Function updateTree

packages/react-stately/src/data/useTreeData.ts:191–257

(
    items: TreeNode<T>[],
    key: Key | null,
    update: (node: TreeNode<T>) => TreeNode<T> | null,
    originalMap: Map<Key, TreeNode<T>>
  )

  }

  function updateTree(
    items: TreeNode<T>[],
    key: Key | null,
    update: (node: TreeNode<T>) => TreeNode<T> | null,
    originalMap: Map<Key, TreeNode<T>>
  ) {
    let node = key == null ? null : originalMap.get(key);
    if (node == null) {
      return {items, nodeMap: originalMap};
    }
    let map = new Map<Key, TreeNode<T>>(originalMap);

    // Create a new node. If null, then delete the node, otherwise replace.
    let newNode = update(node);
    if (newNode == null) {
      deleteNode(node, map);
    } else {
      addNode(newNode, map);
    }

    // Walk up the tree and update each parent to refer to the new children.
    while (node && node.parentKey) {
      let nextParent = map.get(node.parentKey)!;
      let copy: TreeNode<T> = {
        key: nextParent.key,
        parentKey: nextParent.parentKey,
        value: nextParent.value,
        children: null
      };

      let children = nextParent.children;
      if (newNode == null && children) {
        children = children.filter(c => c !== node);
      }

      copy.children =
        children?.map(child => {
          if (child === node) {
            // newNode cannot be null here due to the above filter.
            return newNode!;
          }

          return child;
        }) ?? null;

      map.set(copy.key, copy);

      newNode = copy;
      node = nextParent;
    }

    if (newNode == null) {
      items = items.filter(c => c !== node);
    }

    return {
      items: items.map(item => {
        if (item === node) {