anchor.diff:      if (_filterString == null) {
         _filteredFiles = null;
         _filteredChildrenCache = null;
  -      _reloadData();
  +      _reloadDataAndRestoreExpandedState(_currentExpandedState);
       } else {
         Set<String> filtered = new Set();
         _filteredFiles = [];
  
positive.code:   }
  
    void treeViewSaveExpandedState(TreeView view) {
      localPrefs.setValue('FilesExpandedState',
          JSON.encode(_treeView.expandedState));
    }
  
negative.code:         });
        });
  
        _reloadDataAndRestoreExpandedState(filtered.toList());
      }
    }
  }
  