--- /dev/null
+<?php
+
+namespace Drupal\workspaces\Plugin\Validation\Constraint;
+
+use Drupal\Core\DependencyInjection\ContainerInjectionInterface;
+use Drupal\Core\Entity\EntityTypeManagerInterface;
+use Drupal\workspaces\WorkspaceManagerInterface;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+use Symfony\Component\Validator\Constraint;
+use Symfony\Component\Validator\ConstraintValidator;
+
+/**
+ * Validates the EntityWorkspaceConflict constraint.
+ */
+class EntityWorkspaceConflictConstraintValidator extends ConstraintValidator implements ContainerInjectionInterface {
+
+ /**
+ * The entity type manager.
+ *
+ * @var \Drupal\Core\Entity\EntityTypeManagerInterface
+ */
+ protected $entityTypeManager;
+
+ /**
+ * The workspace manager service.
+ *
+ * @var \Drupal\workspaces\WorkspaceManagerInterface
+ */
+ protected $workspaceManager;
+
+ /**
+ * Constructs an EntityUntranslatableFieldsConstraintValidator object.
+ *
+ * @param \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager
+ * The entity type manager service.
+ * @param \Drupal\workspaces\WorkspaceManagerInterface $workspace_manager
+ * The workspace manager service.
+ */
+ public function __construct(EntityTypeManagerInterface $entity_type_manager, WorkspaceManagerInterface $workspace_manager) {
+ $this->entityTypeManager = $entity_type_manager;
+ $this->workspaceManager = $workspace_manager;
+ }
+
+ /**
+ * {@inheritdoc}
+ */
+ public static function create(ContainerInterface $container) {
+ return new static(
+ $container->get('entity_type.manager'),
+ $container->get('workspaces.manager')
+ );
+ }
+
+ /**
+ * {@inheritdoc}
+ */
+ public function validate($entity, Constraint $constraint) {
+ /** @var \Drupal\Core\Entity\EntityInterface $entity */
+ if (isset($entity) && !$entity->isNew()) {
+ /** @var \Drupal\workspaces\WorkspaceAssociationStorageInterface $workspace_association_storage */
+ $workspace_association_storage = $this->entityTypeManager->getStorage('workspace_association');
+ $workspace_ids = $workspace_association_storage->getEntityTrackingWorkspaceIds($entity);
+ $active_workspace = $this->workspaceManager->getActiveWorkspace();
+
+ if ($workspace_ids && !in_array($active_workspace->id(), $workspace_ids, TRUE)) {
+ // An entity can only be edited in one workspace.
+ $workspace_id = reset($workspace_ids);
+ $workspace = $this->entityTypeManager->getStorage('workspace')->load($workspace_id);
+
+ $this->context->buildViolation($constraint->message)
+ ->setParameter('%label', $workspace->label())
+ ->addViolation();
+ }
+ }
+ }
+
+}