Issue #3015886 by bircher, alexpott, Upchuk: Add an in-memory config storage

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

+<?php
+
+namespace Drupal\Core\Config;
+
+/**
+ * Provides an in memory configuration storage.
+ */
+class MemoryStorage implements StorageInterface {
+
+  /**
+   * The configuration, an object shared by reference across collections.
+   *
+   * @var \ArrayAccess
+   */
+  protected $config;
+
+  /**
+   * The storage collection.
+   *
+   * @var string
+   */
+  protected $collection;
+
+  /**
+   * Constructs a new MemoryStorage.
+   *
+   * @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;
+    $this->config = new \ArrayObject();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function exists($name) {
+    return isset($this->config[$this->collection][$name]);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function read($name) {
+    if ($this->exists($name)) {
+      return $this->config[$this->collection][$name];
+    }
+
+    return FALSE;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function readMultiple(array $names) {
+    return array_intersect_key($this->config[$this->collection], array_flip($names));
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function write($name, array $data) {
+    $this->config[$this->collection][$name] = $data;
+    return TRUE;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function delete($name) {
+    if (isset($this->config[$this->collection][$name])) {
+      unset($this->config[$this->collection][$name]);
+      // Remove the collection if it is empty.
+      if (empty($this->config[$this->collection])) {
+        $this->config->offsetUnset($this->collection);
+      }
+      return TRUE;
+    }
+    return FALSE;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function rename($name, $new_name) {
+    if (!$this->exists($name)) {
+      return FALSE;
+    }
+    $this->config[$this->collection][$new_name] = $this->config[$this->collection][$name];
+    unset($this->config[$this->collection][$name]);
+    return TRUE;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function encode($data) {
+    return $data;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function decode($raw) {
+    return $raw;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function listAll($prefix = '') {
+    if (empty($this->config[$this->collection])) {
+      // If the collection is empty no keys are set.
+      return [];
+    }
+    $names = array_keys($this->config[$this->collection]);
+    if ($prefix !== '') {
+      $names = array_filter($names, function ($name) use ($prefix) {
+        return strpos($name, $prefix) === 0;
+      });
+    }
+    return $names;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function deleteAll($prefix = '') {
+    if (!$this->config->offsetExists($this->collection)) {
+      // There's nothing to delete.
+      return FALSE;
+    }
+    if ($prefix === '') {
+      $this->config->offsetUnset($this->collection);
+      return TRUE;
+    }
+    $success = FALSE;
+    foreach (array_keys($this->config[$this->collection]) as $name) {
+      if (strpos($name, $prefix) === 0) {
+        $success = TRUE;
+        unset($this->config[$this->collection][$name]);
+      }
+    }
+    // Remove the collection if it is empty.
+    if (empty($this->config[$this->collection])) {
+      $this->config->offsetUnset($this->collection);
+    }
+
+    return $success;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function createCollection($collection) {
+    $collection = new static($collection);
+    $collection->config = $this->config;
+    return $collection;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getAllCollectionNames() {
+    $collection_names = [];
+    foreach ($this->config as $collection_name => $data) {
+      // Exclude the default collection and empty collections.
+      if ($collection_name !== StorageInterface::DEFAULT_COLLECTION && !empty($data)) {
+        $collection_names[] = $collection_name;
+      }
+    }
+    sort($collection_names);
+
+    return $collection_names;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getCollectionName() {
+    return $this->collection;
+  }
+
+}

core/tests/Drupal/KernelTests/Core/Config/Storage/MemoryStorageTest.php

+<?php
+
+namespace Drupal\KernelTests\Core\Config\Storage;
+
+use Drupal\Core\Config\MemoryStorage;
+
+/**
+ * Tests MemoryStorage operations.
+ *
+ * @group config
+ */
+class MemoryStorageTest extends ConfigStorageTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp() {
+    parent::setUp();
+    $this->storage = new MemoryStorage();
+    // ::listAll() verifications require other configuration data to exist.
+    $this->storage->write('system.performance', []);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function read($name) {
+    return $this->storage->read($name);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function insert($name, $data) {
+    $this->storage->write($name, $data);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function update($name, $data) {
+    $this->storage->write($name, $data);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function delete($name) {
+    $this->storage->delete($name);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function testInvalidStorage() {
+    $this->markTestSkipped('MemoryStorage cannot be invalid.');
+  }
+
+}