Revert "[web:a11y] make header a proper <header> (flutter#55747)"

This reverts commit 2fbb0c1.

Author: yjbanov

ci/licenses_golden/licenses_flutter

@@ -43886,7 +43886,6 @@ ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/semantics.dart + ../../../flu
 ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/semantics/accessibility.dart + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/semantics/checkable.dart + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/semantics/focusable.dart + ../../../flutter/LICENSE
-ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/semantics/header.dart + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/lib/web_ui/lib/src/engine/semantics/heading.dart + ../../../flutter/LICENSE
 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
@@ -46765,7 +46764,6 @@ FILE: ../../../flutter/lib/web_ui/lib/src/engine/semantics.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/semantics/accessibility.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/semantics/checkable.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/semantics/focusable.dart
-FILE: ../../../flutter/lib/web_ui/lib/src/engine/semantics/header.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/semantics/heading.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/semantics/image.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/semantics/incrementable.dart

lib/web_ui/lib/src/engine.dart

@@ -147,7 +147,6 @@ export 'engine/scene_view.dart';
 export 'engine/semantics/accessibility.dart';
 export 'engine/semantics/checkable.dart';
 export 'engine/semantics/focusable.dart';
-export 'engine/semantics/header.dart';
 export 'engine/semantics/heading.dart';
 export 'engine/semantics/image.dart';
 export 'engine/semantics/incrementable.dart';

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

@@ -5,7 +5,6 @@
 export 'semantics/accessibility.dart';
 export 'semantics/checkable.dart';
 export 'semantics/focusable.dart';
-export 'semantics/header.dart';
 export 'semantics/heading.dart';
 export 'semantics/image.dart';
 export 'semantics/incrementable.dart';

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

@@ -21,7 +21,6 @@ import '../window.dart';
 import 'accessibility.dart';
 import 'checkable.dart';
 import 'focusable.dart';
-import 'header.dart';
 import 'heading.dart';
 import 'image.dart';
 import 'incrementable.dart';
@@ -397,17 +396,14 @@ enum SemanticRoleKind {
   /// The node's role is to host a platform view.
   platformView,
 
-  /// Contains a link.
-  link,
-
-  /// Denotes a header.
-  header,
-
   /// A role used when a more specific role cannot be assigend to
   /// a [SemanticsObject].
   ///
   /// Provides a label or a value.
   generic,
+
+  /// Contains a link.
+  link,
 }
 
 /// Responsible for setting the `role` ARIA attribute, for attaching
@@ -681,18 +677,23 @@ final class GenericRole extends SemanticRole {
       return;
     }
 
-    // Assign one of two roles to the element: group or text.
+    // Assign one of three roles to the element: group, heading, text.
     //
     // - "group" is used when the node has children, irrespective of whether the
     //   node is marked as a header or not. This is because marking a group
     //   as a "heading" will prevent the AT from reaching its children.
+    // - "heading" is used when the framework explicitly marks the node as a
+    //   heading and the node does not have children.
     // - If a node has a label and no children, assume is a paragraph of text.
     //   In HTML text has no ARIA role. It's just a DOM node with text inside
     //   it. Previously, role="text" was used, but it was only supported by
     //   Safari, and it was removed starting Safari 17.
     if (semanticsObject.hasChildren) {
       labelAndValue!.preferredRepresentation = LabelRepresentation.ariaLabel;
       setAriaRole('group');
+    } else if (semanticsObject.hasFlag(ui.SemanticsFlag.isHeader)) {
+      labelAndValue!.preferredRepresentation = LabelRepresentation.domText;
+      setAriaRole('heading');
     } else {
       labelAndValue!.preferredRepresentation = LabelRepresentation.sizedSpan;
       removeAttribute('role');
@@ -1260,24 +1261,11 @@ class SemanticsObject {
   bool get isTextField => hasFlag(ui.SemanticsFlag.isTextField);
 
   /// Whether this object represents a heading element.
-  ///
-  /// Typically, a heading is a prominent piece of text that describes what the
-  /// rest of the screen or page is about.
-  ///
-  /// Not to be confused with [isHeader].
   bool get isHeading => headingLevel != 0;
 
-  /// Whether this object represents an interactive link.
+    /// Whether this object represents an editable text field.
   bool get isLink => hasFlag(ui.SemanticsFlag.isLink);
 
-  /// Whether this object represents a header.
-  ///
-  /// A header is a group of widgets that introduce the content of the screen
-  /// or a page.
-  ///
-  /// Not to be confused with [isHeading].
-  bool get isHeader => hasFlag(ui.SemanticsFlag.isHeader);
-
   /// Whether this object needs screen readers attention right away.
   bool get isLiveRegion =>
       hasFlag(ui.SemanticsFlag.isLiveRegion) &&
@@ -1691,8 +1679,6 @@ class SemanticsObject {
       return SemanticRoleKind.route;
     } else if (isLink) {
       return SemanticRoleKind.link;
-    } else if (isHeader) {
-      return SemanticRoleKind.header;
     } else {
       return SemanticRoleKind.generic;
     }
@@ -1710,7 +1696,6 @@ class SemanticsObject {
       SemanticRoleKind.platformView => SemanticPlatformView(this),
       SemanticRoleKind.link => SemanticLink(this),
       SemanticRoleKind.heading => SemanticHeading(this),
-      SemanticRoleKind.header => SemanticHeader(this),
       SemanticRoleKind.generic => GenericRole(this),
     };
   }

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

@@ -736,7 +736,7 @@ class MockSemanticsEnabler implements SemanticsEnabler {
 }
 
 void _testHeader() {
-  test('renders a header with a label and uses a sized span for label', () {
+  test('renders heading role for headers', () {
     semantics()
       ..debugOverrideTimestampFunction(() => _testTime)
       ..semanticsEnabled = true;
@@ -752,13 +752,19 @@ void _testHeader() {
 
     owner().updateSemantics(builder.build());
     expectSemanticsTree(owner(), '''
-<header><span>Header of the page</span></header>
+<sem role="heading">Header of the page</sem>
 ''');
 
     semantics().semanticsEnabled = false;
   });
 
-  test('renders a header with children and uses aria-label', () {
+  // When a header has child elements, role="heading" prevents AT from reaching
+  // child elements. To fix that role="group" is used, even though that causes
+  // the heading to not be announced as a heading. If the app really needs the
+  // heading to be announced as a heading, the developer can restructure the UI
+  // such that the heading is not a parent node, but a side-note, e.g. preceding
+  // the child list.
+  test('uses group role for headers when children are present', () {
     semantics()
       ..debugOverrideTimestampFunction(() => _testTime)
       ..semanticsEnabled = true;
@@ -782,7 +788,7 @@ void _testHeader() {
 
     owner().updateSemantics(builder.build());
     expectSemanticsTree(owner(), '''
-<header aria-label="Header of the page"><sem-c><sem></sem></sem-c></header>
+<sem role="group" aria-label="Header of the page"><sem-c><sem></sem></sem-c></sem>
 ''');
 
     semantics().semanticsEnabled = false;