Only parse XSLT files once

lib/dor/datastreams/default_object_rights_ds.rb

@@ -1,5 +1,9 @@
 module Dor
   class DefaultObjectRightsDS < ActiveFedora::OmDatastream
+    # Note that the XSL file was taken from the (apparently defunct) nokogiri-pretty project:
+    # https://github.com/tobym/nokogiri-pretty/blob/master/lib/indent.xsl
+    # The only modification made was to declare UTF-8 to be the encoding, instead of ISO-8859-1.
+    HUMAN_XSLT = Nokogiri::XSLT(File.read(File.expand_path('../human.xslt', __FILE__)))
 
     set_terminology do |t|
       t.root :path => 'rightsMetadata', :index_as => [:not_searchable]
@@ -131,12 +135,8 @@ def normalize!
     end
 
     # Returns a nicely indented XML document.
-    # Note that the XSL file was taken from the (apparently defunct) nokogiri-pretty project:
-    # https://github.com/tobym/nokogiri-pretty/blob/master/lib/indent.xsl
-    # The only modification made was to declare UTF-8 to be the encoding, instead of ISO-8859-1.
     def prettify(xml_doc)
-      template = Nokogiri::XSLT(File.read(File.expand_path('../human.xslt', __FILE__)))
-      template.apply_to(xml_doc)
+      HUMAN_XSLT.apply_to(xml_doc)
     end
 
     # maintain AF < 8 indexing behavior

lib/dor/utils/ng_tidy.rb

@@ -20,8 +20,7 @@ def normalize_text!
 
 class Nokogiri::XML::Document
 
-  def prettify
-    xslt = Nokogiri::XSLT <<-EOC
+  PRETTIFY_XSLT = Nokogiri::XSLT <<-EOC
     <xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
       <xsl:output omit-xml-declaration="yes" indent="yes"/>
       <xsl:template match="node()|@*">
@@ -31,7 +30,9 @@ def prettify
       </xsl:template>
     </xsl:stylesheet>
     EOC
-    xslt.transform(self).to_xml
+
+  def prettify
+    PRETTIFY_XSLT.transform(self).to_xml
   end
 
 end