Reload MRs memoization after diffs creation

app/services/merge_requests/refresh_service.rb

@@ -90,6 +90,10 @@ module MergeRequests
         merge_request.mark_as_unchecked
         UpdateHeadPipelineForMergeRequestWorker.perform_async(merge_request.id)
       end
+
+      # Upcoming method calls need the refreshed version of
+      # @source_merge_requests diffs (for MergeRequest#commit_shas for instance).
+      merge_requests_for_source_branch(reload: true)
     end
 
     def reset_merge_when_pipeline_succeeds
@@ -195,7 +199,8 @@ module MergeRequests
       merge_requests.uniq.select(&:source_project)
     end
 
-    def merge_requests_for_source_branch
+    def merge_requests_for_source_branch(reload: false)
+      @source_merge_requests = nil if reload
       @source_merge_requests ||= merge_requests_for(@branch_name)
     end
 

changelogs/unreleased/osw-system-notes-for-commits-regression.yml

+---
+title: Reload MRs memoization after diffs creation
+merge_request:
+author:
+type: fixed

spec/services/merge_requests/refresh_service_spec.rb

@@ -74,6 +74,14 @@ describe MergeRequests::RefreshService do
         expect(@fork_build_failed_todo).to be_done
       end
 
+      it 'reloads source branch MRs memoization' do
+        refresh_service.execute(@oldrev, @newrev, 'refs/heads/master')
+
+        expect { refresh_service.execute(@oldrev, @newrev, 'refs/heads/master') }.to change {
+          refresh_service.instance_variable_get("@source_merge_requests").first.merge_request_diff
+        }
+      end
+
       context 'when source branch ref does not exists' do
         before do
           DeleteBranchService.new(@project, @user).execute(@merge_request.source_branch)