From 4d549f69f8913bf3633f69bf7930bc124f3756fa Mon Sep 17 00:00:00 2001
From: Pawel Kozlowski <pkozlowski.opensource@gmail.com>
Date: Wed, 14 Aug 2019 10:44:29 +0200
Subject: [PATCH] perf(ivy): auto-call select(0) for non-empty views only
 (#32131)

PR Close #32131
---
 packages/core/src/render3/instructions/select.ts | 15 ++++++---------
 packages/core/src/render3/instructions/shared.ts |  4 ++--
 2 files changed, 8 insertions(+), 11 deletions(-)

diff --git a/packages/core/src/render3/instructions/select.ts b/packages/core/src/render3/instructions/select.ts
index e24f7c77bbd..e10b782fadf 100644
--- a/packages/core/src/render3/instructions/select.ts
+++ b/packages/core/src/render3/instructions/select.ts
@@ -5,7 +5,7 @@
  * Use of this source code is governed by an MIT-style license that can be
  * found in the LICENSE file at https://angular.io/license
  */
-import {assertGreaterThan, assertLessThan} from '../../util/assert';
+import {assertDataInRange, assertGreaterThan} from '../../util/assert';
 import {executePreOrderHooks} from '../hooks';
 import {HEADER_OFFSET, LView, TVIEW} from '../interfaces/view';
 import {getCheckNoChangesMode, getLView, setSelectedIndex} from '../state';
@@ -33,18 +33,15 @@ import {getCheckNoChangesMode, getLView, setSelectedIndex} from '../state';
  * @codeGenApi
  */
 export function ɵɵselect(index: number): void {
-  ngDevMode && assertGreaterThan(index, -1, 'Invalid index');
-  ngDevMode &&
-      assertLessThan(
-          index, getLView().length - HEADER_OFFSET, 'Should be within range for the view data');
-  const lView = getLView();
-  selectInternal(lView, index);
+  selectInternal(getLView(), index, getCheckNoChangesMode());
 }
 
+export function selectInternal(lView: LView, index: number, checkNoChangesMode: boolean) {
+  ngDevMode && assertGreaterThan(index, -1, 'Invalid index');
+  ngDevMode && assertDataInRange(lView, index + HEADER_OFFSET);
 
-export function selectInternal(lView: LView, index: number) {
   // Flush the initial hooks for elements in the view that have been added up to this point.
-  executePreOrderHooks(lView, lView[TVIEW], getCheckNoChangesMode(), index);
+  executePreOrderHooks(lView, lView[TVIEW], checkNoChangesMode, index);
 
   // We must set the selected index *after* running the hooks, because hooks may have side-effects
   // that cause other template functions to run, thus updating the selected index, which is global
diff --git a/packages/core/src/render3/instructions/shared.ts b/packages/core/src/render3/instructions/shared.ts
index 5fa4f238198..7ba9f5cabfb 100644
--- a/packages/core/src/render3/instructions/shared.ts
+++ b/packages/core/src/render3/instructions/shared.ts
@@ -452,10 +452,10 @@ function executeTemplate<T>(
   const prevSelectedIndex = getSelectedIndex();
   try {
     setActiveHostElement(null);
-    if (rf & RenderFlags.Update) {
+    if (rf & RenderFlags.Update && lView.length > HEADER_OFFSET) {
       // When we're updating, have an inherent ɵɵselect(0) so we don't have to generate that
       // instruction for most update blocks
-      selectInternal(lView, 0);
+      selectInternal(lView, 0, getCheckNoChangesMode());
     }
     templateFn(rf, context);
   } finally {