Only call getGroupDetails if the group exists in the backend

Author: phil-davis

changelog/unreleased/40261

@@ -0,0 +1,7 @@
+Bugfix: Only call getGroupDetails when the group exists
+
+When getting a group, the getGroupDetails method could be called for a group
+that does not exist. That is unnecessary and may cause a group backend implementation
+to log an error. The code has been refactored to avoid this happening.
+
+https://github.com/owncloud/core/pull/40261

lib/private/Group/Manager.php

@@ -176,17 +176,17 @@ public function get($gid) {
 	protected function getGroupObject($gid, $displayName = null) {
 		$backends = [];
 		foreach ($this->backends as $backend) {
-			if ($backend->implementsActions(\OC\Group\Backend::GROUP_DETAILS)) {
-				/* @phan-suppress-next-line PhanUndeclaredMethod */
-				$groupData = $backend->getGroupDetails($gid);
-				if (\is_array($groupData)) {
-					// take the display name from the first backend that has a non-null one
-					if ($displayName === null && isset($groupData['displayName'])) {
-						$displayName = $groupData['displayName'];
+			if ($backend->groupExists($gid)) {
+				if ($backend->implementsActions(\OC\Group\Backend::GROUP_DETAILS)) {
+					/* @phan-suppress-next-line PhanUndeclaredMethod */
+					$groupData = $backend->getGroupDetails($gid);
+					if (\is_array($groupData)) {
+						// take the display name from the first backend that has a non-null one
+						if ($displayName === null && isset($groupData['displayName'])) {
+							$displayName = $groupData['displayName'];
+						}
 					}
-					$backends[] = $backend;
 				}
-			} elseif ($backend->groupExists($gid)) {
 				$backends[] = $backend;
 			}
 		}

tests/lib/Group/ManagerTest.php

@@ -1158,6 +1158,9 @@ public function testGroupDisplayName() {
 			GroupInterface::DELETE_GROUP |
 			GroupInterface::GROUP_DETAILS
 		);
+		$backend->expects($this->any())
+			->method('groupExists')
+			->will($this->returnValue(true));
 		$backend->expects($this->any())
 			->method('getGroupDetails')
 			->will($this->returnValueMap([