion(semanticsObject, this));
   }
 
   /// Adds generic route name features.
   void addRouteName() {
-    addSecondaryRole(RouteName(semanticsObject));
+    addSecondaryRole(RouteName(semanticsObject, this));
   }
 
   /// Adds generic label features.
   void addLabelAndValue() {
-    addSecondaryRole(LabelAndValue(semanticsObject));
+    addSecondaryRole(LabelAndValue(semanticsObject, this));
   }
 
   /// Adds generic functionality for handling taps and clicks.
   void addTappable() {
-    addSecondaryRole(Tappable(semanticsObject));
+    addSecondaryRole(Tappable(semanticsObject, this));
   }
 
   /// Adds a secondary role to this primary role manager.
@@ -525,7 +584,7 @@ abstract class PrimaryRoleManager {
   /// gesture mode changes.
   @mustCallSuper
   void dispose() {
-    semanticsObject.element.removeAttribute('role');
+    removeAttribute('role');
     _isDisposed = true;
   }
 }
@@ -566,11 +625,11 @@ final class GenericRole extends PrimaryRoleManager {
     //   Flutter renders into canvas, so the focus ring looks wrong.
     // - Read out the same label multiple times.
     if (semanticsObject.hasChildren) {
-      semanticsObject.setAriaRole('group');
+      setAriaRole('group');
     } else if (semanticsObject.hasFlag(ui.SemanticsFlag.isHeader)) {
-      semanticsObject.setAriaRole('heading');
+      setAriaRole('heading');
     } else {
-      semanticsObject.setAriaRole('text');
+      setAriaRole('text');
     }
   }
 }
@@ -588,7 +647,7 @@ abstract class RoleManager {
   /// Initializes a secondary role for [semanticsObject].
   ///
   /// A single role object manages exactly one [SemanticsObject].
-  RoleManager(this.role, this.semanticsObject);
+  RoleManager(this.role, this.semanticsObject, this.owner);
 
   /// Role identifier.
   final Role role;
@@ -596,6 +655,8 @@ abstract class RoleManager {
   /// The semantics object managed by this role.
   final SemanticsObject semanticsObject;
 
+  final PrimaryRoleManager owner;
+
   /// Called immediately after the [semanticsObject] updates some of its fields.
   ///
   /// A concrete implementation of this method would typically use some of the
@@ -627,34 +688,7 @@ abstract class RoleManager {
 /// information to the browser.
 class SemanticsObject {
   /// Creates a semantics tree node with the given [id] and [owner].
-  SemanticsObject(this.id, this.owner) {
-    // DOM nodes created for semantics objects are positioned absolutely using
-    // transforms.
-    element.style.position = 'absolute';
-    element.setAttribute('id', 'flt-semantic-node-$id');
-
-    // The root node has some properties that other nodes do not.
-    if (id == 0 && !configuration.debugShowSemanticsNodes) {
-      // Make all semantics transparent. Use `filter` instead of `opacity`
-      // attribute because `filter` is stronger. `opacity` does not apply to
-      // some elements, particularly on iOS, such as the slider thumb and track.
-      //
-      // Use transparency instead of "visibility:hidden" or "display:none"
-      // so that a screen reader does not ignore these elements.
-      element.style.filter = 'opacity(0%)';
-
-      // Make text explicitly transparent to signal to the browser that no
-      // rasterization needs to be done.
-      element.style.color = 'rgba(0,0,0,0)';
-    }
-
-    // Make semantic elements visible for debugging by outlining them using a
-    // green border. Do not use `border` attribute because it affects layout
-    // (`outline` does not).
-    if (configuration.debugShowSemanticsNodes) {
-      element.style.outline = '1px solid green';
-    }
-  }
+  SemanticsObject(this.id, this.owner);
 
   /// See [ui.SemanticsUpdateBuilder.updateNode].
   int get flags => _flags;
@@ -981,9 +1015,6 @@ class SemanticsObject {
   /// Controls the semantics tree that this node participates in.
   final EngineSemanticsOwner owner;
 
-  /// The DOM element used to convey semantics information to the browser.
-  final DomElement element = domDocument.createElement('flt-semantics');
-
   /// Bitfield showing which fields have been updated but have not yet been
   /// applied to the DOM.
   ///
@@ -996,6 +1027,9 @@ class SemanticsObject {
   /// Whether the field corresponding to the [fieldIndex] has been updated.
   bool _isDirty(int fieldIndex) => (_dirtyFields & fieldIndex) != 0;
 
+  /// The dom element of this semantics object.
+  DomElement get element => primaryRole!.element;
+
   /// Returns the HTML element that contains the HTML elements of direct
   /// children of this object.
   ///
@@ -1079,6 +1113,9 @@ class SemanticsObject {
   /// Whether this object represents an editable text field.
   bool get isTextField => hasFlag(ui.SemanticsFlag.isTextField);
 
+    /// Whether this object represents an editable text field.
+  bool get isLink => hasFlag(ui.SemanticsFlag.isLink);
+
   /// Whether this object needs screen readers attention right away.
   bool get isLiveRegion =>
       hasFlag(ui.SemanticsFlag.isLiveRegion) &&
@@ -1456,11 +1493,6 @@ class SemanticsObject {
     _currentChildrenInRenderOrder = childrenInRenderOrder;
   }
 
-  /// Sets the `role` ARIA attribute.
-  void setAriaRole(String ariaRoleName) {
-    element.setAttribute('role', ariaRoleName);
-  }
-
   /// The primary role of this node.
   ///
   /// The primary role is assigned by [updateSelf] based on the combination of
@@ -1485,6 +1517,8 @@ class SemanticsObject {
       return PrimaryRole.scrollable;
     } else if (scopesRoute) {
       return PrimaryRole.dialog;
+    } else if (isLink) {
+      return PrimaryRole.link;
     } else {
       return PrimaryRole.generic;
     }
@@ -1500,6 +1534,7 @@ class SemanticsObject {
       PrimaryRole.dialog => Dialog(this),
       PrimaryRole.image => ImageRoleManager(this),
       PrimaryRole.platformView => PlatformViewRoleManager(this),
+      PrimaryRole.link => Link(this),
       PrimaryRole.generic => GenericRole(this),
     };
   }
@@ -1509,6 +1544,7 @@ class SemanticsObject {
   void _updateRoles() {
     PrimaryRoleManager? currentPrimaryRole = primaryRole;
     final PrimaryRole roleId = _getPrimaryRoleIdentifier();
+    final DomElement? previousElement = primaryRole?.element;
 
     if (currentPrimaryRole != null) {
       if (currentPrimaryRole.role == roleId) {
@@ -1535,6 +1571,19 @@ class SemanticsObject {
       primaryRole = currentPrimaryRole;
       currentPrimaryRole.update();
     }
+
+    // Reparent element.
+    if (previousElement != element) {
+      final DomElement? container = _childContainerElement;
+      if (container != null) {
+        element.append(container);
+      }
+      final DomElement? parent = previousElement?.parent;
+      if (parent != null) {
+        parent.insertBefore(element, previousElement);
+        previousElement!.remove();
+      }
+    }
   }
 
   /// Whether the object represents an UI element with "increase" or "decrease"

engine/src/flutter/lib/web_ui/lib/src/engine/semantics/tappable.dart

@@ -11,7 +11,7 @@ import 'semantics.dart';
 /// Sets the "button" ARIA role.
 class Button extends PrimaryRoleManager {
   Button(SemanticsObject semanticsObject) : super.withBasics(PrimaryRole.button, semanticsObject) {
-    semanticsObject.setAriaRole('button');
+    setAriaRole('button');
   }
 
   @override
@@ -19,9 +19,9 @@ class Button extends PrimaryRoleManager {
     super.update();
 
     if (semanticsObject.enabledState() == EnabledState.disabled) {
-      semanticsObject.element.setAttribute('aria-disabled', 'true');
+      setAttribute('aria-disabled', 'true');
     } else {
-      semanticsObject.element.removeAttribute('aria-disabled');
+      removeAttribute('aria-disabled');
     }
   }
 }
@@ -33,26 +33,28 @@ class Button extends PrimaryRoleManager {
 /// the browser may not send us pointer events. In that mode we forward HTML
 /// click as [ui.SemanticsAction.tap].
 class Tappable extends RoleManager {
-  Tappable(SemanticsObject semanticsObject)
-      : super(Role.tappable, semanticsObject);
+  Tappable(SemanticsObject semanticsObject, PrimaryRoleManager owner)
+      : super(Role.tappable, semanticsObject, owner);
 
   DomEventListener? _clickListener;
 
   @override
   void update() {
-    if (!semanticsObject.isTappable || semanticsObject.enabledState() == EnabledState.disabled) {
-      _stopListening();
-    } else {
-      if (_clickListener == null) {
-        _clickListener = createDomEventListener((DomEvent event) {
-          if (semanticsObject.owner.gestureMode != GestureMode.browserGestures) {
-            return;
-          }
-          EnginePlatformDispatcher.instance.invokeOnSemanticsAction(
-              semanticsObject.id, ui.SemanticsAction.tap, null);
-        });
-        semanticsObject.element.addEventListener('click', _clickListener);
-      }
+    if (_clickListener == null) {
+      _clickListener = createDomEventListener((DomEvent event) {
+        // Stop dom from reacting since it will be handled entirely on the
+        // flutter side.
+        event.preventDefault();
+        if (!semanticsObject.isTappable || semanticsObject.enabledState() == EnabledState.disabled) {
+          return;
+        }
+        if (semanticsObject.owner.gestureMode != GestureMode.browserGestures) {
+          return;
+        }
+        EnginePlatformDispatcher.instance.invokeOnSemanticsAction(
+            semanticsObject.id, ui.SemanticsAction.tap, null);
+      });
+      owner.addEventListener('click', _clickListener);
     }
   }
 
@@ -61,7 +63,7 @@ class Tappable extends RoleManager {
       return;
     }
 
-    semanticsObject.element.removeEventListener('click', _clickListener);
+    owner.removeEventListener('click', _clickListener);
     _clickListener = null;
   }
 

engine/src/flutter/lib/web_ui/lib/src/engine/semantics/text_field.dart

@@ -275,7 +275,7 @@ class TextField extends PrimaryRoleManager {
       ..left = '0'
       ..width = '${semanticsObject.rect!.width}px'
       ..height = '${semanticsObject.rect!.height}px';
-    semanticsObject.element.append(activeEditableElement);
+    append(activeEditableElement);
   }
 
   void _setupDomElement() {
@@ -336,22 +336,21 @@ class TextField extends PrimaryRoleManager {
       return;
     }
 
-    semanticsObject.element
-      ..setAttribute('role', 'textbox')
-      ..setAttribute('contenteditable', 'false')
-      ..setAttribute('tabindex', '0');
+    setAttribute('role', 'textbox');
+    setAttribute('contenteditable', 'false');
+    setAttribute('tabindex', '0');
 
     num? lastPointerDownOffsetX;
     num? lastPointerDownOffsetY;
 
-    semanticsObject.element.addEventListener('pointerdown',
+    addEventListener('pointerdown',
         createDomEventListener((DomEvent event) {
           final DomPointerEvent pointerEvent = event as DomPointerEvent;
           lastPointerDownOffsetX = pointerEvent.clientX;
           lastPointerDownOffsetY = pointerEvent.clientY;
         }), true);
 
-    semanticsObject.element.addEventListener('pointerup',
+    addEventListener('pointerup',
         createDomEventListener((DomEvent event) {
       final DomPointerEvent pointerEvent = event as DomPointerEvent;
 
@@ -399,17 +398,17 @@ class TextField extends PrimaryRoleManager {
     // represent the same text field. It will confuse VoiceOver, so `role` needs to
     // be assigned and removed, based on whether or not editableElement exists.
     activeEditableElement.focus();
-    semanticsObject.element.removeAttribute('role');
+    removeAttribute('role');
 
     activeEditableElement.addEventListener('blur',
         createDomEventListener((DomEvent event) {
-      semanticsObject.element.setAttribute('role', 'textbox');
+      setAttribute('role', 'textbox');
       activeEditableElement.remove();
       SemanticsTextEditingStrategy._instance?.deactivate(this);
 
       // Focus on semantics element before removing the editable element, so that
       // the user can continue navigating the page with the assistive technology.
-      semanticsObject.element.focus();
+      element.focus();
       editableElement = null;
     }));
   }
@@ -447,7 +446,7 @@ class TextField extends PrimaryRoleManager {
       }
     }
 
-    final DomElement element = editableElement ?? semanticsObject.element;
+    final DomElement element = editableElement ?? this.element;
     if (semanticsObject.hasLabel) {
       element.setAttribute(
         'aria-label',

engine/src/flutter/lib/web_ui/test/engine/semantics/semantics_test.dart

@@ -92,6 +92,9 @@ void runSemanticsTests() {
   group('focusable', () {
     _testFocusable();
   });
+  group('link', () {
+    _testLink();
+  });
 }
 
 void _testRoleManagerLifecycle() {
@@ -337,7 +340,11 @@ void _testEngineSemanticsOwner() {
     expect(placeholder.isConnected, isFalse);
   });
 
-  void renderSemantics({String? label, String? tooltip}) {
+  void renderSemantics({String? label, String? tooltip, Set<ui.SemanticsFlag> flags = const <ui.SemanticsFlag>{}}) {
+    int flagValues = 0;
+    for (final ui.SemanticsFlag flag in flags) {
+      flagValues = flagValues | flag.index;
+    }
     final ui.SemanticsUpdateBuilder builder = ui.SemanticsUpdateBuilder();
     updateNode(
       builder,
@@ -351,6 +358,7 @@ void _testEngineSemanticsOwner() {
       id: 1,
       label: label ?? '',
       tooltip: tooltip ?? '',
+      flags: flagValues,
       transform: Matrix4.identity().toFloat64(),
       rect: const ui.Rect.fromLTRB(0, 0, 20, 20),
     );
@@ -404,6 +412,45 @@ void _testEngineSemanticsOwner() {
     semantics().semanticsEnabled = false;
   });
 
+  test('can switch role', () async {
+    semantics().semanticsEnabled = true;
+
+    // Create
+    renderSemantics(label: 'Hello');
+
+    Map<int, SemanticsObject> tree = semantics().debugSemanticsTree!;
+    expect(tree.length, 2);
+    expect(tree[1]!.element.tagName.toLowerCase(), 'flt-semantics');
+    expect(tree[1]!.id, 1);
+    expect(tree[1]!.label, 'Hello');
+    final DomElement existingParent = tree[1]!.element.parent!;
+
+    expectSemanticsTree('''
+<sem style="$rootSemanticStyle">
+  <sem-c>
+    <sem aria-label="Hello"></sem>
+  </sem-c>
+</sem>''');
+
+    // Update
+    renderSemantics(label: 'Hello', flags: <ui.SemanticsFlag>{ ui.SemanticsFlag.isLink });
+
+    tree = semantics().debugSemanticsTree!;
+    expect(tree.length, 2);
+    expect(tree[1]!.id, 1);
+    expect(tree[1]!.label, 'Hello');
+    expect(tree[1]!.element.tagName.toLowerCase(), 'a');
+    expectSemanticsTree('''
+<sem style="$rootSemanticStyle">
+  <sem-c>
+    <a aria-label="Hello" role="button" style="display: block;"></a>
+  </sem-c>
+</sem>''');
+    expect(existingParent, tree[1]!.element.parent);
+
+    semantics().semanticsEnabled = false;
+  });
+
   test('tooltip is part of label', () async {
     semantics().semanticsEnabled = true;
 
@@ -2892,6 +2939,28 @@ void _testFocusable() {
   });
 }
 
+void _testLink() {
+  test('nodes with link: true creates anchor tag', () {
+    semantics()
+      ..debugOverrideTimestampFunction(() => _testTime)
+      ..semanticsEnabled = true;
+
+    SemanticsObject pumpSemantics() {
+      final SemanticsTester tester = SemanticsTester(semantics());
+      tester.updateNode(
+        id: 0,
+        isLink: true,
+        rect: const ui.Rect.fromLTRB(0, 0, 100, 50),
+      );
+      tester.apply();
+      return tester.getSemanticsObject(0);
+    }
+
+    final SemanticsObject object = pumpSemantics();
+    expect(object.element.tagName.toLowerCase(), 'a');
+  });
+}
+
 /// A facade in front of [ui.SemanticsUpdateBuilder.updateNode] that
 /// supplies default values for semantics attributes.
 void updateNode(