Views arguments

I think there is something to fix in the code handling the embedded view.

      $view = Views::getView($display_field['settings']['embed_view']);
      $view->setDisplay($display_settings['settings']['view_display'] ?? 'default');

      $view->setAjaxEnabled($display_settings['settings']['enable_ajax'] ?? 'default');

      // Set the view URL to the current page for the exposed filter form
      // redirection.
      $view->override_url = Url::fromRoute('<current>');

      // Build the view arguments.
      $args = [];
      if (!empty($display_settings['settings']['arguments'])) {
        $view_object = \Drupal::service('entity_type.manager')->getStorage('view')->load($display_field['settings']['embed_view']);
        $view_display = $view_object->getDisplay();
        foreach ($view_display['display_options']['arguments'] as $argument) {
          if (isset($display_settings['settings']['arguments'][$argument['id']])) {
            $arg_values = $this->getViewsArgumentsValues($entities, $display_field, $display_settings['settings']['arguments'][$argument['id']], $parent_entity, $view_mode, $language);
            if (!empty($arg_values)) {
              $args[] = implode('+', $arg_values);
            }
          }
        }
      }

The code loads twice the view, when it should be sufficient to load it via Views::getView().

It also expects that $view_object->getDisplay() returns an array, while the documentation for that method says it return a \Drupal\views\Plugin\views\display\DisplayPluginBase instance.
I cannot find any magic method that would allow to handle the value returned by $view_object->getDisplay() as an array.

Furthermore, $view->setAjaxEnabled() casts its argument to a Boolean value. Instead of passing $display_settings['settings']['enable_ajax'] ?? 'default', it would be probably better to pass $display_settings['settings']['enable_ajax'] ?? TRUE.

Looking at the following code, used by DisplayPluginBase, I think I know how to change the code.

  /**
   * The display information coming directly from the view entity.
   *
   * @see \Drupal\views\Entity\View::getDisplay()
   *
   * @todo \Drupal\views\Entity\View::duplicateDisplayAsType directly access it.
   *
   * @var array
   */
  public $display;

  // Omissis

  public function initDisplay(ViewExecutable $view, array &$display, array &$options = NULL) {
    $this->view = $view;

    // Load extenders as soon as possible.
    $display['display_options'] += [
      'display_extenders' => [],
    ];
    $this->extenders = [];
    if ($extenders = Views::getEnabledDisplayExtenders()) {
      $manager = Views::pluginManager('display_extender');
      $display_extender_options = $display['display_options']['display_extenders'];
      foreach ($extenders as $extender) {

        /** @var \Drupal\views\Plugin\views\display_extender\DisplayExtenderPluginBase $plugin */
        if ($plugin = $manager
          ->createInstance($extender)) {
          $extender_options = isset($display_extender_options[$plugin
            ->getPluginId()]) ? $display_extender_options[$plugin
            ->getPluginId()] : [];
          $plugin
            ->init($this->view, $this, $extender_options);
          $this->extenders[$extender] = $plugin;
        }
      }
    }
    $this
      ->setOptionDefaults($this->options, $this
      ->defineOptions());
    $this->display =& $display;

    // Track changes that the user should know about.
    $changed = FALSE;
    if (!isset($options) && isset($display['display_options'])) {
      $options = $display['display_options'];
    }
    if ($this
      ->isDefaultDisplay() && isset($options['defaults'])) {
      unset($options['defaults']);
    }
    $skip_cache = \Drupal::config('views.settings')
      ->get('skip_cache');
    if (!$skip_cache) {
      $cid = 'views:unpack_options:' . hash('sha256', serialize([
        $this->options,
        $options,
      ])) . ':' . \Drupal::languageManager()
        ->getCurrentLanguage()
        ->getId();
      if (empty(static::$unpackOptions[$cid])) {
        $cache = \Drupal::cache('data')
          ->get($cid);
        if (!empty($cache->data)) {
          $this->options = $cache->data;
        }
        else {
          $this
            ->unpackOptions($this->options, $options);
          \Drupal::cache('data')
            ->set($cid, $this->options, Cache::PERMANENT, $this->view->storage
            ->getCacheTags());
        }
        static::$unpackOptions[$cid] = $this->options;
      }
      else {
        $this->options = static::$unpackOptions[$cid];
      }
    }
    else {
      $this
        ->unpackOptions($this->options, $options);
    }

It seems that, instead of $view_display['display_options'], the module should use $view_display->display['display_options']. From that class, I cannot say $view_display['display_options']['arguments'] is even set, though. My Views knowledge does not allow me to find the answer.

I guess that what I reported in my comments should be reported in a new issue, even though I do not know how to correct the code.