Issue #3189064 by Matroskeen, quietone, benjifisher: Migration sql source...

Issue #3189064 by Matroskeen, quietone, benjifisher: Migration sql source plugins can not be serialised because of reference to the database connection

(cherry picked from commit e2289f20)

core/modules/migrate/src/Plugin/migrate/source/SqlBase.php

@@ -461,4 +461,11 @@ protected function mapJoinable() {
     return TRUE;
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function __sleep() {
+    return array_diff(parent::__sleep(), ['database']);
+  }
+
 }

core/modules/migrate/tests/src/Kernel/Plugin/MigrationPluginListTest.php

@@ -146,6 +146,15 @@ public function testGetDefinitions() {
     }
     Database::addConnectionInfo('migrate', 'default', $connection_info['default']);
 
+    // Make sure source plugins can be serialized.
+    foreach ($migration_plugins as $migration_plugin) {
+      $source_plugin = $migration_plugin->getSourcePlugin();
+      if ($source_plugin instanceof SqlBase) {
+        $source_plugin->getDatabase();
+      }
+      $this->assertNotEmpty(serialize($source_plugin));
+    }
+
     $migration_plugins = $this->container->get('plugin.manager.migration')->getDefinitions();
     // All the plugins provided by core depend on migrate_drupal.
     $this->assertNotEmpty($migration_plugins);