Propagate current locale to custom 404/403/500 error pages

When no route matches (404/403), Symfony's LocaleListener never runs, so
custom error pages and their records rendered in the default locale and
ignored the locale in the URL (e.g. /nl/...).

- ErrorController recovers the locale from the URL path and applies it to
  the request, the Twig sub-request, and the translator; the record locale
  is now passed explicitly to DetailController::record().
- Add redirectToDefaultLocaleOrFallback(): when there's no route to redirect
  to (error page / forwarded request), reset to the default locale and render
  instead of erroring. Guards the missing _route case that previously threw a
  TypeError (a 404-within-a-404).
- ListingController uses the fallback so a forwarded listing renders in the
  default locale instead of erroring.

Adds ErrorControllerTest and ListingControllerTest covering localized and
default-locale rendering, translator locale recovery, the 403 path, the
non-localized ContentType regression, the listing redirect, and the
forwarded-listing fallback.

Author: Vondry

phpstan-baseline.php

@@ -1435,12 +1435,6 @@
 	'count' => 1,
 	'path' => __DIR__ . '/src/Controller/Frontend/ListingController.php',
 ];
-$ignoreErrors[] = [
-	'message' => '#^Method Bolt\\\\Controller\\\\Frontend\\\\ListingController\\:\\:listing\\(\\) should return Symfony\\\\Component\\\\HttpFoundation\\\\Response but returns Symfony\\\\Component\\\\HttpFoundation\\\\Response\\|null\\.$#',
-	'identifier' => 'return.type',
-	'count' => 1,
-	'path' => __DIR__ . '/src/Controller/Frontend/ListingController.php',
-];
 $ignoreErrors[] = [
 	'message' => '#^Method Bolt\\\\Controller\\\\Frontend\\\\ListingController\\:\\:parseQueryParams\\(\\) return type has no value type specified in iterable type array\\.$#',
 	'identifier' => 'missingType.iterableValue',
@@ -1525,12 +1519,6 @@
 	'count' => 1,
 	'path' => __DIR__ . '/src/Controller/TwigAwareController.php',
 ];
-$ignoreErrors[] = [
-	'message' => '#^Method Bolt\\\\Controller\\\\TwigAwareController\\:\\:renderSingle\\(\\) should return Symfony\\\\Component\\\\HttpFoundation\\\\Response but returns Symfony\\\\Component\\\\HttpFoundation\\\\Response\\|null\\.$#',
-	'identifier' => 'return.type',
-	'count' => 1,
-	'path' => __DIR__ . '/src/Controller/TwigAwareController.php',
-];
 $ignoreErrors[] = [
 	'message' => '#^Method Bolt\\\\Controller\\\\TwigAwareController\\:\\:renderTemplate\\(\\) has parameter \\$parameters with no value type specified in iterable type array\\.$#',
 	'identifier' => 'missingType.iterableValue',

src/Controller/ErrorController.php

@@ -21,6 +21,8 @@
 use Symfony\Component\HttpKernel\Exception\NotFoundHttpException;
 use Symfony\Component\HttpKernel\HttpKernelInterface;
 use Symfony\Component\Routing\Generator\UrlGeneratorInterface;
+use Symfony\Contracts\Translation\LocaleAwareInterface;
+use Symfony\Contracts\Translation\TranslatorInterface;
 use Throwable;
 use Twig\Environment;
 use Twig\Error\LoaderError;
@@ -37,10 +39,17 @@ public function __construct(
         private readonly UrlGeneratorInterface $urlGenerator,
         private readonly Security $security,
         private readonly RequestStack $requestStack,
+        private readonly TranslatorInterface $translator,
+        string $locales,
     ) {
         parent::__construct($httpKernel, $this->templateController, $errorRenderer);
+
+        $this->localeCodes = explode('|', $locales);
     }
 
+    /** @var list<string> */
+    private readonly array $localeCodes;
+
     /**
      * Show an exception. Mainly used for custom 404 pages, otherwise falls back
      * to Symfony's error handling
@@ -61,6 +70,11 @@ public function showAction(Environment $twig, Throwable $exception): Response
 
         // We need the parent request here, but fall back to current if not found
         if ($request = $this->requestStack->getParentRequest() ?? $this->requestStack->getCurrentRequest()) {
+            // On a 404/403, no route matched, so Symfony's LocaleListener never set
+            // the locale from the URL. Recover it from the path so localized error
+            // pages (and their records) render in the right language.
+            $this->setLocaleFromPath($request);
+
             if ($code === Response::HTTP_SERVICE_UNAVAILABLE || $this->isMaintenanceEnabled($code)) {
                 $twig->addGlobal('exception', $exception);
 
@@ -156,6 +170,41 @@ private function isMaintenanceEnabled(int $code): bool
         return filter_var($this->config->get('general/maintenance_mode', false), FILTER_VALIDATE_BOOLEAN);
     }
 
+    /**
+     * Sets the locale based on the first segment of the path, if it matches one
+     * of the configured locales (e.g. `/de/...` => `de`).
+     *
+     * The locale is applied to both the given request (used when rendering a
+     * record) and the current request (which Twig's `app.request` resolves to,
+     * and is a sub-request when an error page is being rendered). It's also set on
+     * the translator, so `{% trans %}` strings in the error template are localized
+     * too - normally Symfony's `LocaleListener`/`LocaleAwareListener` does this,
+     * but neither runs when no route matched.
+     */
+    private function setLocaleFromPath(Request $request): void
+    {
+        // Cast: on PHP 8.4 `mb_trim()` is analysed as `string|false`, but `getPathInfo()`
+        // always yields a string, so the result is effectively always a string here.
+        $segment = explode('/', (string) mb_trim($request->getPathInfo(), '/'))[0];
+
+        if ($segment === '' || ! in_array($segment, $this->localeCodes, true)) {
+            return;
+        }
+
+        $request->setLocale($segment);
+
+        $currentRequest = $this->requestStack->getCurrentRequest();
+        if ($currentRequest instanceof Request && $currentRequest !== $request) {
+            $currentRequest->setLocale($segment);
+        }
+
+        // The concrete translator is locale-aware; the contracts interface we depend
+        // on isn't, so guard the call to keep the dependency narrow.
+        if ($this->translator instanceof LocaleAwareInterface) {
+            $this->translator->setLocale($segment);
+        }
+    }
+
     private function attemptToRender(Request $request, string $item): ?Response
     {
         // First, see if it's a contenttype/slug pair:
@@ -165,7 +214,9 @@ private function attemptToRender(Request $request, string $item): ?Response
             // We wrap it in a try/catch, because we wouldn't want to
             // trigger a 404 within a 404 now, would we?
             try {
-                return $this->detailController->record($request, $slug, $contentType, false, null);
+                // Pass the request's locale explicitly, so `DetailController` keeps
+                // it instead of falling back to the default locale.
+                return $this->detailController->record($request, $slug, $contentType, false, $request->getLocale());
             } catch (NotFoundHttpException) {
                 // Just continue to the next one.
             }

src/Controller/Frontend/ListingController.php

@@ -44,9 +44,12 @@ public function listing(Request $request, ContentRepository $contentRepository,
             throw new NotFoundHttpException('Content is not viewable');
         }
 
-        // If the locale is the wrong locale
-        if (! $this->validLocaleForContentType($request, $contentType)) {
-            return $this->redirectToDefaultLocale($request);
+        // If the locale is the wrong locale, redirect to the default locale, or -
+        // when that's not possible (e.g. a forwarded request without a matched
+        // route) - render the listing in the default locale.
+        if (! $this->validLocaleForContentType($request, $contentType)
+            && ($redirect = $this->redirectToDefaultLocaleOrFallback($request)) instanceof Response) {
+            return $redirect;
         }
 
         $page = (int) $this->getFromRequest($request, 'page', '1');

src/Controller/TwigAwareController.php

@@ -113,9 +113,11 @@ public function renderSingle(Request $request, ?Content $record, bool $requirePu
             throw new NotFoundHttpException('Content is not viewable');
         }
 
-        // If the locale is the wrong locale
-        if (! $this->validLocaleForContentType($request, $recordDefinition)) {
-            return $this->redirectToDefaultLocale($request);
+        // If the locale is the wrong locale, redirect to the default locale, or -
+        // when that's not possible - render the record in the default locale.
+        if (! $this->validLocaleForContentType($request, $recordDefinition)
+            && ($redirect = $this->redirectToDefaultLocaleOrFallback($request)) instanceof Response) {
+            return $redirect;
         }
 
         $singularSlug = $record->getContentTypeSingularSlug();
@@ -145,8 +147,41 @@ protected function validLocaleForContentType(Request $request, ContentType $cont
         return $request->getLocale() === $this->defaultLocale;
     }
 
+    /**
+     * Either redirect to the same route in the default locale, or - when there's
+     * no route to redirect to (e.g. a forwarded request, or an error page where
+     * routing never matched) - reset the request to the default locale and return
+     * `null`, so the caller can render in the default locale instead.
+     *
+     * Note: this resets the locale on the _given_ request only. When rendering an
+     * error page, Twig's `app.request` is a sub-request whose locale was set
+     * separately (see ErrorController::setLocaleFromPath()), so the `<html lang>`
+     * may still reflect the URL locale while the - non-localizable - record content
+     * is rendered in the default locale. That's harmless: such content is identical
+     * across locales.
+     */
+    protected function redirectToDefaultLocaleOrFallback(Request $request): ?Response
+    {
+        $redirect = $this->redirectToDefaultLocale($request);
+
+        if ($redirect instanceof Response) {
+            return $redirect;
+        }
+
+        $request->setLocale($this->defaultLocale);
+
+        return null;
+    }
+
     protected function redirectToDefaultLocale(Request $request): ?Response
     {
+        // No route was matched (e.g. on an error page): there's nothing to
+        // redirect to, so let the caller decide how to handle this.
+        $route = $request->attributes->get('_route');
+        if (! $route) {
+            return null;
+        }
+
         $request->getSession()->set('_locale', $this->defaultLocale);
 
         $params = $request->attributes->get('_route_params');
@@ -155,7 +190,7 @@ protected function redirectToDefaultLocale(Request $request): ?Response
             $params['_locale'] = $this->defaultLocale;
         }
 
-        return $this->redirectToRoute($request->get('_route'), $params);
+        return $this->redirectToRoute($route, $params);
     }
 
     private function setTwigLoader(): void