Render the Contao login page even if the current route is not a Contao page

core-bundle/src/EventListener/PrettyErrorScreenListener.php

@@ -14,11 +14,13 @@
 
 use Contao\Config;
 use Contao\CoreBundle\Exception\InvalidRequestTokenException;
+use Contao\CoreBundle\Exception\NoRootPageFoundException;
 use Contao\CoreBundle\Exception\ResponseException;
 use Contao\CoreBundle\Exception\RouteParametersException;
 use Contao\CoreBundle\Framework\ContaoFramework;
 use Contao\CoreBundle\Routing\Page\PageRegistry;
 use Contao\CoreBundle\Util\LocaleUtil;
+use Contao\Frontend;
 use Contao\PageModel;
 use Contao\StringUtil;
 use Symfony\Component\HttpFoundation\AcceptHeader;
@@ -149,7 +151,13 @@ private function renderErrorScreenByType(int $type, ExceptionEvent $event): void
             $pageModel = $request->attributes->get('pageModel');
 
             if (!$pageModel instanceof PageModel) {
-                return;
+                // The try/catch must not be merged upstream to Contao 5!
+                try {
+                    $frontendAdapter = $this->framework->getAdapter(Frontend::class);
+                    $pageModel = $frontendAdapter->getRootPageFromUrl();
+                } catch (NoRootPageFoundException $exception) {
+                    return;
+                }
             }
 
             $pageAdapter = $this->framework->getAdapter(PageModel::class);

core-bundle/tests/EventListener/PrettyErrorScreenListenerTest.php

@@ -19,12 +19,15 @@
 use Contao\CoreBundle\Exception\InsufficientAuthenticationException;
 use Contao\CoreBundle\Exception\InternalServerErrorException;
 use Contao\CoreBundle\Exception\InternalServerErrorHttpException;
+use Contao\CoreBundle\Exception\NoRootPageFoundException;
 use Contao\CoreBundle\Exception\PageNotFoundException;
 use Contao\CoreBundle\Exception\ResponseException;
 use Contao\CoreBundle\Exception\ServiceUnavailableException;
+use Contao\CoreBundle\Framework\ContaoFramework;
 use Contao\CoreBundle\Routing\Page\PageRegistry;
 use Contao\CoreBundle\Routing\Page\PageRoute;
 use Contao\CoreBundle\Tests\TestCase;
+use Contao\Frontend;
 use Contao\PageModel;
 use PHPUnit\Framework\MockObject\MockObject;
 use Symfony\Component\HttpFoundation\Request;
@@ -397,6 +400,21 @@ public function testDoesNotLogUnloggableExceptions(): void
         $this->assertSame(500, $event->getResponse()->getStatusCode());
     }
 
+    protected function mockContaoFramework(array $adapters = []): ContaoFramework
+    {
+        if (!isset($adapters[Frontend::class])) {
+            $frontendAdapter = $this->mockAdapter(['getRootPageFromUrl']);
+            $frontendAdapter
+                ->method('getRootPageFromUrl')
+                ->willThrowException(new NoRootPageFoundException())
+            ;
+
+            $adapters[Frontend::class] = $frontendAdapter;
+        }
+
+        return parent::mockContaoFramework($adapters);
+    }
+
     private function getListener(bool $isBackendUser = false, bool $expectLogging = false, Environment $twig = null, PageModel $errorPage = null, HttpKernelInterface $httpKernel = null): PrettyErrorScreenListener
     {
         $twig ??= $this->createMock(Environment::class);