Fix attribute nodes namespace when using XML::Reader

Fixes assertion failure. xml reader is choking while trying to access
namespace information tied to the attribute nodes. The assertion was:

Assertion failed: (doc->_private), function Nokogiri_wrap_xml_namespace,
file xml_namespace.c, line 41

ext/nokogiri/xml_namespace.c

@@ -37,20 +37,24 @@ static VALUE href(VALUE self)
 VALUE Nokogiri_wrap_xml_namespace(xmlDocPtr doc, xmlNsPtr node)
 {
   VALUE ns, document, node_cache;
+  nokogiriTuplePtr node_has_a_document;
 
-  assert(doc->_private);
+  if (doc->type == XML_DOCUMENT_FRAG_NODE) doc = doc->doc;
+  node_has_a_document = DOC_RUBY_OBJECT_TEST(doc);
 
-  if(node->_private)
+  if(node->_private && node_has_a_document)
     return (VALUE)node->_private;
 
   ns = Data_Wrap_Struct(cNokogiriXmlNamespace, 0, 0, node);
 
-  document = DOC_RUBY_OBJECT(doc);
+  if (doc->_private) {
+    document = DOC_RUBY_OBJECT(doc);
 
-  node_cache = rb_iv_get(document, "@node_cache");
-  rb_ary_push(node_cache, ns);
+    node_cache = rb_iv_get(document, "@node_cache");
+    rb_ary_push(node_cache, ns);
 
-  rb_iv_set(ns, "@document", DOC_RUBY_OBJECT(doc));
+    rb_iv_set(ns, "@document", DOC_RUBY_OBJECT(doc));
+  }
 
   node->_private = (void *)ns;
 

test/test_reader.rb

@@ -386,6 +386,25 @@ def test_ns_uri
                   reader.map { |n| n.namespace_uri })
   end
 
+  def test_namespaced_attributes
+    reader = Nokogiri::XML::Reader.from_memory(<<-eoxml)
+    <x xmlns:edi='http://ecommerce.example.org/schema' xmlns:commons="http://rets.org/xsd/RETSCommons">
+      <edi:foo commons:street-number="43">hello</edi:foo>
+      <y edi:name="francis" bacon="87"/>
+    </x>
+    eoxml
+    attr_ns = []
+    while reader.read
+      if reader.node_type == Nokogiri::XML::Node::ELEMENT_NODE
+        reader.attribute_nodes.each {|attr| attr_ns << (attr.namespace.nil? ? nil : attr.namespace.prefix) }
+      end
+    end
+    assert_equal(['commons',
+                  'edi',
+                  nil],
+                 attr_ns)
+  end
+
   def test_local_name
     reader = Nokogiri::XML::Reader.from_memory(<<-eoxml)
     <x xmlns:edi='http://ecommerce.example.org/schema'>