Fix xmlns attributes properly

lib/DOM/Document.php

@@ -50,19 +50,15 @@ class Document extends \DOMDocument {
 
     public function createAttributeNS($namespaceURI, $qualifiedName) {
         try {
-            $out = @parent::createAttributeNS($namespaceURI, $qualifiedName);
+            return parent::createAttributeNS($namespaceURI, $qualifiedName);
         } catch (\DOMException $e) {
             // The element name is invalid for XML
             // Replace any offending characters with "UHHHHHH" where H are the
             //   uppercase hexadecimal digits of the character's code point
             $this->mangledAttributes = true;
             $qualifiedName = $this->coerceName($qualifiedName);
-            $out = parent::createAttributeNS($namespaceURI, $qualifiedName);
+            return parent::createAttributeNS($namespaceURI, $qualifiedName);
         }
-        if ($out === false) {
-            throw new \DOMException("Document element must be inserted first");
-        }
-        return $out;
     }
 
     public function createElement($name, $value = "") {

lib/DOM/Element.php

@@ -76,20 +76,30 @@ class Element extends \DOMElement {
         // set it.
         if ($qualifiedName === 'class' && $namespaceURI === null && $this->_classList !== null) {
             $this->_classList->value = $value;
+        } elseif ($namespaceURI === Parser::XMLNS_NAMESPACE) {
+            // NOTE: We create attribute nodes so that xmlns attributes
+            //   don't get lost; otherwise they cannot be serialized
+            $a = @$this->ownerDocument->createAttributeNS($namespaceURI, $qualifiedName);
+            if ($a === false) {
+                // The document element does not exist yet, so we need
+                //   to insert this element into the document
+                $this->ownerDocument->appendChild($this);
+                $a = $this->ownerDocument->createAttributeNS($namespaceURI, $qualifiedName);
+                $this->ownerDocument->removeChild($this);
+            }
+            $a->value = $this->escapeString($value, true);
+            $this->appendChild($a);
         } else {
             try {
-                // NOTE: We create attribute nodes so that xmlns attributes don't get lost
-                $a = $this->ownerDocument->createAttributeNS($namespaceURI, $qualifiedName);
+                parent::setAttributeNS($namespaceURI, $qualifiedName, $value);
             } catch (\DOMException $e) {
                 // The attribute name is invalid for XML
                 // Replace any offending characters with "UHHHHHH" where H are the
                 //   uppercase hexadecimal digits of the character's code point
                 $this->ownerDocument->mangledAttributes = true;
                 $qualifiedName = $this->coerceName($qualifiedName);
-                $a = $this->ownerDocument->createAttributeNS($namespaceURI, $qualifiedName);
+                parent::setAttributeNS($namespaceURI, $qualifiedName, $value);
             }
-            $a->value = $this->escapeString($value, true);
-            $this->appendChild($a);
             if ($qualifiedName === "id" && $namespaceURI === null) {
                 $this->setIdAttribute($qualifiedName, true);
             }

lib/TreeBuilder.php

@@ -4150,12 +4150,6 @@ class TreeBuilder {
         # Let element be the result of creating an element given document,
         #   localName, given namespace, null, and is.
         $element = $this->DOM->createElementNS($namespace, $token->name);
-        // DEVIATION: If there is no document (root) element yet, temporarily
-        //   insert this element so that creating attributes for it does not
-        //   fail due to a PHP DOM limitation
-        if (!$this->DOM->documentElement) {
-            $this->DOM->appendChild($element);
-        }
         # Append each attribute in the given token to element.
         foreach ($token->attributes as $attr) {
             # If element has an xmlns attribute in the XMLNS namespace whose value
@@ -4174,10 +4168,6 @@ class TreeBuilder {
                 $element->setAttributeNS($attr->namespace, $attr->name, $attr->value);
             }
         }
-        if ($this->DOM->documentElement && $this->DOM->documentElement->isSameNode($element)) {
-            // Pop off the document element if it was inserted above
-            $this->DOM->removeChild($element);
-        }
         # Return element.
         return $element;
     }