fix(quota): invalidate user folder etag when quota changes

Signed-off-by: Git'Fellow <12234510+solracsf@users.noreply.github.com>

Author: solracsf

lib/private/User/User.php

@@ -15,6 +15,7 @@
 use OCP\Comments\ICommentsManager;
 use OCP\EventDispatcher\IEventDispatcher;
 use OCP\Files\FileInfo;
+use OCP\Files\IRootFolder;
 use OCP\Group\Events\BeforeUserRemovedEvent;
 use OCP\Group\Events\UserRemovedEvent;
 use OCP\IAvatarManager;
@@ -572,6 +573,20 @@ public function setQuota($quota): void {
 		if ($quota !== $oldQuota) {
 			$this->config->setUserValue($this->uid, 'files', 'quota', $quota);
 			$this->triggerChange('quota', $quota, $oldQuota);
+			// Invalidate the etag of the user's home folder so desktop clients
+			// re-fetch quota-available-bytes via PROPFIND on the next sync cycle.
+			// ICache::update() routes by fileid (the shard key), so this is safe
+			// in sharded database setups. getUserFolder() uses LazyUserFolder when
+			// no active mount exists, deferring setup until the getId() call below.
+			try {
+				$userFolder = Server::get(IRootFolder::class)->getUserFolder($this->uid);
+				$userFolder->getStorage()->getCache()->update(
+					$userFolder->getId(),
+					['etag' => uniqid()]
+				);
+			} catch (\Throwable) {
+				// Non-fatal: best-effort etag invalidation; stale quota corrects on next full sync.
+			}
 		}
 		\OC_Helper::clearStorageInfo('/' . $this->uid . '/files');
 	}

tests/lib/User/UserIntegrationTest.php

@@ -0,0 +1,65 @@
+<?php
+
+/**
+ * SPDX-FileCopyrightText: 2024 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+namespace Test\User;
+
+use OCP\Files\IRootFolder;
+use OCP\IUserManager;
+use OCP\Server;
+use PHPUnit\Framework\Attributes\Group;
+use Test\TestCase;
+use Test\Traits\UserTrait;
+
+#[Group('DB')]
+class UserIntegrationTest extends TestCase {
+	use UserTrait;
+
+	protected function setUp(): void {
+		parent::setUp();
+		$this->setUpUserTrait();
+	}
+
+	protected function tearDown(): void {
+		$this->tearDownUserTrait();
+		parent::tearDown();
+	}
+
+	public function testSetQuotaInvalidatesUserFolderEtag(): void {
+		$userId = $this->getUniqueID('quota_etag_test_');
+		$userManager = Server::get(IUserManager::class);
+		$this->createUser($userId, 'password123');
+
+		try {
+			static::loginAsUser($userId);
+
+			$etagBefore = $this->readFilesEtag($userId);
+
+			$user = $userManager->get($userId);
+			$user->setQuota('5 GB');
+
+			$etagAfter = $this->readFilesEtag($userId);
+
+			$this->assertNotNull($etagBefore, 'files/ cache entry must exist before quota change');
+			$this->assertNotEquals($etagBefore, $etagAfter, 'User folder etag must change when quota is updated');
+		} finally {
+			static::logout();
+			$userManager->get($userId)?->delete();
+		}
+	}
+
+	/**
+	 * Reads the current etag of the user's 'files' directory via the storage's
+	 * own ICache implementation. This uses the storage-scoped, shard-aware query
+	 * builder and avoids cross-partition JOINs, so it works correctly in both
+	 * standard and sharded database setups.
+	 */
+	private function readFilesEtag(string $userId): ?string {
+		$userFolder = Server::get(IRootFolder::class)->getUserFolder($userId);
+		$entry = $userFolder->getStorage()->getCache()->get('files');
+		return $entry !== false ? (string)$entry['etag'] : null;
+	}
+}