feat(dav): dispatch SabrePluginAddEvent for the legacy CalDAV and CardDAV endpoints

apps/dav/appinfo/v1/caldav.php

@@ -22,6 +22,7 @@
 use OCA\DAV\Connector\Sabre\ExceptionLoggerPlugin;
 use OCA\DAV\Connector\Sabre\MaintenancePlugin;
 use OCA\DAV\Connector\Sabre\Principal;
+use OCA\DAV\Events\SabrePluginAddEvent;
 use OCP\Accounts\IAccountManager;
 use OCP\App\IAppManager;
 use OCP\EventDispatcher\IEventDispatcher;
@@ -128,5 +129,8 @@
 $server->addPlugin(Server::get(RateLimitingPlugin::class));
 $server->addPlugin(Server::get(CalDavValidatePlugin::class));
 
+// allow setup of additional plugins
+$dispatcher->dispatchTyped(new SabrePluginAddEvent($server));
+
 // And off we go!
 $server->start();

apps/dav/appinfo/v1/carddav.php

@@ -21,6 +21,7 @@
 use OCA\DAV\Connector\Sabre\ExceptionLoggerPlugin;
 use OCA\DAV\Connector\Sabre\MaintenancePlugin;
 use OCA\DAV\Connector\Sabre\Principal;
+use OCA\DAV\Events\SabrePluginAddEvent;
 use OCP\Accounts\IAccountManager;
 use OCP\App\IAppManager;
 use OCP\EventDispatcher\IEventDispatcher;
@@ -106,5 +107,8 @@
 $server->addPlugin(Server::get(CardDavRateLimitingPlugin::class));
 $server->addPlugin(Server::get(CardDavValidatePlugin::class));
 
+// allow setup of additional plugins
+Server::get(IEventDispatcher::class)->dispatchTyped(new SabrePluginAddEvent($server));
+
 // And off we go!
 $server->start();

apps/dav/tests/unit/AppInfo/LegacyEndpointsTest.php

@@ -0,0 +1,76 @@
+<?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\AppInfo;
+
+use OCA\DAV\Events\SabrePluginAddEvent;
+use OCP\EventDispatcher\IEventDispatcher;
+use OCP\IRequest;
+use OCP\Server;
+use PHPUnit\Framework\Attributes\DataProvider;
+use PHPUnit\Framework\Attributes\Group;
+use Sabre\DAV\Server as SabreServer;
+use Test\TestCase;
+
+/**
+ * The legacy endpoints (remote.php/webdav, caldav and carddav) let apps add
+ * their plugins, like remote.php/dav does.
+ */
+#[Group(name: 'DB')]
+class LegacyEndpointsTest extends TestCase {
+	public static function endpoints(): array {
+		return [
+			'webdav' => ['v1/webdav.php', '/remote.php/webdav', null],
+			'caldav' => ['v1/caldav.php', '/remote.php/caldav', 'caldav'],
+			'carddav' => ['v1/carddav.php', '/remote.php/carddav', 'carddav'],
+		];
+	}
+
+	#[DataProvider(methodName: 'endpoints')]
+	public function testTheEndpointDispatchesSabrePluginAddEvent(string $file, string $baseuri, ?string $plugin): void {
+		$server = $this->serverOf(__DIR__ . '/../../../appinfo/' . $file, $baseuri);
+
+		$this->assertInstanceOf(SabreServer::class, $server, 'The event was dispatched before the server started');
+		if ($plugin !== null) {
+			$this->assertNotNull($server->getPlugin($plugin));
+		}
+	}
+
+	/**
+	 * Runs an endpoint up to the event and returns the server it carries.
+	 */
+	private function serverOf(string $endpoint, string $baseuri): ?SabreServer {
+		$request = $this->createMock(IRequest::class);
+		$request->method('getRequestUri')->willReturn($baseuri . '/');
+		$this->overwriteService(IRequest::class, $request);
+		$captured = null;
+		$listener = static function (SabrePluginAddEvent $event) use (&$captured): void {
+			$captured = $event->getServer();
+			throw new \RuntimeException('stop before the server starts');
+		};
+		$dispatcher = Server::get(IEventDispatcher::class);
+		$dispatcher->addListener(SabrePluginAddEvent::class, $listener, -1000);
+		// The endpoints close every output buffer; PHPUnit expects its own back.
+		$level = ob_get_level();
+		try {
+			(static function (string $endpoint, string $baseuri): void {
+				require $endpoint;
+			})($endpoint, $baseuri);
+		} catch (\RuntimeException $e) {
+			$this->assertSame('stop before the server starts', $e->getMessage());
+		} finally {
+			while (ob_get_level() < $level) {
+				ob_start();
+			}
+			$dispatcher->removeListener(SabrePluginAddEvent::class, $listener);
+			$this->restoreService(IRequest::class);
+		}
+		return $captured;
+	}
+}