private void fileDeleted(@NotNull VFileDeleteEvent e) {
    VirtualFile f = e.getFile();
    if (!shouldProcess(e, f)) return;

    DocumentReference ref = f.getUserData(DELETION_WAS_UNDOABLE);
    if (ref != null) {
      registerUndoableAction(ref);
      f.putUserData(DELETION_WAS_UNDOABLE, null);
    }
  }
private void fileDeleted(@NotNull VFileDeleteEvent e)