Use relative paths on debug error page

classes/App.php

@@ -37,6 +37,8 @@ class App extends \Slim\App
         /** @var Container $container */
         $container = $this->getContainer();
 
+        $container['root_path'] = $this->getRootPath();
+
         // Config.
         $container['config'] = ConfigFactory::create($container);
 
@@ -110,4 +112,17 @@ class App extends \Slim\App
             [$jsonController, 'json']
         )->setName('json');
     }
+
+    /**
+     * @return string|null
+     */
+    private function getRootPath(): ?string
+    {
+        // realpath() can return false but we prefer using null.
+        if ($rootPath = realpath(__DIR__ . '/../')) {
+            return $rootPath;
+        }
+
+        return null;
+    }
 }

classes/Controller/FrontController.php

@@ -285,7 +285,7 @@ class FrontController extends BaseController
         $response = $cspMiddleware->applyHeader($response);
 
         if ($this->config->debug) {
-            $renderer = new HtmlErrorRenderer(true);
+            $renderer = new HtmlErrorRenderer(true, null, null, $this->container->get('root_path'));
             $exception = $renderer->render($error);
 
             $response->getBody()->write($exception->getAsString());

classes/ErrorHandler.php

@@ -23,7 +23,7 @@ class ErrorHandler
 
         if (class_exists(HtmlErrorRenderer::class)) {
             // If dev dependencies are loaded, we can use symfony/error-handler.
-            $renderer = new HtmlErrorRenderer(true);
+            $renderer = new HtmlErrorRenderer(true, null, null, dirname(__DIR__));
             $exception = $renderer->render($e);
 
             http_response_code($exception->getStatusCode());