Function useTreeState

packages/react-stately/src/tree/useTreeState.ts:57–98

(props: TreeProps<T>)

 * of items from props, item expanded state, and manages multiple selection state.
 */
export function useTreeState<T>(props: TreeProps<T>): TreeState<T> {
  let {onExpandedChange} = props;

  let [expandedKeys, setExpandedKeys] = useControlledState(
    props.expandedKeys ? new Set(props.expandedKeys) : undefined,
    props.defaultExpandedKeys ? new Set(props.defaultExpandedKeys) : new Set(),
    onExpandedChange
  );

  let selectionState = useMultipleSelectionState(props);
  let disabledKeys = useMemo(
    () => (props.disabledKeys ? new Set(props.disabledKeys) : new Set<Key>()),
    [props.disabledKeys]
  );

  let tree = useCollection(
    props,
    useCallback(nodes => new TreeCollection(nodes, {expandedKeys}), [expandedKeys]),
    null
  );

  // Reset focused key if that item is deleted from the collection.
  useEffect(() => {
    if (selectionState.focusedKey != null && !tree.getItem(selectionState.focusedKey)) {
      selectionState.setFocusedKey(null);
    }
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, [tree, selectionState.focusedKey]);

  let onToggle = (key: Key) => {
    setExpandedKeys(toggleKey(expandedKeys, key));
  };

  return {
    collection: tree,
    expandedKeys,
    disabledKeys,
    toggleKey: onToggle,
    setExpandedKeys,
    selectionManager: new SelectionManager(tree, selectionState)
  };
}

function toggleKey(set: Set<Key>, key: Key): Set<Key> {
  let res = new Set(set);