feat: add tree.siblings

modules/@angular/router/src/tree.ts

@@ -21,6 +21,14 @@ export class Tree<T> {
     return n && n.children.length > 0 ? n.children[0].value : null;
   }
 
+  siblings(t: T): T[] {
+    const p = findPath(t, this._root, []);
+    if (p.length < 2) return [];
+
+    const c = p[p.length - 2].children.map(c => c.value);
+    return c.filter(cc => cc !== t);
+  }
+
   pathFromRoot(t: T): T[] { return findPath(t, this._root, []).map(s => s.value); }
 
   contains(tree: Tree<T>): boolean { return contains(this._root, tree._root); }

modules/@angular/router/test/tree.spec.ts

@@ -24,6 +24,12 @@ describe('tree', () => {
     expect(t.firstChild(2)).toEqual(null);
   });
 
+  it("should return the siblings of a node", () => {
+    const t = new Tree<any>(new TreeNode<number>(1, [new TreeNode<number>(2, []), new TreeNode<number>(3, [])]));
+    expect(t.siblings(2)).toEqual([3]);
+    expect(t.siblings(1)).toEqual([]);
+  });
+
   it("should return the path to the root", () => {
     const t = new Tree<any>(new TreeNode<number>(1, [new TreeNode<number>(2, [])]));
     expect(t.pathFromRoot(2)).toEqual([1, 2]);