LibWeb: Implement the HTMLAreaElement.relList attribute

This returns a DOMTokenList that reflects the `rel` attribute.

Tests/LibWeb/Text/expected/HTML/relList-attribute.txt

@@ -4,3 +4,9 @@ a.relList for after setting rel to "whatever": whatever
 a.relList for after setting rel to "prefetch": prefetch
 a.relList contains "prefetch": true
 a.relList contains "whatever": false
+area.relList initial length: 0
+area.relList always returns the same value: true
+area.relList for after setting rel to "whatever": whatever
+area.relList for after setting rel to "prefetch": prefetch
+area.relList contains "prefetch": true
+area.relList contains "whatever": false

Tests/LibWeb/Text/input/HTML/relList-attribute.html

@@ -17,6 +17,7 @@
     test(() => {
         const tagNamesToTest = [
             "a",
+            "area",
         ];
 
         for (const tagName of tagNamesToTest) {

Userland/Libraries/LibWeb/HTML/HTMLAreaElement.cpp

@@ -6,6 +6,7 @@
 
 #include <LibWeb/ARIA/Roles.h>
 #include <LibWeb/Bindings/HTMLAreaElementPrototype.h>
+#include <LibWeb/DOM/DOMTokenList.h>
 #include <LibWeb/HTML/HTMLAreaElement.h>
 #include <LibWeb/HTML/Window.h>
 
@@ -31,9 +32,21 @@ void HTMLAreaElement::attribute_changed(FlyString const& name, Optional<String>
     HTMLElement::attribute_changed(name, value);
     if (name == HTML::AttributeNames::href) {
         set_the_url();
+    } else if (name == HTML::AttributeNames::rel) {
+        if (m_rel_list)
+            m_rel_list->associated_attribute_changed(value.value_or(String {}));
     }
 }
 
+// https://html.spec.whatwg.org/multipage/image-maps.html#dom-area-rellist
+JS::GCPtr<DOM::DOMTokenList> HTMLAreaElement::rel_list()
+{
+    // The IDL attribute relList must reflect the rel content attribute.
+    if (!m_rel_list)
+        m_rel_list = DOM::DOMTokenList::create(*this, HTML::AttributeNames::rel);
+    return m_rel_list;
+}
+
 Optional<String> HTMLAreaElement::hyperlink_element_utils_href() const
 {
     return attribute(HTML::AttributeNames::href);

Userland/Libraries/LibWeb/HTML/HTMLAreaElement.h

@@ -20,6 +20,7 @@ class HTMLAreaElement final
 
 public:
     virtual ~HTMLAreaElement() override;
+    JS::GCPtr<DOM::DOMTokenList> rel_list();
 
 private:
     HTMLAreaElement(DOM::Document&, DOM::QualifiedName);
@@ -50,6 +51,8 @@ private:
     }
 
     virtual Optional<ARIA::Role> default_role() const override;
+
+    JS::GCPtr<DOM::DOMTokenList> m_rel_list;
 };
 
 }

Userland/Libraries/LibWeb/HTML/HTMLAreaElement.idl

@@ -14,7 +14,7 @@ interface HTMLAreaElement : HTMLElement {
     [CEReactions, Reflect] attribute DOMString download;
     [CEReactions, Reflect] attribute USVString ping;
     [CEReactions, Reflect] attribute DOMString rel;
-    // FIXME: [SameObject, PutForwards=value] readonly attribute DOMTokenList relList;
+    [SameObject, PutForwards=value] readonly attribute DOMTokenList relList;
     // FIXME: [CEReactions] attribute DOMString referrerPolicy;
 
     // Obsolete