Here’s my problem (D8):

There’s a content type concert. In a paragraph type concerts_list a list of upcoming concerts (concert nodes) is displayed. This concerts_list paragraph is referenced in field_right_column of another paragraph of type 2_columns.

What I want to do is: Hide the right column if there are no upcoming concerts in the concerts paragraph.

My issue is that the outer (parent) paragraph is rendered and preprocessed before the child paragraph and the resulting render array only includes #theme, #paragraph and #cache but not the actual render array used to render the paragraph.

How can I access a child paragraph’s render array from the parent? I don’t want/need to access the child paragraph’s fields since the concerts are no field because the data is simply added to the build array in hook_entity_type view.

When rendering the 2_columns paragraph I need to know whether or not there are any upcoming concerts and if not I’d like to hide the right column.

Is there a better approach to achieving a similar result?

I’d appreciate any hints/tips/…!

Here’s the relevant code:

function MODULE_paragraph_view(array &$build, EntityInterface $entity, EntityViewDisplayInterface $display, $view_mode) {   $bundle = $entity->bundle();   if ($bundle === 'concerts_list') {     // Get the max number of concerts we want to display.     $max_concerts = (int)$entity->get('field_count')->value;     $build['concerts'] = MODULE_get_upcoming_concersts($max_concerts, 'teaser');   }   elseif ($bundle === '2_columns') {     // Determine whether to show one or 2 columns depending on the number of     // upcoming concerts in 'concerts_list'.     // It would also be ok to do that in twig but I'd need to get the data     // somewhere.   } }  function MODULE_get_upcoming_concerts($limit = 0, $view_mode = 'default') {   $entity_type_manager = Drupal::entityTypeManager();   $query = $entity_type_manager     ->getStorage('node')     ->getQuery()     ->condition('type', 'concert')     ->condition('field_date', strtotime('midnight'), '>')     ->sort('field_date', 'ASC');    if ($limit) {     $query->range(0, $limit);   }    $nids = $query->execute();   if (count($nids) < 1) {     return [];   }   $nodes = $entity_type_manager->getStorage('node')->loadMultiple($nids);   return $entity_type_manager->getViewBuilder('node')->viewMultiple($nodes, $view_mode); }