fix: Make user removal more resilient

Currently there is a problem if an exception is thrown in `User::delete`,
because at that point the user is already removed from the backend,
but not all data is deleted.

There is no way to recover from this state, as the user is gone no information is available anymore.
This means the data is still available on the server but can not removed by any API anymore.

The solution here is to first set a flag and backup the user home,
this can be used to recover failed user deletions in a way the delete can be re-tried.

Signed-off-by: Ferdinand Thiessen <opensource@fthiessen.de>

lib/composer/composer/autoload_classmap.php

@@ -1796,6 +1796,7 @@ return array(
     'OC\\RepairException' => $baseDir . '/lib/private/RepairException.php',
     'OC\\Repair\\AddAppConfigLazyMigration' => $baseDir . '/lib/private/Repair/AddAppConfigLazyMigration.php',
     'OC\\Repair\\AddBruteForceCleanupJob' => $baseDir . '/lib/private/Repair/AddBruteForceCleanupJob.php',
+    'OC\\Repair\\AddCleanupDeletedUsersBackgroundJob' => $baseDir . '/lib/private/Repair/AddCleanupDeletedUsersBackgroundJob.php',
     'OC\\Repair\\AddCleanupUpdaterBackupsJob' => $baseDir . '/lib/private/Repair/AddCleanupUpdaterBackupsJob.php',
     'OC\\Repair\\AddMetadataGenerationJob' => $baseDir . '/lib/private/Repair/AddMetadataGenerationJob.php',
     'OC\\Repair\\AddRemoveOldTasksBackgroundJob' => $baseDir . '/lib/private/Repair/AddRemoveOldTasksBackgroundJob.php',
@@ -1995,8 +1996,10 @@ return array(
     'OC\\UserStatus\\Manager' => $baseDir . '/lib/private/UserStatus/Manager.php',
     'OC\\User\\AvailabilityCoordinator' => $baseDir . '/lib/private/User/AvailabilityCoordinator.php',
     'OC\\User\\Backend' => $baseDir . '/lib/private/User/Backend.php',
+    'OC\\User\\BackgroundJobs\\CleanupDeletedUsers' => $baseDir . '/lib/private/User/BackgroundJobs/CleanupDeletedUsers.php',
     'OC\\User\\Database' => $baseDir . '/lib/private/User/Database.php',
     'OC\\User\\DisplayNameCache' => $baseDir . '/lib/private/User/DisplayNameCache.php',
+    'OC\\User\\FailedUsersBackend' => $baseDir . '/lib/private/User/FailedUsersBackend.php',
     'OC\\User\\LazyUser' => $baseDir . '/lib/private/User/LazyUser.php',
     'OC\\User\\Listeners\\BeforeUserDeletedListener' => $baseDir . '/lib/private/User/Listeners/BeforeUserDeletedListener.php',
     'OC\\User\\Listeners\\UserChangedListener' => $baseDir . '/lib/private/User/Listeners/UserChangedListener.php',

lib/composer/composer/autoload_static.php

@@ -1829,6 +1829,7 @@ class ComposerStaticInit749170dad3f5e7f9ca158f5a9f04f6a2
         'OC\\RepairException' => __DIR__ . '/../../..' . '/lib/private/RepairException.php',
         'OC\\Repair\\AddAppConfigLazyMigration' => __DIR__ . '/../../..' . '/lib/private/Repair/AddAppConfigLazyMigration.php',
         'OC\\Repair\\AddBruteForceCleanupJob' => __DIR__ . '/../../..' . '/lib/private/Repair/AddBruteForceCleanupJob.php',
+        'OC\\Repair\\AddCleanupDeletedUsersBackgroundJob' => __DIR__ . '/../../..' . '/lib/private/Repair/AddCleanupDeletedUsersBackgroundJob.php',
         'OC\\Repair\\AddCleanupUpdaterBackupsJob' => __DIR__ . '/../../..' . '/lib/private/Repair/AddCleanupUpdaterBackupsJob.php',
         'OC\\Repair\\AddMetadataGenerationJob' => __DIR__ . '/../../..' . '/lib/private/Repair/AddMetadataGenerationJob.php',
         'OC\\Repair\\AddRemoveOldTasksBackgroundJob' => __DIR__ . '/../../..' . '/lib/private/Repair/AddRemoveOldTasksBackgroundJob.php',
@@ -2028,8 +2029,10 @@ class ComposerStaticInit749170dad3f5e7f9ca158f5a9f04f6a2
         'OC\\UserStatus\\Manager' => __DIR__ . '/../../..' . '/lib/private/UserStatus/Manager.php',
         'OC\\User\\AvailabilityCoordinator' => __DIR__ . '/../../..' . '/lib/private/User/AvailabilityCoordinator.php',
         'OC\\User\\Backend' => __DIR__ . '/../../..' . '/lib/private/User/Backend.php',
+        'OC\\User\\BackgroundJobs\\CleanupDeletedUsers' => __DIR__ . '/../../..' . '/lib/private/User/BackgroundJobs/CleanupDeletedUsers.php',
         'OC\\User\\Database' => __DIR__ . '/../../..' . '/lib/private/User/Database.php',
         'OC\\User\\DisplayNameCache' => __DIR__ . '/../../..' . '/lib/private/User/DisplayNameCache.php',
+        'OC\\User\\FailedUsersBackend' => __DIR__ . '/../../..' . '/lib/private/User/FailedUsersBackend.php',
         'OC\\User\\LazyUser' => __DIR__ . '/../../..' . '/lib/private/User/LazyUser.php',
         'OC\\User\\Listeners\\BeforeUserDeletedListener' => __DIR__ . '/../../..' . '/lib/private/User/Listeners/BeforeUserDeletedListener.php',
         'OC\\User\\Listeners\\UserChangedListener' => __DIR__ . '/../../..' . '/lib/private/User/Listeners/UserChangedListener.php',

lib/private/Authentication/Listeners/UserDeletedFilesCleanupListener.php

@@ -16,27 +16,31 @@ use OCP\Files\Config\IMountProviderCollection;
 use OCP\Files\Storage\IStorage;
 use OCP\User\Events\BeforeUserDeletedEvent;
 use OCP\User\Events\UserDeletedEvent;
+use Psr\Log\LoggerInterface;
 
 /** @template-implements IEventListener<BeforeUserDeletedEvent|UserDeletedEvent> */
 class UserDeletedFilesCleanupListener implements IEventListener {
 	/** @var array<string,IStorage> */
 	private $homeStorageCache = [];
 
-	/** @var IMountProviderCollection */
-	private $mountProviderCollection;
-
-	public function __construct(IMountProviderCollection $mountProviderCollection) {
-		$this->mountProviderCollection = $mountProviderCollection;
+	public function __construct(
+		private IMountProviderCollection $mountProviderCollection,
+		private LoggerInterface $logger,
+	) {
 	}
 
 	public function handle(Event $event): void {
+		$user = $event->getUser();
+
 		// since we can't reliably get the user home storage after the user is deleted
 		// but the user deletion might get canceled during the before event
 		// we only cache the user home storage during the before event and then do the
 		// action deletion during the after event
 
 		if ($event instanceof BeforeUserDeletedEvent) {
-			$userHome = $this->mountProviderCollection->getHomeMountForUser($event->getUser());
+			$this->logger->debug('Prepare deleting storage for user {userId}', ['userId' => $user->getUID()]);
+
+			$userHome = $this->mountProviderCollection->getHomeMountForUser($user);
 			$storage = $userHome->getStorage();
 			if (!$storage) {
 				throw new \Exception('Account has no home storage');
@@ -51,12 +55,14 @@ class UserDeletedFilesCleanupListener implements IEventListener {
 			$this->homeStorageCache[$event->getUser()->getUID()] = $storage;
 		}
 		if ($event instanceof UserDeletedEvent) {
-			if (!isset($this->homeStorageCache[$event->getUser()->getUID()])) {
+			if (!isset($this->homeStorageCache[$user->getUID()])) {
 				throw new \Exception('UserDeletedEvent fired without matching BeforeUserDeletedEvent');
 			}
-			$storage = $this->homeStorageCache[$event->getUser()->getUID()];
+			$storage = $this->homeStorageCache[$user->getUID()];
 			$cache = $storage->getCache();
 			$storage->rmdir('');
+			$this->logger->debug('Deleted storage for user {userId}', ['userId' => $user->getUID()]);
+
 			if ($cache instanceof Cache) {
 				$cache->clear();
 			} else {

lib/private/Repair.php

@@ -11,6 +11,7 @@ use OC\DB\Connection;
 use OC\DB\ConnectionAdapter;
 use OC\Repair\AddAppConfigLazyMigration;
 use OC\Repair\AddBruteForceCleanupJob;
+use OC\Repair\AddCleanupDeletedUsersBackgroundJob;
 use OC\Repair\AddCleanupUpdaterBackupsJob;
 use OC\Repair\AddMetadataGenerationJob;
 use OC\Repair\AddRemoveOldTasksBackgroundJob;
@@ -192,6 +193,7 @@ class Repair implements IOutput {
 			\OCP\Server::get(AddAppConfigLazyMigration::class),
 			\OCP\Server::get(RepairLogoDimension::class),
 			\OCP\Server::get(RemoveLegacyDatadirFile::class),
+			\OCP\Server::get(AddCleanupDeletedUsersBackgroundJob::class),
 		];
 	}
 

lib/private/Repair/AddCleanupDeletedUsersBackgroundJob.php

@@ -0,0 +1,30 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * SPDX-FileCopyrightText: 2024 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+namespace OC\Repair;
+
+use OC\User\BackgroundJobs\CleanupDeletedUsers;
+use OCP\BackgroundJob\IJobList;
+use OCP\Migration\IOutput;
+use OCP\Migration\IRepairStep;
+
+class AddCleanupDeletedUsersBackgroundJob implements IRepairStep {
+	private IJobList $jobList;
+
+	public function __construct(IJobList $jobList) {
+		$this->jobList = $jobList;
+	}
+
+	public function getName(): string {
+		return 'Add cleanup-deleted-users background job';
+	}
+
+	public function run(IOutput $output) {
+		$this->jobList->add(CleanupDeletedUsers::class);
+	}
+}

lib/private/Setup.php

@@ -17,6 +17,7 @@ use OC\Authentication\Token\TokenCleanupJob;
 use OC\Log\Rotate;
 use OC\Preview\BackgroundCleanupJob;
 use OC\TextProcessing\RemoveOldTasksBackgroundJob;
+use OC\User\BackgroundJobs\CleanupDeletedUsers;
 use OCP\AppFramework\Utility\ITimeFactory;
 use OCP\BackgroundJob\IJobList;
 use OCP\Defaults;
@@ -415,6 +416,7 @@ class Setup {
 		$jobList->add(Rotate::class);
 		$jobList->add(BackgroundCleanupJob::class);
 		$jobList->add(RemoveOldTasksBackgroundJob::class);
+		$jobList->add(CleanupDeletedUsers::class);
 	}
 
 	/**

lib/private/User/Backend.php

@@ -107,9 +107,9 @@ abstract class Backend implements UserInterface {
 	/**
 	 * get the user's home directory
 	 * @param string $uid the username
-	 * @return boolean
+	 * @return string|boolean
 	 */
-	public function getHome($uid) {
+	public function getHome(string $uid) {
 		return false;
 	}
 

lib/private/User/BackgroundJobs/CleanupDeletedUsers.php

@@ -0,0 +1,55 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * SPDX-FileCopyrightText: 2024 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+namespace OC\User\BackgroundJobs;
+
+use OC\User\FailedUsersBackend;
+use OC\User\Manager;
+use OC\User\User;
+use OCP\AppFramework\Utility\ITimeFactory;
+use OCP\BackgroundJob\TimedJob;
+use OCP\EventDispatcher\IEventDispatcher;
+use OCP\IConfig;
+use Psr\Log\LoggerInterface;
+
+class CleanupDeletedUsers extends TimedJob {
+	public function __construct(
+		ITimeFactory $time,
+		private Manager $userManager,
+		private IConfig $config,
+		private LoggerInterface $logger,
+	) {
+		parent::__construct($time);
+		$this->setInterval(3600);
+	}
+
+	protected function run($argument): void {
+		$backend = new FailedUsersBackend($this->config);
+		$users = $backend->getUsers();
+
+		if (empty($users)) {
+			$this->logger->debug('No failed deleted users found.');
+			return;
+		}
+
+		foreach ($users as $userId) {
+			try {
+				$user = new User(
+					$userId,
+					$backend,
+					\OCP\Server::get(IEventDispatcher::class),
+					config: $this->config,
+				);
+				$user->delete();
+				$this->logger->info('Cleaned up deleted user {userId}', ['userId' => $userId]);
+			} catch (\Throwable $error) {
+				$this->logger->warning('Could not cleanup deleted user {userId}', ['userId' => $userId, 'exception' => $error]);
+			}
+		}
+	}
+}

lib/private/User/FailedUsersBackend.php

@@ -0,0 +1,46 @@
+<?php
+
+/**
+ * SPDX-FileCopyrightText: 2024 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+namespace OC\User;
+
+use OCP\IConfig;
+use OCP\IUserBackend;
+use OCP\User\Backend\IGetHomeBackend;
+
+/**
+ * This is a "fake" backend for users that were deleted,
+ * but not properly removed from Nextcloud (e.g. an exception occurred).
+ * This backend is only needed because some APIs in user-deleted-events require a "real" user with backend.
+ */
+class FailedUsersBackend extends Backend implements IGetHomeBackend, IUserBackend {
+
+	public function __construct(
+		private IConfig $config,
+	) {
+	}
+
+	public function deleteUser($uid): bool {
+		// fake true, deleting failed users is automatically handled by User::delete()
+		return true;
+	}
+
+	public function getBackendName(): string {
+		return 'deleted users';
+	}
+
+	public function userExists($uid) {
+		return $this->config->getUserValue($uid, 'core', 'deleted') === 'true';
+	}
+
+	public function getHome(string $uid): string|false {
+		return $this->config->getUserValue($uid, 'core', 'deleted.backup-home') ?: false;
+	}
+
+	public function getUsers($search = '', $limit = null, $offset = null) {
+		return $this->config->getUsersForUserValue('core', 'deleted', 'true');
+	}
+
+}

lib/private/User/User.php

@@ -19,6 +19,8 @@ use OCP\Group\Events\BeforeUserRemovedEvent;
 use OCP\Group\Events\UserRemovedEvent;
 use OCP\IAvatarManager;
 use OCP\IConfig;
+use OCP\IDBConnection;
+use OCP\IGroupManager;
 use OCP\IImage;
 use OCP\IURLGenerator;
 use OCP\IUser;
@@ -37,30 +39,27 @@ use OCP\User\Events\UserChangedEvent;
 use OCP\User\Events\UserDeletedEvent;
 use OCP\User\GetQuotaEvent;
 use OCP\UserInterface;
+use Psr\Log\LoggerInterface;
+
 use function json_decode;
 use function json_encode;
 
 class User implements IUser {
 	private const CONFIG_KEY_MANAGERS = 'manager';
 
+	private IConfig $config;
+	private IURLGenerator $urlGenerator;
+
 	/** @var IAccountManager */
 	protected $accountManager;
-	/** @var string */
-	private $uid;
 
 	/** @var string|null */
 	private $displayName;
 
-	/** @var UserInterface|null */
-	private $backend;
-
-	/** @var IEventDispatcher */
-	private $dispatcher;
-
 	/** @var bool|null */
 	private $enabled;
 
-	/** @var Emitter|Manager */
+	/** @var Emitter|Manager|null */
 	private $emitter;
 
 	/** @var string */
@@ -69,28 +68,20 @@ class User implements IUser {
 	/** @var int|null */
 	private $lastLogin;
 
-	/** @var \OCP\IConfig */
-	private $config;
-
 	/** @var IAvatarManager */
 	private $avatarManager;
 
-	/** @var IURLGenerator */
-	private $urlGenerator;
-
-	public function __construct(string $uid, ?UserInterface $backend, IEventDispatcher $dispatcher, $emitter = null, ?IConfig $config = null, $urlGenerator = null) {
-		$this->uid = $uid;
-		$this->backend = $backend;
+	public function __construct(
+		private string $uid,
+		private ?UserInterface $backend,
+		private IEventDispatcher $dispatcher,
+		$emitter = null,
+		?IConfig $config = null,
+		$urlGenerator = null,
+	) {
 		$this->emitter = $emitter;
-		if (is_null($config)) {
-			$config = \OC::$server->getConfig();
-		}
-		$this->config = $config;
-		$this->urlGenerator = $urlGenerator;
-		if (is_null($this->urlGenerator)) {
-			$this->urlGenerator = \OC::$server->getURLGenerator();
-		}
-		$this->dispatcher = $dispatcher;
+		$this->config = $config ?? \OCP\Server::get(IConfig::class);
+		$this->urlGenerator = $urlGenerator ?? \OCP\Server::get(IURLGenerator::class);
 	}
 
 	/**
@@ -244,50 +235,85 @@ class User implements IUser {
 	 * @return bool
 	 */
 	public function delete() {
+		if ($this->backend === null) {
+			\OCP\Server::get(LoggerInterface::class)->error('Cannot delete user: No backend set');
+			return false;
+		}
+
 		if ($this->emitter) {
 			/** @deprecated 21.0.0 use BeforeUserDeletedEvent event with the IEventDispatcher instead */
 			$this->emitter->emit('\OC\User', 'preDelete', [$this]);
 		}
 		$this->dispatcher->dispatchTyped(new BeforeUserDeletedEvent($this));
+
+		// Set delete flag on the user - this is needed to ensure that the user data is removed if there happen any exception in the backend
+		// because we can not restore the user meaning we could not rollback to any stable state otherwise.
+		$this->config->setUserValue($this->uid, 'core', 'deleted', 'true');
+		// We also need to backup the home path as this can not be reconstructed later if the original backend uses custom home paths
+		$this->config->setUserValue($this->uid, 'core', 'deleted.backup-home', $this->getHome());
+
+		// Try to delete the user on the backend
 		$result = $this->backend->deleteUser($this->uid);
-		if ($result) {
-			// FIXME: Feels like an hack - suggestions?
-
-			$groupManager = \OC::$server->getGroupManager();
-			// We have to delete the user from all groups
-			foreach ($groupManager->getUserGroupIds($this) as $groupId) {
-				$group = $groupManager->get($groupId);
-				if ($group) {
-					$this->dispatcher->dispatchTyped(new BeforeUserRemovedEvent($group, $this));
-					$group->removeUser($this);
-					$this->dispatcher->dispatchTyped(new UserRemovedEvent($group, $this));
-				}
-			}
-			// Delete the user's keys in preferences
-			\OC::$server->getConfig()->deleteAllUserValues($this->uid);
-
-			\OC::$server->get(ICommentsManager::class)->deleteReferencesOfActor('users', $this->uid);
-			\OC::$server->get(ICommentsManager::class)->deleteReadMarksFromUser($this);
-
-			/** @var AvatarManager $avatarManager */
-			$avatarManager = \OCP\Server::get(AvatarManager::class);
-			$avatarManager->deleteUserAvatar($this->uid);
-
-			$notification = \OC::$server->get(INotificationManager::class)->createNotification();
-			$notification->setUser($this->uid);
-			\OC::$server->get(INotificationManager::class)->markProcessed($notification);
-
-			/** @var AccountManager $accountManager */
-			$accountManager = \OCP\Server::get(AccountManager::class);
-			$accountManager->deleteUser($this);
-
-			if ($this->emitter) {
-				/** @deprecated 21.0.0 use UserDeletedEvent event with the IEventDispatcher instead */
-				$this->emitter->emit('\OC\User', 'postDelete', [$this]);
-			}
-			$this->dispatcher->dispatchTyped(new UserDeletedEvent($this));
+		if ($result === false) {
+			// The deletion was aborted or something else happened, we are in a defined state, so remove the delete flag
+			$this->config->deleteUserValue($this->uid, 'core', 'deleted');
+			return false;
 		}
-		return !($result === false);
+
+		// We have to delete the user from all groups
+		$groupManager = \OCP\Server::get(IGroupManager::class);
+		foreach ($groupManager->getUserGroupIds($this) as $groupId) {
+			$group = $groupManager->get($groupId);
+			if ($group) {
+				$this->dispatcher->dispatchTyped(new BeforeUserRemovedEvent($group, $this));
+				$group->removeUser($this);
+				$this->dispatcher->dispatchTyped(new UserRemovedEvent($group, $this));
+			}
+		}
+
+		$commentsManager = \OCP\Server::get(ICommentsManager::class);
+		$commentsManager->deleteReferencesOfActor('users', $this->uid);
+		$commentsManager->deleteReadMarksFromUser($this);
+
+		$avatarManager = \OCP\Server::get(AvatarManager::class);
+		$avatarManager->deleteUserAvatar($this->uid);
+
+		$notificationManager = \OCP\Server::get(INotificationManager::class);
+		$notification = $notificationManager->createNotification();
+		$notification->setUser($this->uid);
+		$notificationManager->markProcessed($notification);
+
+		$accountManager = \OCP\Server::get(AccountManager::class);
+		$accountManager->deleteUser($this);
+
+		$database = \OCP\Server::get(IDBConnection::class);
+		try {
+			// We need to create a transaction to make sure we are in a defined state
+			// because if all user values are removed also the flag is gone, but if an exception happens (e.g. database lost connection on the set operation)
+			// exactly here we are in an undefined state as the data is still present but the user does not exist on the system anymore.
+			$database->beginTransaction();
+			// Remove all user settings
+			$this->config->deleteAllUserValues($this->uid);
+			// But again set flag that this user is about to be deleted
+			$this->config->setUserValue($this->uid, 'core', 'deleted', 'true');
+			$this->config->setUserValue($this->uid, 'core', 'deleted.backup-home', $this->getHome());
+			// Commit the transaction so we are in a defined state: either the preferences are removed or an exception occurred but the delete flag is still present
+			$database->commit();
+		} catch (\Throwable $e) {
+			$database->rollback();
+			throw $e;
+		}
+
+		if ($this->emitter) {
+			/** @deprecated 21.0.0 use UserDeletedEvent event with the IEventDispatcher instead */
+			$this->emitter->emit('\OC\User', 'postDelete', [$this]);
+		}
+		$this->dispatcher->dispatchTyped(new UserDeletedEvent($this));
+
+		// Finally we can unset the delete flag and all other states
+		$this->config->deleteAllUserValues($this->uid);
+
+		return true;
 	}
 
 	/**
@@ -344,10 +370,8 @@ class User implements IUser {
 			/** @psalm-suppress UndefinedInterfaceMethod Once we get rid of the legacy implementsActions, psalm won't complain anymore */
 			if (($this->backend instanceof IGetHomeBackend || $this->backend->implementsActions(Backend::GET_HOME)) && $home = $this->backend->getHome($this->uid)) {
 				$this->home = $home;
-			} elseif ($this->config) {
-				$this->home = $this->config->getSystemValueString('datadirectory', \OC::$SERVERROOT . '/data') . '/' . $this->uid;
 			} else {
-				$this->home = \OC::$SERVERROOT . '/data/' . $this->uid;
+				$this->home = $this->config->getSystemValueString('datadirectory', \OC::$SERVERROOT . '/data') . '/' . $this->uid;
 			}
 		}
 		return $this->home;

tests/lib/User/UserTest.php

@@ -513,14 +513,25 @@ class UserTest extends TestCase {
 		$test = $this;
 
 		/**
-		 * @var Backend | MockObject $backend
+		 * @var UserInterface&MockObject $backend
 		 */
 		$backend = $this->createMock(\Test\Util\User\Dummy::class);
 		$backend->expects($this->once())
 			->method('deleteUser')
 			->willReturn($result);
+
+		$config = $this->createMock(IConfig::class);
+		$config->method('getSystemValue')
+			->willReturnArgument(1);
+		$config->method('getSystemValueString')
+			->willReturnArgument(1);
+		$config->method('getSystemValueBool')
+			->willReturnArgument(1);
+		$config->method('getSystemValueInt')
+			->willReturnArgument(1);
+
 		$emitter = new PublicEmitter();
-		$user = new User('foo', $backend, $this->dispatcher, $emitter);
+		$user = new User('foo', $backend, $this->dispatcher, $emitter, $config);
 
 		/**
 		 * @param User $user
@@ -533,21 +544,11 @@ class UserTest extends TestCase {
 		$emitter->listen('\OC\User', 'preDelete', $hook);
 		$emitter->listen('\OC\User', 'postDelete', $hook);
 
-		$config = $this->createMock(IConfig::class);
 		$commentsManager = $this->createMock(ICommentsManager::class);
 		$notificationManager = $this->createMock(INotificationManager::class);
 
-		$config->method('getSystemValue')
-			->willReturnArgument(1);
-		$config->method('getSystemValueString')
-			->willReturnArgument(1);
-		$config->method('getSystemValueBool')
-			->willReturnArgument(1);
-		$config->method('getSystemValueInt')
-			->willReturnArgument(1);
-
 		if ($result) {
-			$config->expects($this->once())
+			$config->expects($this->atLeastOnce())
 				->method('deleteAllUserValues')
 				->with('foo');
 
@@ -586,7 +587,6 @@ class UserTest extends TestCase {
 
 		$this->overwriteService(\OCP\Notification\IManager::class, $notificationManager);
 		$this->overwriteService(\OCP\Comments\ICommentsManager::class, $commentsManager);
-		$this->overwriteService(AllConfig::class, $config);
 
 		$this->assertSame($result, $user->delete());
 
@@ -597,6 +597,59 @@ class UserTest extends TestCase {
 		$this->assertEquals($expectedHooks, $hooksCalled);
 	}
 
+	public function testDeleteRecoverState() {
+		$backend = $this->createMock(\Test\Util\User\Dummy::class);
+		$backend->expects($this->once())
+			->method('deleteUser')
+			->willReturn(true);
+
+		$config = $this->createMock(IConfig::class);
+		$config->method('getSystemValue')
+			->willReturnArgument(1);
+		$config->method('getSystemValueString')
+			->willReturnArgument(1);
+		$config->method('getSystemValueBool')
+			->willReturnArgument(1);
+		$config->method('getSystemValueInt')
+			->willReturnArgument(1);
+
+		$userConfig = [];
+		$config->expects(self::atLeast(2))
+			->method('setUserValue')
+			->willReturnCallback(function () {
+				$userConfig[] = func_get_args();
+			});
+
+		$commentsManager = $this->createMock(ICommentsManager::class);
+		$commentsManager->expects($this->once())
+			->method('deleteReferencesOfActor')
+			->willThrowException(new \Error('Test exception'));
+
+		$this->overwriteService(\OCP\Comments\ICommentsManager::class, $commentsManager);
+		$this->expectException(\Error::class);
+
+		$user = $this->getMockBuilder(User::class)
+			->onlyMethods(['getHome'])
+			->setConstructorArgs(['foo', $backend, $this->dispatcher, null, $config])
+			->getMock();
+		
+		$user->expects(self::atLeastOnce())
+			->method('getHome')
+			->willReturn('/home/path');
+
+		$user->delete();
+
+		$this->assertEqualsCanonicalizing(
+			[
+				['foo', 'core', 'deleted', 'true', null],
+				['foo', 'core', 'deleted.backup-home', '/home/path', null],
+			],
+			$userConfig,
+		);
+
+		$this->restoreService(\OCP\Comments\ICommentsManager::class);
+	}
+
 	public function dataGetCloudId(): array {
 		return [
 			['https://localhost:8888/nextcloud', 'foo@localhost:8888/nextcloud'],