class View

class View extends AreaPluginBase {
    
    /**
     * Stores whether the embedded view is actually empty.
     *
     * @var bool
     */
    protected $isEmpty;
    
    /**
     * The view storage.
     *
     * @var \Drupal\Core\Entity\EntityStorageInterface
     */
    protected $viewStorage;
    
    /**
     * Constructs a View object.
     *
     * @param array $configuration
     *   A configuration array containing information about the plugin instance.
     * @param string $plugin_id
     *   The plugin_id for the plugin instance.
     * @param mixed $plugin_definition
     *   The plugin implementation definition.
     * @param \Drupal\Core\Entity\EntityStorageInterface $view_storage
     *   The view storage.
     */
    public function __construct(array $configuration, $plugin_id, $plugin_definition, EntityStorageInterface $view_storage) {
        parent::__construct($configuration, $plugin_id, $plugin_definition);
        $this->viewStorage = $view_storage;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
        return new static($configuration, $plugin_id, $plugin_definition, $container->get('entity_type.manager')
            ->getStorage('view'));
    }
    
    /**
     * {@inheritdoc}
     */
    protected function defineOptions() {
        $options = parent::defineOptions();
        $options['view_to_insert'] = [
            'default' => '',
        ];
        $options['inherit_arguments'] = [
            'default' => FALSE,
        ];
        return $options;
    }
    
    /**
     * {@inheritdoc}
     */
    public function buildOptionsForm(&$form, FormStateInterface $form_state) {
        parent::buildOptionsForm($form, $form_state);
        $view_display = $this->view->storage
            ->id() . ':' . $this->view->current_display;
        $options = [
            '' => $this->t('-Select-'),
        ];
        $options += Views::getViewsAsOptions(FALSE, 'all', $view_display, FALSE, TRUE);
        $form['view_to_insert'] = [
            '#type' => 'select',
            '#title' => $this->t('View to insert'),
            '#default_value' => $this->options['view_to_insert'],
            '#description' => $this->t('The view to insert into this area.'),
            '#options' => $options,
        ];
        $form['inherit_arguments'] = [
            '#type' => 'checkbox',
            '#title' => $this->t('Inherit contextual filters'),
            '#default_value' => $this->options['inherit_arguments'],
            '#description' => $this->t('If checked, this view will receive the same contextual filters as its parent.'),
        ];
    }
    
    /**
     * {@inheritdoc}
     */
    public function render($empty = FALSE) {
        if (!empty($this->options['view_to_insert'])) {
            [
                $view_name,
                $display_id,
            ] = explode(':', $this->options['view_to_insert']);
            $view = $this->viewStorage
                ->load($view_name)
                ->getExecutable();
            if (empty($view) || !$view->access($display_id)) {
                return [];
            }
            $view->setDisplay($display_id);
            // Avoid recursion
            $view->parent_views += $this->view->parent_views;
            $view->parent_views[] = "{$view_name}:{$display_id}";
            // Check if the view is part of the parent views of this view
            $search = "{$view_name}:{$display_id}";
            if (in_array($search, $this->view->parent_views)) {
                \Drupal::messenger()->addError($this->t("Recursion detected in view @view display @display.", [
                    '@view' => $view_name,
                    '@display' => $display_id,
                ]));
            }
            else {
                if (!empty($this->options['inherit_arguments']) && !empty($this->view->args)) {
                    $output = $view->preview($display_id, $this->view->args);
                }
                else {
                    $output = $view->preview($display_id);
                }
                $this->isEmpty = $view->display_handler
                    ->outputIsEmpty();
                return $output;
            }
        }
        return [];
    }
    
    /**
     * {@inheritdoc}
     */
    public function isEmpty() {
        if (isset($this->isEmpty)) {
            return $this->isEmpty;
        }
        else {
            return parent::isEmpty();
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public function calculateDependencies() {
        $dependencies = parent::calculateDependencies();
        [
            $view_id,
        ] = explode(':', $this->options['view_to_insert'], 2);
        // Don't call the current view, as it would result into an infinite recursion.
        if ($view_id && $this->view->storage
            ->id() != $view_id) {
            $view = $this->viewStorage
                ->load($view_id);
            $dependencies[$view->getConfigDependencyKey()][] = $view->getConfigDependencyName();
        }
        return $dependencies;
    }

}