Basic work for supporting namespace URIs.

lib/oga/xml/element.rb

@@ -145,6 +145,27 @@ module Oga
         return :element
       end
 
+      ##
+      # Returns a node set of all the namespaces that are available to the
+      # current node. This includes the namespaces registered on the current
+      # node.
+      #
+      # @return [Oga::XML::NodeSet]
+      #
+      def available_namespaces
+
+      end
+
+      ##
+      # Returns a node set of all the namespaces registered with the current
+      # node.
+      #
+      # @return [Oga::XML::NodeSet]
+      #
+      def namespaces
+
+      end
+
       private
 
       ##

lib/oga/xpath/evaluator.rb

@@ -398,6 +398,24 @@ module Oga
         return nodes
       end
 
+      ##
+      # Evaluates the `namespace` axis.
+      #
+      # @param [Oga::XPath::Node] ast_node
+      # @param [Oga::XML::NodeSet] context
+      # @return [Oga::XML::NodeSet]
+      #
+      def on_axis_namespace(ast_node, context)
+        nodes = XML::NodeSet.new
+        name  = ast_node.children[1]
+
+        context.each do |context_node|
+
+        end
+
+        return nodes
+      end
+
       ##
       # Returns a node set containing all the child nodes of the given set of
       # nodes.
@@ -431,15 +449,13 @@ module Oga
       # @return [Oga::XML::NodeSet]
       #
       def node_matches?(xml_node, ast_node)
-        return false unless can_match_node?(xml_node)
-
         ns, name = *ast_node
 
-        name_matches = xml_node.name == name || name == '*'
+        name_matches = name_matches?(xml_node, name)
         ns_matches   = false
 
         if ns
-          ns_matches = xml_node.namespace.to_s == ns || ns == '*'
+          ns_matches = namespace_matches?(xml_node, ns)
 
         # If there's no namespace given but the name matches we'll also mark
         # the namespace as matching.
@@ -454,13 +470,29 @@ module Oga
       end
 
       ##
-      # Returns `true` if the given XML node can be compared using
-      # {#node_matches?}.
+      # Returns `true` if the name of the XML node matches the given name *or*
+      # matches a wildcard.
       #
-      # @param [Oga::XML::Node] ast_node
+      # @param [Oga::XML::Node] xml_node
+      # @param [String] name
       #
-      def can_match_node?(ast_node)
-        return ast_node.respond_to?(:name) && ast_node.respond_to?(:namespace)
+      def name_matches?(xml_node, name)
+        return false unless xml_node.respond_to?(:name)
+
+        return xml_node.name == name || name == '*'
+      end
+
+      ##
+      # Returns `true` if the namespace of the XML node matches the given
+      # namespace *or* matches a wildcard.
+      #
+      # @param [Oga::XML::Node] xml_node
+      # @param [String] ns
+      #
+      def namespace_matches?(xml_node, ns)
+        return false unless xml_node.respond_to?(:namespace)
+
+        return xml_node.namespace.to_s == ns || ns == '*'
       end
 
       ##

spec/oga/xml/element_spec.rb

@@ -177,4 +177,8 @@ describe Oga::XML::Element do
       described_class.new.node_type.should == :element
     end
   end
+
+  context '#available_namespaces' do
+    # TODO: write me
+  end
 end

spec/oga/xpath/evaluator/axes/namespace_spec.rb

@@ -0,0 +1,55 @@
+require 'spec_helper'
+
+describe Oga::XPath::Evaluator do
+  context 'namespace axis' do
+    before do
+      @document = parse(<<-EOF.strip)
+<root xmlns:x="x">
+  <foo xmlns:y="y"></foo>
+</root>
+      EOF
+
+      @evaluator = described_class.new(@document)
+    end
+
+    context 'matching namespaces in the root element' do
+      before do
+        @set = @evaluator.evaluate('root/namespace::x')
+      end
+
+      it_behaves_like :node_set, :length => 1
+
+      example 'return a Namespace instance' do
+        @set[0].is_a?(Oga::XML::Namespace).should == true
+      end
+
+      example 'return the "x" namespace' do
+        @set[0].name.should == 'x'
+      end
+    end
+
+    context 'matching namespaces in a nested element' do
+      before do
+        @set = @evaluator.evaluate('root/namespace::x')
+      end
+
+      it_behaves_like :node_set, :length => 2
+
+      example 'return the "x" namespace' do
+        @set[0].name.should == 'x'
+      end
+
+      example 'return the "y" namespace' do
+        @set[1].name.should == 'y'
+      end
+    end
+
+    context 'matching namespace nodes using a wildcard' do
+      before do
+        @set = @evaluator.evaluate('root/namespace::*')
+      end
+
+      it_behaves_like :node_set, :length => 1
+    end
+  end
+end

spec/oga/xpath/evaluator/general_spec.rb

@@ -71,20 +71,6 @@ describe Oga::XPath::Evaluator do
     end
   end
 
-  context '#can_match_node?' do
-    example 'return true for an XML::Element instance' do
-      @evaluator.can_match_node?(Oga::XML::Element.new).should == true
-    end
-
-    example 'return true for an XML::Attribute instance' do
-      @evaluator.can_match_node?(Oga::XML::Attribute.new).should == true
-    end
-
-    example 'return false for an XML::Text instance' do
-      @evaluator.can_match_node?(Oga::XML::Text.new).should == false
-    end
-  end
-
   context '#has_parent?' do
     before do
       @parent = Oga::XML::Element.new