Issue #2966137 by vaplas, tim.plunkett: Circular entity references cause...

Issue #2966137 by vaplas, tim.plunkett: Circular entity references cause infinite loop in EntityReferenceItem::generateSampleValue()

core/lib/Drupal/Core/Field/Plugin/Field/FieldType/EntityReferenceItem.php

@@ -272,6 +272,10 @@ public function preSave() {
    * {@inheritdoc}
    */
   public static function generateSampleValue(FieldDefinitionInterface $field_definition) {
+    // An associative array keyed by the reference type, target type, and
+    // bundle.
+    static $recursion_tracker = [];
+
     $manager = \Drupal::service('plugin.manager.entity_reference_selection');
 
     // Instead of calling $manager->getSelectionHandler($field_definition)
@@ -300,9 +304,25 @@ public static function generateSampleValue(FieldDefinitionInterface $field_defin
 
     // Attempt to create a sample entity, avoiding recursion.
     $entity_storage = \Drupal::entityTypeManager()->getStorage($options['target_type']);
-    if ($options['target_type'] !== $field_definition->getTargetEntityTypeId() && $entity_storage instanceof ContentEntityStorageInterface) {
+    if ($entity_storage instanceof ContentEntityStorageInterface) {
       $bundle = static::getRandomBundle($entity_type, $options['handler_settings']);
-      $values['entity'] = $entity_storage->createWithSampleValues($bundle);
+
+      // Track the generated entity by reference type, target type, and bundle.
+      $key = $field_definition->getTargetEntityTypeId() . ':' . $options['target_type'] . ':' . $bundle;
+
+      // If entity generation was attempted but did not finish, do not continue.
+      if (isset($recursion_tracker[$key])) {
+        return [];
+      }
+
+      // Mark this as an attempt at generation.
+      $recursion_tracker[$key] = TRUE;
+
+      // Mark the sample entity as being a preview.
+      $values['entity'] = $entity_storage->createWithSampleValues($bundle, ['in_preview' => TRUE]);
+
+      // Remove the indicator once the entity is successfully generated.
+      unset($recursion_tracker[$key]);
       return $values;
     }
   }

core/modules/field/tests/src/Kernel/EntityReference/EntityReferenceItemTest.php

@@ -3,6 +3,7 @@
 namespace Drupal\Tests\field\Kernel\EntityReference;
 
 use Drupal\comment\Entity\Comment;
+use Drupal\comment\Entity\CommentType;
 use Drupal\Component\Render\FormattableMarkup;
 use Drupal\Core\Field\FieldItemListInterface;
 use Drupal\Core\Field\FieldItemInterface;
@@ -14,6 +15,7 @@
 use Drupal\field\Entity\FieldConfig;
 use Drupal\field\Entity\FieldStorageConfig;
 use Drupal\field\Tests\EntityReference\EntityReferenceTestTrait;
+use Drupal\node\Entity\NodeType;
 use Drupal\node\NodeInterface;
 use Drupal\taxonomy\TermInterface;
 use Drupal\Tests\field\Kernel\FieldKernelTestBase;
@@ -89,6 +91,14 @@ protected function setUp() {
     ]);
     $this->term->save();
 
+    NodeType::create([
+      'type' => $this->randomMachineName(),
+    ])->save();
+    CommentType::create([
+      'id' => $this->randomMachineName(),
+      'target_entity_type_id' => 'node',
+    ])->save();
+
     $this->entityStringId = EntityTestStringId::create([
       'id' => $this->randomMachineName(),
     ]);
@@ -102,6 +112,7 @@ protected function setUp() {
     $this->createEntityReferenceField('entity_test', 'entity_test', 'field_test_user', 'Test user entity reference', 'user');
     $this->createEntityReferenceField('entity_test', 'entity_test', 'field_test_comment', 'Test comment entity reference', 'comment');
     $this->createEntityReferenceField('entity_test', 'entity_test', 'field_test_file', 'Test file entity reference', 'file');
+    $this->createEntityReferenceField('entity_test_string_id', 'entity_test_string_id', 'field_test_entity_test', 'Test content entity reference with string ID', 'entity_test');
   }
 
   /**
@@ -211,6 +222,19 @@ public function testGenerateSampleValue() {
     $this->entityValidateAndSave($entity);
   }
 
+  /**
+   * Tests the ::generateSampleValue() method when it has a circular reference.
+   */
+  public function testGenerateSampleValueCircularReference() {
+    // Delete the existing entity.
+    $this->entityStringId->delete();
+
+    $entity_storage = \Drupal::entityTypeManager()->getStorage('entity_test');
+    $entity = $entity_storage->createWithSampleValues('entity_test');
+    $this->assertInstanceOf(EntityTestStringId::class, $entity->field_test_entity_test_string_id->entity);
+    $this->assertInstanceOf(EntityTest::class, $entity->field_test_entity_test_string_id->entity->field_test_entity_test->entity);
+  }
+
   /**
    * Tests referencing content entities with string IDs.
    */