Support for the XPath local-name() function.

lib/oga/xpath/evaluator.rb

@@ -157,12 +157,12 @@ module Oga
             xpath_index = index + 1
             retval      = with_node(current) { process(predicate, nodes) }
 
-            # Non empty node set? Keep the current node
-            if retval.is_a?(XML::NodeSet) and !retval.empty?
-              new_nodes << current
+            # Numeric values are used as node set indexes.
+            if retval.is_a?(Numeric)
+              new_nodes << current if retval.to_i == xpath_index
 
-            # In case of a number we'll use it as the index.
-            elsif retval.is_a?(Numeric) && retval.to_i == xpath_index
+            # Node sets, strings, etc
+            elsif retval and !retval.empty?
               new_nodes << current
             end
           end
@@ -693,6 +693,34 @@ module Oga
         return nodes
       end
 
+      ##
+      # Processes the `local-name()` function call.
+      #
+      # This function call returns the name of one of the following:
+      #
+      # * The current context node (if any)
+      # * The first node in the supplied node set
+      #
+      # @param [Oga::XML::NodeSet] context
+      # @param [Oga::XPath::Node] expression
+      # @return [Oga::XML::NodeSet]
+      #
+      def on_call_local_name(context, expression = nil)
+        if expression
+          node = process(expression, context)
+
+          if node.is_a?(XML::NodeSet)
+            node = node.first
+          else
+            raise TypeError, 'local-name() only takes node sets as arguments'
+          end
+        else
+          node = current_node
+        end
+
+        return node.is_a?(XML::Element) ? node.name : ''
+      end
+
       ##
       # Processes an `(int)` node. This method simply returns the value as a
       # Float.

spec/oga/xpath/evaluator/calls/local_name_spec.rb

@@ -0,0 +1,46 @@
+require 'spec_helper'
+
+describe Oga::XPath::Evaluator do
+  context 'local-name() function' do
+    before do
+      @document  = parse('<root xmlns:x="y"><x:a></x:a><b></b></root>')
+      @evaluator = described_class.new(@document)
+    end
+
+    context 'outside predicates' do
+      example 'return the local name of the <x:a> node' do
+        @evaluator.evaluate('local-name(root/x:a)').should == 'a'
+      end
+
+      example 'return the local name of the <b> node' do
+        @evaluator.evaluate('local-name(root/b)').should == 'b'
+      end
+
+      example 'return only the name of the first node in the set' do
+        @evaluator.evaluate('local-name(root/*)').should == 'a'
+      end
+
+      example 'return an empty string by default' do
+        @evaluator.evaluate('local-name(foo)').should == ''
+      end
+
+      example 'raise a TypeError for invalid argument types' do
+        block = lambda { @evaluator.evaluate('local-name("foo")') }
+
+        block.should raise_error(TypeError)
+      end
+    end
+
+    context 'inside predicates' do
+      before do
+        @set = @evaluator.evaluate('root/b[local-name()]')
+      end
+
+      it_behaves_like :node_set, :length => 1
+
+      example 'return the <b> node' do
+        @set[0].should == @document.children[0].children[1]
+      end
+    end
+  end
+end