Mark inline difference between old and new paths when a file is renamed

3 files changed, 52 insertions, 36 deletions

diff --git a/lib/gitlab/diff/highlight.rb b/lib/gitlab/diff/highlight.rb
index a7f925ce134..9429b3ff88d 100644
--- a/lib/gitlab/diff/highlight.rb
+++ b/lib/gitlab/diff/highlight.rb
@@ -21,13 +21,13 @@ module Gitlab
           # ignore highlighting for "match" lines
           next diff_line if diff_line.type == 'match' || diff_line.type == 'nonewline'
 
-          rich_line = highlight_line(diff_line, i)
+          rich_line = highlight_line(diff_line) || diff_line.text
 
           if line_inline_diffs = inline_diffs[i]
             rich_line = InlineDiffMarker.new(diff_line.text, rich_line).mark(line_inline_diffs)
           end
 
-          diff_line.text = rich_line.html_safe
+          diff_line.text = rich_line
 
           diff_line
         end
@@ -35,8 +35,8 @@ module Gitlab
 
       private
 
-      def highlight_line(diff_line, index)
-        return html_escape(diff_line.text) unless diff_file && diff_file.diff_refs
+      def highlight_line(diff_line)
+        return unless diff_file && diff_file.diff_refs
 
         line_prefix = diff_line.text.match(/\A(.)/) ? $1 : ' '
 
@@ -49,11 +49,11 @@ module Gitlab
 
         # Only update text if line is found. This will prevent
         # issues with submodules given the line only exists in diff content.
-        rich_line ? line_prefix + rich_line : html_escape(diff_line.text)
+        "#{line_prefix}#{rich_line}".html_safe if rich_line
       end
 
       def inline_diffs
-        @inline_diffs ||= InlineDiff.new(@raw_lines).inline_diffs
+        @inline_diffs ||= InlineDiff.for_lines(@raw_lines)
       end
 
       def old_lines
@@ -72,11 +72,6 @@ module Gitlab
 
         [ref.project.repository, ref.id, path]
       end
-
-      def html_escape(str)
-        replacements = { '&' => '&amp;', '>' => '&gt;', '<' => '&lt;', '"' => '&quot;', "'" => '&#39;' }
-        str.gsub(/[&"'><]/, replacements)
-      end
     end
   end
 end
diff --git a/lib/gitlab/diff/inline_diff.rb b/lib/gitlab/diff/inline_diff.rb
index b8a61ad6115..789c14518b0 100644
--- a/lib/gitlab/diff/inline_diff.rb
+++ b/lib/gitlab/diff/inline_diff.rb
@@ -1,43 +1,58 @@
 module Gitlab
   module Diff
     class InlineDiff
-      attr_accessor :lines
+      attr_accessor :old_line, :new_line, :offset
 
-      def initialize(lines)
-        @lines = lines
-      end
+      def self.for_lines(lines)
+        local_edit_indexes = self.find_local_edits(lines)
 
-      def inline_diffs
         inline_diffs = []
 
         local_edit_indexes.each do |index|
           old_index = index
           new_index = index + 1
-          old_line = @lines[old_index]
-          new_line = @lines[new_index]
-
-          # Skip inline diff if empty line was replaced with content
-          next if old_line[1..-1] == ""
-
-          # Add one, because this is based on the prefixless version
-          lcp = longest_common_prefix(old_line[1..-1], new_line[1..-1]) + 1
-          lcs = longest_common_suffix(old_line[lcp..-1], new_line[lcp..-1])
+          old_line = lines[old_index]
+          new_line = lines[new_index]
 
-          old_diff_range = lcp..(old_line.length - lcs - 1)
-          new_diff_range = lcp..(new_line.length - lcs - 1)
+          old_diffs, new_diffs = new(old_line, new_line, offset: 1).inline_diffs
 
-          inline_diffs[old_index] = [old_diff_range] if old_diff_range.begin <= old_diff_range.end
-          inline_diffs[new_index] = [new_diff_range] if new_diff_range.begin <= new_diff_range.end
+          inline_diffs[old_index] = old_diffs
+          inline_diffs[new_index] = new_diffs
         end
 
         inline_diffs
       end
 
+      def initialize(old_line, new_line, offset: 0)
+        @old_line = old_line[offset..-1]
+        @new_line = new_line[offset..-1]
+        @offset = offset
+      end
+
+      def inline_diffs
+        # Skip inline diff if empty line was replaced with content
+        return if old_line == ""
+
+        lcp = longest_common_prefix(old_line, new_line)
+        lcs = longest_common_suffix(old_line[lcp..-1], new_line[lcp..-1])
+
+        lcp += offset
+        old_length = old_line.length + offset
+        new_length = new_line.length + offset
+
+        old_diff_range = lcp..(old_length - lcs - 1)
+        new_diff_range = lcp..(new_length - lcs - 1)
+
+        old_diffs = [old_diff_range] if old_diff_range.begin <= old_diff_range.end
+        new_diffs = [new_diff_range] if new_diff_range.begin <= new_diff_range.end
+
+        [old_diffs, new_diffs]
+      end
+
       private
 
-      # Find runs of single line edits
-      def local_edit_indexes
-        line_prefixes = @lines.map { |line| line.match(/\A([+-])/) ? $1 : ' ' }
+      def self.find_local_edits(lines)
+        line_prefixes = lines.map { |line| line.match(/\A([+-])/) ? $1 : ' ' }
         joined_line_prefixes = " #{line_prefixes.join} "
 
         offset = 0
diff --git a/lib/gitlab/diff/inline_diff_marker.rb b/lib/gitlab/diff/inline_diff_marker.rb
index 1d7fa1bce06..dccb717e95d 100644
--- a/lib/gitlab/diff/inline_diff_marker.rb
+++ b/lib/gitlab/diff/inline_diff_marker.rb
@@ -5,10 +5,12 @@ module Gitlab
 
       def initialize(raw_line, rich_line = raw_line)
         @raw_line = raw_line
-        @rich_line = rich_line
+        @rich_line = ERB::Util.html_escape(rich_line)
       end
 
       def mark(line_inline_diffs)
+        return rich_line unless line_inline_diffs
+
         marker_ranges = []
         line_inline_diffs.each do |inline_diff_range|
           # Map the inline-diff range based on the raw line to character positions in the rich line
@@ -19,11 +21,15 @@ module Gitlab
 
         offset = 0
         # Mark each range
-        marker_ranges.each do |range|
-          offset = insert_around_range(rich_line, range, "<span class='idiff'>", "</span>", offset)
+        marker_ranges.each_with_index do |range, i|
+          class_names = ["idiff"]
+          class_names << "left"   if i == 0
+          class_names << "right"  if i == marker_ranges.length - 1
+
+          offset = insert_around_range(rich_line, range, "<span class='#{class_names.join(" ")}'>", "</span>", offset)
         end
 
-        rich_line
+        rich_line.html_safe
       end
 
       private