From 8aca7b5e331d7cc933d41dec4f4533064ac77690 Mon Sep 17 00:00:00 2001
From: Carl Schwan <carl@carlschwan.eu>
Date: Wed, 22 Jul 2026 11:54:33 +0200
Subject: [PATCH 1/2] feat: Allow to check user existence outside specific user
 backends

Signed-off-by: Carl Schwan <carl@carlschwan.eu>
---
 lib/private/User/Manager.php        | 18 ++++++++++++++----
 lib/public/IUserManager.php         |  5 +++--
 tests/Core/Command/User/AddTest.php |  5 +++++
 3 files changed, 22 insertions(+), 6 deletions(-)

diff --git a/lib/private/User/Manager.php b/lib/private/User/Manager.php
index e48304183bda8..546f95945e26a 100644
--- a/lib/private/User/Manager.php
+++ b/lib/private/User/Manager.php
@@ -121,15 +121,21 @@ public function clearBackends() {
 	 * @param string $uid
 	 * @return \OC\User\User|null Either the user or null if the specified user does not exist
 	 */
-	public function get($uid) {
+	public function get($uid, array $excludeBackends = []) {
 		if (is_null($uid) || $uid === '' || $uid === false) {
 			return null;
 		}
-		if (isset($this->cachedUsers[$uid])) { //check the cache first to prevent having to loop over the backends
+
+		// check the cache first to prevent having to loop over the backends
+		if ($excludeBackends === [] && isset($this->cachedUsers[$uid])) {
 			return $this->cachedUsers[$uid];
 		}
 
 		$cachedBackend = $this->cache->get(sha1($uid));
+		if (in_array($cachedBackend, $excludeBackends)) {
+			$cachedBackend = null;
+		}
+
 		if ($cachedBackend !== null && isset($this->backends[$cachedBackend])) {
 			// Cache has the info of the user backend already, so ask that one directly
 			$backend = $this->backends[$cachedBackend];
@@ -144,6 +150,10 @@ public function get($uid) {
 				continue;
 			}
 
+			if (in_array($i, $excludeBackends)) {
+				continue;
+			}
+
 			if ($backend->userExists($uid)) {
 				// Hash $uid to ensure that only valid characters are used for the cache key
 				$this->cache->set(sha1($uid), $i, 300);
@@ -187,8 +197,8 @@ public function getUserObject($uid, $backend, $cacheUser = true) {
 	 * @param string $uid
 	 * @return bool
 	 */
-	public function userExists($uid) {
-		$user = $this->get($uid);
+	public function userExists($uid, array $excludeBackends = []) {
+		$user = $this->get($uid, $excludeBackends);
 		return ($user !== null);
 	}
 
diff --git a/lib/public/IUserManager.php b/lib/public/IUserManager.php
index cd86d81cf6d0e..41888d2e049ca 100644
--- a/lib/public/IUserManager.php
+++ b/lib/public/IUserManager.php
@@ -77,13 +77,14 @@ public function get($uid);
 	public function getDisplayName(string $uid): ?string;
 
 	/**
-	 * check if a user exists
+	 * Check if a user exists.
 	 *
 	 * @param string $uid
+	 * @param list<string> $excludeBackends A list of IUserBackend::getBackendName() that need to be excluded from the search.
 	 * @return bool
 	 * @since 8.0.0
 	 */
-	public function userExists($uid);
+	public function userExists($uid, array $excludeBackends = []);
 
 	/**
 	 * Check if the password is valid for the user
diff --git a/tests/Core/Command/User/AddTest.php b/tests/Core/Command/User/AddTest.php
index 902d073e74a27..84197ff9d2a3b 100644
--- a/tests/Core/Command/User/AddTest.php
+++ b/tests/Core/Command/User/AddTest.php
@@ -111,6 +111,11 @@ public function testAddEmail(
 		$this->mailHelper->expects($isEmailValid && $shouldSendEmail ? static::once() : static::never())
 			->method('sendMail');
 
+		$this->consoleInput->method('getArgument')
+			->willReturnMap([
+				['uid', 'JohnDoe'],
+			]);
+
 		$this->consoleInput->method('getOption')
 			->will(static::returnValueMap([
 				['generate-password', 'true'],

From 7d64c9a84970a79b50b9c85731a3e165e49d2a53 Mon Sep 17 00:00:00 2001
From: Carl Schwan <carl@carlschwan.eu>
Date: Thu, 6 Aug 2026 15:35:43 +0200
Subject: [PATCH 2/2] fix: Adapt tests

Signed-off-by: Carl Schwan <carl@carlschwan.eu>
---
 tests/lib/Repair/CleanTagsTest.php | 4 ++--
 tests/lib/Share20/ManagerTest.php  | 8 ++++----
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/tests/lib/Repair/CleanTagsTest.php b/tests/lib/Repair/CleanTagsTest.php
index 6fe7c6be9de0e..b7e59c091007c 100644
--- a/tests/lib/Repair/CleanTagsTest.php
+++ b/tests/lib/Repair/CleanTagsTest.php
@@ -103,8 +103,8 @@ public function testRun() {
 		$this->userManager->expects($this->exactly(2))
 			->method('userExists')
 			->willReturnMap([
-				['userExists', true],
-				['TestRepairCleanTags', false],
+				['userExists', [], true],
+				['TestRepairCleanTags', [], false],
 			]);
 
 		self::invokePrivate($this->repair, 'deleteOrphanTags', [$this->outputMock]);
diff --git a/tests/lib/Share20/ManagerTest.php b/tests/lib/Share20/ManagerTest.php
index 274cb7b62cdb6..eba1008070e31 100644
--- a/tests/lib/Share20/ManagerTest.php
+++ b/tests/lib/Share20/ManagerTest.php
@@ -986,8 +986,8 @@ public function testGeneralChecks($share, $exceptionMessage, $exception) {
 		$thrown = null;
 
 		$this->userManager->method('userExists')->willReturnMap([
-			['user0', true],
-			['user1', true],
+			['user0', [], true],
+			['user1', [], true],
 		]);
 
 		$this->groupManager->method('groupExists')->willReturnMap([
@@ -1030,8 +1030,8 @@ public function testGeneralCheckShareRoot() {
 		$thrown = null;
 
 		$this->userManager->method('userExists')->willReturnMap([
-			['user0', true],
-			['user1', true],
+			['user0', [], true],
+			['user1', [], true],
 		]);
 
 		$userFolder = $this->createMock(Folder::class);