fix(trashbin): properly show deleted by for federated shares

Signed-off-by: Kent Delante <kent@delante.me>
Assisted-by: ClaudeCode:claude-sonnet-5

When a remote user deletes a file in a federated share, the deleted by
column in trashbin shows "Unknown" instead of the remote user. This
fixes it so that it properly shows the remote user under the deleted
by column.

Author: leftybournes

apps/files_trashbin/lib/Trash/LegacyTrashBackend.php

@@ -12,6 +12,7 @@
 use OCA\Files_Trashbin\Helper;
 use OCA\Files_Trashbin\Storage;
 use OCA\Files_Trashbin\Trashbin;
+use OCP\Federation\ICloudIdManager;
 use OCP\Files\FileInfo;
 use OCP\Files\Folder;
 use OCP\Files\IRootFolder;
@@ -28,6 +29,7 @@ class LegacyTrashBackend implements ITrashBackend {
 	public function __construct(
 		private readonly IRootFolder $rootFolder,
 		private readonly IUserManager $userManager,
+		private readonly ICloudIdManager $cloudIdManager,
 	) {
 	}
 
@@ -40,7 +42,7 @@ private function mapTrashItem(FileInfo $file, IUser $user, ?ITrashItem $parent =
 			$originalLocation = $file->getName();
 		}
 		/** @psalm-suppress UndefinedInterfaceMethod */
-		$deletedBy = $this->userManager->get($file['deletedBy']) ?? $parent?->getDeletedBy();
+		$deletedBy = $this->resolveDeletedBy($file['deletedBy']) ?? $parent?->getDeletedBy();
 		$trashFilename = Trashbin::getTrashFilename($file->getName(), $file->getMtime());
 		return new TrashItem(
 			$this,
@@ -127,4 +129,27 @@ public function getTrashNodeById(IUser $user, int $fileId): ?Node {
 			return null;
 		}
 	}
+
+	/**
+	 * Resolve the user that deleted a trash item. Files deleted by a federated share
+	 * recipient only carry the recipient's remote cloud ID, which no local IUserManager
+	 * backend can resolve, so fall back to a display-only user for the cloud ID in that
+	 * case instead of leaving the item without an "Unknown" deleted by user.
+	 */
+	private function resolveDeletedBy(?string $uid): ?IUser {
+		if (!$uid) {
+			return null;
+		}
+
+		$user = $this->userManager->get($uid);
+		if ($user !== null) {
+			return $user;
+		}
+
+		if ($this->cloudIdManager->isValidCloudId($uid)) {
+			return $this->userManager->getDisplayUser($uid);
+		}
+
+		return null;
+	}
 }

lib/private/User/Manager.php

@@ -13,6 +13,7 @@
 use OCP\Config\IUserConfig;
 use OCP\DB\QueryBuilder\IQueryBuilder;
 use OCP\EventDispatcher\IEventDispatcher;
+use OCP\Federation\ICloudIdManager;
 use OCP\HintException;
 use OCP\ICache;
 use OCP\ICacheFactory;
@@ -82,6 +83,7 @@ public function __construct(
 		ICacheFactory $cacheFactory,
 		private IEventDispatcher $eventDispatcher,
 		private LoggerInterface $logger,
+		private ICloudIdManager $cloudIdManager,
 	) {
 		$this->cache = new WithLocalCache($cacheFactory->createDistributed('user_backend_map'));
 		$this->listen('\OC\User', 'postDelete', function (IUser $user): void {
@@ -883,4 +885,16 @@ public function getAvatarUrlLight(string $userId, int $size): string {
 	public function getAvatarUrlDark(string $userId, int $size): string {
 		return ($this->urlGenerator ??= Server::get(IURLGenerator::class))->linkToRouteAbsolute('core.avatar.getAvatarDark', ['userId' => $userId, 'size' => $size]);
 	}
+
+	#[\Override]
+	public function getDisplayUser(string $federatedUserId): ?IUser {
+		try {
+			$cloudId = $this->cloudIdManager->resolveCloudId($federatedUserId);
+		} catch (\InvalidArgumentException $e) {
+			$this->logger->debug($federatedUserId . ' is not a valid cloud id', ['exception' => $e]);
+			return null;
+		}
+
+		return new LazyUser($federatedUserId, $this, $cloudId->getDisplayId());
+	}
 }

lib/public/IUserManager.php

@@ -282,4 +282,15 @@ public function getAvatarUrlLight(string $userId, int $size): string;
 	 * @since 34.0.0
 	 */
 	public function getAvatarUrlDark(string $userId, int $size): string;
+
+	/**
+	 * Get a read-only user for a cloud ID, for showing the display name of a remote
+	 * federation user (e.g. the "deleted by" user of a federated share) that has no
+	 * local account.
+	 *
+	 * @param $federatedUserId A cloud ID in the form of user@example.com
+	 * @return ?IUser
+	 * @since 35.0.0
+	 */
+	public function getDisplayUser(string $federatedUserId): ?IUser;
 }