Issue #2447049 by Cottser, joelpittet: Add a render filter to twig

core/lib/Drupal/Core/Template/TwigExtension.php

@@ -110,6 +110,8 @@ public function getFilters() {
       // CSS class and ID filters.
       new \Twig_SimpleFilter('clean_class', '\Drupal\Component\Utility\Html::getClass'),
       new \Twig_SimpleFilter('clean_id', '\Drupal\Component\Utility\Html::getId'),
+      // This filter will render a renderable array to use the string results.
+      new \Twig_SimpleFilter('render', 'twig_render_var'),
     );
   }
 

core/modules/system/src/Tests/Theme/TwigFilterTest.php

@@ -115,6 +115,10 @@ public function testTwigWithoutFilter() {
         'expected' => '<div id="quotes-here"><span class="gray-like-a-bunny bem__ized--top-feature" id="quotes-here">ID and class. Having the same ID twice is not valid markup but we want to make sure the filter doesn\'t use \Drupal\Component\Utility\Html::getUniqueId().</span></div>',
         'message' => 'Class and ID filtered.',
       ),
+      array(
+        'expected' => '<div><strong>Rendered author string length:</strong> 24.</div>',
+        'message' => 'Render filter string\'s length.',
+      ),
     );
 
     foreach ($elements as $element) {

core/modules/system/tests/modules/twig_theme_test/templates/twig_theme_test.filter.html.twig

@@ -21,3 +21,4 @@
 <div><span{{ attributes|without('id', 'class') }}>Without id and class attributes.</span></div>
 <div><span{{ attributes }}>All attributes again.</span></div>
 <div id="{{ 'quotes Here!'|clean_id }}"><span class="{{ 'Gray like a bunny!'|clean_class }} {{ 'BEM__ized--Top Feature'|clean_class }}" id="{{ 'quotes Here!'|clean_id }}">ID and class. Having the same ID twice is not valid markup but we want to make sure the filter doesn't use \Drupal\Component\Utility\Html::getUniqueId().</span></div>
+<div><strong>Rendered author string length:</strong> {{ quote.author|render|length }}.</div>