Use persisted diff data instead fetching Git on discussions

Today, when fetching diffs of a note, we always go to Gitaly in order to diff between commits and return the diff of each discussion note. With this change we avoid doing that for notes on the "current version" of the MR.

1 files changed, 28 insertions, 5 deletions

diff --git a/spec/models/diff_note_spec.rb b/spec/models/diff_note_spec.rb
index 2705421e540..fb51c0172ab 100644
--- a/spec/models/diff_note_spec.rb
+++ b/spec/models/diff_note_spec.rb
@@ -85,12 +85,35 @@ describe DiffNote do
   end
 
   describe "#diff_file" do
-    it "returns the correct diff file" do
-      diff_file = subject.diff_file
+    context 'when the discussion was created in the diff' do
+      it 'returns correct diff file' do
+        diff_file = subject.diff_file
 
-      expect(diff_file.old_path).to eq(position.old_path)
-      expect(diff_file.new_path).to eq(position.new_path)
-      expect(diff_file.diff_refs).to eq(position.diff_refs)
+        expect(diff_file.old_path).to eq(position.old_path)
+        expect(diff_file.new_path).to eq(position.new_path)
+        expect(diff_file.diff_refs).to eq(position.diff_refs)
+      end
+    end
+
+    context 'when discussion is outdated or not created in the diff' do
+      let(:diff_refs) { project.commit(sample_commit.id).diff_refs }
+      let(:position) do
+        Gitlab::Diff::Position.new(
+          old_path: "files/ruby/popen.rb",
+          new_path: "files/ruby/popen.rb",
+          old_line: nil,
+          new_line: 14,
+          diff_refs: diff_refs
+        )
+      end
+
+      it 'returns the correct diff file' do
+        diff_file = subject.diff_file
+
+        expect(diff_file.old_path).to eq(position.old_path)
+        expect(diff_file.new_path).to eq(position.new_path)
+        expect(diff_file.diff_refs).to eq(position.diff_refs)
+      end
     end
   end