From f8dc579261dcea5744cb909785821b8996c8d312 Mon Sep 17 00:00:00 2001
From: daniel <dkinzler@wikimedia.org>
Date: Fri, 22 Mar 2019 13:26:21 +0100
Subject: [PATCH] Only load latest revision in MessageCache::loadFromDB

In Id044b8dcd7c, we lost a condition that ensured that the cache would
be populated with the latest revision. Now it was being populated with
all revisions, with a random one winning.

Bug: T218918
Change-Id: I1a47356ea35f0abf35bb1a3489d0d3442a3400a5
---
 includes/cache/MessageCache.php               |  5 +-
 .../includes/cache/MessageCacheTest.php       | 47 ++++++++++++++++++-
 2 files changed, 50 insertions(+), 2 deletions(-)

diff --git a/includes/cache/MessageCache.php b/includes/cache/MessageCache.php
index e78dfa16bb..157d88eb34 100644
--- a/includes/cache/MessageCache.php
+++ b/includes/cache/MessageCache.php
@@ -540,7 +540,10 @@ class MessageCache {
 		$res = $dbr->select(
 			$revQuery['tables'],
 			$revQuery['fields'],
-			array_merge( $conds, [ 'page_len <= ' . intval( $wgMaxMsgCacheEntrySize ) ] ),
+			array_merge( $conds, [
+				'page_len <= ' . intval( $wgMaxMsgCacheEntrySize ),
+				'page_latest = rev_id' // get the latest revision only
+			] ),
 			__METHOD__ . "($code)-small",
 			[],
 			$revQuery['joins']
diff --git a/tests/phpunit/includes/cache/MessageCacheTest.php b/tests/phpunit/includes/cache/MessageCacheTest.php
index c340c08e49..8fdc1f1d8f 100644
--- a/tests/phpunit/includes/cache/MessageCacheTest.php
+++ b/tests/phpunit/includes/cache/MessageCacheTest.php
@@ -1,6 +1,7 @@
 <?php
 
 use MediaWiki\MediaWikiServices;
+use Wikimedia\TestingAccessWrapper;
 
 /**
  * @group Database
@@ -58,6 +59,8 @@ class MessageCacheTest extends MediaWikiLangTestCase {
 	 * @param string $title Title of page to be created
 	 * @param string $lang Language and content of the created page
 	 * @param string|null $content Content of the created page, or null for a generic string
+	 *
+	 * @return Revision
 	 */
 	protected function makePage( $title, $lang, $content = null ) {
 		if ( $content === null ) {
@@ -70,7 +73,11 @@ class MessageCacheTest extends MediaWikiLangTestCase {
 		$title = Title::newFromText( $title, NS_MEDIAWIKI );
 		$wikiPage = new WikiPage( $title );
 		$contentHandler = ContentHandler::makeContent( $content, $title );
-		$wikiPage->doEditContent( $contentHandler, "$lang translation test case" );
+		$status = $wikiPage->doEditContent( $contentHandler, "$lang translation test case" );
+
+		// sanity
+		$this->assertTrue( $status->isOK(), 'Create page ' . $title->getPrefixedDBkey() );
+		return $status->value['revision'];
 	}
 
 	/**
@@ -213,4 +220,42 @@ class MessageCacheTest extends MediaWikiLangTestCase {
 
 		$this->assertEquals( 0, $dbr->trxLevel(), "No DB read queries" );
 	}
+
+	/**
+	 * Regression test for T218918
+	 */
+	public function testLoadFromDB_fetchLatestRevision() {
+		// Create three revisions of the same message page.
+		// Must be an existing message key.
+		$key = 'Log';
+		$this->makePage( $key, 'de', 'Test eins' );
+		$this->makePage( $key, 'de', 'Test zwei' );
+		$r3 = $this->makePage( $key, 'de', 'Test drei' );
+
+		// Create an out-of-sequence revision by importing a
+		// revision with an old timestamp. Hacky.
+		$importRevision = new WikiRevision( new HashConfig() );
+		$importRevision->setTitle( $r3->getTitle() );
+		$importRevision->setComment( 'Imported edit' );
+		$importRevision->setTimestamp( '19991122334455' );
+		$importRevision->setText( 'IMPORTED OLD TEST' );
+		$importRevision->setUsername( 'Alan Smithee' );
+
+		$importer = MediaWikiServices::getInstance()->getWikiRevisionOldRevisionImporterNoUpdates();
+		$importer->import( $importRevision );
+
+		// Now, load the message from the wiki page
+		MessageCache::destroyInstance();
+		$messageCache = MessageCache::singleton();
+		$messageCache->enable();
+		$messageCache = TestingAccessWrapper::newFromObject( $messageCache );
+
+		$cache = $messageCache->loadFromDB( 'de' );
+
+		$this->assertArrayHasKey( $key, $cache );
+
+		// Text in the cache has an extra space in front!
+		$this->assertSame( ' ' . 'Test drei', $cache[$key] );
+	}
+
 }
-- 
2.20.1