ensure that sorting is stable

Signed-off-by: Arthur Schiwon <blizzz@arthur-schiwon.de>

2 files changed, 22 insertions, 7 deletions

diff --git a/apps/files_sharing/lib/Collaboration/ShareRecipientSorter.php b/apps/files_sharing/lib/Collaboration/ShareRecipientSorter.php
index ba07d9d44d0..1a722817cbd 100644
--- a/apps/files_sharing/lib/Collaboration/ShareRecipientSorter.php
+++ b/apps/files_sharing/lib/Collaboration/ShareRecipientSorter.php
@@ -61,9 +61,24 @@ class ShareRecipientSorter implements ISorter {
 			if(!isset($al[$type]) || !is_array($al[$type])) {
 				continue;
 			}
-			usort($byType, function ($a, $b) use ($al, $type) {
-				return  $this->compare($a, $b, $al[$type]);
+
+			// at least on PHP 5.6 usort turned out to be not stable. So we add
+			// the current index to the value and compare it on a draw
+			$i = 0;
+			$workArray = array_map(function($element) use (&$i) {
+				return [$i++, $element];
+			}, $byType);
+
+			usort($workArray, function ($a, $b) use ($al, $type) {
+				$result = $this->compare($a[1], $b[1], $al[$type]);
+				if($result === 0) {
+					$result = $a[0] - $b[0];
+				}
+				return $result;
 			});
+
+			// and remove the index values again
+			$byType = array_column($workArray, 1);
 		}
 	}
 
diff --git a/apps/files_sharing/tests/Collaboration/ShareRecipientSorterTest.php b/apps/files_sharing/tests/Collaboration/ShareRecipientSorterTest.php
index edcc9b9ae3a..42487e61622 100644
--- a/apps/files_sharing/tests/Collaboration/ShareRecipientSorterTest.php
+++ b/apps/files_sharing/tests/Collaboration/ShareRecipientSorterTest.php
@@ -74,7 +74,7 @@ class ShareRecipientSorterTest extends TestCase {
 		$workArray = $data['input'];
 		$this->sorter->sort($workArray, $data['context']);
 
-		$this->assertSame($data['expected'], $workArray);
+		$this->assertEquals($data['expected'], $workArray);
 	}
 
 	public function testSortNoNodes() {
@@ -98,7 +98,7 @@ class ShareRecipientSorterTest extends TestCase {
 	public function sortDataProvider() {
 		return [[
 			[
-				#1 – sort properly and otherwise keep existing order
+				#0 – sort properly and otherwise keep existing order
 				'context' => ['itemType' => 'files', 'itemId' => 42],
 				'accessList' => ['users' => ['celia', 'darius', 'faruk', 'gail'], 'bots' => ['r2-d2']],
 				'input' => [
@@ -135,7 +135,7 @@ class ShareRecipientSorterTest extends TestCase {
 				],
 			],
 			[
-				# 2 – no recipients
+				#1 – no recipients
 				'context' => ['itemType' => 'files', 'itemId' => 42],
 				'accessList' => ['users' => false],
 				'input' => [
@@ -172,7 +172,7 @@ class ShareRecipientSorterTest extends TestCase {
 				],
 			],
 			[
-				#3 – unsupported item  type
+				#2 – unsupported item  type
 				'context' => ['itemType' => 'announcements', 'itemId' => 42],
 				'accessList' => null, // not needed
 				'input' => [
@@ -209,7 +209,7 @@ class ShareRecipientSorterTest extends TestCase {
 				],
 			],
 			[
-				#4 – no nothing
+				#3 – no nothing
 				'context' => ['itemType' => 'files', 'itemId' => 42],
 				'accessList' => [],
 				'input' => [],