From 02e8e531ddfd86e9abf7ef47fbf30445afeb37cf Mon Sep 17 00:00:00 2001
From: Bartol Karuza <bartol@immidi.com>
Date: Wed, 20 Mar 2019 01:38:03 -0700
Subject: [PATCH] Fix #24053 prevent division by zero error in VirtualizedList
 debug overlay (#24058)

Summary:
This PR fixes the case where the content a VirtualizedList loads with a contentLength of 0,  causing a crash in the `renderDebugOverlay` function. The result of that crash is a red screen when turning on debug on FlatList and other VirtualizedList components as described in #24053.

[LIST] [FIX] - Fix VirtualizedList debug mode crash
Pull Request resolved: https://github.com/facebook/react-native/pull/24058

Differential Revision: D14538317

Pulled By: cpojer

fbshipit-source-id: 7b17bf51c388561c517bab1f775a31200abdc5a9
---
 Libraries/Lists/VirtualizedList.js | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/Libraries/Lists/VirtualizedList.js b/Libraries/Lists/VirtualizedList.js
index dc0c508dc9a..e97f96f915c 100644
--- a/Libraries/Lists/VirtualizedList.js
+++ b/Libraries/Lists/VirtualizedList.js
@@ -1169,7 +1169,8 @@ class VirtualizedList extends React.PureComponent<Props, State> {
 
   _renderDebugOverlay() {
     const normalize =
-      this._scrollMetrics.visibleLength / this._scrollMetrics.contentLength;
+      this._scrollMetrics.visibleLength /
+      (this._scrollMetrics.contentLength || 1);
     const framesInLayout = [];
     const itemCount = this.props.getItemCount(this.props.data);
     for (let ii = 0; ii < itemCount; ii++) {