New implementation for highlighting diff files. #3945

* It is more performant given now we process all the diff file instead
  of processing line by line.
* Multiline comments are highlighted correctly.

3 files changed, 60 insertions, 0 deletions

diff --git a/lib/gitlab/diff/file.rb b/lib/gitlab/diff/file.rb
index 79061cd0141..ff8765b8e26 100644
--- a/lib/gitlab/diff/file.rb
+++ b/lib/gitlab/diff/file.rb
@@ -15,6 +15,10 @@ module Gitlab
         @lines ||= parser.parse(raw_diff.lines)
       end
 
+      def highlighted_diff_lines
+        Gitlab::Diff::Highlight.process_diff_lines(self)
+      end
+
       def mode_changed?
         !!(diff.a_mode && diff.b_mode && diff.a_mode != diff.b_mode)
       end
diff --git a/lib/gitlab/diff/highlight.rb b/lib/gitlab/diff/highlight.rb
new file mode 100644
index 00000000000..f10b55eb00b
--- /dev/null
+++ b/lib/gitlab/diff/highlight.rb
@@ -0,0 +1,55 @@
+module Gitlab
+  module Diff
+    class Highlight
+      def self.process_diff_lines(diff_file)
+        processor = new(diff_file)
+        processor.highlight
+      end
+
+      def initialize(diff_file)
+        text_lines          = diff_file.diff_lines.map(&:text)
+        @diff_file          = diff_file
+        @diff_lines         = diff_file.diff_lines
+        @diff_line_prefixes = text_lines.map { |line| line.sub!(/\A((\+|\-)\s*)/, '');$1 }
+        @raw_lines          = text_lines.join("\n")
+      end
+
+      def highlight
+        @code = unescape_html(@raw_lines)
+        @highlighted_code = formatter.format(lexer.lex(@code))
+
+        update_diff_lines
+      end
+
+      private
+
+      def update_diff_lines
+        @highlighted_code.lines.each_with_index do |line, i|
+          @diff_lines[i].highlighted_text = "#{@diff_line_prefixes[i]}#{line}"
+        end
+
+        @diff_lines
+      end
+
+      def lexer
+        parent = Rouge::Lexer.guess(filename: @diff_file.new_path, source: @code).new rescue Rouge::Lexers::PlainText.new
+        Rouge::Lexers::GitlabDiff.new(parent_lexer: parent)
+      end
+
+      def unescape_html(content)
+        text = CGI.unescapeHTML(content)
+        text.gsub!(' ', ' ')
+        text
+      end
+
+      def formatter
+        @formatter ||= Rouge::Formatters::HTMLGitlab.new(
+                         nowrap: true,
+                         cssclass: 'code highlight',
+                         lineanchors: true,
+                         lineanchorsid: 'LC'
+                       )
+      end
+    end
+  end
+end
diff --git a/lib/gitlab/diff/line.rb b/lib/gitlab/diff/line.rb
index 0072194606e..c48c69fb344 100644
--- a/lib/gitlab/diff/line.rb
+++ b/lib/gitlab/diff/line.rb
@@ -2,6 +2,7 @@ module Gitlab
   module Diff
     class Line
       attr_reader :type, :text, :index, :old_pos, :new_pos
+      attr_accessor :highlighted_text
 
       def initialize(text, type, index, old_pos, new_pos)
         @text, @type, @index = text, type, index