degov-8.x-2.0/modules/degov_media_caption_helper/degov_media_caption_helper.module

<?php

/**
 * Implements hook_preprocess().
 */
function degov_media_caption_helper_preprocess(&$variables, $hook) {
  if ($hook == 'media') {
    // Add url contexts to cache.
    $variables['#cache']['contexts'][] = 'url.path';
    $variables['elements']['#cache']['contexts'][] = 'url.path';
    // Сheck if the media is referenced from another entity.
    if (!empty($variables['elements']['#media']->_referringItem)) {
      $type = $variables['elements']['#media']->bundle();
      // We only preprocess here image and video media entities.
      if (!in_array($type, ['image', 'video', 'video_upload'])) {
        return;
      }
      // Preprocessable field.
      $caption_field = 'field_video_caption';
      if ($type == 'image') {
        $caption_field = 'field_image_caption';
      }
      $referencingEntity = $variables['elements']['#media']->_referringItem->getEntity();
      if ($referencingEntity instanceof \Drupal\Core\Entity\ContentEntityInterface) {
        // Add cache tags, so the media cache depend on the referencing entity.
        $variables['elements']['#cache']['tags'][] = $referencingEntity->getEntityTypeId().':'.$referencingEntity->id();
        $variables['elements']['#cache']['tags'][] = $referencingEntity->getEntityTypeId().'_view';
        _degov_media_caption_add_paragraph_cache_keys($referencingEntity, $variables);
        if (empty($variables['#cache']['tags'])) {
          $variables['#cache']['tags'] = [];
        }
        $variables['#cache']['tags'] = $variables['#cache']['tags'] + $variables['elements']['#cache']['tags'];
        // If referencing entity has overriden caption use it instead.
        if ($referencingEntity->hasField('field_override_caption') && !$referencingEntity->get('field_override_caption')->isEmpty()) {
          $variables['content'][$caption_field] = $referencingEntity->get('field_override_caption')->view('full');
        }
      }
    }
  }
  if (in_array($hook, ['node', 'paragraph'])) {
    // Unset this field override caption because we don't need in parent entity display.
    if (!empty($variables['content']['field_override_caption'])) {
      unset($variables['content']['field_override_caption']);
    }
  }
}

/**
 * Add paragraph cache keys and tags to media.
 * @param $referencingEntity
 * @param $variables
 */
function _degov_media_caption_add_paragraph_cache_keys($referencingEntity, &$variables) {
  if ($referencingEntity instanceof \Drupal\paragraphs\ParagraphInterface) {
    /** @var \Drupal\paragraphs\ParagraphInterface $referencingEntity */
    $paragraphHost = $referencingEntity->getParentEntity();
    if ($paragraphHost && $paragraphHost instanceof \Drupal\Core\Entity\ContentEntityInterface) {
      $variables['elements']['#cache']['tags'][] = $paragraphHost->getEntityTypeId() . ':' . $paragraphHost->id();
      $variables['elements']['#cache']['tags'][] = $paragraphHost->getEntityTypeId() . '_view';
      _degov_media_caption_add_paragraph_cache_keys($paragraphHost, $variables);
    }
  }
}