From 70b012c595c5ba6f33f17bd3b8e0106345621cab Mon Sep 17 00:00:00 2001
From: bsitu <bsitu@wikimedia.org>
Date: Tue, 19 Aug 2014 15:23:05 -0700
Subject: [PATCH] Add support for adding deferred update within a deferred
 update

Under some configurations all Echo notifications are inserted
via a DeferredUpdate.  When an extension delays its own notification
trigger via DeferredUpdate as well the Echo notification will not
be run.

Change-Id: Ib40fcd4939ede5b0ff986ab109432630efd1be74
---
 includes/deferred/DeferredUpdates.php         | 32 +++++++++-------
 .../includes/deferred/DeferredUpdatesTest.php | 38 +++++++++++++++++++
 2 files changed, 56 insertions(+), 14 deletions(-)
 create mode 100644 tests/phpunit/includes/deferred/DeferredUpdatesTest.php

diff --git a/includes/deferred/DeferredUpdates.php b/includes/deferred/DeferredUpdates.php
index 2178281c17..b0c1899f78 100644
--- a/includes/deferred/DeferredUpdates.php
+++ b/includes/deferred/DeferredUpdates.php
@@ -99,25 +99,29 @@ class DeferredUpdates {
 			$dbw = wfGetDB( DB_MASTER );
 		}
 
-		/** @var DeferrableUpdate $update */
-		foreach ( $updates as $update ) {
-			try {
-				$update->doUpdate();
+		while ( $updates ) {
+			self::clearPendingUpdates();
 
-				if ( $doCommit && $dbw->trxLevel() ) {
-					$dbw->commit( __METHOD__, 'flush' );
-				}
-			} catch ( MWException $e ) {
-				// We don't want exceptions thrown during deferred updates to
-				// be reported to the user since the output is already sent.
-				// Instead we just log them.
-				if ( !$e instanceof ErrorPageError ) {
-					MWExceptionHandler::logException( $e );
+			/** @var DeferrableUpdate $update */
+			foreach ( $updates as $update ) {
+				try {
+					$update->doUpdate();
+
+					if ( $doCommit && $dbw->trxLevel() ) {
+						$dbw->commit( __METHOD__, 'flush' );
+					}
+				} catch ( MWException $e ) {
+					// We don't want exceptions thrown during deferred updates to
+					// be reported to the user since the output is already sent.
+					// Instead we just log them.
+					if ( !$e instanceof ErrorPageError ) {
+						MWExceptionHandler::logException( $e );
+					}
 				}
 			}
+			$updates = array_merge( $wgDeferredUpdateList, self::$updates );
 		}
 
-		self::clearPendingUpdates();
 		wfProfileOut( __METHOD__ );
 	}
 
diff --git a/tests/phpunit/includes/deferred/DeferredUpdatesTest.php b/tests/phpunit/includes/deferred/DeferredUpdatesTest.php
new file mode 100644
index 0000000000..b3d57e796a
--- /dev/null
+++ b/tests/phpunit/includes/deferred/DeferredUpdatesTest.php
@@ -0,0 +1,38 @@
+<?php
+
+class DeferredUpdatesTest extends MediaWikiTestCase {
+
+	public function testDoUpdates() {
+		$updates = array (
+			'1' => 'deferred update 1',
+			'2' => 'deferred update 2',
+			'3' => 'deferred update 3',
+			'2-1' => 'deferred update 1 within deferred update 2',
+		);
+		DeferredUpdates::addCallableUpdate(
+			function () use ( $updates ) {
+				echo $updates['1'];
+			}
+		);
+		DeferredUpdates::addCallableUpdate(
+			function () use ( $updates ) {
+				echo $updates['2'];
+				DeferredUpdates::addCallableUpdate(
+					function() use ( $updates ) {
+						echo $updates['2-1'];
+					}
+				);
+			}
+		);
+		DeferredUpdates::addCallableUpdate(
+			function () use ( $updates ) {
+				echo $updates[3];
+			}
+		);
+
+		$this->expectOutputString( implode( '', $updates ) );
+
+		DeferredUpdates::doUpdates();
+	}
+
+}
-- 
2.20.1