From 47b73fd153aef14bc774a1d90c0e9882b155ed05 Mon Sep 17 00:00:00 2001
From: Emilio <e.marticor@gmail.com>
Date: Thu, 1 Feb 2018 22:26:27 -0800
Subject: [PATCH] fix(core): ensure initial value of QueryList length (#21980)
 (#21982)

Set initial value of `length` to `0`.

Fixes regression introduced by https://github.com/angular/angular/commit/e54474215629aa6a0e0497fe61bfc896cea532c9#diff-a85dbe0991a7577ea24b49374e9ae90b where the `length` property ceased to have initial value.

Closes #21980

PR Close #21982
---
 packages/core/src/linker/query_list.ts       |  2 +-
 packages/core/test/linker/query_list_spec.ts | 16 ++++++++++++++++
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/packages/core/src/linker/query_list.ts b/packages/core/src/linker/query_list.ts
index 07edc590e9..af978bbc7e 100644
--- a/packages/core/src/linker/query_list.ts
+++ b/packages/core/src/linker/query_list.ts
@@ -41,7 +41,7 @@ export class QueryList<T>/* implements Iterable<T> */ {
   private _results: Array<T> = [];
   public readonly changes: Observable<any> = new EventEmitter();
 
-  readonly length: number;
+  readonly length: number = 0;
   readonly first: T;
   readonly last: T;
 
diff --git a/packages/core/test/linker/query_list_spec.ts b/packages/core/test/linker/query_list_spec.ts
index a7fc644296..d0c795b7f1 100644
--- a/packages/core/test/linker/query_list_spec.ts
+++ b/packages/core/test/linker/query_list_spec.ts
@@ -23,6 +23,22 @@ import {getDOM} from '@angular/platform-browser/src/dom/dom_adapter';
 
     function logAppend(item: any /** TODO #9100 */) { log += (log.length == 0 ? '' : ', ') + item; }
 
+    describe('dirty and reset', () => {
+
+      it('should initially be dirty and empty', () => {
+        expect(queryList.dirty).toBeTruthy();
+        expect(queryList.length).toBe(0);
+      });
+
+      it('should be not dirty after reset', () => {
+        expect(queryList.dirty).toBeTruthy();
+        queryList.reset(['one', 'two']);
+        expect(queryList.dirty).toBeFalsy();
+        expect(queryList.length).toBe(2);
+      });
+
+    });
+
     it('should support resetting and iterating over the new objects', () => {
       queryList.reset(['one']);
       queryList.reset(['two']);