1 files changed, 43 insertions, 0 deletions
diff --git a/app/services/merge_requests/reload_diffs_service.rb b/app/services/merge_requests/reload_diffs_service.rb
new file mode 100644
index 00000000000..2ec7b403903
--- /dev/null
+++ b/app/services/merge_requests/reload_diffs_service.rb
@@ -0,0 +1,43 @@
+module MergeRequests
+  class ReloadDiffsService
+    def initialize(merge_request, current_user)
+      @merge_request = merge_request
+      @current_user = current_user
+    end
+
+    def execute
+      old_diff_refs = merge_request.diff_refs
+      new_diff = merge_request.create_merge_request_diff
+
+      clear_cache(new_diff)
+      update_diff_discussion_positions(old_diff_refs)
+    end
+
+    private
+
+    attr_reader :merge_request, :current_user
+
+    def update_diff_discussion_positions(old_diff_refs)
+      new_diff_refs = merge_request.diff_refs
+
+      merge_request.update_diff_discussion_positions(old_diff_refs: old_diff_refs,
+                                                     new_diff_refs: new_diff_refs,
+                                                     current_user: current_user)
+    end
+
+    def clear_cache(new_diff)
+      # Executing the iteration we cache highlighted diffs for each diff file of
+      # MergeRequestDiff.
+      new_diff.diffs_collection.diff_files.to_a
+
+      # Remove cache for all diffs on this MR. Do not use the association on the
+      # model, as that will interfere with other actions happening when
+      # reloading the diff.
+      MergeRequestDiff.where(merge_request: merge_request).each do |merge_request_diff|
+        next if merge_request_diff == new_diff
+
+        merge_request_diff.diffs_collection.clear_cache!
+      end
+    end
+  end
+end