Issue #2216579 by sun: Add a KeyValueStoreInterface::rename() method.

core/lib/Drupal/Core/KeyValueStore/DatabaseStorage.php

@@ -121,6 +121,17 @@ class DatabaseStorage extends StorageBase {
     return $result == Merge::STATUS_INSERT;
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function rename($key, $new_key) {
+    $this->connection->update($this->table)
+      ->fields(array('name' => $new_key))
+      ->condition('collection', $this->collection)
+      ->condition('name', $key)
+      ->execute();
+  }
+
   /**
    * Implements Drupal\Core\KeyValueStore\KeyValueStoreInterface::deleteMultiple().
    */

core/lib/Drupal/Core/KeyValueStore/KeyValueStoreInterface.php

@@ -96,6 +96,16 @@ interface KeyValueStoreInterface {
    */
   public function setMultiple(array $data);
 
+  /**
+   * Renames a key.
+   *
+   * @param string $key
+   *   The key to rename.
+   * @param string $new_key
+   *   The new key name.
+   */
+  public function rename($key, $new_key);
+
   /**
    * Deletes an item from the key/value store.
    *

core/lib/Drupal/Core/KeyValueStore/MemoryStorage.php

@@ -72,6 +72,14 @@ class MemoryStorage extends StorageBase {
     $this->data = $data + $this->data;
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function rename($key, $new_key) {
+    $this->data[$new_key] = $this->data[$key];
+    unset($this->data[$key]);
+  }
+
   /**
    * Implements Drupal\Core\KeyValueStore\KeyValueStoreInterface::delete().
    */

core/lib/Drupal/Core/KeyValueStore/NullStorageExpirable.php

@@ -76,6 +76,12 @@ class NullStorageExpirable implements KeyValueStoreExpirableInterface {
    */
   public function setMultiple(array $data) { }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function rename($key, $new_key) {
+  }
+
   /**
    * Implements Drupal\Core\KeyValueStore\KeyValueStoreInterface::delete().
    */

core/modules/system/lib/Drupal/system/Tests/KeyValueStore/StorageTestBase.php

@@ -205,6 +205,20 @@ abstract class StorageTestBase extends UnitTestBase {
     $this->assertFalse($stores[1]->get($key));
   }
 
+  /**
+   * Tests the rename operation.
+   */
+  public function testRename() {
+    $stores = $this->createStorage();
+    $store = $stores[0];
+
+    $store->set('old', 'thing');
+    $this->assertIdentical($store->get('old'), 'thing');
+    $store->rename('old', 'new');
+    $this->assertIdentical($store->get('new'), 'thing');
+    $this->assertNull($store->get('old'));
+  }
+
   /**
    * Creates storage objects for each collection defined for this class.
    *