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.

11 files changed, 139 insertions, 22 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
 
diff --git a/app/views/discussions/_diff_with_notes.html.haml b/app/views/discussions/_diff_with_notes.html.haml
index 3a95a652810..06493ba0105 100644
--- a/app/views/discussions/_diff_with_notes.html.haml
+++ b/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,
diff --git a/app/views/notify/_note_mr_or_commit_email.html.haml b/app/views/notify/_note_mr_or_commit_email.html.haml
index 3e2046aa9cf..7033842b557 100644
--- a/app/views/notify/_note_mr_or_commit_email.html.haml
+++ b/app/views/notify/_note_mr_or_commit_email.html.haml
@@ -1,15 +1,16 @@
 = 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 }
 
diff --git a/app/views/notify/_simple_diff.text.erb b/app/views/notify/_simple_diff.text.erb
new file mode 100644
index 00000000000..a5a796bc168
--- /dev/null
+++ b/app/views/notify/_simple_diff.text.erb
@@ -0,0 +1,4 @@
+<% lines = @discussion.truncated_diff_lines %>
+<% @discussion.text_parsed_diff_lines(lines).each do |line| %>
+  <%= line %>
+<% end %>
diff --git a/app/views/notify/note_commit_email.html.haml b/app/views/notify/note_commit_email.html.haml
index f4293a3aa50..17dcf36689f 100644
--- a/app/views/notify/note_commit_email.html.haml
+++ b/app/views/notify/note_commit_email.html.haml
@@ -1,7 +1,5 @@
 %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'
diff --git a/app/views/notify/note_commit_email.text.erb b/app/views/notify/note_commit_email.text.erb
index a1ef9858021..715e58af61c 100644
--- a/app/views/notify/note_commit_email.text.erb
+++ b/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 %>
diff --git a/app/views/notify/note_merge_request_email.html.haml b/app/views/notify/note_merge_request_email.html.haml
index 75250b0383d..b7758f191dc 100644
--- a/app/views/notify/note_merge_request_email.html.haml
+++ b/app/views/notify/note_merge_request_email.html.haml
@@ -1,7 +1,5 @@
 %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'
diff --git a/app/views/notify/note_merge_request_email.text.erb b/app/views/notify/note_merge_request_email.text.erb
index 42d29b34ebc..d24e15af91f 100644
--- a/app/views/notify/note_merge_request_email.text.erb
+++ b/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 %>
diff --git a/lib/gitlab/diff/file.rb b/lib/gitlab/diff/file.rb
index c6bf25b5874..9b60102947a 100644
--- a/lib/gitlab/diff/file.rb
+++ b/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
diff --git a/spec/mailers/notify_spec.rb b/spec/mailers/notify_spec.rb
index 932a5dc4862..a80eb114c17 100644
--- a/spec/mailers/notify_spec.rb
+++ b/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
diff --git a/spec/models/discussion_spec.rb b/spec/models/discussion_spec.rb
index 0142706d140..d4b1f480c56 100644
--- a/spec/models/discussion_spec.rb
+++ b/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