Handle undefined children in useTreeData (#2549)

* handle no children in useTreeData

* fix tests to cover

Co-authored-by: Robert Snow <[email protected]>
Co-authored-by: Danni <[email protected]>

Author: 3 people

packages/@react-stately/data/src/useTreeData.ts

@@ -123,7 +123,7 @@ export function useTreeData<T extends object>(options: TreeOptions<T>): TreeData
     initialItems = [],
     initialSelectedKeys,
     getKey = (item: any) => item.id || item.key,
-    getChildren = (item: any) => item.children || []
+    getChildren = (item: any) => item.children
   } = options;
   let map = useMemo(() => new Map<Key, TreeNode<T>>(), []);
 
@@ -133,7 +133,7 @@ export function useTreeData<T extends object>(options: TreeOptions<T>): TreeData
   let [items, setItems] = useState(initialNodes);
   let [selectedKeys, setSelectedKeys] = useState(new Set<Key>(initialSelectedKeys || []));
 
-  function buildTree(initialItems: T[], parentKey?: Key | null) {
+  function buildTree(initialItems: T[] = [], parentKey?: Key | null) {
     return initialItems.map(item => {
       let node: TreeNode<T> = {
         key: getKey(item),

packages/@react-stately/data/test/useTreeData.test.js

@@ -31,7 +31,7 @@ const initial = [
 ];
 
 let getKey = (item) => item.name;
-let getChildren = (item) => item.children || [];
+let getChildren = (item) => item.children;
 
 describe('useTreeData', function () {
   it('should construct a tree using initial data', function () {