LibWeb: Implement Element.getAttributeNS

Tests/LibWeb/Text/expected/DOM/Element-getAttributeNS.txt

@@ -0,0 +1,4 @@
+     xlink:ref getAttribute = 'null'
+xlink:ref getAttributeNS = 'test'
+href getAttribute = 'test'
+href getAttributeNS = 'null'

Tests/LibWeb/Text/input/DOM/Element-getAttributeNS.html

@@ -0,0 +1,16 @@
+<script src="../include.js"></script>
+<svg xmlns="http://www.w3.org/2000/svg">
+    <script id="with-xlink-href" xlink:href="test"></script>
+    <script id="no-xlink-href" href="test"></script>
+</svg>
+<script id="svg-script-element">
+    test(() => {
+        const xlinkNS = document.getElementById("with-xlink-href");
+        println(`xlink:ref getAttribute = '${xlinkNS.getAttribute("href")}'`);
+        println(`xlink:ref getAttributeNS = '${xlinkNS.getAttributeNS("http://www.w3.org/1999/xlink", "href")}'`);
+
+        const noNS = document.getElementById("no-xlink-href");
+        println(`href getAttribute = '${noNS.getAttribute("href")}'`);
+        println(`href getAttributeNS = '${noNS.getAttributeNS("http://www.w3.org/1999/xlink", "href")}'`);
+    });
+</script>

Userland/Libraries/LibWeb/DOM/Element.cpp

@@ -120,6 +120,20 @@ Optional<String> Element::get_attribute(FlyString const& name) const
     return attribute->value();
 }
 
+// https://dom.spec.whatwg.org/#dom-element-getattributens
+Optional<String> Element::get_attribute_ns(Optional<FlyString> const& namespace_, FlyString const& name) const
+{
+    // 1. Let attr be the result of getting an attribute given namespace, localName, and this.
+    auto const* attribute = m_attributes->get_attribute_ns(namespace_, name);
+
+    // 2. If attr is null, return null.
+    if (!attribute)
+        return {};
+
+    // 3. Return attr’s value.
+    return attribute->value();
+}
+
 ByteString Element::deprecated_get_attribute(FlyString const& name) const
 {
     auto maybe_attribute = get_attribute(name);

Userland/Libraries/LibWeb/DOM/Element.h

@@ -99,6 +99,7 @@ public:
     Optional<String> attribute(FlyString const& name) const { return get_attribute(name); }
 
     Optional<String> get_attribute(FlyString const& name) const;
+    Optional<String> get_attribute_ns(Optional<FlyString> const& namespace_, FlyString const& name) const;
     ByteString deprecated_get_attribute(FlyString const& name) const;
     String get_attribute_value(FlyString const& local_name, Optional<FlyString> const& namespace_ = {}) const;
 

Userland/Libraries/LibWeb/DOM/Element.idl

@@ -29,6 +29,7 @@ interface Element : Node {
     readonly attribute DOMString tagName;
 
     DOMString? getAttribute(DOMString qualifiedName);
+    DOMString? getAttributeNS([FlyString] DOMString? namespace, [FlyString] DOMString localName);
     [CEReactions] undefined setAttribute(DOMString qualifiedName, DOMString value);
     [CEReactions] undefined setAttributeNS([FlyString] DOMString? namespace , [FlyString] DOMString qualifiedName , DOMString value);
     [CEReactions] Attr? setAttributeNode(Attr attr);