XPath "self" axis inside predicates.

The "self" axis should use the current context node when inside a predicate.

lib/oga/xpath/evaluator.rb

@@ -490,8 +490,12 @@ module Oga
       def on_axis_self(ast_node, context)
         nodes = XML::NodeSet.new
 
-        context.each do |context_node|
-          nodes << context_node if node_matches?(context_node, ast_node)
+        if current_node
+          nodes << current_node if node_matches?(current_node, ast_node)
+        else
+          context.each do |context_node|
+            nodes << context_node if node_matches?(context_node, ast_node)
+          end
         end
 
         return nodes

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

@@ -3,7 +3,7 @@ require 'spec_helper'
 describe Oga::XPath::Evaluator do
   context 'self axis' do
     before do
-      @document  = parse('<a></a>')
+      @document  = parse('<a><b>foo</b><b>bar</b></a>')
       @evaluator = described_class.new(@document)
     end
 
@@ -38,5 +38,17 @@ describe Oga::XPath::Evaluator do
         @set[0].should == @document.children[0]
       end
     end
+
+    context 'matching nodes inside predicates' do
+      before do
+        @set = @evaluator.evaluate('a/b[.="foo"]')
+      end
+
+      it_behaves_like :node_set, :length => 1
+
+      example 'return the first <b> node' do
+        @set[0].should == @document.children[0].children[0]
+      end
+    end
   end
 end