Issue #3056617 by jcisio, tstoeckler, alexpott: NullStorage does not support collection

core/lib/Drupal/Core/Config/NullStorage.php

@@ -18,6 +18,24 @@ namespace Drupal\Core\Config;
  */
 class NullStorage implements StorageInterface {
 
+  /**
+   * The storage collection.
+   *
+   * @var string
+   */
+  protected $collection;
+
+  /**
+   * Constructs a new NullStorage.
+   *
+   * @param string $collection
+   *   (optional) The collection to store configuration in. Defaults to the
+   *   default collection.
+   */
+  public function __construct($collection = StorageInterface::DEFAULT_COLLECTION) {
+    $this->collection = $collection;
+  }
+
   /**
    * {@inheritdoc}
    */
@@ -92,13 +110,14 @@ class NullStorage implements StorageInterface {
    * {@inheritdoc}
    */
   public function createCollection($collection) {
-    // No op.
+    return new static($collection);
   }
 
   /**
    * {@inheritdoc}
    */
   public function getAllCollectionNames() {
+    // Returns only non empty collections.
     return [];
   }
 
@@ -106,7 +125,7 @@ class NullStorage implements StorageInterface {
    * {@inheritdoc}
    */
   public function getCollectionName() {
-    return '';
+    return $this->collection;
   }
 
 }

core/tests/Drupal/Tests/Core/Config/NullStorageTest.php

@@ -0,0 +1,28 @@
+<?php
+
+namespace Drupal\Tests\Core\Config;
+
+use Drupal\Core\Config\NullStorage;
+use Drupal\Core\Config\StorageInterface;
+use Drupal\Tests\UnitTestCase;
+
+/**
+ * Tests the NullStorage.
+ *
+ * @group Config
+ */
+class NullStorageTest extends UnitTestCase {
+
+  /**
+   * Test createCollection.
+   */
+  public function testCollection() {
+    $nullStorage = new NullStorage();
+    $collection = $nullStorage->createCollection('test');
+    $this->assertInstanceOf(StorageInterface::class, $collection);
+    $this->assertEquals(StorageInterface::DEFAULT_COLLECTION, $nullStorage->getCollectionName());
+    $this->assertEquals('test', $collection->getCollectionName());
+    $this->assertArrayEquals([], $collection->getAllCollectionNames());
+  }
+
+}