Handle registering of default XML namespaces.

When the default namespace is registered (using xmlns="...") Oga now properly
sets the namespace of the container and all child elements.

This fixes #44.

lib/oga/xml/element.rb

@@ -144,7 +144,13 @@ module Oga
       # @return [Oga::XML::Namespace]
       #
       def namespace
-        return @namespace ||= available_namespaces[namespace_name]
+        unless @namespace
+          available = available_namespaces
+
+          @namespace = available[namespace_name] || available[XMLNS_PREFIX]
+        end
+
+        return @namespace
       end
 
       ##
@@ -283,7 +289,14 @@ module Oga
         self.attributes = attributes.reject do |attr|
           # We're using `namespace_name` opposed to `namespace.name` as "xmlns"
           # is not a registered namespace.
-          remove = attr.namespace_name && attr.namespace_name == XMLNS_PREFIX
+          remove = attr.name == XMLNS_PREFIX ||
+            attr.namespace_name == XMLNS_PREFIX
+
+          # If the attribute sets the default namespace we'll also overwrite the
+          # namespace_name.
+          if attr.name == XMLNS_PREFIX
+            @namespace_name = XMLNS_PREFIX
+          end
 
           register_namespace(attr.name, attr.value) if remove
 

spec/oga/xml/element_spec.rb

@@ -34,6 +34,22 @@ describe Oga::XML::Element do
     end
   end
 
+  context 'setting the default namespace without a prefix' do
+    before do
+      attr = Oga::XML::Attribute.new(:name => 'xmlns', :value => 'foo')
+
+      @element = described_class.new(:attributes => [attr])
+    end
+
+    example 'register the default namespace' do
+      @element.namespaces['xmlns'].is_a?(Oga::XML::Namespace).should == true
+    end
+
+    example 'remove the namespace attribute from the list of attributes' do
+      @element.attributes.empty?.should == true
+    end
+  end
+
   context '#attribute' do
     before do
       attributes = [
@@ -159,16 +175,23 @@ describe Oga::XML::Element do
   end
 
   context '#namespace' do
-    before do
+    example 'return the namespace' do
-      @namespace = Oga::XML::Namespace.new(:name => 'x')
+      namespace = Oga::XML::Namespace.new(:name => 'x')
-      @element   = described_class.new(
+      element   = described_class.new(
         :namespace_name => 'x',
-        :namespaces     => {'x' => @namespace}
+        :namespaces     => {'x' => namespace}
       )
+
+      element.namespace.should == namespace
     end
 
-    example 'return the namespace' do
+    example 'return the default namespace if available' do
-      @element.namespace.should == @namespace
+      namespace = Oga::XML::Namespace.new(:name => 'xmlns')
+      element   = described_class.new(
+        :namespaces => {'xmlns' => namespace}
+      )
+
+      element.namespace.should == namespace
     end
   end
 

spec/oga/xml/parser/elements_spec.rb

@@ -37,6 +37,31 @@ describe Oga::XML::Parser do
     end
   end
 
+  context 'elements with default namespaces' do
+    before :all do
+      @document = parse('<foo xmlns="bar"><bar></bar></foo>')
+
+      @foo = @document.children[0]
+      @bar = @foo.children[0]
+    end
+
+    example 'set the namespace name of the <foo> element' do
+      @foo.namespace.name.should == 'xmlns'
+    end
+
+    example 'set the namespace URI of the <foo> element' do
+      @foo.namespace.uri.should == 'bar'
+    end
+
+    example 'set the namespace name of the <bar> element' do
+      @bar.namespace.name.should == 'xmlns'
+    end
+
+    example 'set the namespace URI of the <bar> element' do
+      @bar.namespace.uri.should == 'bar'
+    end
+  end
+
   context 'elements with attributes' do
     before :all do
       @element = parse('<foo bar="baz"></foo>').children[0]