fix(jruby): create_element should not set the doc's default ns

The ns should be set explicitly or when the node is parented.

Fixes #3457

Author: flavorjones

ext/java/nokogiri/XmlNode.java

@@ -321,12 +321,8 @@ public class XmlNode extends RubyObject
 
     Element element;
     String node_name = rubyStringToString(name);
-    String prefix = NokogiriHelpers.getPrefix(node_name);
-    String namespace_uri = null;
-    if (document.getDocumentElement() != null) {
-      namespace_uri = document.getDocumentElement().lookupNamespaceURI(prefix);
-    }
-    element = document.createElementNS(namespace_uri, node_name);
+
+    element = document.createElementNS(null, node_name);
     setNode(context.runtime, element);
   }
 

test/namespaces/test_serializing_namespaces.rb

@@ -80,11 +80,7 @@
       assert_includes(doc, '<root xmlns="http://outer-namespace.org/">')
       assert_includes(doc, "<outer>in outer namespace</outer>")
       assert_includes(doc, '<inner xmlns="http://inner-namespace.org/">')
-      pending_if("https://github.com/sparklemotion/nokogiri/issues/3457", Nokogiri.jruby?) do
-        # Here JRuby is incorrectly adding the xmlns namespace declaration, i.e.:
-        # '<element xmlns="http://outer-namespace.org/">in inner namespace</element>'
-        assert_includes(doc, "<element>in inner namespace</element>")
-      end
+      assert_includes(doc, "<element>in inner namespace</element>")
       assert_includes(doc, "<another>back in outer namespace</another>")
     end
   end
@@ -184,11 +180,7 @@
       assert_includes(doc, "<default_element>in default namespace</default_element>")
       assert_includes(doc, "<ns:prefixed_element>in prefixed namespace</ns:prefixed_element>")
       assert_includes(doc, '<mixed xmlns="http://new-default.org/">')
-      pending_if("https://github.com/sparklemotion/nokogiri/issues/3457", Nokogiri.jruby?) do
-        # Here JRuby is incorrectly adding the xmlns namespace declaration, i.e.:
-        # '<new_default xmlns="http://default.org/">in new default namespace</new_default>'
-        assert_includes(doc, "<new_default>in new default namespace</new_default>")
-      end
+      assert_includes(doc, "<new_default>in new default namespace</new_default>")
       assert_includes(doc, "<ns:still_prefixed>still using original prefixed namespace</ns:still_prefixed>")
     end
   end

test/xml/test_document.rb

@@ -188,6 +188,14 @@ def test_create_element_with_attributes
           assert_equal("1", elm["a"])
         end
 
+        # https://github.com/sparklemotion/nokogiri/issues/3457
+        def test_create_element_doc_default_namespace_not_automatically_applied
+          doc = Nokogiri::XML(%(<root xmlns='http://example.org/default'>))
+          node = doc.create_element("child")
+
+          assert_nil(node.namespace)
+        end
+
         def test_create_element_with_namespace
           elm = xml.create_element("foo", "xmlns:foo": "http://tenderlovemaking.com")
           assert_equal("http://tenderlovemaking.com", elm.namespaces["xmlns:foo"])