Handle open empty folder (#859)

* Handle open empty folder

* Changelog

Author: mbraak

docs/_entries/general/changelog.md

@@ -3,6 +3,10 @@ title: Changelog
 name: changelog
 ---
 
+#### Development version
+
+-   Issue #858: load on demand with empty children (thanks to Ivan Kolesov)
+
 #### 1.8.7 (november 2 2024)
 
 -   Issue #853: fix dnd to first child (thanks to Oskar von Dungern)

src/test/jqTree/methods.test.ts

@@ -959,6 +959,15 @@ describe("openNode", () => {
             });
         });
     });
+
+    it("handles an empty folder", () => {
+        const child1 = given.$tree.tree("getNodeByNameMustExist", "child1");
+        child1.isEmptyFolder = true;
+
+        expect(() => {
+            given.$tree.tree("openNode", child1, false);
+        }).not.toThrow();
+    });
 });
 
 describe("prependNode", () => {

src/tree.jquery.ts

@@ -626,6 +626,10 @@ export class JqTreeWidget extends SimpleWidget<JQTreeOptions> {
             _slide: boolean,
             _onFinished?: OnFinishOpenNode,
         ): void => {
+            if (!node.children.length) {
+                return;
+            }
+
             const folderElement = this.createFolderElement(_node);
             folderElement.open(
                 _onFinished,