Chris@0: <?php
Chris@0: 
Chris@0: namespace Drupal\block;
Chris@0: 
Chris@0: use Drupal\Core\Block\MainContentBlockPluginInterface;
Chris@0: use Drupal\Core\Block\TitleBlockPluginInterface;
Chris@0: use Drupal\Core\Cache\Cache;
Chris@0: use Drupal\Core\Cache\CacheableMetadata;
Chris@0: use Drupal\Core\Entity\EntityViewBuilder;
Chris@0: use Drupal\Core\Entity\EntityInterface;
Chris@0: use Drupal\Core\Extension\ModuleHandlerInterface;
Chris@0: use Drupal\Core\Plugin\ContextAwarePluginInterface;
Chris@0: use Drupal\Core\Render\Element;
Chris@0: use Drupal\block\Entity\Block;
Chris@0: 
Chris@0: /**
Chris@0:  * Provides a Block view builder.
Chris@0:  */
Chris@0: class BlockViewBuilder extends EntityViewBuilder {
Chris@0: 
Chris@0:   /**
Chris@0:    * {@inheritdoc}
Chris@0:    */
Chris@0:   public function buildComponents(array &$build, array $entities, array $displays, $view_mode) {
Chris@0:   }
Chris@0: 
Chris@0:   /**
Chris@0:    * {@inheritdoc}
Chris@0:    */
Chris@0:   public function view(EntityInterface $entity, $view_mode = 'full', $langcode = NULL) {
Chris@0:     $build = $this->viewMultiple([$entity], $view_mode, $langcode);
Chris@0:     return reset($build);
Chris@0:   }
Chris@0: 
Chris@0:   /**
Chris@0:    * {@inheritdoc}
Chris@0:    */
Chris@0:   public function viewMultiple(array $entities = [], $view_mode = 'full', $langcode = NULL) {
Chris@0:     /** @var \Drupal\block\BlockInterface[] $entities */
Chris@0:     $build = [];
Chris@0:     foreach ($entities as $entity) {
Chris@0:       $entity_id = $entity->id();
Chris@0:       $plugin = $entity->getPlugin();
Chris@0: 
Chris@0:       $cache_tags = Cache::mergeTags($this->getCacheTags(), $entity->getCacheTags());
Chris@0:       $cache_tags = Cache::mergeTags($cache_tags, $plugin->getCacheTags());
Chris@0: 
Chris@0:       // Create the render array for the block as a whole.
Chris@0:       // @see template_preprocess_block().
Chris@0:       $build[$entity_id] = [
Chris@0:         '#cache' => [
Chris@0:           'keys' => ['entity_view', 'block', $entity->id()],
Chris@0:           'contexts' => Cache::mergeContexts(
Chris@0:             $entity->getCacheContexts(),
Chris@0:             $plugin->getCacheContexts()
Chris@0:           ),
Chris@0:           'tags' => $cache_tags,
Chris@0:           'max-age' => $plugin->getCacheMaxAge(),
Chris@0:         ],
Chris@0:         '#weight' => $entity->getWeight(),
Chris@0:       ];
Chris@0: 
Chris@0:       // Allow altering of cacheability metadata or setting #create_placeholder.
Chris@0:       $this->moduleHandler->alter(['block_build', "block_build_" . $plugin->getBaseId()], $build[$entity_id], $plugin);
Chris@0: 
Chris@0:       if ($plugin instanceof MainContentBlockPluginInterface || $plugin instanceof TitleBlockPluginInterface) {
Chris@0:         // Immediately build a #pre_render-able block, since this block cannot
Chris@0:         // be built lazily.
Chris@0:         $build[$entity_id] += static::buildPreRenderableBlock($entity, $this->moduleHandler());
Chris@0:       }
Chris@0:       else {
Chris@0:         // Assign a #lazy_builder callback, which will generate a #pre_render-
Chris@0:         // able block lazily (when necessary).
Chris@0:         $build[$entity_id] += [
Chris@0:           '#lazy_builder' => [static::class . '::lazyBuilder', [$entity_id, $view_mode, $langcode]],
Chris@0:         ];
Chris@0:       }
Chris@0:     }
Chris@0: 
Chris@0:     return $build;
Chris@0:   }
Chris@0: 
Chris@0:   /**
Chris@0:    * Builds a #pre_render-able block render array.
Chris@0:    *
Chris@0:    * @param \Drupal\block\BlockInterface $entity
Chris@0:    *   A block config entity.
Chris@0:    * @param \Drupal\Core\Extension\ModuleHandlerInterface $module_handler
Chris@0:    *   The module handler service.
Chris@0:    *
Chris@0:    * @return array
Chris@0:    *   A render array with a #pre_render callback to render the block.
Chris@0:    */
Chris@0:   protected static function buildPreRenderableBlock($entity, ModuleHandlerInterface $module_handler) {
Chris@0:     $plugin = $entity->getPlugin();
Chris@0:     $plugin_id = $plugin->getPluginId();
Chris@0:     $base_id = $plugin->getBaseId();
Chris@0:     $derivative_id = $plugin->getDerivativeId();
Chris@0:     $configuration = $plugin->getConfiguration();
Chris@0: 
Chris@0:     // Inject runtime contexts.
Chris@0:     if ($plugin instanceof ContextAwarePluginInterface) {
Chris@0:       $contexts = \Drupal::service('context.repository')->getRuntimeContexts($plugin->getContextMapping());
Chris@0:       \Drupal::service('context.handler')->applyContextMapping($plugin, $contexts);
Chris@0:     }
Chris@0: 
Chris@0:     // Create the render array for the block as a whole.
Chris@0:     // @see template_preprocess_block().
Chris@0:     $build = [
Chris@0:       '#theme' => 'block',
Chris@0:       '#attributes' => [],
Chris@0:       // All blocks get a "Configure block" contextual link.
Chris@0:       '#contextual_links' => [
Chris@0:         'block' => [
Chris@0:           'route_parameters' => ['block' => $entity->id()],
Chris@0:         ],
Chris@0:       ],
Chris@0:       '#weight' => $entity->getWeight(),
Chris@0:       '#configuration' => $configuration,
Chris@0:       '#plugin_id' => $plugin_id,
Chris@0:       '#base_plugin_id' => $base_id,
Chris@0:       '#derivative_plugin_id' => $derivative_id,
Chris@0:       '#id' => $entity->id(),
Chris@0:       '#pre_render' => [
Chris@0:         static::class . '::preRender',
Chris@0:       ],
Chris@0:       // Add the entity so that it can be used in the #pre_render method.
Chris@0:       '#block' => $entity,
Chris@0:     ];
Chris@0: 
Chris@0:     // If an alter hook wants to modify the block contents, it can append
Chris@0:     // another #pre_render hook.
Chris@0:     $module_handler->alter(['block_view', "block_view_$base_id"], $build, $plugin);
Chris@0: 
Chris@0:     return $build;
Chris@0:   }
Chris@0: 
Chris@0:   /**
Chris@0:    * #lazy_builder callback; builds a #pre_render-able block.
Chris@0:    *
Chris@0:    * @param $entity_id
Chris@0:    *   A block config entity ID.
Chris@0:    * @param $view_mode
Chris@0:    *   The view mode the block is being viewed in.
Chris@0:    *
Chris@0:    * @return array
Chris@0:    *   A render array with a #pre_render callback to render the block.
Chris@0:    */
Chris@0:   public static function lazyBuilder($entity_id, $view_mode) {
Chris@0:     return static::buildPreRenderableBlock(Block::load($entity_id), \Drupal::service('module_handler'));
Chris@0:   }
Chris@0: 
Chris@0:   /**
Chris@0:    * #pre_render callback for building a block.
Chris@0:    *
Chris@0:    * Renders the content using the provided block plugin, and then:
Chris@0:    * - if there is no content, aborts rendering, and makes sure the block won't
Chris@0:    *   be rendered.
Chris@0:    * - if there is content, moves the contextual links from the block content to
Chris@0:    *   the block itself.
Chris@0:    */
Chris@0:   public static function preRender($build) {
Chris@0:     $content = $build['#block']->getPlugin()->build();
Chris@0:     // Remove the block entity from the render array, to ensure that blocks
Chris@0:     // can be rendered without the block config entity.
Chris@0:     unset($build['#block']);
Chris@0:     if ($content !== NULL && !Element::isEmpty($content)) {
Chris@0:       // Place the $content returned by the block plugin into a 'content' child
Chris@0:       // element, as a way to allow the plugin to have complete control of its
Chris@0:       // properties and rendering (for instance, its own #theme) without
Chris@0:       // conflicting with the properties used above, or alternate ones used by
Chris@0:       // alternate block rendering approaches in contrib (for instance, Panels).
Chris@0:       // However, the use of a child element is an implementation detail of this
Chris@0:       // particular block rendering approach. Semantically, the content returned
Chris@0:       // by the plugin "is the" block, and in particular, #attributes and
Chris@0:       // #contextual_links is information about the *entire* block. Therefore,
Chris@0:       // we must move these properties from $content and merge them into the
Chris@0:       // top-level element.
Chris@0:       foreach (['#attributes', '#contextual_links'] as $property) {
Chris@0:         if (isset($content[$property])) {
Chris@0:           $build[$property] += $content[$property];
Chris@0:           unset($content[$property]);
Chris@0:         }
Chris@0:       }
Chris@0:       $build['content'] = $content;
Chris@0:     }
Chris@0:     // Either the block's content is completely empty, or it consists only of
Chris@0:     // cacheability metadata.
Chris@0:     else {
Chris@0:       // Abort rendering: render as the empty string and ensure this block is
Chris@0:       // render cached, so we can avoid the work of having to repeatedly
Chris@0:       // determine whether the block is empty. For instance, modifying or adding
Chris@0:       // entities could cause the block to no longer be empty.
Chris@0:       $build = [
Chris@0:         '#markup' => '',
Chris@0:         '#cache' => $build['#cache'],
Chris@0:       ];
Chris@0:       // If $content is not empty, then it contains cacheability metadata, and
Chris@0:       // we must merge it with the existing cacheability metadata. This allows
Chris@0:       // blocks to be empty, yet still bubble cacheability metadata, to indicate
Chris@0:       // why they are empty.
Chris@0:       if (!empty($content)) {
Chris@0:         CacheableMetadata::createFromRenderArray($build)
Chris@0:           ->merge(CacheableMetadata::createFromRenderArray($content))
Chris@0:           ->applyTo($build);
Chris@0:       }
Chris@0:     }
Chris@0:     return $build;
Chris@0:   }
Chris@0: 
Chris@0: }