fix(tree): should not load children when they were already loaded (closes #149)

Author: rychkog

src/tree.ts

@@ -143,7 +143,7 @@ export class Tree {
    * @returns {boolean} A flag indicating that children should be loaded for the current node.
    */
   public childrenShouldBeLoaded(): boolean {
-    return !!this._loadChildren || this.node.emitLoadNextLevel === true;
+    return !this.childrenWereLoaded() && (!!this._loadChildren || this.node.emitLoadNextLevel === true);
   }
 
   /**

test/tree.spec.ts

@@ -1,5 +1,5 @@
 import { Tree } from '../src/tree';
-import { TreeModel, TreeModelSettings, FoldingType, CssClasses } from '../src/tree.types';
+import { TreeModel, TreeModelSettings, FoldingType, CssClasses, ChildrenLoadingFunction } from '../src/tree.types';
 
 describe('Tree', () => {
   it('should detect empty string', () => {
@@ -1086,6 +1086,17 @@ describe('Tree', () => {
     expect(masterTree.children[1].leftMenuTemplate).toEqual('<i class="navigation"></i>');
   });
 
+  it('should not load children when they are already loaded', () => {
+      const model: TreeModel = {
+        value: 'root',
+      };
+
+      const tree: Tree = new Tree(model);
+      spyOn(tree, 'childrenWereLoaded').and.returnValue(true);
+
+      expect(tree.childrenShouldBeLoaded()).toBe(false);
+   });
+
   it('should load children when hasChildren is true', () => {
 
     const model: TreeModel = {