Expanded supported input for Conversion.to_float

This extends XPath::Conversion.to_float so it can also convert NodeSet
and Node instances.

lib/oga/xpath/conversion.rb

@@ -43,8 +43,7 @@ module Oga
         end
 
         if value.is_a?(XML::NodeSet)
-          first = value.first
+          value = first_node_text(value)
-          value = first.respond_to?(:text) ? first.text : ''
         end
 
         if value.respond_to?(:text)
@@ -56,7 +55,19 @@ module Oga
 
       # @return [Float]
       def self.to_float(value)
-        Float(value) rescue Float::NAN
+        if value.is_a?(XML::NodeSet)
+          value = first_node_text(value)
+        end
+
+        if value.respond_to?(:text)
+          value = value.text
+        end
+
+        if value.is_a?(String)
+          value = Float(value) rescue Float::NAN
+        end
+
+        value
       end
 
       # @return [TrueClass|FalseClass]
@@ -78,6 +89,12 @@ module Oga
       def self.boolean?(value)
         value.is_a?(TrueClass) || value.is_a?(FalseClass)
       end
+
+      # @param [Oga::XML::NodeSet] set
+      # @return [String]
+      def self.first_node_text(set)
+        set[0].respond_to?(:text) ? set[0].text : ''
+      end
     end # Conversion
   end # XPath
 end # Oga

spec/oga/xpath/conversion_spec.rb

@@ -125,6 +125,13 @@ describe Oga::XPath::Conversion do
   end
 
   describe 'to_float' do
+    describe 'using a Float' do
+      it 'returns the input Float' do
+        described_class.to_float(10.5).should == 10.5
+      end
+    end
+
+    describe 'using a String' do
       it 'returns a Float for a valid value' do
         described_class.to_float('10.5').should == 10.5
       end
@@ -134,6 +141,23 @@ describe Oga::XPath::Conversion do
       end
     end
 
+    describe 'using a NodeSet' do
+      it 'returns a Float using the text of the first node' do
+        set = node_set(Oga::XML::Text.new(:text => '10.5'))
+
+        described_class.to_float(set).should == 10.5
+      end
+    end
+
+    describe 'using an Node' do
+      it 'returns a Float using the text of the node' do
+        node = Oga::XML::Text.new(:text => '10.5')
+
+        described_class.to_float(node).should == 10.5
+      end
+    end
+  end
+
   describe 'to_boolean' do
     it 'returns true for a non-empty String' do
       described_class.to_boolean('foo').should == true