Change diff highlight/truncate for reusability

Previously the `truncated_diff_lines` method for outputting a discussion diff took in already highlighted lines, which meant it wasn't reuseable for truncating ANY lines. In the way it was used, it also meant that for any email truncation, the whole diff was being highlighted before being truncated, meaning wasted time highlighting lines that wouldn't even be used (granted, they were being memoized, so perhaps this wasn't that great of an issue). I refactored truncation away from highlighting, in order to truncate formatted diffs for text templates in email, using `>`s to designate each line, but otherwise retaining the parsing already done to create `diff_lines`.

Additionally, while notes on merge requests or commits had already been tested, there was no existing test for notes on a diff on an MR or commit. Added mailer tests for such, and a unit test for truncating diff lines.

1 files changed, 7 insertions, 5 deletions

diff --git a/app/models/discussion.rb b/app/models/discussion.rb
index de06c13481a..486bfd2c766 100644
--- a/app/models/discussion.rb
+++ b/app/models/discussion.rb
@@ -25,7 +25,12 @@ class Discussion
             to: :last_resolved_note,
             allow_nil: true
 
-  delegate :blob, :highlighted_diff_lines, to: :diff_file, allow_nil: true
+  delegate  :blob,
+            :highlighted_diff_lines,
+            :text_parsed_diff_lines,
+
+            to: :diff_file,
+            allow_nil: true
 
   def self.for_notes(notes)
     notes.group_by(&:discussion_id).values.map { |notes| new(notes) }
@@ -162,18 +167,15 @@ class Discussion
   def truncated_diff_lines
     prev_lines = []
 
-    highlighted_diff_lines.each do |line|
+    diff_file.diff_lines.each do |line|
       if line.meta?
         prev_lines.clear
       else
         prev_lines << line
-
         break if for_line?(line)
-
         prev_lines.shift if prev_lines.length >= NUMBER_OF_TRUNCATED_DIFF_LINES
       end
     end
-
     prev_lines
   end