From 8004aa77212eed6dd1142c713275a4e0c5d0c40e Mon Sep 17 00:00:00 2001
From: Carl Schwan <carl@carlschwan.eu>
Date: Tue, 16 Aug 2022 14:10:05 +0200
Subject: [PATCH] Make DisplayNameCache return null if user doesn't exists

Signed-off-by: Carl Schwan <carl@carlschwan.eu>
---
 apps/files_sharing/lib/Cache.php      | 2 +-
 lib/private/User/DisplayNameCache.php | 4 ++--
 lib/private/User/LazyUser.php         | 2 +-
 lib/private/User/Manager.php          | 2 +-
 lib/public/IUserManager.php           | 6 ++----
 5 files changed, 7 insertions(+), 9 deletions(-)

diff --git a/apps/files_sharing/lib/Cache.php b/apps/files_sharing/lib/Cache.php
index 9f11431008f35..707b64b79d737 100644
--- a/apps/files_sharing/lib/Cache.php
+++ b/apps/files_sharing/lib/Cache.php
@@ -170,7 +170,7 @@ protected function formatCacheEntry($entry, $path = null) {
 	private function getOwnerDisplayName() {
 		if (!$this->ownerDisplayName) {
 			$uid = $this->storage->getOwner('');
-			$this->ownerDisplayName = $this->displayNameCache->getDisplayName($uid);
+			$this->ownerDisplayName = $this->displayNameCache->getDisplayName($uid) ?? $uid;
 		}
 		return $this->ownerDisplayName;
 	}
diff --git a/lib/private/User/DisplayNameCache.php b/lib/private/User/DisplayNameCache.php
index 22a79863e4978..5d1cc8940d760 100644
--- a/lib/private/User/DisplayNameCache.php
+++ b/lib/private/User/DisplayNameCache.php
@@ -47,7 +47,7 @@ public function __construct(ICacheFactory $cacheFactory, IUserManager $userManag
 		$this->userManager = $userManager;
 	}
 
-	public function getDisplayName(string $userId) {
+	public function getDisplayName(string $userId): ?string {
 		if (isset($this->cache[$userId])) {
 			return $this->cache[$userId];
 		}
@@ -61,7 +61,7 @@ public function getDisplayName(string $userId) {
 		if ($user) {
 			$displayName = $user->getDisplayName();
 		} else {
-			$displayName = $userId;
+			$displayName = null;
 		}
 		$this->cache[$userId] = $displayName;
 		$this->memCache->set($userId, $displayName, 60 * 10); // 10 minutes
diff --git a/lib/private/User/LazyUser.php b/lib/private/User/LazyUser.php
index 118dd3d0699bb..096578b8f375d 100644
--- a/lib/private/User/LazyUser.php
+++ b/lib/private/User/LazyUser.php
@@ -51,7 +51,7 @@ public function getUID() {
 	}
 
 	public function getDisplayName() {
-		return $this->userManager->getDisplayName($this->uid);
+		return $this->userManager->getDisplayName($this->uid) ?? $this->uid;
 	}
 
 	public function setDisplayName($displayName) {
diff --git a/lib/private/User/Manager.php b/lib/private/User/Manager.php
index 55ac663f3ecae..be5151313c4c8 100644
--- a/lib/private/User/Manager.php
+++ b/lib/private/User/Manager.php
@@ -188,7 +188,7 @@ public function get($uid) {
 		return null;
 	}
 
-	public function getDisplayName(string $uid): string {
+	public function getDisplayName(string $uid): ?string {
 		return $this->displayNameCache->getDisplayName($uid);
 	}
 
diff --git a/lib/public/IUserManager.php b/lib/public/IUserManager.php
index c107b2c5025aa..af0d5f08809a8 100644
--- a/lib/public/IUserManager.php
+++ b/lib/public/IUserManager.php
@@ -87,13 +87,11 @@ public function get($uid);
 	/**
 	 * Get the display name of a user
 	 *
-	 * Note that this will return the uid if the user is not found instead of throwing an exception
-	 *
 	 * @param string $uid
-	 * @return string
+	 * @return string|null
 	 * @since 25.0.0
 	 */
-	public function getDisplayName(string $uid): string;
+	public function getDisplayName(string $uid): ?string;
 
 	/**
 	 * check if a user exists