Intelligent diff highlighting

Index: lib/coderay/encoders/html.rb
===================================================================
--- lib/coderay/encoders/html.rb  (revision 200)
+++ lib/coderay/encoders/html.rb  (revision 250)
@@ -1,3 +1,5 @@
+require "set"
+
 module CodeRay
 module Encoders
 
@@ -10,7 +12,8 @@
   #
   #  require 'coderay'
   #  puts CodeRay.scan('Some /code/', :ruby).html  #-> a HTML page
-  #  puts CodeRay.scan('Some /code/', :ruby).html(:wrap => :span) #-> <span class="CodeRay"><span class="co">Some</span> /code/</span>
+  #  puts CodeRay.scan('Some /code/', :ruby).html(:wrap => :span)
+  #  #-> <span class="CodeRay"><span class="co">Some</span> /code/</span>
   #  puts CodeRay.scan('Some /code/', :ruby).span  #-> the same
   #  
   #  puts CodeRay.scan('Some code', :ruby).html(
@@ -55,7 +58,8 @@
   #
   # === :hint
   # Include some information into the output using the title attribute.
-  # Can be :info (show token type on mouse-over), :info_long (with full path) or :debug (via inspect).
+  # Can be :info (show token type on mouse-over), :info_long (with full path)
+  # or :debug (via inspect).
   #
   # Default: false
   class HTML < Encoder
@@ -82,7 +86,7 @@
       :hint => false,
     }
 
-    helper :classes, :output, :css
+    helper :output, :css
 
     attr_reader :css
 
@@ -115,11 +119,14 @@
         end
     }
 
+    TRANSPARENT_TOKEN_KINDS = [
+      :delimiter, :modifier, :content, :escape, :inline_delimiter,
+    ].to_set
+
     # Generate a hint about the given +classes+ in a +hint+ style.
     #
     # +hint+ may be :info, :info_long or :debug.
     def self.token_path_to_hint hint, classes
-      return '' unless hint
       title =
         case hint
         when :info
@@ -129,7 +136,7 @@
         when :debug
           classes.inspect
         end
-      " title=\"#{title}\""
+      title ? " title=\"#{title}\"" : ''
     end
 
     def setup options
@@ -143,42 +150,45 @@
 
       hint = options[:hint]
       if hint and not [:debug, :info, :info_long].include? hint
-        raise ArgumentError, "Unknown value %p for :hint; expected :info, :debug, false or nil." % hint
+        raise ArgumentError, "Unknown value %p for :hint; \
+          expected :info, :debug, false, or nil." % hint
       end
 
       case options[:css]
 
       when :class
         @css_style = Hash.new do |h, k|
-          if k.is_a? Array
-            type = k.first
-          else
-            type = k
-          end
-          c = ClassOfKind[type]
+          c = CodeRay::Tokens::ClassOfKind[k.first]
           if c == :NO_HIGHLIGHT and not hint
-            h[k] = false
+            h[k.dup] = false
           else
-            title = HTML.token_path_to_hint hint, (k[1..-1] << k.first)
-            h[k] = '<span%s class="%s">' % [title, c]
+            title = if hint
+              HTML.token_path_to_hint(hint, k[1..-1] << k.first)
+            else
+              ''
+            end
+            if c == :NO_HIGHLIGHT
+              h[k.dup] = '<span%s>' % [title]
+            else
+              h[k.dup] = '<span%s class="%s">' % [title, c]
+            end
           end
         end
 
       when :style
         @css_style = Hash.new do |h, k|
-          if k.is_a? Array
+          if k.is_a? ::Array
             styles = k.dup
           else
             styles = [k]
           end
           type = styles.first
-          classes = styles.map { |c| ClassOfKind[c] }
+          classes = styles.map { |c| Tokens::ClassOfKind[c] }
           if classes.first == :NO_HIGHLIGHT and not hint
             h[k] = false
           else
-            styles.shift if [:delimiter, :modifier, :content, :escape].include? styles.first
+            styles.shift if TRANSPARENT_TOKEN_KINDS.include? styles.first
             title = HTML.token_path_to_hint hint, styles
-            classes.delete 'il'
             style = @css[*classes]
             h[k] =
               if style
@@ -198,7 +208,9 @@
     def finish options
       not_needed = @opened.shift
       @out << '</span>' * @opened.size
-      warn '%d tokens still open: %p' % [@opened.size, @opened] unless @opened.empty?
+      unless @opened.empty?
+        warn '%d tokens still open: %p' % [@opened.size, @opened]
+      end
 
       @out.extend Output
       @out.css = @css
@@ -229,8 +241,9 @@
           if @opened.empty?
             # nothing to close
           else
-            if @opened.size == 1 or @opened.last != type
-              raise 'Malformed token stream: Trying to close a token (%p) that is not open. Open are: %p.' % [type, @opened[1..-1]] if $DEBUG
+            if $DEBUG and (@opened.size == 1 or @opened.last != type)
+              raise 'Malformed token stream: Trying to close a token (%p) \
+                that is not open. Open are: %p.' % [type, @opened[1..-1]]
             end
             @out << '</span>'
             @opened.pop