Fix tests, and fix Group::searchUsers to avoid duplicates

Also went back to searchUsers indexing the array by uid as it was the
 previous behavior and the IGroup phpdoc does not say anything about the
 keys.

Signed-off-by: Côme Chilliet <come.chilliet@nextcloud.com>

lib/private/Group/Group.php

@@ -251,15 +251,15 @@ class Group implements IGroup {
 		$users = [];
 		foreach ($this->backends as $backend) {
 			if ($backend instanceof ISearchableGroupBackend) {
-				$users = array_merge($users, array_values($backend->searchInGroup($this->gid, $search, $limit ?? -1, $offset ?? 0)));
+				$users += $backend->searchInGroup($this->gid, $search, $limit ?? -1, $offset ?? 0);
 			} else {
 				$userIds = $backend->usersInGroup($this->gid, $search, $limit ?? -1, $offset ?? 0);
 				$userManager = \OCP\Server::get(IUserManager::class);
-				$userObjects = array_map(
-					fn (string $userId): IUser => new LazyUser($userId, $userManager),
-					$userIds
-				);
-				$users = array_merge($users, $userObjects);
+				foreach ($userIds as $userId) {
+					if (!isset($users[$userId])) {
+						$users[$userId] = new LazyUser($userId, $userManager);
+					}
+				}
 			}
 			if (!is_null($limit) and $limit <= 0) {
 				return $users;
@@ -375,10 +375,7 @@ class Group implements IGroup {
 	 * @param string[] $userIds an array containing user IDs
 	 * @return \OC\User\User[] an Array with the userId as Key and \OC\User\User as value
 	 */
-	private function getVerifiedUsers($userIds) {
-		if (!is_array($userIds)) {
-			return [];
-		}
+	private function getVerifiedUsers(array $userIds): array {
 		$users = [];
 		foreach ($userIds as $userId) {
 			$user = $this->userManager->get($userId);

tests/lib/Group/GroupTest.php

@@ -310,7 +310,7 @@ class GroupTest extends \Test\TestCase {
 		$users = $group->searchUsers('2');
 
 		$this->assertEquals(1, count($users));
-		$user2 = $users['user2'];
+		$user2 = reset($users);
 		$this->assertEquals('user2', $user2->getUID());
 	}
 
@@ -336,7 +336,7 @@ class GroupTest extends \Test\TestCase {
 		$users = $group->searchUsers('2');
 
 		$this->assertEquals(1, count($users));
-		$user2 = $users['user2'];
+		$user2 = reset($users);
 		$this->assertEquals('user2', $user2->getUID());
 	}
 
@@ -355,7 +355,7 @@ class GroupTest extends \Test\TestCase {
 		$users = $group->searchUsers('user', 1, 1);
 
 		$this->assertEquals(1, count($users));
-		$user2 = $users['user2'];
+		$user2 = reset($users);
 		$this->assertEquals('user2', $user2->getUID());
 	}
 
@@ -381,8 +381,8 @@ class GroupTest extends \Test\TestCase {
 		$users = $group->searchUsers('user', 2, 1);
 
 		$this->assertEquals(2, count($users));
-		$user2 = $users['user2'];
-		$user1 = $users['user1'];
+		$user2 = reset($users);
+		$user1 = next($users);
 		$this->assertEquals('user2', $user2->getUID());
 		$this->assertEquals('user1', $user1->getUID());
 	}

tests/lib/Group/ManagerTest.php

@@ -27,6 +27,7 @@ use OC\Group\Database;
 use OC\User\User;
 use OC\User\Manager;
 use OCP\GroupInterface;
+use OCP\Group\Backend\ISearchableGroupBackend;
 use OCP\ICacheFactory;
 use OCP\IUser;
 use PHPUnit\Framework\MockObject\MockObject;
@@ -34,6 +35,9 @@ use Psr\Log\LoggerInterface;
 use Symfony\Component\EventDispatcher\EventDispatcherInterface;
 use Test\TestCase;
 
+interface ISearchableGroupInterface extends ISearchableGroupBackend, GroupInterface {
+}
+
 class ManagerTest extends TestCase {
 	/** @var Manager|MockObject */
 	protected $userManager;
@@ -79,7 +83,7 @@ class ManagerTest extends TestCase {
 		}
 		// need to declare it this way due to optional methods
 		// thanks to the implementsActions logic
-		$backend = $this->getMockBuilder(GroupInterface::class)
+		$backend = $this->getMockBuilder(ISearchableGroupInterface::class)
 			->disableOriginalConstructor()
 			->setMethods([
 				'getGroupDetails',