From 02195c7a817aa381c526ca71fbdeeea88e7302dd Mon Sep 17 00:00:00 2001
From: Brad Jorsch <bjorsch@wikimedia.org>
Date: Tue, 19 Feb 2019 15:54:33 -0500
Subject: [PATCH] DifferenceEngine: Allow cache hits for empty diffs

PHP considers the empty string as falsey, so check for a string
result instead.

Bug: T216554
Change-Id: I3b7d1199acbfede8a95761c5cb1c797b9a3d64cb
---
 includes/diff/DifferenceEngine.php | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/includes/diff/DifferenceEngine.php b/includes/diff/DifferenceEngine.php
index 43bc6e470c..87863a4c12 100644
--- a/includes/diff/DifferenceEngine.php
+++ b/includes/diff/DifferenceEngine.php
@@ -1033,7 +1033,7 @@ class DifferenceEngine extends ContextSource {
 			// Try cache
 			if ( !$this->mRefreshCache ) {
 				$difftext = $cache->get( $key );
-				if ( $difftext ) {
+				if ( is_string( $difftext ) ) {
 					wfIncrStats( 'diff_cache.hit' );
 					$difftext = $this->localiseDiff( $difftext );
 					$difftext .= "\n<!-- diff cache key $key -->\n";
-- 
2.20.1