Show un-highlighted diffs when blobs are the same

For some old merge requests, we don't have enough information to figure out the
old blob and the new blob for the file. This means that we can't highlight the
diff correctly, but we can still display it without highlighting.

1 files changed, 40 insertions, 4 deletions

diff --git a/spec/lib/gitlab/diff/file_spec.rb b/spec/lib/gitlab/diff/file_spec.rb
index ab60d62d88e..c91895cedc3 100644
--- a/spec/lib/gitlab/diff/file_spec.rb
+++ b/spec/lib/gitlab/diff/file_spec.rb
@@ -15,6 +15,17 @@ describe Gitlab::Diff::File do
     it { expect(diff_lines.first).to be_kind_of(Gitlab::Diff::Line) }
   end
 
+  describe '#highlighted_diff_lines' do
+    it 'highlights the diff and memoises the result' do
+      expect(Gitlab::Diff::Highlight).to receive(:new)
+                                           .with(diff_file, repository: project.repository)
+                                           .once
+                                           .and_call_original
+
+      diff_file.highlighted_diff_lines
+    end
+  end
+
   describe '#mode_changed?' do
     it { expect(diff_file.mode_changed?).to be_falsey }
   end
@@ -122,8 +133,20 @@ describe Gitlab::Diff::File do
         let(:commit) { project.commit('2f63565e7aac07bcdadb654e253078b727143ec4') }
         let(:diff_file) { commit.diffs.diff_file_with_new_path('files/images/6049019_460s.jpg') }
 
-        it 'returns true' do
-          expect(diff_file.content_changed?).to be_truthy
+        context 'when the blobs are different' do
+          it 'returns true' do
+            expect(diff_file.content_changed?).to be_truthy
+          end
+        end
+
+        context 'when there are no diff refs' do
+          before do
+            allow(diff_file).to receive(:diff_refs).and_return(nil)
+          end
+
+          it 'returns false' do
+            expect(diff_file.content_changed?).to be_falsey
+          end
         end
       end
 
@@ -131,8 +154,20 @@ describe Gitlab::Diff::File do
         let(:commit) { project.commit('570e7b2abdd848b95f2f578043fc23bd6f6fd24d') }
         let(:diff_file) { commit.diffs.diff_file_with_new_path('files/ruby/popen.rb') }
 
-        it 'returns true' do
-          expect(diff_file.content_changed?).to be_truthy
+        context 'when the blobs are different' do
+          it 'returns true' do
+            expect(diff_file.content_changed?).to be_truthy
+          end
+        end
+
+        context 'when there are no diff refs' do
+          before do
+            allow(diff_file).to receive(:diff_refs).and_return(nil)
+          end
+
+          it 'returns true' do
+            expect(diff_file.content_changed?).to be_truthy
+          end
         end
       end
     end
@@ -278,6 +313,7 @@ describe Gitlab::Diff::File do
         allow(diff_file).to receive(:deleted_file?).and_return(false)
         allow(diff_file).to receive(:renamed_file?).and_return(false)
         allow(diff_file).to receive(:mode_changed?).and_return(false)
+        allow(diff_file).to receive(:raw_text?).and_return(false)
       end
 
       it 'returns a No Preview viewer' do