fix(dav): fail propfind for unavailable mounts

apps/dav/composer/composer/autoload_classmap.php

@@ -248,6 +248,7 @@
     'OCA\\DAV\\Connector\\Sabre\\ObjectTree' => $baseDir . '/../lib/Connector/Sabre/ObjectTree.php',
     'OCA\\DAV\\Connector\\Sabre\\Principal' => $baseDir . '/../lib/Connector/Sabre/Principal.php',
     'OCA\\DAV\\Connector\\Sabre\\PropFindMonitorPlugin' => $baseDir . '/../lib/Connector/Sabre/PropFindMonitorPlugin.php',
+    'OCA\\DAV\\Connector\\Sabre\\PropFindMountAvailabilityPlugin' => $baseDir . '/../lib/Connector/Sabre/PropFindMountAvailabilityPlugin.php',
     'OCA\\DAV\\Connector\\Sabre\\PropFindPreloadNotifyPlugin' => $baseDir . '/../lib/Connector/Sabre/PropFindPreloadNotifyPlugin.php',
     'OCA\\DAV\\Connector\\Sabre\\PropfindCompressionPlugin' => $baseDir . '/../lib/Connector/Sabre/PropfindCompressionPlugin.php',
     'OCA\\DAV\\Connector\\Sabre\\PublicAuth' => $baseDir . '/../lib/Connector/Sabre/PublicAuth.php',

apps/dav/composer/composer/autoload_static.php

@@ -263,6 +263,7 @@ class ComposerStaticInitDAV
         'OCA\\DAV\\Connector\\Sabre\\ObjectTree' => __DIR__ . '/..' . '/../lib/Connector/Sabre/ObjectTree.php',
         'OCA\\DAV\\Connector\\Sabre\\Principal' => __DIR__ . '/..' . '/../lib/Connector/Sabre/Principal.php',
         'OCA\\DAV\\Connector\\Sabre\\PropFindMonitorPlugin' => __DIR__ . '/..' . '/../lib/Connector/Sabre/PropFindMonitorPlugin.php',
+        'OCA\\DAV\\Connector\\Sabre\\PropFindMountAvailabilityPlugin' => __DIR__ . '/..' . '/../lib/Connector/Sabre/PropFindMountAvailabilityPlugin.php',
         'OCA\\DAV\\Connector\\Sabre\\PropFindPreloadNotifyPlugin' => __DIR__ . '/..' . '/../lib/Connector/Sabre/PropFindPreloadNotifyPlugin.php',
         'OCA\\DAV\\Connector\\Sabre\\PropfindCompressionPlugin' => __DIR__ . '/..' . '/../lib/Connector/Sabre/PropfindCompressionPlugin.php',
         'OCA\\DAV\\Connector\\Sabre\\PublicAuth' => __DIR__ . '/..' . '/../lib/Connector/Sabre/PublicAuth.php',

apps/dav/lib/Connector/Sabre/Directory.php

@@ -25,6 +25,7 @@
 use OCP\Files\Mount\IMovableMount;
 use OCP\Files\NotFoundException;
 use OCP\Files\NotPermittedException;
+use OCP\Files\StorageInvalidException;
 use OCP\Files\StorageNotAvailableException;
 use OCP\IL10N;
 use OCP\IRequest;
@@ -53,6 +54,7 @@ class Directory extends Node implements
 	 * @var FileInfo[]
 	 */
 	private ?array $dirContent = null;
+	private bool $dirContentIsStrict = false;
 
 	/** Cached quota info */
 	private ?array $quotaInfo = null;
@@ -251,7 +253,26 @@ public function getChild($name, $info = null, ?IRequest $request = null, ?IL10N
 	 */
 	#[\Override]
 	public function getChildren() {
-		if (!is_null($this->dirContent)) {
+		return $this->getChildrenInternal(false);
+	}
+
+	/**
+	 * Return all child nodes, failing if an unavailable mount would make the listing incomplete.
+	 *
+	 * @return \Sabre\DAV\INode[]
+	 * @throws \Sabre\DAV\Exception\Locked
+	 * @throws \Sabre\DAV\Exception\ServiceUnavailable
+	 * @throws Forbidden
+	 */
+	public function getChildrenStrict(): array {
+		return $this->getChildrenInternal(true);
+	}
+
+	/**
+	 * @return \Sabre\DAV\INode[]
+	 */
+	private function getChildrenInternal(bool $failOnUnavailableMount): array {
+		if (!is_null($this->dirContent) && (!$failOnUnavailableMount || $this->dirContentIsStrict)) {
 			return $this->dirContent;
 		}
 		try {
@@ -264,9 +285,16 @@ public function getChildren() {
 					throw new Forbidden('No read permissions');
 				}
 			}
-			$folderContent = $this->getNode()->getDirectoryListing();
+			if ($failOnUnavailableMount) {
+				/** @psalm-suppress InternalMethod The Node API cannot request a strict mount-aware listing. */
+				$folderContent = $this->fileView->getDirectoryContent($this->path, null, $this->info, true);
+			} else {
+				$folderContent = $this->getNode()->getDirectoryListing();
+			}
 		} catch (LockedException $e) {
 			throw new Locked();
+		} catch (StorageNotAvailableException|StorageInvalidException $e) {
+			throw new ServiceUnavailable('Storage is temporarily not available', 0, $e);
 		}
 
 		$nodes = [];
@@ -278,6 +306,7 @@ public function getChildren() {
 			$nodes[] = $node;
 		}
 		$this->dirContent = $nodes;
+		$this->dirContentIsStrict = $failOnUnavailableMount;
 		return $this->dirContent;
 	}
 

apps/dav/lib/Connector/Sabre/PropFindMountAvailabilityPlugin.php

@@ -0,0 +1,52 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * SPDX-FileCopyrightText: 2026 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+namespace OCA\DAV\Connector\Sabre;
+
+use Sabre\DAV\Server;
+use Sabre\DAV\ServerPlugin;
+use Sabre\HTTP\RequestInterface;
+
+/**
+ * Checks that a Files collection can be listed before Sabre starts streaming a PROPFIND response.
+ */
+class PropFindMountAvailabilityPlugin extends ServerPlugin {
+	private Server $server;
+
+	#[\Override]
+	public function initialize(Server $server): void {
+		$this->server = $server;
+		$this->server->on('method:PROPFIND', [$this, 'preflight'], 10);
+	}
+
+	public function preflight(RequestInterface $request): void {
+		$depth = $this->server->getHTTPDepth(1);
+		if ($depth === 0) {
+			return;
+		}
+
+		$node = $this->server->tree->getNodeForPath($request->getPath());
+		if ($node instanceof Directory) {
+			$this->preflightDirectory($node, $depth === Server::DEPTH_INFINITY);
+		}
+	}
+
+	private function preflightDirectory(Directory $directory, bool $recursive): void {
+		$children = $directory->getChildrenStrict();
+		if (!$recursive) {
+			return;
+		}
+
+		foreach ($children as $child) {
+			if ($child instanceof Directory) {
+				$this->preflightDirectory($child, true);
+			}
+		}
+	}
+}

apps/dav/lib/Connector/Sabre/ServerFactory.php

@@ -102,6 +102,7 @@ public function createServer(
 			$server->addPlugin(new PropFindMonitorPlugin());
 		}
 
+		$server->addPlugin(new PropFindMountAvailabilityPlugin());
 		$server->addPlugin(new PropFindPreloadNotifyPlugin());
 		// FIXME: The following line is a workaround for legacy components relying on being able to send a GET to /
 		$server->addPlugin(new DummyGetResponsePlugin());

apps/dav/lib/Server.php

@@ -48,6 +48,7 @@
 use OCA\DAV\Connector\Sabre\MaintenancePlugin;
 use OCA\DAV\Connector\Sabre\PropfindCompressionPlugin;
 use OCA\DAV\Connector\Sabre\PropFindMonitorPlugin;
+use OCA\DAV\Connector\Sabre\PropFindMountAvailabilityPlugin;
 use OCA\DAV\Connector\Sabre\PropFindPreloadNotifyPlugin;
 use OCA\DAV\Connector\Sabre\QuotaPlugin;
 use OCA\DAV\Connector\Sabre\RequestIdHeaderPlugin;
@@ -262,6 +263,7 @@ public function __construct(
 			\OCP\Server::get(IDateTimeZone::class),
 		));
 		$this->server->addPlugin(\OCP\Server::get(PaginatePlugin::class));
+		$this->server->addPlugin(new PropFindMountAvailabilityPlugin());
 		$this->server->addPlugin(new PropFindPreloadNotifyPlugin());
 
 		// allow setup of additional plugins

apps/dav/tests/unit/Connector/Sabre/DirectoryTest.php

@@ -24,6 +24,7 @@
 use OCP\Files\InvalidPathException;
 use OCP\Files\Mount\IMountPoint;
 use OCP\Files\Storage\IStorage;
+use OCP\Files\StorageInvalidException;
 use OCP\Files\StorageNotAvailableException;
 use OCP\Lock\ILockingProvider;
 use PHPUnit\Framework\MockObject\MockObject;
@@ -259,6 +260,53 @@ public function testGetChildren(): void {
 		$dir->getChildren();
 	}
 
+	public function testGetChildrenStrictUsesStrictDirectoryListing(): void {
+		$this->view->expects($this->once())
+			->method('getDirectoryContent')
+			->with('folder', null, $this->anything(), true)
+			->willReturn([]);
+		$this->view->method('getRelativePath')
+			->willReturnCallback(static fn ($path) => str_replace('/admin/files/', '', $path));
+		$this->view->method('getAbsolutePath')
+			->willReturn('/admin/files/folder');
+		$this->overwriteService(View::class, $this->view);
+
+		$dir = new Directory($this->view, $this->info);
+		$this->assertSame([], $dir->getChildrenStrict());
+
+		// The regular traversal reuses the strict result instead of listing the directory again.
+		$this->assertSame([], $dir->getChildren());
+	}
+
+	public static function strictStorageExceptionProvider(): array {
+		return [
+			'unavailable storage' => [StorageNotAvailableException::class],
+			'invalid storage' => [StorageInvalidException::class],
+		];
+	}
+
+	#[\PHPUnit\Framework\Attributes\DataProvider('strictStorageExceptionProvider')]
+	public function testGetChildrenStrictConvertsStorageException(string $exceptionClass): void {
+		$storageException = new $exceptionClass('Unavailable mount');
+		$this->view->expects($this->once())
+			->method('getDirectoryContent')
+			->with('folder', null, $this->anything(), true)
+			->willThrowException($storageException);
+		$this->view->method('getRelativePath')
+			->willReturnCallback(static fn ($path) => str_replace('/admin/files/', '', $path));
+		$this->view->method('getAbsolutePath')
+			->willReturn('/admin/files/folder');
+		$this->overwriteService(View::class, $this->view);
+
+		try {
+			(new Directory($this->view, $this->info))->getChildrenStrict();
+			$this->fail('Expected strict directory listing to fail');
+		} catch (\Sabre\DAV\Exception\ServiceUnavailable $e) {
+			$this->assertSame('Storage is temporarily not available', $e->getMessage());
+			$this->assertSame($storageException, $e->getPrevious());
+		}
+	}
+
 	public function testGetChildrenNoPermission(): void {
 		$this->expectException(\Sabre\DAV\Exception\Forbidden::class);
 

apps/dav/tests/unit/Connector/Sabre/PropFindMountAvailabilityPluginTest.php

@@ -0,0 +1,161 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * SPDX-FileCopyrightText: 2026 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+namespace OCA\DAV\Tests\unit\Connector\Sabre;
+
+use OCA\DAV\Connector\Sabre\Directory;
+use OCA\DAV\Connector\Sabre\PropFindMountAvailabilityPlugin;
+use PHPUnit\Framework\MockObject\MockObject;
+use Sabre\DAV\Exception\ServiceUnavailable;
+use Sabre\DAV\ICollection;
+use Sabre\DAV\Server;
+use Sabre\DAV\Tree;
+use Sabre\HTTP\Request;
+use Sabre\HTTP\RequestInterface;
+use Sabre\HTTP\ResponseInterface;
+use Sabre\HTTP\Sapi;
+use Test\TestCase;
+
+class PropFindMountAvailabilityTestSapi extends Sapi {
+	public static ?Request $request = null;
+	public static ?ResponseInterface $response = null;
+
+	public static function getRequest(): Request {
+		return self::$request ?? new Request('GET', '/');
+	}
+
+	public static function sendResponse(ResponseInterface $response): void {
+		self::$response = $response;
+	}
+}
+
+class PropFindMountAvailabilityPluginTest extends TestCase {
+	private Server&MockObject $server;
+	private Tree&MockObject $tree;
+	private PropFindMountAvailabilityPlugin $plugin;
+
+	protected function setUp(): void {
+		parent::setUp();
+
+		$this->server = $this->createMock(Server::class);
+		$this->tree = $this->createMock(Tree::class);
+		$this->server->tree = $this->tree;
+		$this->plugin = new PropFindMountAvailabilityPlugin();
+		PropFindMountAvailabilityTestSapi::$request = null;
+		PropFindMountAvailabilityTestSapi::$response = null;
+	}
+
+	public function testInitialize(): void {
+		$this->server->expects(self::once())
+			->method('on')
+			->with('method:PROPFIND', [$this->plugin, 'preflight'], 10);
+
+		$this->plugin->initialize($this->server);
+	}
+
+	public function testDepthZeroDoesNotEnumerateChildren(): void {
+		$request = $this->createMock(RequestInterface::class);
+		$this->server->expects(self::once())
+			->method('getHTTPDepth')
+			->with(1)
+			->willReturn(0);
+		$this->tree->expects(self::never())
+			->method('getNodeForPath');
+
+		$this->plugin->initialize($this->server);
+		$this->plugin->preflight($request);
+	}
+
+	public function testNonFilesCollectionIsNotEnumerated(): void {
+		$request = $this->createMock(RequestInterface::class);
+		$request->expects(self::once())
+			->method('getPath')
+			->willReturn('calendars/user');
+		$this->server->expects(self::once())
+			->method('getHTTPDepth')
+			->with(1)
+			->willReturn(1);
+		$this->tree->expects(self::once())
+			->method('getNodeForPath')
+			->with('calendars/user')
+			->willReturn($this->createMock(ICollection::class));
+
+		$this->plugin->initialize($this->server);
+		$this->plugin->preflight($request);
+	}
+
+	public function testFilesCollectionIsStrictlyEnumerated(): void {
+		$request = $this->createMock(RequestInterface::class);
+		$request->expects(self::once())
+			->method('getPath')
+			->willReturn('files/user');
+		$this->server->expects(self::once())
+			->method('getHTTPDepth')
+			->with(1)
+			->willReturn(1);
+		$directory = $this->createMock(Directory::class);
+		$directory->expects(self::once())
+			->method('getChildrenStrict')
+			->willReturn([]);
+		$this->tree->expects(self::once())
+			->method('getNodeForPath')
+			->with('files/user')
+			->willReturn($directory);
+
+		$this->plugin->initialize($this->server);
+		$this->plugin->preflight($request);
+	}
+
+	public function testDepthInfinityStrictlyEnumeratesNestedDirectories(): void {
+		$request = $this->createMock(RequestInterface::class);
+		$request->method('getPath')
+			->willReturn('files/user');
+		$this->server->method('getHTTPDepth')
+			->with(1)
+			->willReturn(Server::DEPTH_INFINITY);
+		$nestedDirectory = $this->createMock(Directory::class);
+		$nestedDirectory->expects(self::once())
+			->method('getChildrenStrict')
+			->willReturn([]);
+		$directory = $this->createMock(Directory::class);
+		$directory->expects(self::once())
+			->method('getChildrenStrict')
+			->willReturn([$nestedDirectory]);
+		$this->tree->method('getNodeForPath')
+			->with('files/user')
+			->willReturn($directory);
+
+		$this->plugin->initialize($this->server);
+		$this->plugin->preflight($request);
+	}
+
+	public function testUnavailableMountReturnsServiceUnavailableBeforeStreamingMultiStatus(): void {
+		$directory = $this->createMock(Directory::class);
+		$directory->expects(self::once())
+			->method('getChildrenStrict')
+			->willThrowException(new ServiceUnavailable('Storage is temporarily not available'));
+		PropFindMountAvailabilityTestSapi::$request = new Request('PROPFIND', '/', ['Depth' => '1']);
+		$sapi = new PropFindMountAvailabilityTestSapi();
+		$server = new Server($directory, $sapi);
+		$server->addPlugin(new PropFindMountAvailabilityPlugin());
+		$previousStreamMultiStatus = Server::$streamMultiStatus;
+		try {
+			Server::$streamMultiStatus = true;
+			$server->start();
+		} finally {
+			Server::$streamMultiStatus = $previousStreamMultiStatus;
+		}
+
+		$response = PropFindMountAvailabilityTestSapi::$response;
+		$this->assertNotNull($response);
+		$this->assertSame(503, $response->getStatus());
+		$this->assertStringContainsString(ServiceUnavailable::class, $response->getBodyAsString());
+		$this->assertStringNotContainsString('multistatus', $response->getBodyAsString());
+	}
+}