Support pushing large number of items in tree iterators

packages/core/src/browser/tree/tree-iterator.ts

@@ -202,25 +202,25 @@ export namespace Iterators {
      * Generator for depth first, pre-order tree traversal iteration.
      */
     export function* depthFirst<T>(root: T, children: (node: T) => T[] | undefined, include: (node: T) => boolean = () => true): IterableIterator<T> {
-        const stack: T[] = [];
+        let stack: T[] = [];
         stack.push(root);
         while (stack.length > 0) {
             const top = stack.pop()!;
             yield top;
-            stack.push(...(children(top) || []).filter(include).reverse());
+            stack = stack.concat((children(top) || []).filter(include).reverse());
         }
     }
 
     /**
      * Generator for breadth first tree traversal iteration.
      */
     export function* breadthFirst<T>(root: T, children: (node: T) => T[] | undefined, include: (node: T) => boolean = () => true): IterableIterator<T> {
-        const queue: T[] = [];
+        let queue: T[] = [];
         queue.push(root);
         while (queue.length > 0) {
             const head = queue.shift()!;
             yield head;
-            queue.push(...(children(head) || []).filter(include));
+            queue = queue.concat((children(head) || []).filter(include));
         }
     }
 

packages/core/src/browser/tree/tree-selection-state.spec.ts

@@ -16,10 +16,10 @@
 
 import { expect } from 'chai';
 import { MockTreeModel } from './test/mock-tree-model';
-import { TreeSelectionState } from './tree-selection-state';
 import { createTreeTestContainer } from './test/tree-test-container';
-import { SelectableTreeNode, TreeSelection } from './tree-selection';
 import { TreeModel } from './tree-model';
+import { SelectableTreeNode, TreeSelection } from './tree-selection';
+import { TreeSelectionState } from './tree-selection-state';
 
 namespace TreeSelectionState {
 
@@ -34,6 +34,16 @@ namespace TreeSelectionState {
 
 }
 
+const LARGE_FLAT_MOCK_ROOT = (length = 250000) => {
+    const children = Array.from({ length }, (_, idx) => ({ 'id': (idx + 1).toString() }));
+    return MockTreeModel.Node.toTreeNode({
+        'id': 'ROOT',
+        'children': [
+            ...children
+        ]
+    });
+};
+
 describe('tree-selection-state', () => {
 
     const model = createTreeModel();
@@ -391,6 +401,23 @@ describe('tree-selection-state', () => {
             });
     });
 
+    it('should be able to handle range selection on large tree', () => {
+        model.root = LARGE_FLAT_MOCK_ROOT();
+        expect(model.selectedNodes).to.be.empty;
+
+        const start = 10;
+        const end = 20;
+        newState()
+            .nextState('toggle', start.toString(), {
+                focus: start.toString(),
+                selection: [start.toString()]
+            })
+            .nextState('range', end.toString(), {
+                focus: start.toString(),
+                selection: Array.from({ length: end - start + 1 }, (_, idx) => (start + idx).toString())
+            });
+    });
+
     function newState(): TreeSelectionState.Assert {
         return nextState(new TreeSelectionState(model));
     }