Fix the allow_twig option to work in the preview

src/Controller/Backend/ContentEditController.php

@@ -171,19 +171,11 @@ public function preview(?Content $content = null): Response
         $this->validateCsrf('editrecord');
 
         $content = $this->contentFromPost($content);
-        $recordSlug = $content->getDefinition()->get('singular_slug');
 
         $event = new ContentEvent($content);
         $this->dispatcher->dispatch($event, ContentEvent::ON_PREVIEW);
 
-        $context = [
-            'record' => $content,
-            $recordSlug => $content,
-        ];
-
-        $templates = $this->templateChooser->forRecord($content);
-
-        return $this->render($templates, $context);
+        return $this->renderSingle($content, false);
     }
 
     /**

src/Entity/Field.php

@@ -9,6 +9,7 @@
 use ApiPlatform\Core\Bridge\Doctrine\Orm\Filter\SearchFilter;
 use Bolt\Common\Arr;
 use Bolt\Configuration\Content\FieldType;
+use Bolt\Event\Listener\FieldFillListener;
 use Doctrine\ORM\Mapping as ORM;
 use Knp\DoctrineBehaviors\Contract\Entity\TranslatableInterface;
 use Knp\DoctrineBehaviors\Model\Translatable\TranslatableTrait;
@@ -235,6 +236,10 @@ public function getTwigValue()
             $value = $this->getContent()->sanitise($value);
         }
 
+        // Trim the zero spaces even before saving in FieldFillListener.
+        // Otherwise, the preview contains zero width whitespace.
+        $value = is_string($value) ? FieldFillListener::trimZeroWidthWhitespace($value) : $value;
+
         if ($this->shouldBeRenderedAsTwig($value)) {
             $twig = $this->getContent()->getTwig();
 

src/Event/Listener/FieldFillListener.php

@@ -58,11 +58,11 @@ private function clean($value): array
 
         foreach ($value as $key => $v) {
             if ($v instanceof Markup) {
-                $v = $this->trimZeroWidthWhitespace((string) $v);
+                $v = self::trimZeroWidthWhitespace((string) $v);
                 // todo: Figure out how to preserve original encoding
                 $v = new Markup($this->sanitiser->clean($v), 'UTF-8');
             } elseif (is_string($v)) {
-                $v = $this->trimZeroWidthWhitespace($v);
+                $v = self::trimZeroWidthWhitespace($v);
                 $v = $this->sanitiser->clean($v);
             }
 
@@ -75,7 +75,7 @@ private function clean($value): array
     /**
      * Remove the 'zero width space' from `{{` and `}}`, added in the editor.
      */
-    public function trimZeroWidthWhitespace(string $string): string
+    public static function trimZeroWidthWhitespace(string $string): string
     {
         return preg_replace('/([{}])[\x{200B}-\x{200D}\x{FEFF}]([{}])/u', '$1$2', $string);
     }