LibWeb: Support the ariaActiveDescendantElement IDL attribute

Libraries/LibWeb/ARIA/ARIAMixin.idl

@@ -1,6 +1,7 @@
 // https://w3c.github.io/aria/#ARIAMixin
 interface mixin ARIAMixin {
     [CEReactions] attribute DOMString? role;
+    [Reflect=aria-activedescendant, CEReactions] attribute Element? ariaActiveDescendantElement;
     [CEReactions] attribute DOMString? ariaAtomic;
     [CEReactions] attribute DOMString? ariaAutoComplete;
     [CEReactions] attribute DOMString? ariaBrailleLabel;

Libraries/LibWeb/DOM/Element.cpp

@@ -96,6 +96,7 @@ void Element::visit_edges(Cell::Visitor& visitor)
     SlottableMixin::visit_edges(visitor);
     Animatable::visit_edges(visitor);
 
+    visitor.visit(m_aria_active_descendant_element);
     visitor.visit(m_attributes);
     visitor.visit(m_inline_style);
     visitor.visit(m_class_list);
@@ -2926,6 +2927,10 @@ void Element::attribute_changed(FlyString const& local_name, Optional<String> co
             m_dir = Dir::Auto;
         else
             m_dir = {};
+    } else if (local_name == ARIA::AttributeNames::aria_active_descendant) {
+        // https://html.spec.whatwg.org/multipage/common-dom-interfaces.html#reflecting-content-attributes-in-idl-attributes:concept-element-attributes-change-ext
+        // Set element's explicitly set attr-element to null.
+        m_aria_active_descendant_element = nullptr;
     }
 }
 

Libraries/LibWeb/DOM/Element.h

@@ -295,6 +295,9 @@ class Element
     ENUMERATE_ARIA_ATTRIBUTES
 #undef __ENUMERATE_ARIA_ATTRIBUTE
 
+    GC::Ptr<DOM::Element> aria_active_descendant_element() { return m_aria_active_descendant_element; }
+    void set_aria_active_descendant_element(GC::Ptr<DOM::Element> value) { m_aria_active_descendant_element = value; }
+
     virtual bool exclude_from_accessibility_tree() const override;
 
     virtual bool include_in_accessibility_tree() const override;
@@ -464,6 +467,8 @@ class Element
     bool m_in_top_layer { false };
 
     OwnPtr<CSS::CountersSet> m_counters_set;
+
+    GC::Ptr<DOM::Element> m_aria_active_descendant_element;
 };
 
 template<>

Tests/LibWeb/Text/expected/wpt-import/html/dom/aria-element-reflection.txt

@@ -0,0 +1,33 @@
+Harness status: OK
+
+Found 27 tests
+
+16 Pass
+11 Fail
+Pass	aria-activedescendant element reflection
+Pass	aria-activedescendant If the content attribute is set directly, the IDL attribute getter always returns the first element whose ID matches the content attribute.
+Pass	aria-activedescendant Setting the IDL attribute to an element which is not the first element in DOM order with its ID causes the content attribute to be an empty string
+Pass	aria-activedescendant Setting an element reference that crosses into a shadow tree is disallowed, but setting one that is in a shadow inclusive ancestor is allowed.
+Fail	aria-errormessage
+Pass	ariaErrorMessageElement is not defined
+Fail	aria-details
+Pass	aria-activedescendant Deleting a reflected element should return null for the IDL attribute and the content attribute will be empty.
+Pass	aria-activedescendant Changing the ID of an element doesn't lose the reference.
+Pass	aria-activedescendant Reparenting an element into a descendant shadow scope hides the element reference.
+Pass	aria-activedescendant Reparenting referenced element cannot cause retargeting of reference.
+Pass	aria-activedescendant Element reference set in invalid scope remains intact throughout move to valid scope.
+Fail	aria-labelledby.
+Fail	aria-controls.
+Fail	aria-describedby.
+Fail	aria-flowto.
+Fail	aria-owns.
+Fail	shadow DOM behaviour for FrozenArray element reflection.
+Fail	Moving explicitly set elements across shadow DOM boundaries.
+Fail	Moving explicitly set elements around within the same scope, and removing from the DOM.
+Pass	aria-activedescendant Reparenting.
+Pass	aria-activedescendant Attaching element reference before it's inserted into the DOM.
+Pass	aria-activedescendant Cross-document references and moves.
+Pass	aria-activedescendant Adopting element keeps references.
+Pass	Caching invariant different attributes.
+Pass	Caching invariant different elements.
+Fail	Passing values of the wrong type should throw a TypeError