Prevent empty groups to be displayed.

Author: Edouard Cunibil

modules/ui_patterns_field_group/src/Plugin/field_group/FieldGroupFormatter/PatternFormatter.php

@@ -128,6 +128,8 @@ protected function preRenderGroup(array &$element, $group_name, array $rendering
 
     // Handle groups managed by UI Patterns recursively.
     if ($group->format_type == 'pattern_formatter') {
+      $element['#is_empty'] = TRUE;
+
       // Move content into their fields.
       foreach ($group->format_settings['pattern_mapping'] as $field) {
         if ($field['plugin'] == 'fieldgroup') {
@@ -136,13 +138,35 @@ protected function preRenderGroup(array &$element, $group_name, array $rendering
           }
           else {
             $this->preRenderGroup($element[$field['source']], $field['source'], $rendering_object);
+            if (!empty($element[$field['source']]) && !$element[$field['source']]['#is_empty']) {
+              $element['#is_empty'] = FALSE;
+            }
+          }
+        }
+        elseif ($field['plugin'] == 'fields') {
+          /** @var \Drupal\Core\Entity\EntityInterface $entity */
+          $entity = $rendering_object['#' . $rendering_object['#entity_type']];
+
+          // Use entity field so the hypothetical rendering elements are not
+          // to be taken into account to consider the field empty or not.
+          if ($entity->hasField($field['source']) && !$entity->{$field['source']}->isEmpty()) {
+            $element['#is_empty'] = FALSE;
           }
         }
+        elseif (!empty($element[$field['source']])) {
+          $element['#is_empty'] = FALSE;
+        }
         $element['#fields'][$field['destination']][$field['source']] = $element[$field['source']];
       }
 
-      // Add render array metadata.
-      $this->addRenderContext($element, $group->format_settings);
+      // Prevent to show the group if fields are empty.
+      if ($element['#is_empty'] && empty($group->format_settings['show_empty_fields'])) {
+        $element = [];
+      }
+      else {
+        // Add render array metadata.
+        $this->addRenderContext($element, $group->format_settings);
+      }
     }
     // Fallback to default pre_rendering for fieldgroups not managed by UI
     // Patterns.