Issue #1847582 by amateescu: Create a foreign key to the target entity type...

Issue #1847582 by amateescu: Create a foreign key to the target entity type base type in Entity-reference.

core/modules/entity_reference/entity_reference.install

@@ -28,22 +28,21 @@ function entity_reference_field_schema($field) {
     'indexes' => array(
       'target_id' => array('target_id'),
     ),
-    'foreign keys' => array(),
   );
 
   // Create a foreign key to the target entity type base type.
-  // @todo It's still not safe to call entity_get_info() in here.
-  // see http://drupal.org/node/1847582
-  //  $entity_type = $field['settings']['target_type'];
-  //  $entity_info = entity_get_info($entity_type);
-  //
-  //  $base_table = $entity_info['base_table'];
-  //  $id_column = $entity_info['entity_keys']['id'];
-  //
-  //  $schema['foreign keys'][$base_table] = array(
-  //    'table' => $base_table,
-  //    'columns' => array('target_id' => $id_column),
-  //  );
+  $entity_manager = Drupal::service('plugin.manager.entity');
+  if (is_subclass_of($entity_manager->getControllerClass($field['settings']['target_type'], 'storage'), 'Drupal\Core\Entity\DatabaseStorageController')) {
+    $entity_info = $entity_manager->getDefinition($field['settings']['target_type']);
+
+    $base_table = $entity_info['base_table'];
+    $id_column = $entity_info['entity_keys']['id'];
+
+    $schema['foreign keys'][$base_table] = array(
+      'table' => $base_table,
+      'columns' => array('target_id' => $id_column),
+    );
+  }
 
   return $schema;
 }

core/modules/entity_reference/lib/Drupal/entity_reference/Tests/EntityReferenceItemTest.php

@@ -98,4 +98,32 @@ public function testEntityReferenceItem() {
     $this->assertEqual($entity->field_test_taxonomy->entity->id(), $term2->id());
     $this->assertEqual($entity->field_test_taxonomy->entity->name->value, $term2->name->value);
   }
+
+  /**
+   * Tests foreign key support.
+   */
+  public function testEntityReferenceFieldSchema() {
+    $field = field_info_field('field_test_taxonomy');
+    $foreign_key_column_name = 'target_id';
+
+    // Grab the SQL schema and verify that the 'foreign keys' are present.
+    $schemas = _field_sql_storage_schema($field);
+    $schema = $schemas[_field_sql_storage_tablename($field)];
+    $this->assertEqual(count($schema['foreign keys']), 1, 'There is 1 foreign key in the schema.');
+
+    $foreign_key = reset($schema['foreign keys']);
+    $foreign_key_column = _field_sql_storage_columnname($field['field_name'], $foreign_key_column_name);
+    $this->assertEqual($foreign_key['table'], 'taxonomy_term_data', 'Foreign key table name preserved in the schema.');
+    $this->assertEqual($foreign_key['columns'][$foreign_key_column], 'tid', 'Foreign key column name preserved in the schema.');
+
+    // Create a field that references a config entity type and check that no
+    // foreign key is present.
+    $field_name = 'field_test_vocabulary';
+    entity_reference_create_instance('entity_test', 'entity_test', $field_name, 'Test vocabulary reference', 'taxonomy_vocabulary');
+    $field = field_info_field($field_name);
+
+    $schemas = _field_sql_storage_schema($field);
+    $schema = $schemas[_field_sql_storage_tablename($field)];
+    $this->assertFalse(isset($schema['foreign keys']), 'There is no foreign key in the schema.');
+  }
 }