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.

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

app/views/discussions/_diff_with_notes.html.haml

@@ -9,7 +9,7 @@
     %table
       - discussions = { discussion.original_line_code => discussion }
       = render partial: "projects/diffs/line",
-        collection: discussion.truncated_diff_lines,
+        collection: discussion.highlighted_diff_lines(discussion.truncated_diff_lines),
         as: :line,
         locals: { diff_file: diff_file,
           discussions: discussions,

app/views/notify/_note_mr_or_commit_email.html.haml

 = content_for :head do
   = stylesheet_link_tag 'mailers/highlighted_diff_email'
-- if note.diff_note? && note.diff_file
-  = link_to note.diff_file.file_path, @target_url, class: 'details'
+- if @note.diff_note? && @note.diff_file
+  on
+  = link_to @note.diff_file.file_path, @target_url, class: 'details'
   \:
   %table
     = render partial: "projects/diffs/line",
-      collection: discussion.truncated_diff_lines,
+      collection: @discussion.highlighted_diff_lines(@discussion.truncated_diff_lines),
       as: :line,
-      locals: { diff_file: note.diff_file,
+      locals: { diff_file: @note.diff_file,
       plain: true,
       email: true }

app/views/notify/_simple_diff.text.erb

+<% lines = @discussion.truncated_diff_lines %>
+<% @discussion.text_parsed_diff_lines(lines).each do |line| %>
+  <%= line %>
+<% end %>

app/views/notify/note_commit_email.html.haml

 %p.details
   New comment for Commit
   = @commit.short_id
-  on
-  = render partial: 'note_mr_or_commit_email',
-    locals: { note: @note,
-    discussion: @discussion}
+
+  = render 'note_mr_or_commit_email'

app/views/notify/note_commit_email.text.erb

@@ -2,6 +2,8 @@ New comment for Commit <%= @commit.short_id %>
 <%= url_for(namespace_project_commit_url(@note.project.namespace, @note.project, id: @commit.id, anchor: "note_#{@note.id}")) %>
+<%= render 'simple_diff' if @discussion %>
+
 <% if current_application_settings.email_author_in_body %>
   <%= @note.author_name %> wrote:
 <% end %>

app/views/notify/note_merge_request_email.html.haml

 %p.details
   New comment for Merge Request
   = @merge_request.to_reference
-  on
-  = render partial: 'note_mr_or_commit_email',
-    locals: { note: @note,
-    discussion: @discussion}
+
+  = render 'note_mr_or_commit_email'

app/views/notify/note_merge_request_email.text.erb

@@ -2,6 +2,8 @@ New comment for Merge Request <%= @merge_request.to_reference %>
 <%= url_for(namespace_project_merge_request_url(@merge_request.target_project.namespace, @merge_request.target_project, @merge_request, anchor: "note_#{@note.id}")) %>
+<%= render 'simple_diff' if @discussion %>
+
 <% if current_application_settings.email_author_in_body %>
   <%= @note.author_name %> wrote:
 <% end %>

lib/gitlab/diff/file.rb

@@ -69,15 +69,22 @@ module Gitlab
         diff_refs.try(:head_sha)
       end
-      attr_writer :highlighted_diff_lines
+      attr_writer :highlighted_diff_lines, :text_parsed_diff_lines
       # Array of Gitlab::Diff::Line objects
       def diff_lines
         @diff_lines ||= Gitlab::Diff::Parser.new.parse(raw_diff.each_line).to_a
       end
-      def highlighted_diff_lines
-        @highlighted_diff_lines ||= Gitlab::Diff::Highlight.new(self, repository: self.repository).highlight
+      def highlighted_diff_lines(lines = self)
+        @highlighted_diff_lines ||= Gitlab::Diff::Highlight.new(lines, repository: self.repository).highlight
+      end
+
+      def text_parsed_diff_lines(lines)
+        @text_parsed_diff_lines ||=
+        lines.map do | line |
+          "> " + line.text
+        end
       end
       # Array[<Hash>] with right/left keys that contains Gitlab::Diff::Line objects which text is hightlighted

spec/mailers/notify_spec.rb

@@ -646,7 +646,6 @@ describe Notify do
         before(:each) { allow(note).to receive(:noteable).and_return(merge_request) }
         subject { Notify.note_merge_request_email(recipient.id, note.id) }
-
         it_behaves_like 'a note email'
         it_behaves_like 'an answer to an existing thread with reply-by-email enabled' do
           let(:model) { merge_request }
@@ -686,6 +685,85 @@ describe Notify do
         end
       end
     end
+
+    context 'items that are noteable, emails for a note on a diff' do
+      let(:note_author) { create(:user, name: 'author_name') }
+
+      before :each do
+        allow(Note).to receive(:find).with(note.id).and_return(note)
+      end
+
+      shared_examples 'a note email on a diff' do  | model |
+        let(:note) { create(model, project: project, author: note_author) }
+
+        it "includes diffs with character-level highlighting" do
+          is_expected.to have_body_text /\<span class='idiff left right'>vars = {<\/span>/
+        end
+
+        it 'contains a link to the diff file' do
+          is_expected.to have_body_text /#{note.diff_file.file_path}/
+        end
+
+        it_behaves_like 'it should have Gmail Actions links'
+
+        it 'is sent as the author' do
+          sender = subject.header[:from].addrs[0]
+          expect(sender.display_name).to eq(note_author.name)
+          expect(sender.address).to eq(gitlab_sender)
+        end
+
+        it 'is sent to the given recipient' do
+          is_expected.to deliver_to recipient.notification_email
+        end
+
+        it 'contains the message from the note' do
+          is_expected.to have_body_text /#{note.note}/
+        end
+
+        it 'does not contain note author' do
+          is_expected.not_to have_body_text /wrote\:/
+        end
+
+        context 'when enabled email_author_in_body' do
+          before do
+            allow_any_instance_of(ApplicationSetting).to receive(:email_author_in_body).and_return(true)
+          end
+
+          it 'contains a link to note author' do
+            is_expected.to have_body_text note.author_name
+            is_expected.to have_body_text /wrote\:/
+          end
+        end
+      end
+
+      describe 'on a commit' do
+        let(:commit) { project.commit }
+        let(:note) { create(:diff_note_on_commit) }
+
+        subject { Notify.note_commit_email(recipient.id, note.id) }
+
+        it_behaves_like 'a note email on a diff', :diff_note_on_commit
+        # it_behaves_like 'an answer to an existing thread with reply-by-email enabled' do
+        #   let(:model) { commit }
+        # end
+        it_behaves_like 'it should show Gmail Actions View Commit link'
+        it_behaves_like 'a user cannot unsubscribe through footer link'
+      end
+
+      describe 'on a merge request' do
+        let(:merge_request) { create(:merge_request, source_project: project, target_project: project) }
+        let(:note) { create(:diff_note_on_merge_request) }
+
+        subject { Notify.note_merge_request_email(recipient.id, note.id) }
+
+        it_behaves_like 'a note email on a diff', :diff_note_on_merge_request
+        # it_behaves_like 'an answer to an existing thread with reply-by-email enabled' do
+        #   let(:model) { merge_request }
+        # end
+        it_behaves_like 'it should show Gmail Actions View Merge request link'
+        it_behaves_like 'an unsubscribeable thread'
+      end
+    end
   end
   context 'for a group' do

spec/models/discussion_spec.rb

@@ -590,4 +590,29 @@ describe Discussion, model: true do
       end
     end
   end
+
+  describe "#truncated_diff_lines" do
+    let(:truncated_lines) { subject.truncated_diff_lines }
+
+    context "when diff is greater than allowed number of truncated diff lines " do
+      let(:initial_line_count) { subject.diff_file.diff_lines.count }
+      let(:truncated_line_count) { truncated_lines.count }
+
+      it "returns fewer lines"  do
+        expect(initial_line_count).to be > described_class::NUMBER_OF_TRUNCATED_DIFF_LINES
+
+        expect(truncated_line_count).to be <= described_class::NUMBER_OF_TRUNCATED_DIFF_LINES
+      end
+    end
+
+    context "when some diff lines are meta" do
+      let(:initial_meta_lines?) { subject.diff_file.diff_lines.any?(&:meta?) }
+      let(:truncated_meta_lines?) { truncated_lines.any?(&:meta?) }
+
+      it "returns no meta lines"  do
+        expect(initial_meta_lines?).to be true
+        expect(truncated_meta_lines?).to be false
+      end
+    end
+  end
 end