Issue #3412040 by LupusGr3y: UnhandledMatchError: Unhandled match case 'transform'

src/Form/EntityDisplayModeAddForm.php

+<?php
+
+namespace Drupal\transform_api\Form;
+
+use Drupal\Core\Form\FormStateInterface;
+use Symfony\Component\HttpKernel\Exception\NotFoundHttpException;
+
+/**
+ * Provides the add form for entity display modes.
+ *
+ * @internal
+ */
+class EntityDisplayModeAddForm extends EntityDisplayModeFormBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, FormStateInterface $form_state, $entity_type_id = NULL) {
+    $form = parent::buildForm($form, $form_state, $entity_type_id);
+
+    // Change replace_pattern to avoid undesired dots.
+    $form['id']['#machine_name']['replace_pattern'] = '[^a-z0-9_]+';
+    $definition = $this->entityTypeManager->getDefinition($this->targetEntityTypeId);
+    $form['#title'] = $this->t('Add new @entity-type %label', ['@entity-type' => $definition->getLabel(), '%label' => $this->entityType->getSingularLabel()]);
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function validateForm(array &$form, FormStateInterface $form_state) {
+    parent::validateForm($form, $form_state);
+
+    $form_state->setValueForElement($form['id'], $this->targetEntityTypeId . '.' . $form_state->getValue('id'));
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function prepareEntity() {
+    $definition = $this->entityTypeManager->getDefinition($this->targetEntityTypeId);
+    if (!$definition->get('field_ui_base_route') || !$definition->hasViewBuilderClass()) {
+      throw new NotFoundHttpException();
+    }
+
+    $this->entity->setTargetType($this->targetEntityTypeId);
+  }
+
+}

src/Form/EntityDisplayModeEditForm.php

+<?php
+
+namespace Drupal\transform_api\Form;
+
+/**
+ * Provides the edit form for entity display modes.
+ *
+ * @internal
+ */
+class EntityDisplayModeEditForm extends EntityDisplayModeFormBase {
+
+}

src/Form/EntityDisplayModeFormBase.php

+<?php
+
+namespace Drupal\transform_api\Form;
+
+use Drupal\Core\Entity\Display\EntityFormDisplayInterface;
+use Drupal\Core\Entity\Display\EntityViewDisplayInterface;
+use Drupal\Core\Entity\EntityForm;
+use Drupal\Core\Entity\EntityTypeBundleInfoInterface;
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\Url;
+use Drupal\field_ui\FieldUI;
+use Drupal\transform_api\Repository\EntityTransformRepositoryInterface;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+
+/**
+ * Provides the generic base class for entity display mode forms.
+ */
+abstract class EntityDisplayModeFormBase extends EntityForm {
+
+  /**
+   * The entity type definition.
+   *
+   * @var \Drupal\Core\Entity\EntityTypeInterface
+   */
+  protected $entityType;
+
+  /**
+   * The display context. Will always be 'transform'.
+   *
+   * @var string
+   */
+  protected string $displayContext;
+
+  /**
+   * The entity type for which the display mode is being created or edited.
+   *
+   * @var string|null
+   */
+  protected ?string $targetEntityTypeId;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function init(FormStateInterface $form_state) {
+    parent::init($form_state);
+    $this->entityType = $this->entityTypeManager->getDefinition($this->entity->getEntityTypeId());
+    $this->displayContext = str_replace(['entity_', '_mode'], '', $this->entityType->id());
+  }
+
+  /**
+   * Constructs a EntityDisplayModeFormBase object.
+   *
+   * @param \Drupal\Core\Entity\EntityTypeBundleInfoInterface $entityTypeBundleInfo
+   *   The entity type bundle service.
+   * @param \Drupal\transform_api\Repository\EntityTransformRepositoryInterface $entityDisplayRepository
+   *   The entity display repository.
+   */
+  public function __construct(protected EntityTypeBundleInfoInterface $entityTypeBundleInfo, protected EntityTransformRepositoryInterface $entityDisplayRepository) {}
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function create(ContainerInterface $container) {
+    return new static(
+      $container->get('entity_type.bundle.info'),
+      $container->get('transform_api.entity_display.repository'),
+    );
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, FormStateInterface $form_state, $entity_type_id = NULL) {
+    if (!$entity_type_id && !$this->entity->isNew()) {
+      $entity_type_id = $this->entity->getTargetType();
+    }
+    $this->targetEntityTypeId = $entity_type_id;
+    return parent::buildForm($form, $form_state);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function form(array $form, FormStateInterface $form_state) {
+    $form['label'] = [
+      '#type' => 'textfield',
+      '#title' => $this->t('Name'),
+      '#maxlength' => 100,
+      '#default_value' => $this->entity->label(),
+    ];
+
+    $form['description'] = [
+      '#title' => $this->t('Description'),
+      '#type' => 'textarea',
+      '#default_value' => $this->entity->getDescription(),
+      '#description' => $this->t('This text will be displayed on the @mode_label list page.', [
+        '@mode_label' => $this->entity->getEntityType()->getPluralLabel(),
+      ]),
+    ];
+
+    $form['id'] = [
+      '#type' => 'machine_name',
+      '#description' => $this->t('A unique machine-readable name. Can only contain lowercase letters, numbers, and underscores.'),
+      '#disabled' => !$this->entity->isNew(),
+      '#default_value' => $this->entity->id(),
+      '#field_prefix' => $this->entity->isNew() ? $this->entity->getTargetType() . '.' : '',
+      '#machine_name' => [
+        'exists' => [$this, 'exists'],
+        'replace_pattern' => '[^a-z0-9_.]+',
+      ],
+    ];
+    $bundle_info_service = $this->entityTypeBundleInfo;
+    $bundles = $bundle_info_service->getAllBundleInfo();
+    $definition = $this->entityTypeManager->getDefinition($this->entity->isNew() ? $this->targetEntityTypeId : $this->entity->getTargetType());
+
+    $bundles_by_entity = [];
+    $defaults = [];
+    foreach (array_keys($bundles[$definition->id()]) as $bundle) {
+      $bundles_by_entity[$bundle] = $bundles[$definition->id()][$bundle]['label'];
+      // Determine default display modes.
+      if (!$this->entity->isNew()) {
+        [, $display_mode_name] = explode('.', $this->entity->id());
+        if ($this->getDisplayByContext($bundle, $display_mode_name)) {
+          $defaults[$bundle] = $bundle;
+        }
+      }
+    }
+
+    $form['bundles_by_entity'] = [
+      '#type' => 'checkboxes',
+      '#title' => $this->t('Enable this @display-mode for the following @bundle-label types:', ['@display-mode' => $this->entityType->getSingularLabel(), '@bundle-label' => $definition->getLabel()]),
+      '#description' => $this->t('This @display-mode will still be available for the rest of the @bundle-label types if not checked here, but it will not be enabled by default.', ['@bundle-label' => $definition->getLabel(), '@display-mode' => $this->entityType->getSingularLabel()]),
+      '#options' => $bundles_by_entity,
+      '#default_value' => $defaults,
+    ];
+
+    return $form;
+  }
+
+  /**
+   * Determines if the display mode already exists.
+   *
+   * @param string|int $entity_id
+   *   The entity ID.
+   * @param array $element
+   *   The form element.
+   *
+   * @return bool
+   *   TRUE if the display mode exists, FALSE otherwise.
+   */
+  public function exists($entity_id, array $element) {
+    // Do not allow to add internal 'default' view mode.
+    if ($entity_id == 'default') {
+      return TRUE;
+    }
+    /** @var \Drupal\Core\Config\Entity\ConfigEntityStorageInterface $storage */
+    $storage = $this->entityTypeManager->getStorage($this->entity->getEntityTypeId());
+    return (bool) $storage
+      ->getQuery()
+      ->condition('id', $element['#field_prefix'] . $entity_id)
+      ->execute();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function save(array $form, FormStateInterface $form_state) {
+    $this->messenger()->addStatus($this->t('Saved the %label @entity-type.', ['%label' => $this->entity->label(), '@entity-type' => $this->entityType->getSingularLabel()]));
+    $this->entity->save();
+    \Drupal::service('entity_field.manager')->clearCachedFieldDefinitions();
+    $form_state->setRedirectUrl($this->entity->toUrl('collection'));
+
+    [, $display_mode_name] = explode('.', $form_state->getValue('id'));
+    $target_entity_id = $this->targetEntityTypeId;
+
+    foreach ($form_state->getValue('bundles_by_entity') as $bundle => $value) {
+      if (!empty($value)) {
+        // Add a new entity view/form display if it doesn't already exist.
+        if (!$this->getDisplayByContext($bundle, $display_mode_name)) {
+          $display = $this->getEntityDisplay($target_entity_id, $bundle, 'default')->createCopy($display_mode_name);
+          $display->save();
+        }
+
+        // This message is still helpful, even if the view/form display hasn't
+        // changed, so we keep it outside the above check.
+        $url = $this->getOverviewUrl($display_mode_name, $value);
+
+        $bundle_info_service = $this->entityTypeBundleInfo;
+        $bundles = $bundle_info_service->getAllBundleInfo();
+        $bundle_label = $bundles[$target_entity_id][$bundle]['label'];
+        $display_mode_label = $form_state->getValue('label');
+
+        $this->messenger()->addStatus($this->t('<a href=":url">Configure the %display_mode_label %mode mode for %bundle_label</a>.', ['%mode' => $this->displayContext, '%display_mode_label' => $display_mode_label, '%bundle_label' => $bundle_label, ':url' => $url->toString()]));
+      }
+      else {
+        // The view/form display has been unchecked, so we need to delete this.
+        // There's no confirmation of deleting the view/form display on the node
+        // content type forms either, so we match that behavior.
+        if ($display = $this->getDisplayByContext($bundle, $display_mode_name)) {
+          $display->delete();
+        }
+      }
+
+    }
+  }
+
+  /**
+   * Returns an entity display object to be used by this form.
+   *
+   * @param string $entity_type_id
+   *   The target entity type ID of the entity display.
+   * @param string $bundle
+   *   The target bundle of the entity display.
+   * @param string $mode
+   *   A view or form mode.
+   *
+   * @return \Drupal\Core\Entity\Display\EntityDisplayInterface
+   *   An entity display.
+   */
+  private function getEntityDisplay($entity_type_id, $bundle, $mode) {
+    return match($this->displayContext) {
+      'transform' => $this->entityDisplayRepository->getTransformDisplay($entity_type_id, $bundle, $mode),
+    };
+  }
+
+  /**
+   * Returns the Url object for a specific entity (form) display edit form.
+   *
+   * @param string $mode
+   *   The form or view mode.
+   * @param string $bundle
+   *   The entity bundle name.
+   *
+   * @return \Drupal\Core\Url
+   *   A Url object for the overview route.
+   */
+  private function getOverviewUrl($mode, $bundle): Url {
+    $entity_type = $this->entityTypeManager->getDefinition($this->targetEntityTypeId);
+    return match($this->displayContext) {
+      'transform' => Url::fromRoute('entity.entity_transform_display.' . $this->targetEntityTypeId . '.transform_mode', [
+          'transform_mode_name' => $mode,
+        ] + FieldUI::getRouteBundleParameter($entity_type, $bundle)),
+    };
+  }
+
+
+  /**
+   * Load the transform display for a given bundle and transform mode name.
+   *
+   * @param string $bundle
+   *   The entity bundle to load the transform display for.
+   * @param string $form_mode_name
+   *   The form mode name to load the transform display for.
+   *
+   * @return \Drupal\Core\Entity\Display\EntityFormDisplayInterface|null
+   *   Returns the transform display, or NULL if one does not exist.
+   */
+  private function getTransformDisplay(string $bundle, string $form_mode_name): ?EntityFormDisplayInterface {
+    $form_mode_id = $this->targetEntityTypeId . '.' . $bundle . '.' . $form_mode_name;
+    return $this->entityTypeManager->getStorage('entity_transform_display')->load($form_mode_id);
+  }
+
+  /**
+   * Returns View or Form display based on display context.
+   *
+   * @param string $bundle
+   *   The entity bundle to load the display for.
+   * @param string $display_mode_name
+   *   The display mode name to load the display for.
+   *
+   * @return \Drupal\Core\Entity\Display\EntityFormDisplayInterface|\Drupal\Core\Entity\Display\EntityViewDisplayInterface|null
+   *   Returns the display, or NULL if one does not exist.
+   */
+  private function getDisplayByContext(string $bundle, string $display_mode_name): EntityFormDisplayInterface|EntityViewDisplayInterface|null {
+    return match($this->displayContext) {
+      'transform' => $this->getTransformDisplay($bundle, $display_mode_name),
+    };
+  }
+
+}

transform_api.module

@@ -19,15 +19,21 @@ function transform_api_entity_type_build(array &$entity_types) {
 
   $transform_mode = $entity_types['entity_transform_mode'];
   $transform_mode->setListBuilderClass('Drupal\transform_api\EntityTransformModeListBuilder');
+  // @todo Remove once Drupal 10.1.x is only supported.
+  if (floatval(\Drupal::VERSION) >= 10.2) {
+    $transform_mode->setFormClass('add', 'Drupal\transform_api\Form\EntityDisplayModeAddForm');
+    $transform_mode->setFormClass('edit', 'Drupal\transform_api\Form\EntityDisplayModeEditForm');
+  }
+  else {
     $transform_mode->setFormClass('add', 'Drupal\field_ui\Form\EntityDisplayModeAddForm');
     $transform_mode->setFormClass('edit', 'Drupal\field_ui\Form\EntityDisplayModeEditForm');
+  }
   $transform_mode->setFormClass('delete', 'Drupal\field_ui\Form\EntityDisplayModeDeleteForm');
   $transform_mode->set('admin_permission', 'administer display modes');
   $transform_mode->setLinkTemplate('delete-form', '/admin/structure/display-modes/transform/manage/{entity_transform_mode}/delete');
   $transform_mode->setLinkTemplate('edit-form', '/admin/structure/display-modes/transform/manage/{entity_transform_mode}');
   $transform_mode->setLinkTemplate('add-form', '/admin/structure/display-modes/transform/add/{entity_transform_mode}');
   $transform_mode->setLinkTemplate('collection', '/admin/structure/display-modes/transform');
-
 }
 
 /**