--- /dev/null
+<?php
+
+namespace Drupal\entity_test\Plugin\Validation\Constraint;
+
+use Symfony\Component\Validator\Constraint;
+
+/**
+ * Supports validating widget constraints.
+ *
+ * @Constraint(
+ * id = "FieldWidgetConstraint",
+ * label = @Translation("Field widget constraint.")
+ * )
+ */
+class FieldWidgetConstraint extends Constraint {
+
+ public $message = 'Widget constraint has failed.';
+
+}