Issue #2976356 by phenaproxima, amateescu, Sam152: Add a validation constraint...

Issue #2976356 by phenaproxima, amateescu, Sam152: Add a validation constraint to check if an entity has a field

core/lib/Drupal/Core/Entity/Plugin/Validation/Constraint/EntityHasFieldConstraint.php

+<?php
+
+namespace Drupal\Core\Entity\Plugin\Validation\Constraint;
+
+use Symfony\Component\Validator\Constraint;
+
+/**
+ * Checks if a value is an entity that has a specific field.
+ *
+ * @Constraint(
+ *   id = "EntityHasField",
+ *   label = @Translation("Entity has field", context = "Validation"),
+ *   type = { "entity" },
+ * )
+ */
+class EntityHasFieldConstraint extends Constraint {
+
+  /**
+   * The default violation message.
+   *
+   * @var string
+   */
+  public $message = 'The entity must have the %field_name field.';
+
+  /**
+   * The violation message for non-fieldable entities.
+   *
+   * @var string
+   */
+  public $notFieldableMessage = 'The entity does not support fields.';
+
+  /**
+   * The field name option.
+   *
+   * @var string
+   */
+  public $field_name;
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getDefaultOption() {
+    return 'field_name';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getRequiredOptions() {
+    return (array) $this->getDefaultOption();
+  }
+
+}

core/lib/Drupal/Core/Entity/Plugin/Validation/Constraint/EntityHasFieldConstraintValidator.php

+<?php
+
+namespace Drupal\Core\Entity\Plugin\Validation\Constraint;
+
+use Drupal\Core\Entity\FieldableEntityInterface;
+use Symfony\Component\Validator\Constraint;
+use Symfony\Component\Validator\ConstraintValidator;
+
+/**
+ * Validates the EntityHasField constraint.
+ */
+class EntityHasFieldConstraintValidator extends ConstraintValidator {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function validate($entity, Constraint $constraint) {
+    if (!isset($entity)) {
+      return;
+    }
+
+    /** @var \Drupal\Core\Entity\Plugin\Validation\Constraint\EntityHasFieldConstraint $constraint */
+    if (!($entity instanceof FieldableEntityInterface)) {
+      $this->context->addViolation($constraint->notFieldableMessage);
+      return;
+    }
+
+    if (!$entity->hasField($constraint->field_name)) {
+      $this->context->addViolation($constraint->message, [
+        '%field_name' => $constraint->field_name,
+      ]);
+    }
+  }
+
+}

core/tests/Drupal/KernelTests/Core/Entity/EntityHasFieldConstraintValidatorTest.php

+<?php
+
+namespace Drupal\KernelTests\Core\Entity;
+
+use Drupal\field\Entity\FieldConfig;
+use Drupal\field\Entity\FieldStorageConfig;
+
+/**
+ * @covers \Drupal\Core\Entity\Plugin\Validation\Constraint\EntityHasFieldConstraintValidator
+ *
+ * @group Entity
+ */
+class EntityHasFieldConstraintValidatorTest extends EntityKernelTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public static $modules = ['entity_test_constraints'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp() {
+    parent::setUp();
+    $this->installEntitySchema('entity_test_constraints');
+    $this->createUser();
+  }
+
+  public function testValidation() {
+    $this->state->set('entity_test_constraints.build', [
+      'EntityHasField' => 'body',
+    ]);
+
+    /** @var \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager */
+    $entity_type_manager = $this->container->get('entity_type.manager');
+    $entity_type_manager->clearCachedDefinitions();
+
+    // Clear the typed data cache so that the entity has the correct constraints
+    // during validation.
+    $this->container->get('typed_data_manager')->clearCachedDefinitions();
+
+    $storage = $entity_type_manager->getStorage('entity_test_constraints');
+
+    /** @var \Drupal\entity_test\Entity\EntityTestConstraints $entity */
+    $entity = $storage->create();
+    // We should get a violation if we try to validate the entity before the
+    // field has been created.
+    $violations = $entity->validate();
+    $this->assertCount(1, $violations);
+    $this->assertEquals($violations[0]->getMessage(), 'The entity must have the <em class="placeholder">body</em> field.');
+    $storage->save($entity);
+
+    // Create the field.
+    $field_storage = FieldStorageConfig::create([
+      'type' => 'string',
+      'entity_type' => $entity->getEntityTypeId(),
+      'field_name' => 'body',
+    ]);
+    $field_storage->save();
+
+    FieldConfig::create([
+      'field_storage' => $field_storage,
+      'bundle' => $entity->bundle(),
+    ])->save();
+
+    // Now that the field has been created, there should be no violations.
+    $this->assertCount(0, $storage->loadUnchanged(1)->validate());
+  }
+
+}