LibWeb: Add NamedNodeMap::removeNamedItemNS() method

This patch adds implementation of the missing `removeNamedItemNS()`
method.

Userland/Libraries/LibWeb/DOM/NamedNodeMap.cpp

@@ -106,6 +106,20 @@ WebIDL::ExceptionOr<Attr const*> NamedNodeMap::remove_named_item(StringView qual
     return attribute;
 }
 
+// https://dom.spec.whatwg.org/#dom-namednodemap-removenameditemns
+WebIDL::ExceptionOr<Attr const*> NamedNodeMap::remove_named_item_ns(StringView namespace_, StringView local_name)
+{
+    // 1. Let attr be the result of removing an attribute given namespace, localName, and element.
+    auto const* attribute = remove_attribute_ns(namespace_, local_name);
+
+    // 2. If attr is null, then throw a "NotFoundError" DOMException.
+    if (!attribute)
+        return WebIDL::NotFoundError::create(realm(), DeprecatedString::formatted("Attribute with namespace '{}' and local name '{}' not found", namespace_, local_name));
+
+    // 3. Return attr.
+    return attribute;
+}
+
 // https://dom.spec.whatwg.org/#concept-element-attributes-get-by-name
 Attr* NamedNodeMap::get_attribute(StringView qualified_name, size_t* item_index)
 {
@@ -257,6 +271,22 @@ Attr const* NamedNodeMap::remove_attribute(StringView qualified_name)
     return attribute;
 }
 
+// https://dom.spec.whatwg.org/#concept-element-attributes-remove-by-namespace
+Attr const* NamedNodeMap::remove_attribute_ns(StringView namespace_, StringView local_name)
+{
+    size_t item_index = 0;
+
+    // 1. Let attr be the result of getting an attribute given namespace, localName, and element.
+    auto const* attribute = get_attribute_ns(namespace_, local_name, &item_index);
+
+    // 2. If attr is non-null, then remove attr.
+    if (attribute)
+        remove_attribute_at_index(item_index);
+
+    // 3. Return attr.
+    return attribute;
+}
+
 JS::Value NamedNodeMap::item_value(size_t index) const
 {
     auto const* node = item(index);

Userland/Libraries/LibWeb/DOM/NamedNodeMap.h

@@ -39,6 +39,7 @@ public:
     Attr const* get_named_item_ns(StringView namespace_, StringView local_name) const;
     WebIDL::ExceptionOr<Attr const*> set_named_item(Attr& attribute);
     WebIDL::ExceptionOr<Attr const*> remove_named_item(StringView qualified_name);
+    WebIDL::ExceptionOr<Attr const*> remove_named_item_ns(StringView namespace_, StringView local_name);
 
     // Methods defined by the spec for internal use:
     Attr* get_attribute(StringView qualified_name, size_t* item_index = nullptr);
@@ -49,6 +50,7 @@ public:
     void replace_attribute(Attr& old_attribute, Attr& new_attribute, size_t old_attribute_index);
     void append_attribute(Attr& attribute);
     Attr const* remove_attribute(StringView qualified_name);
+    Attr const* remove_attribute_ns(StringView namespace_, StringView local_name);
 
 private:
     explicit NamedNodeMap(Element&);

Userland/Libraries/LibWeb/DOM/NamedNodeMap.idl

@@ -12,5 +12,5 @@ interface NamedNodeMap {
     // [CEReactions] Attr? setNamedItemNS(Attr attr);
 
     [CEReactions] Attr removeNamedItem(DOMString qualifiedName);
-    // [CEReactions] Attr removeNamedItemNS(DOMString? namespace, DOMString localName);
+    [CEReactions] Attr removeNamedItemNS(DOMString? namespace, DOMString localName);
 };