Allow Site Settings Block to select view_mode

Problem/Motivation

Site Settings provides 2 blocks, one is a rendered entity, the other is just plain field values, which is great, but limits the flexibility for site builders to control what is displayed and how.

Use case: I have a Site Setting type, Locations. In this type, I have an address field ( rendered as an address ) and a Geolocation field rendered as a Google Map. I have 3 view modes, Default, Address, and Map.

• Default displays the address and map.
• Address just displays the address.
• Map just displays the map.

I want site builders to be able to place a map block in some contexts, and just an address block in other contexts. However, the Site Settings block only ever renders the default view_mode.

https://git.drupalcode.org/project/site_settings/-/blob/8.x-1.x/src/Plug...

$pre_render = $view_builder->view($entity, 'default');

Proposed resolution

Add a setting to the RenderedSiteSettingsBlock that allows for selecting any enabled view_mode for the selected bundle.

My thoughts are, add an AJAX callback on the BlockForm such that when a Site Setting Type is selected, a second select box is displayed with enabled view_modes for that Site Setting Type.

use Drupal\Core\Ajax\AjaxResponse;
use Drupal\Core\Ajax\ReplaceCommand;
use Drupal\Core\Entity\EntityDisplayRepositoryInterface;
// Inject this service.
// ...
  public function defaultConfiguration() {
    return [
      'setting' => NULL,
      'label_display' => FALSE,
      'view_mode' => NULL,
    ] + parent::defaultConfiguration();
  }

 public function blockForm($form, FormStateInterface $form_state) {

    // Allow selection of a site settings entity type.
    $form['setting'] = [
      '#type' => 'entity_autocomplete',
      '#target_type' => 'site_setting_entity_type',
      '#title' => $this->t('Site setting type'),
      '#weight' => '20',
      '#required' => TRUE,
      // Add ajax callback
      '#ajax' => [
        'callback' => '::viewModeCallback',
        'event' => 'autocompleteclose change',
        'wrapper' => 'edit-view-mode',
      ],
    ];
    if (isset($this->configuration['setting']) && !empty($this->configuration['setting'])) {
      $setting_entity_type = $this->entityTypeManager
        ->getStorage('site_setting_entity_type')
        ->load($this->configuration['setting']);
      $form['setting']['#default_value'] = $setting_entity_type;

      // Load the view_mode widget if configuration 'view_mode' is set.
      $view_mode_default = NULL;
      if (isset($this->configuration['view_mode']) && !empty($this->configuration['view_mode'])) {
        $view_mode_default = $this->configuration['view_mode'];
      }
      array_push($form, $this->viewModeElement($setting_entity_type, $view_mode_default);
    }
    else {
      // Return empty div so we have a target container.
      $form['view_mode'] = [
        '#markup' => '<div class="view-mode"></div>',
        '#allowed_tags' => ['div'],
      ];
    }
    return $form;
  }

  public function getViewModes($entity_type) {
    $view_modes = $this->repository->getViewModeOptionsByBundle('site_setting_entity_type', $entity_type);
    return $view_modes;
  }

  public function viewModeCallback(array &$form, FormStateInterface $form_state) {
    $entity_type = $form_state->getValue('setting');
    $element = $this->viewModeElement($entity_type);
    return $element;
  }

  public function viewModeElement($entity_type = NULL, $default = NULL) {
    $view_modes = $this->getViewModes($entity_type);
    $options = $this->getViewModes($entity_type);
    if (is_array($options) && count($options) > 1) {
      $element['view_mode'] = [
        '#type' => 'select',
        '#title' => $this->t('Select View Mode'),
        '#options' => $options,
      ];
      if ($default != NULL) {
        $element['view_mode']['#default_value'] = $default;
      }
    }
    else {
      $element['view_mode'] = [
        '#type' => 'hidden',
        '#value' => ($default) ? $default : $options,
      ];
    }
    return $element;
  }

I haven't tested any of this, but I feel like it's the correct approach.

Remaining tasks

Build / test.

User interface changes

New field to select view mode.

API changes

Data model changes

Add a new setting for view mode.