Merge pull request #32866 from nextcloud/performance/searchInGroup-displayname-cache

Optimize retrieving display name when searching for users in a group

17 files changed, 221 insertions, 138 deletions

diff --git a/apps/user_ldap/lib/Access.php b/apps/user_ldap/lib/Access.php
index 9a97a28c376..3f120caefe6 100644
--- a/apps/user_ldap/lib/Access.php
+++ b/apps/user_ldap/lib/Access.php
@@ -631,7 +631,7 @@ class Access extends LDAPUtility {
 	 * gives back the user names as they are used ownClod internally
 	 *
 	 * @param array $ldapUsers as returned by fetchList()
-	 * @return array an array with the user names to use in Nextcloud
+	 * @return array<int,string> an array with the user names to use in Nextcloud
 	 *
 	 * gives back the user names as they are used ownClod internally
 	 * @throws \Exception
@@ -644,7 +644,7 @@ class Access extends LDAPUtility {
 	 * gives back the group names as they are used ownClod internally
 	 *
 	 * @param array $ldapGroups as returned by fetchList()
-	 * @return array an array with the group names to use in Nextcloud
+	 * @return array<int,string> an array with the group names to use in Nextcloud
 	 *
 	 * gives back the group names as they are used ownClod internally
 	 * @throws \Exception
@@ -655,6 +655,7 @@ class Access extends LDAPUtility {
 
 	/**
 	 * @param array[] $ldapObjects as returned by fetchList()
+	 * @return array<int,string>
 	 * @throws \Exception
 	 */
 	private function ldap2NextcloudNames(array $ldapObjects, bool $isUsers): array {
diff --git a/apps/user_ldap/lib/Group_LDAP.php b/apps/user_ldap/lib/Group_LDAP.php
index b32e031175f..84267171d37 100644
--- a/apps/user_ldap/lib/Group_LDAP.php
+++ b/apps/user_ldap/lib/Group_LDAP.php
@@ -45,11 +45,11 @@
 namespace OCA\User_LDAP;
 
 use Exception;
+use OC\ServerNotAvailableException;
 use OCP\Cache\CappedMemoryCache;
 use OCP\GroupInterface;
 use OCP\Group\Backend\IDeleteGroupBackend;
 use OCP\Group\Backend\IGetDisplayNameBackend;
-use OC\ServerNotAvailableException;
 use Psr\Log\LoggerInterface;
 
 class Group_LDAP extends BackendUtility implements GroupInterface, IGroupLDAP, IGetDisplayNameBackend, IDeleteGroupBackend {
@@ -466,7 +466,7 @@ class Group_LDAP extends BackendUtility implements GroupInterface, IGroupLDAP, I
 	}
 
 	/**
-	 * @return array A list of users that have the given group as gid number
+	 * @return array<int,string> A list of users that have the given group as gid number
 	 * @throws ServerNotAvailableException
 	 */
 	public function getUsersInGidNumber(
@@ -591,6 +591,7 @@ class Group_LDAP extends BackendUtility implements GroupInterface, IGroupLDAP, I
 
 	/**
 	 * @throws ServerNotAvailableException
+	 * @return array<int,string>
 	 */
 	public function getUsersInPrimaryGroup(
 		string $groupDN,
@@ -840,7 +841,7 @@ class Group_LDAP extends BackendUtility implements GroupInterface, IGroupLDAP, I
 	 * @param string $search
 	 * @param int $limit
 	 * @param int $offset
-	 * @return array with user ids
+	 * @return array<int,string> user ids
 	 * @throws Exception
 	 * @throws ServerNotAvailableException
 	 */
@@ -909,7 +910,11 @@ class Group_LDAP extends BackendUtility implements GroupInterface, IGroupLDAP, I
 					if (empty($ldap_users)) {
 						break;
 					}
-					$groupUsers[] = $this->access->dn2username($ldap_users[0]['dn'][0]);
+					$uid = $this->access->dn2username($ldap_users[0]['dn'][0]);
+					if (!$uid) {
+						break;
+					}
+					$groupUsers[] = $uid;
 					break;
 				default:
 					//we got DNs, check if we need to filter by search or we can give back all of them
@@ -1163,7 +1168,7 @@ class Group_LDAP extends BackendUtility implements GroupInterface, IGroupLDAP, I
 	 * Returns the supported actions as int to be
 	 * compared with GroupInterface::CREATE_GROUP etc.
 	 */
-	public function implementsActions($actions) {
+	public function implementsActions($actions): bool {
 		return (bool)((GroupInterface::COUNT_USERS |
 				GroupInterface::DELETE_GROUP |
 				$this->groupPluginManager->getImplementedActions()) & $actions);
diff --git a/apps/user_ldap/lib/Group_Proxy.php b/apps/user_ldap/lib/Group_Proxy.php
index c8c986318ec..5f8d0562fd9 100644
--- a/apps/user_ldap/lib/Group_Proxy.php
+++ b/apps/user_ldap/lib/Group_Proxy.php
@@ -171,7 +171,7 @@ class Group_Proxy extends Proxy implements \OCP\GroupInterface, IGroupLDAP, IGet
 	/**
 	 * get a list of all users in a group
 	 *
-	 * @return string[] with user ids
+	 * @return array<int,string> user ids
 	 */
 	public function usersInGroup($gid, $search = '', $limit = -1, $offset = 0) {
 		$this->setup();
@@ -334,4 +334,8 @@ class Group_Proxy extends Proxy implements \OCP\GroupInterface, IGroupLDAP, IGet
 	public function getBackendName(): string {
 		return 'LDAP';
 	}
+
+	public function searchInGroup(string $gid, string $search = '', int $limit = -1, int $offset = 0): array {
+		return $this->handleRequest($gid, 'searchInGroup', [$gid, $search, $limit, $offset]);
+	}
 }
diff --git a/core/Command/User/ListCommand.php b/core/Command/User/ListCommand.php
index c254a8a11cf..bf4bf7f030e 100644
--- a/core/Command/User/ListCommand.php
+++ b/core/Command/User/ListCommand.php
@@ -74,7 +74,7 @@ class ListCommand extends Base {
 	}
 
 	protected function execute(InputInterface $input, OutputInterface $output): int {
-		$users = $this->userManager->search('', (int) $input->getOption('limit'), (int) $input->getOption('offset'));
+		$users = $this->userManager->searchDisplayName('', (int) $input->getOption('limit'), (int) $input->getOption('offset'));
 
 		$this->writeArrayInOutputFormat($input, $output, $this->formatUsers($users, (bool)$input->getOption('info')));
 		return 0;
diff --git a/lib/composer/composer/autoload_classmap.php b/lib/composer/composer/autoload_classmap.php
index 90164534da1..83eef30eed1 100644
--- a/lib/composer/composer/autoload_classmap.php
+++ b/lib/composer/composer/autoload_classmap.php
@@ -412,6 +412,7 @@ return array(
     'OCP\\Group\\Backend\\IIsAdminBackend' => $baseDir . '/lib/public/Group/Backend/IIsAdminBackend.php',
     'OCP\\Group\\Backend\\INamedBackend' => $baseDir . '/lib/public/Group/Backend/INamedBackend.php',
     'OCP\\Group\\Backend\\IRemoveFromGroupBackend' => $baseDir . '/lib/public/Group/Backend/IRemoveFromGroupBackend.php',
+    'OCP\\Group\\Backend\\ISearchableGroupBackend' => $baseDir . '/lib/public/Group/Backend/ISearchableGroupBackend.php',
     'OCP\\Group\\Backend\\ISetDisplayNameBackend' => $baseDir . '/lib/public/Group/Backend/ISetDisplayNameBackend.php',
     'OCP\\Group\\Events\\BeforeGroupChangedEvent' => $baseDir . '/lib/public/Group/Events/BeforeGroupChangedEvent.php',
     'OCP\\Group\\Events\\BeforeGroupCreatedEvent' => $baseDir . '/lib/public/Group/Events/BeforeGroupCreatedEvent.php',
diff --git a/lib/composer/composer/autoload_static.php b/lib/composer/composer/autoload_static.php
index 43cdde51734..1f97b5518f9 100644
--- a/lib/composer/composer/autoload_static.php
+++ b/lib/composer/composer/autoload_static.php
@@ -445,6 +445,7 @@ class ComposerStaticInit749170dad3f5e7f9ca158f5a9f04f6a2
         'OCP\\Group\\Backend\\IIsAdminBackend' => __DIR__ . '/../../..' . '/lib/public/Group/Backend/IIsAdminBackend.php',
         'OCP\\Group\\Backend\\INamedBackend' => __DIR__ . '/../../..' . '/lib/public/Group/Backend/INamedBackend.php',
         'OCP\\Group\\Backend\\IRemoveFromGroupBackend' => __DIR__ . '/../../..' . '/lib/public/Group/Backend/IRemoveFromGroupBackend.php',
+        'OCP\\Group\\Backend\\ISearchableGroupBackend' => __DIR__ . '/../../..' . '/lib/public/Group/Backend/ISearchableGroupBackend.php',
         'OCP\\Group\\Backend\\ISetDisplayNameBackend' => __DIR__ . '/../../..' . '/lib/public/Group/Backend/ISetDisplayNameBackend.php',
         'OCP\\Group\\Events\\BeforeGroupChangedEvent' => __DIR__ . '/../../..' . '/lib/public/Group/Events/BeforeGroupChangedEvent.php',
         'OCP\\Group\\Events\\BeforeGroupCreatedEvent' => __DIR__ . '/../../..' . '/lib/public/Group/Events/BeforeGroupCreatedEvent.php',
diff --git a/lib/private/Group/Backend.php b/lib/private/Group/Backend.php
index 037cdacf445..1e3e5ef1164 100644
--- a/lib/private/Group/Backend.php
+++ b/lib/private/Group/Backend.php
@@ -126,7 +126,7 @@ abstract class Backend implements \OCP\GroupInterface {
 	 * @param string $search
 	 * @param int $limit
 	 * @param int $offset
-	 * @return array an array of user ids
+	 * @return array<int,string> an array of user ids
 	 */
 	public function usersInGroup($gid, $search = '', $limit = -1, $offset = 0) {
 		return [];
diff --git a/lib/private/Group/Database.php b/lib/private/Group/Database.php
index 5f17477db77..569cfa5007f 100644
--- a/lib/private/Group/Database.php
+++ b/lib/private/Group/Database.php
@@ -40,9 +40,12 @@ use OCP\Group\Backend\IDeleteGroupBackend;
 use OCP\Group\Backend\IGetDisplayNameBackend;
 use OCP\Group\Backend\IGroupDetailsBackend;
 use OCP\Group\Backend\IRemoveFromGroupBackend;
+use OCP\Group\Backend\ISearchableGroupBackend;
 use OCP\Group\Backend\ISetDisplayNameBackend;
 use OCP\Group\Backend\INamedBackend;
 use OCP\IDBConnection;
+use OCP\IUserManager;
+use OC\User\LazyUser;
 
 /**
  * Class for group management in a SQL Database (e.g. MySQL, SQLite)
@@ -57,6 +60,7 @@ class Database extends ABackend implements
 	IGroupDetailsBackend,
 	IRemoveFromGroupBackend,
 	ISetDisplayNameBackend,
+	ISearchableGroupBackend,
 	INamedBackend {
 	/** @var string[] */
 	private $groupCache = [];
@@ -324,29 +328,35 @@ class Database extends ABackend implements
 	}
 
 	/**
-	 * get a list of all users in a group
+	 * Get a list of all users in a group
 	 * @param string $gid
 	 * @param string $search
 	 * @param int $limit
 	 * @param int $offset
-	 * @return array an array of user ids
+	 * @return array<int,string> an array of user ids
 	 */
-	public function usersInGroup($gid, $search = '', $limit = -1, $offset = 0) {
+	public function usersInGroup($gid, $search = '', $limit = -1, $offset = 0): array {
+		return array_values(array_map(fn ($user) => $user->getUid(), $this->searchInGroup($gid, $search, $limit, $offset)));
+	}
+
+	public function searchInGroup(string $gid, string $search = '', int $limit = -1, int $offset = 0): array {
 		$this->fixDI();
 
 		$query = $this->dbConn->getQueryBuilder();
-		$query->select('g.uid')
-			->from('group_user', 'g')
+		$query->select('g.uid', 'u.displayname');
+
+		$query->from('group_user', 'g')
 			->where($query->expr()->eq('gid', $query->createNamedParameter($gid)))
 			->orderBy('g.uid', 'ASC');
 
+		$query->leftJoin('g', 'users', 'u', $query->expr()->eq('g.uid', 'u.uid'));
+
 		if ($search !== '') {
-			$query->leftJoin('g', 'users', 'u', $query->expr()->eq('g.uid', 'u.uid'))
-				->leftJoin('u', 'preferences', 'p', $query->expr()->andX(
-					$query->expr()->eq('p.userid', 'u.uid'),
-					$query->expr()->eq('p.appid', $query->expr()->literal('settings')),
-					$query->expr()->eq('p.configkey', $query->expr()->literal('email')))
-				)
+			$query->leftJoin('u', 'preferences', 'p', $query->expr()->andX(
+				$query->expr()->eq('p.userid', 'u.uid'),
+				$query->expr()->eq('p.appid', $query->expr()->literal('settings')),
+				$query->expr()->eq('p.configkey', $query->expr()->literal('email'))
+			))
 				// sqlite doesn't like re-using a single named parameter here
 				->andWhere(
 					$query->expr()->orX(
@@ -365,11 +375,12 @@ class Database extends ABackend implements
 			$query->setFirstResult($offset);
 		}
 
-		$result = $query->execute();
+		$result = $query->executeQuery();
 
 		$users = [];
+		$userManager = \OCP\Server::get(IUserManager::class);
 		while ($row = $result->fetch()) {
-			$users[] = $row['uid'];
+			$users[$row['uid']] = new LazyUser($row['uid'], $userManager, $row['displayname'] ?? null);
 		}
 		$result->closeCursor();
 
diff --git a/lib/private/Group/Group.php b/lib/private/Group/Group.php
index cca179bfe19..efc21ad7c0d 100644
--- a/lib/private/Group/Group.php
+++ b/lib/private/Group/Group.php
@@ -33,14 +33,16 @@
 namespace OC\Group;
 
 use OC\Hooks\PublicEmitter;
+use OC\User\LazyUser;
+use OCP\GroupInterface;
 use OCP\Group\Backend\ICountDisabledInGroup;
 use OCP\Group\Backend\IGetDisplayNameBackend;
 use OCP\Group\Backend\IHideFromCollaborationBackend;
 use OCP\Group\Backend\INamedBackend;
+use OCP\Group\Backend\ISearchableGroupBackend;
 use OCP\Group\Backend\ISetDisplayNameBackend;
 use OCP\Group\Events\BeforeGroupChangedEvent;
 use OCP\Group\Events\GroupChangedEvent;
-use OCP\GroupInterface;
 use OCP\IGroup;
 use OCP\IUser;
 use OCP\IUserManager;
@@ -242,18 +244,23 @@ class Group implements IGroup {
 	}
 
 	/**
-	 * search for users in the group by userid
-	 *
-	 * @param string $search
-	 * @param int $limit
-	 * @param int $offset
-	 * @return \OC\User\User[]
+	 * Search for users in the group by userid or display name
+	 * @return IUser[]
 	 */
-	public function searchUsers($search, $limit = null, $offset = null) {
+	public function searchUsers(string $search, ?int $limit = null, ?int $offset = null): array {
 		$users = [];
 		foreach ($this->backends as $backend) {
-			$userIds = $backend->usersInGroup($this->gid, $search, $limit, $offset);
-			$users += $this->getVerifiedUsers($userIds);
+			if ($backend instanceof ISearchableGroupBackend) {
+				$users += $backend->searchInGroup($this->gid, $search, $limit ?? -1, $offset ?? 0);
+			} else {
+				$userIds = $backend->usersInGroup($this->gid, $search, $limit ?? -1, $offset ?? 0);
+				$userManager = \OCP\Server::get(IUserManager::class);
+				foreach ($userIds as $userId) {
+					if (!isset($users[$userId])) {
+						$users[$userId] = new LazyUser($userId, $userManager);
+					}
+				}
+			}
 			if (!is_null($limit) and $limit <= 0) {
 				return $users;
 			}
@@ -308,18 +315,11 @@ class Group implements IGroup {
 	 * @param string $search
 	 * @param int $limit
 	 * @param int $offset
-	 * @return \OC\User\User[]
+	 * @return IUser[]
+	 * @deprecated 27.0.0 Use searchUsers instead (same implementation)
 	 */
 	public function searchDisplayName($search, $limit = null, $offset = null) {
-		$users = [];
-		foreach ($this->backends as $backend) {
-			$userIds = $backend->usersInGroup($this->gid, $search, $limit, $offset);
-			$users = $this->getVerifiedUsers($userIds);
-			if (!is_null($limit) and $limit <= 0) {
-				return array_values($users);
-			}
-		}
-		return array_values($users);
+		return $this->searchUsers($search, $limit, $offset);
 	}
 
 	/**
@@ -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);
diff --git a/lib/private/User/LazyUser.php b/lib/private/User/LazyUser.php
index 096578b8f37..5472cf6f2b4 100644
--- a/lib/private/User/LazyUser.php
+++ b/lib/private/User/LazyUser.php
@@ -30,16 +30,26 @@ use OCP\UserInterface;
 class LazyUser implements IUser {
 	private ?IUser $user = null;
 	private string $uid;
+	private ?string $displayName;
 	private IUserManager $userManager;
+	private ?UserInterface $backend;
 
-	public function __construct(string $uid, IUserManager $userManager) {
+	public function __construct(string $uid, IUserManager $userManager, ?string $displayName = null, ?UserInterface $backend = null) {
 		$this->uid = $uid;
 		$this->userManager = $userManager;
+		$this->displayName = $displayName;
+		$this->backend = $backend;
 	}
 
 	private function getUser(): IUser {
 		if ($this->user === null) {
-			$this->user = $this->userManager->get($this->uid);
+			if ($this->backend) {
+				/** @var \OC\User\Manager $manager */
+				$manager = $this->userManager;
+				$this->user = $manager->getUserObject($this->uid, $this->backend);
+			} else {
+				$this->user = $this->userManager->get($this->uid);
+			}
 		}
 		/** @var IUser */
 		$user = $this->user;
@@ -51,6 +61,10 @@ class LazyUser implements IUser {
 	}
 
 	public function getDisplayName() {
+		if ($this->displayName) {
+			return $this->displayName;
+		}
+
 		return $this->userManager->getDisplayName($this->uid) ?? $this->uid;
 	}
 
diff --git a/lib/private/User/Manager.php b/lib/private/User/Manager.php
index 859ebd2a604..60059d5badd 100644
--- a/lib/private/User/Manager.php
+++ b/lib/private/User/Manager.php
@@ -202,7 +202,7 @@ class Manager extends PublicEmitter implements IUserManager {
 	 * @param bool $cacheUser If false the newly created user object will not be cached
 	 * @return \OC\User\User
 	 */
-	protected function getUserObject($uid, $backend, $cacheUser = true) {
+	public function getUserObject($uid, $backend, $cacheUser = true) {
 		if ($backend instanceof IGetRealUIDBackend) {
 			$uid = $backend->getRealUID($uid);
 		}
@@ -293,12 +293,13 @@ class Manager extends PublicEmitter implements IUserManager {
 	}
 
 	/**
-	 * search by user id
+	 * Search by user id
 	 *
 	 * @param string $pattern
 	 * @param int $limit
 	 * @param int $offset
-	 * @return \OC\User\User[]
+	 * @return IUser[]
+	 * @deprecated since 27.0.0, use searchDisplayName instead
 	 */
 	public function search($pattern, $limit = null, $offset = null) {
 		$users = [];
@@ -306,28 +307,24 @@ class Manager extends PublicEmitter implements IUserManager {
 			$backendUsers = $backend->getUsers($pattern, $limit, $offset);
 			if (is_array($backendUsers)) {
 				foreach ($backendUsers as $uid) {
-					$users[$uid] = $this->getUserObject($uid, $backend);
+					$users[$uid] = new LazyUser($uid, $this, null, $backend);
 				}
 			}
 		}
 
-		uasort($users, function ($a, $b) {
-			/**
-			 * @var \OC\User\User $a
-			 * @var \OC\User\User $b
-			 */
+		uasort($users, function (IUser $a, IUser $b) {
 			return strcasecmp($a->getUID(), $b->getUID());
 		});
 		return $users;
 	}
 
 	/**
-	 * search by displayName
+	 * Search by displayName
 	 *
 	 * @param string $pattern
 	 * @param int $limit
 	 * @param int $offset
-	 * @return \OC\User\User[]
+	 * @return IUser[]
 	 */
 	public function searchDisplayName($pattern, $limit = null, $offset = null) {
 		$users = [];
@@ -335,16 +332,12 @@ class Manager extends PublicEmitter implements IUserManager {
 			$backendUsers = $backend->getDisplayNames($pattern, $limit, $offset);
 			if (is_array($backendUsers)) {
 				foreach ($backendUsers as $uid => $displayName) {
-					$users[] = $this->getUserObject($uid, $backend);
+					$users[] = new LazyUser($uid, $this, $displayName, $backend);
 				}
 			}
 		}
 
-		usort($users, function ($a, $b) {
-			/**
-			 * @var \OC\User\User $a
-			 * @var \OC\User\User $b
-			 */
+		usort($users, function (IUser $a, IUser $b) {
 			return strcasecmp($a->getDisplayName(), $b->getDisplayName());
 		});
 		return $users;
diff --git a/lib/public/Group/Backend/ISearchableGroupBackend.php b/lib/public/Group/Backend/ISearchableGroupBackend.php
new file mode 100644
index 00000000000..20753822258
--- /dev/null
+++ b/lib/public/Group/Backend/ISearchableGroupBackend.php
@@ -0,0 +1,51 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * @copyright Copyright (c) 2022 Carl Schwan <carl@carlschwan.eu>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+namespace OCP\Group\Backend;
+
+use OCP\IUser;
+
+/**
+ * @since 27.0.0
+ */
+interface ISearchableGroupBackend {
+	/**
+	 * @brief Get a list of users matching the given search parameters.
+	 *
+	 * Implementations of this method should return lazy evaluated user objects and
+	 * preload if possible the display name.
+	 *
+	 * <code>
+	 * $users = $groupBackend->searchInGroup('admin', 'John', 10, 0);
+	 * </code>
+	 *
+	 * @param string $gid    The group id of the user we want to search
+	 * @param string $search The part of the display name or user id of the users we
+	 *                       want to search. This can be empty to get all the users.
+	 * @param int $limit     The limit of results
+	 * @param int $offset    The offset of the results
+	 * @return array<string,IUser> Users indexed by uid
+	 * @since 27.0.0
+	 */
+	public function searchInGroup(string $gid, string $search = '', int $limit = -1, int $offset = 0): array;
+}
diff --git a/lib/public/GroupInterface.php b/lib/public/GroupInterface.php
index b7c07136126..56863100c05 100644
--- a/lib/public/GroupInterface.php
+++ b/lib/public/GroupInterface.php
@@ -106,13 +106,15 @@ interface GroupInterface {
 	public function groupExists($gid);
 
 	/**
-	 * get a list of all users in a group
+	 * @brief Get a list of user ids in a group matching the given search parameters.
+	 *
 	 * @param string $gid
 	 * @param string $search
 	 * @param int $limit
 	 * @param int $offset
-	 * @return array an array of user ids
+	 * @return array<int,string> an array of user ids
 	 * @since 4.5.0
+	 * @deprecated 27.0.0 Use searchInGroup instead, for performance reasons
 	 */
 	public function usersInGroup($gid, $search = '', $limit = -1, $offset = 0);
 }
diff --git a/lib/public/IGroup.php b/lib/public/IGroup.php
index ba13359c472..ec26cc55b69 100644
--- a/lib/public/IGroup.php
+++ b/lib/public/IGroup.php
@@ -99,7 +99,7 @@ interface IGroup {
 	 * @return \OCP\IUser[]
 	 * @since 8.0.0
 	 */
-	public function searchUsers($search, $limit = null, $offset = null);
+	public function searchUsers(string $search, ?int $limit = null, ?int $offset = null): array;
 
 	/**
 	 * returns the number of users matching the search string
diff --git a/tests/lib/Group/GroupTest.php b/tests/lib/Group/GroupTest.php
index 60f15a65732..ac648fd7b4b 100644
--- a/tests/lib/Group/GroupTest.php
+++ b/tests/lib/Group/GroupTest.php
@@ -303,14 +303,14 @@ class GroupTest extends \Test\TestCase {
 		$group = new \OC\Group\Group('group1', [$backend], $this->dispatcher, $userManager);
 
 		$backend->expects($this->once())
-			->method('usersInGroup')
+			->method('searchInGroup')
 			->with('group1', '2')
-			->willReturn(['user2']);
+			->willReturn(['user2' => new \OC\User\User('user2', null, $this->dispatcher)]);
 
 		$users = $group->searchUsers('2');
 
 		$this->assertEquals(1, count($users));
-		$user2 = $users['user2'];
+		$user2 = reset($users);
 		$this->assertEquals('user2', $user2->getUID());
 	}
 
@@ -325,18 +325,18 @@ class GroupTest extends \Test\TestCase {
 		$group = new \OC\Group\Group('group1', [$backend1, $backend2], $this->dispatcher, $userManager);
 
 		$backend1->expects($this->once())
-			->method('usersInGroup')
+			->method('searchInGroup')
 			->with('group1', '2')
-			->willReturn(['user2']);
+			->willReturn(['user2' => new \OC\User\User('user2', null, $this->dispatcher)]);
 		$backend2->expects($this->once())
-			->method('usersInGroup')
+			->method('searchInGroup')
 			->with('group1', '2')
-			->willReturn(['user2']);
+			->willReturn(['user2' => new \OC\User\User('user2', null, $this->dispatcher)]);
 
 		$users = $group->searchUsers('2');
 
 		$this->assertEquals(1, count($users));
-		$user2 = $users['user2'];
+		$user2 = reset($users);
 		$this->assertEquals('user2', $user2->getUID());
 	}
 
@@ -348,14 +348,14 @@ class GroupTest extends \Test\TestCase {
 		$group = new \OC\Group\Group('group1', [$backend], $this->dispatcher, $userManager);
 
 		$backend->expects($this->once())
-			->method('usersInGroup')
+			->method('searchInGroup')
 			->with('group1', 'user', 1, 1)
-			->willReturn(['user2']);
+			->willReturn(['user2' => new \OC\User\User('user2', null, $this->dispatcher)]);
 
 		$users = $group->searchUsers('user', 1, 1);
 
 		$this->assertEquals(1, count($users));
-		$user2 = $users['user2'];
+		$user2 = reset($users);
 		$this->assertEquals('user2', $user2->getUID());
 	}
 
@@ -370,19 +370,19 @@ class GroupTest extends \Test\TestCase {
 		$group = new \OC\Group\Group('group1', [$backend1, $backend2], $this->dispatcher, $userManager);
 
 		$backend1->expects($this->once())
-			->method('usersInGroup')
+			->method('searchInGroup')
 			->with('group1', 'user', 2, 1)
-			->willReturn(['user2']);
+			->willReturn(['user2' => new \OC\User\User('user2', null, $this->dispatcher)]);
 		$backend2->expects($this->once())
-			->method('usersInGroup')
+			->method('searchInGroup')
 			->with('group1', 'user', 2, 1)
-			->willReturn(['user1']);
+			->willReturn(['user1' => new \OC\User\User('user1', null, $this->dispatcher)]);
 
 		$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());
 	}
diff --git a/tests/lib/Group/ManagerTest.php b/tests/lib/Group/ManagerTest.php
index 5e29f974706..710d3888d55 100644
--- a/tests/lib/Group/ManagerTest.php
+++ b/tests/lib/Group/ManagerTest.php
@@ -24,8 +24,10 @@
 namespace Test\Group;
 
 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;
@@ -33,6 +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;
@@ -78,7 +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',
@@ -91,6 +96,7 @@ class ManagerTest extends TestCase {
 				'createGroup',
 				'addToGroup',
 				'removeFromGroup',
+				'searchInGroup',
 			])
 			->getMock();
 		$backend->expects($this->any())
@@ -724,7 +730,7 @@ class ManagerTest extends TestCase {
 
 	public function testDisplayNamesInGroupWithOneUserBackendAndSearchEmpty() {
 		/**
-		 * @var \PHPUnit\Framework\MockObject\MockObject | \OC\Group\Backend $backend
+		 * @var \PHPUnit\Framework\MockObject\MockObject|\OC\Group\Backend $backend
 		 */
 		$backend = $this->getTestBackend();
 		$backend->expects($this->exactly(1))
@@ -733,22 +739,11 @@ class ManagerTest extends TestCase {
 			->willReturn(true);
 
 		$backend->expects($this->once())
-			->method('usersInGroup')
+			->method('searchInGroup')
 			->with('testgroup', '', -1, 0)
-			->willReturn(['user2', 'user33']);
+			->willReturn(['user2' => $this->getTestUser('user2'), 'user33' => $this->getTestUser('user33')]);
 
-		$this->userManager->expects($this->any())
-			->method('get')
-			->willReturnCallback(function ($uid) {
-				switch ($uid) {
-					case 'user1': return $this->getTestUser('user1');
-					case 'user2': return $this->getTestUser('user2');
-					case 'user3': return $this->getTestUser('user3');
-					case 'user33': return $this->getTestUser('user33');
-					default:
-						return null;
-				}
-			});
+		$this->userManager->expects($this->never())->method('get');
 
 		$manager = new \OC\Group\Manager($this->userManager, $this->dispatcher, $this->logger, $this->cache);
 		$manager->addBackend($backend);
@@ -772,22 +767,11 @@ class ManagerTest extends TestCase {
 			->willReturn(true);
 
 		$backend->expects($this->once())
-			->method('usersInGroup')
+			->method('searchInGroup')
 			->with('testgroup', '', 1, 0)
-			->willReturn(['user2']);
+			->willReturn([new User('user2', null, $this->dispatcher)]);
 
-		$this->userManager->expects($this->any())
-			->method('get')
-			->willReturnCallback(function ($uid) {
-				switch ($uid) {
-					case 'user1': return $this->getTestUser('user1');
-					case 'user2': return $this->getTestUser('user2');
-					case 'user3': return $this->getTestUser('user3');
-					case 'user33': return $this->getTestUser('user33');
-					default:
-						return null;
-				}
-			});
+		$this->userManager->expects($this->never())->method('get');
 
 		$manager = new \OC\Group\Manager($this->userManager, $this->dispatcher, $this->logger, $this->cache);
 		$manager->addBackend($backend);
@@ -811,22 +795,11 @@ class ManagerTest extends TestCase {
 			->willReturn(true);
 
 		$backend->expects($this->once())
-			->method('usersInGroup')
+			->method('searchInGroup')
 			->with('testgroup', '', 1, 1)
-			->willReturn(['user33']);
+			->willReturn(['user33' => $this->getTestUser('user33')]);
 
-		$this->userManager->expects($this->any())
-			->method('get')
-			->willReturnCallback(function ($uid) {
-				switch ($uid) {
-					case 'user1': return $this->getTestUser('user1');
-					case 'user2': return $this->getTestUser('user2');
-					case 'user3': return $this->getTestUser('user3');
-					case 'user33': return $this->getTestUser('user33');
-					default:
-						return null;
-				}
-			});
+		$this->userManager->expects($this->never())->method('get');
 
 		$manager = new \OC\Group\Manager($this->userManager, $this->dispatcher, $this->logger, $this->cache);
 		$manager->addBackend($backend);
diff --git a/tests/lib/Util/Group/Dummy.php b/tests/lib/Util/Group/Dummy.php
index 3735a5e1167..a864c8ce9d9 100644
--- a/tests/lib/Util/Group/Dummy.php
+++ b/tests/lib/Util/Group/Dummy.php
@@ -29,12 +29,18 @@
 
 namespace Test\Util\Group;
 
-use OC\Group\Backend;
+use Test\Util\User\Dummy as DummyUser;
+use OCP\Group\Backend\ABackend;
+use OCP\Group\Backend\IDeleteGroupBackend;
+use OCP\Group\Backend\IAddToGroupBackend;
+use OCP\Group\Backend\IRemoveFromGroupBackend;
+use OCP\Group\Backend\ICreateGroupBackend;
+use OCP\Group\Backend\ICountUsersBackend;
 
 /**
- * dummy group backend, does not keep state, only for testing use
+ * Dummy group backend, does not keep state, only for testing use
  */
-class Dummy extends Backend {
+class Dummy extends ABackend implements ICreateGroupBackend, IDeleteGroupBackend, IAddToGroupBackend, IRemoveFromGroupBackend, ICountUsersBackend {
 	private $groups = [];
 	/**
 	 * Try to create a new group
@@ -44,7 +50,7 @@ class Dummy extends Backend {
 	 * Tries to create a new group. If the group name already exists, false will
 	 * be returned.
 	 */
-	public function createGroup($gid) {
+	public function createGroup(string $gid): bool {
 		if (!isset($this->groups[$gid])) {
 			$this->groups[$gid] = [];
 			return true;
@@ -60,7 +66,7 @@ class Dummy extends Backend {
 	 *
 	 * Deletes a group and removes it from the group_user-table
 	 */
-	public function deleteGroup($gid) {
+	public function deleteGroup(string $gid): bool {
 		if (isset($this->groups[$gid])) {
 			unset($this->groups[$gid]);
 			return true;
@@ -93,7 +99,7 @@ class Dummy extends Backend {
 	 *
 	 * Adds a user to a group.
 	 */
-	public function addToGroup($uid, $gid) {
+	public function addToGroup(string $uid, string $gid): bool {
 		if (isset($this->groups[$gid])) {
 			if (array_search($uid, $this->groups[$gid]) === false) {
 				$this->groups[$gid][] = $uid;
@@ -114,7 +120,7 @@ class Dummy extends Backend {
 	 *
 	 * removes the user from a group.
 	 */
-	public function removeFromGroup($uid, $gid) {
+	public function removeFromGroup(string $uid, string $gid): bool {
 		if (isset($this->groups[$gid])) {
 			if (($index = array_search($uid, $this->groups[$gid])) !== false) {
 				unset($this->groups[$gid][$index]);
@@ -192,6 +198,25 @@ class Dummy extends Backend {
 		}
 	}
 
+	public function searchInGroup(string $gid, string $search = '', int $limit = -1, int $offset = 0): array {
+		if (isset($this->groups[$gid])) {
+			if (empty($search)) {
+				$length = $limit < 0 ? null : $limit;
+				$users = array_slice($this->groups[$gid], $offset, $length);
+				return array_map(fn ($user) => new DummyUser($user, ''));
+			}
+			$result = [];
+			foreach ($this->groups[$gid] as $user) {
+				if (stripos($user, $search) !== false) {
+					$result[$user] = new DummyUser($user, '');
+				}
+			}
+			return $result;
+		} else {
+			return [];
+		}
+	}
+
 	/**
 	 * get the number of all users in a group
 	 * @param string $gid
@@ -200,7 +225,7 @@ class Dummy extends Backend {
 	 * @param int $offset
 	 * @return int
 	 */
-	public function countUsersInGroup($gid, $search = '', $limit = -1, $offset = 0) {
+	public function countUsersInGroup(string $gid, string $search = ''): int {
 		if (isset($this->groups[$gid])) {
 			if (empty($search)) {
 				return count($this->groups[$gid]);
@@ -213,5 +238,10 @@ class Dummy extends Backend {
 			}
 			return $count;
 		}
+		return 0;
+	}
+
+	public function groupExists($gid) {
+		return isset($this->groups[$gid]);
 	}
 }