Function useTreeItem

packages/react-aria/src/tree/useTreeItem.ts:51–86

(
  props: AriaTreeItemOptions,
  state: TreeState<T>,
  ref: RefObject<FocusableElement | null>
)

 * @param ref - The ref attached to the row element.
 */
export function useTreeItem<T>(
  props: AriaTreeItemOptions,
  state: TreeState<T>,
  ref: RefObject<FocusableElement | null>
): TreeItemAria {
  let {node} = props;
  let gridListAria = useGridListItem(props, state, ref);
  let isExpanded = gridListAria.rowProps['aria-expanded'] === true;
  let stringFormatter = useLocalizedStringFormatter(intlMessages, '@react-aria/tree');
  let labelProps = useLabels({
    'aria-label': isExpanded
      ? stringFormatter.format('collapse')
      : stringFormatter.format('expand'),
    'aria-labelledby': gridListAria.rowProps.id
  });

  let expandButtonProps = {
    onPress: () => {
      if (!gridListAria.isDisabled) {
        state.toggleKey(node.key);
        state.selectionManager.setFocused(true);
        state.selectionManager.setFocusedKey(node.key);
      }
    },
    excludeFromTabOrder: true,
    preventFocusOnPress: true,
    'data-react-aria-prevent-focus': true,
    ...labelProps
  };

  // TODO: should it return a state specifically for isExpanded? Or is aria attribute sufficient?
  return {
    ...gridListAria,
    expandButtonProps
  };
}