LibWeb: Rename Attribute to Attr

This name is not very good, but it's what the specification calls it.

Userland/Libraries/LibWeb/DOM/Attr.cpp

@@ -0,0 +1,79 @@
+/*
+ * Copyright (c) 2021, Tim Flynn <trflynn89@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibWeb/DOM/Attr.h>
+#include <LibWeb/DOM/Document.h>
+#include <LibWeb/DOM/Element.h>
+#include <LibWeb/DOM/MutationType.h>
+#include <LibWeb/DOM/StaticNodeList.h>
+
+namespace Web::DOM {
+
+JS::NonnullGCPtr<Attr> Attr::create(Document& document, FlyString local_name, String value, Element const* owner_element)
+{
+    return *document.heap().allocate<Attr>(document.realm(), document, move(local_name), move(value), owner_element);
+}
+
+Attr::Attr(Document& document, FlyString local_name, String value, Element const* owner_element)
+    : Node(document, NodeType::ATTRIBUTE_NODE)
+    , m_qualified_name(move(local_name), {}, {})
+    , m_value(move(value))
+    , m_owner_element(owner_element)
+{
+    set_prototype(&window().cached_web_prototype("Attr"));
+}
+
+void Attr::visit_edges(Cell::Visitor& visitor)
+{
+    Base::visit_edges(visitor);
+    visitor.visit(m_owner_element.ptr());
+}
+
+Element* Attr::owner_element()
+{
+    return m_owner_element.ptr();
+}
+
+Element const* Attr::owner_element() const
+{
+    return m_owner_element.ptr();
+}
+
+void Attr::set_owner_element(Element const* owner_element)
+{
+    m_owner_element = owner_element;
+}
+
+// https://dom.spec.whatwg.org/#set-an-existing-attribute-value
+void Attr::set_value(String value)
+{
+    // 1. If attribute’s element is null, then set attribute’s value to value.
+    if (!owner_element()) {
+        m_value = move(value);
+        return;
+    }
+
+    // 2. Otherwise, change attribute to value.
+    // https://dom.spec.whatwg.org/#concept-element-attributes-change
+    // 1. Handle attribute changes for attribute with attribute’s element, attribute’s value, and value.
+    handle_attribute_changes(*owner_element(), m_value, value);
+
+    // 2. Set attribute’s value to value.
+    m_value = move(value);
+}
+
+// https://dom.spec.whatwg.org/#handle-attribute-changes
+void Attr::handle_attribute_changes(Element& element, String const& old_value, [[maybe_unused]] String const& new_value)
+{
+    // 1. Queue a mutation record of "attributes" for element with attribute’s local name, attribute’s namespace, oldValue, « », « », null, and null.
+    element.queue_mutation_record(MutationType::attributes, local_name(), namespace_uri(), old_value, StaticNodeList::create(window(), {}), StaticNodeList::create(window(), {}), nullptr, nullptr);
+
+    // FIXME: 2. If element is custom, then enqueue a custom element callback reaction with element, callback name "attributeChangedCallback", and an argument list containing attribute’s local name, oldValue, newValue, and attribute’s namespace.
+
+    // FIXME: 3. Run the attribute change steps with element, attribute’s local name, oldValue, newValue, and attribute’s namespace.
+}
+
+}