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

phpstan-baseline.php

@@ -1405,12 +1405,6 @@
 	'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',
@@ -1495,12 +1489,6 @@
 	'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 +21,7 @@
 use Symfony\Component\HttpKernel\Exception\NotFoundHttpException;
 use Symfony\Component\HttpKernel\HttpKernelInterface;
 use Symfony\Component\Routing\Generator\UrlGeneratorInterface;
+use Symfony\Component\Translation\LocaleSwitcher;
 use Throwable;
 use Twig\Environment;
 use Twig\Error\LoaderError;
@@ -37,10 +38,17 @@ public function __construct(
         private readonly UrlGeneratorInterface $urlGenerator,
         private readonly Security $security,
         private readonly RequestStack $requestStack,
+        private readonly LocaleSwitcher $localeSwitcher,
+        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 +69,8 @@ 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()) {
+            $this->setLocaleFromPath($request);
+
             if ($code === Response::HTTP_SERVICE_UNAVAILABLE || $this->isMaintenanceEnabled($code)) {
                 $twig->addGlobal('exception', $exception);
 
@@ -156,6 +166,40 @@ private function isMaintenanceEnabled(int $code): bool
         return filter_var($this->config->get('general/maintenance_mode', false), FILTER_VALIDATE_BOOLEAN);
     }
 
+    /**
+     * Recovers the locale from the first path segment (e.g. `/de/...` => `de`),
+     * which Symfony's `LocaleListener` never did because no route matched.
+     *
+     * Applied to the given request and to the current one (a sub-request when an
+     * error page is rendered, which Twig's `app.request` resolves to). The
+     * `LocaleSwitcher` then syncs the translator and the router's `RequestContext`,
+     * so `{% trans %}` strings and `path()` calls follow suit.
+     */
+    private function setLocaleFromPath(Request $request): void
+    {
+        // Only derive the locale from the path when routing didn't run. With a
+        // matched route the locale is already set, and the first segment is a
+        // ContentType slug rather than a locale: a ContentType `it` isn't Italian.
+        if (! $request->attributes->has('_route')) {
+            // Cast: `mb_trim()` is analysed as `string|false`, but `getPathInfo()`
+            // always returns a string.
+            $segment = explode('/', (string) mb_trim($request->getPathInfo(), '/'))[0];
+
+            if ($segment !== '' && in_array($segment, $this->localeCodes, true)) {
+                $request->setLocale($segment);
+            }
+        }
+
+        // The error sub-request is a fresh Request that never saw the URL's locale,
+        // so propagate it regardless of how the locale was determined.
+        $currentRequest = $this->requestStack->getCurrentRequest();
+        if ($currentRequest instanceof Request && $currentRequest !== $request) {
+            $currentRequest->setLocale($request->getLocale());
+        }
+
+        $this->localeSwitcher->setLocale($request->getLocale());
+    }
+
     private function attemptToRender(Request $request, string $item): ?Response
     {
         // First, see if it's a contenttype/slug pair:
@@ -165,7 +209,8 @@ 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 locale explicitly, or the record falls back to the default.
+                return $this->detailController->record($request, $slug, $contentType, false, $request->getLocale());
             } catch (NotFoundHttpException) {
                 // Just continue to the next one.
             }

src/Controller/Frontend/ListingController.php

@@ -45,8 +45,9 @@ public function listing(Request $request, ContentRepository $contentRepository,
         }
 
         // If the locale is the wrong locale
-        if (! $this->validLocaleForContentType($request, $contentType)) {
-            return $this->redirectToDefaultLocale($request);
+        if (! $this->validLocaleForContentType($request, $contentType)
+            && ($redirect = $this->redirectToDefaultLocaleOrFallback($request)) instanceof Response) {
+            return $redirect;
         }
 
         $page = (int) $this->getFromRequest($request, 'page', '1');

src/Controller/TwigAwareController.php

@@ -114,8 +114,9 @@ public function renderSingle(Request $request, ?Content $record, bool $requirePu
         }
 
         // If the locale is the wrong locale
-        if (! $this->validLocaleForContentType($request, $recordDefinition)) {
-            return $this->redirectToDefaultLocale($request);
+        if (! $this->validLocaleForContentType($request, $recordDefinition)
+            && ($redirect = $this->redirectToDefaultLocaleOrFallback($request)) instanceof Response) {
+            return $redirect;
         }
 
         $singularSlug = $record->getContentTypeSingularSlug();
@@ -145,8 +146,37 @@ protected function validLocaleForContentType(Request $request, ContentType $cont
         return $request->getLocale() === $this->defaultLocale;
     }
 
+    /**
+     * Redirects to the same route in the default locale. When there's no route to
+     * redirect to (a forwarded request, or an error page where routing never
+     * matched), resets the request to the default locale and returns `null` so the
+     * caller can render instead of erroring.
+     *
+     * Only the given request is reset, so on an error page `<html lang>` may still
+     * show the URL locale while the record renders in the default one. Harmless:
+     * only non-localized content takes this path.
+     */
+    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 matched (e.g. on an error page): nothing to redirect to.
+        $route = $request->attributes->get('_route');
+        if (! $route) {
+            return null;
+        }
+
         $request->getSession()->set('_locale', $this->defaultLocale);
 
         $params = $request->attributes->get('_route_params');
@@ -155,7 +185,7 @@ 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