Fix notify_conflict? raising exception when branches do not exist

repository.can_be_merged? can raise error if diff_head_sha or
target_branch are absent, therefore check those explicitly.

1 files changed, 16 insertions, 0 deletions

diff --git a/spec/models/merge_request_spec.rb b/spec/models/merge_request_spec.rb
index ec72fefd137..8c6b411ec9a 100644
--- a/spec/models/merge_request_spec.rb
+++ b/spec/models/merge_request_spec.rb
@@ -2190,6 +2190,22 @@ describe MergeRequest do
           end
         end
       end
+
+      context 'source branch is missing' do
+        subject { create(:merge_request, :invalid, :opened, merge_status: :unchecked, target_branch: 'master') }
+
+        before do
+          allow(subject.project.repository).to receive(:can_be_merged?).and_call_original
+        end
+
+        it 'does not raise error' do
+          expect(notification_service).not_to receive(:merge_request_unmergeable)
+          expect(todo_service).not_to receive(:merge_request_became_unmergeable)
+
+          expect { subject.mark_as_unmergeable }.not_to raise_error
+          expect(subject.cannot_be_merged?).to eq(true)
+        end
+      end
     end
 
     describe 'check_state?' do