commit d9d374820269261496fa016bf5b155e890e8fb58
Author: Sally Young <sally@justafish.co.uk>
Date:   Thu Nov 1 10:01:18 2012 -0700

    Config merge

diff --git a/core/includes/update.inc b/core/includes/update.inc
index ec21aca..512c0b7 100644
--- a/core/includes/update.inc
+++ b/core/includes/update.inc
@@ -12,6 +12,7 @@
 use Drupal\Core\Config\FileStorage;
 use Drupal\Core\Config\ConfigException;
 use Drupal\Component\Uuid\Uuid;
+use Drupal\Component\Utility\NestedArray;
 
 /**
  * Minimum schema version of Drupal 7 required for upgrade to Drupal 8.
@@ -1217,18 +1218,15 @@ function update_variables_to_config($config_name, array $variable_map) {
   }
   $default_data = $file->read($config_name);
 
+  // Apply the default values.
+  $config->setData($default_data);
+
   // Merge any possibly existing original data into default values.
   // Only relevant when being called repetitively on the same config object.
   if (!empty($original_data)) {
-    $data = drupal_array_merge_deep($default_data, $original_data);
-  }
-  else {
-    $data = $default_data;
+    $config->merge($original_data);
   }
 
-  // Apply the default values.
-  $config->setData($data);
-
   // Fetch existing variables.
   $variables = db_query('SELECT name, value FROM {variable} WHERE name IN (:variables)', array(':variables' => array_keys($variable_map)))->fetchAllKeyed();
 
diff --git a/core/lib/Drupal/Component/Utility/NestedArray.php b/core/lib/Drupal/Component/Utility/NestedArray.php
index 6617c68..acfdc2f 100644
--- a/core/lib/Drupal/Component/Utility/NestedArray.php
+++ b/core/lib/Drupal/Component/Utility/NestedArray.php
@@ -289,6 +289,10 @@ public static function keyExists(array $array, array $parents) {
    * @param array ...
    *   Arrays to merge.
    *
+   * @param bool $preserve_integer_keys
+   *   (optional) If given, integer keys will be preserved and merged instead of
+   *   appended.
+   *
    * @return array
    *   The merged array.
    *
@@ -315,19 +319,19 @@ public static function mergeDeep() {
    *
    * @see NestedArray::mergeDeep()
    */
-  public static function mergeDeepArray(array $arrays) {
+  public static function mergeDeepArray(array $arrays, $preserve_integer_keys = FALSE) {
     $result = array();
     foreach ($arrays as $array) {
       foreach ($array as $key => $value) {
-        // Renumber integer keys as array_merge_recursive() does. Note that PHP
-        // automatically converts array keys that are integer strings (e.g., '1')
-        // to integers.
-        if (is_integer($key)) {
+        // Renumber integer keys as array_merge_recursive() does unless
+        // $preserve_integer_keys is set to TRUE. Note that PHP automatically
+        // converts array keys that are integer strings (e.g., '1') to integers.
+        if (is_integer($key) && !$preserve_integer_keys) {
           $result[] = $value;
         }
         // Recurse when both values are arrays.
         elseif (isset($result[$key]) && is_array($result[$key]) && is_array($value)) {
-          $result[$key] = self::mergeDeepArray(array($result[$key], $value));
+          $result[$key] = self::mergeDeepArray(array($result[$key], $value), $preserve_integer_keys);
         }
         // Otherwise, use the latter value, overriding any previous value.
         else {
diff --git a/core/lib/Drupal/Core/Config/Config.php b/core/lib/Drupal/Core/Config/Config.php
index 3fe9563..c63b2a0 100644
--- a/core/lib/Drupal/Core/Config/Config.php
+++ b/core/lib/Drupal/Core/Config/Config.php
@@ -401,4 +401,19 @@ public function getStorage() {
   protected function notify($config_event_name) {
     $this->eventDispatcher->dispatch('config.' . $config_event_name, new ConfigEvent($this));
   }
+
+  /*
+   * Merges data into a configuration object.
+   *
+   * @param array $data_to_merge
+   *   An array containing data to merge.
+   *
+   * @return Drupal\Core\Config\Config
+   *   The configuration object.
+   */
+  public function merge(array $data_to_merge) {
+    // Preserve integer keys so that config keys are not changed.
+    $this->data = NestedArray::mergeDeepArray(array($this->data, $data_to_merge), TRUE);
+    return $this;
+  }
 }
diff --git a/core/modules/config/lib/Drupal/config/Tests/ConfigUpgradeTest.php b/core/modules/config/lib/Drupal/config/Tests/ConfigUpgradeTest.php
index 6fe07de..f55921e 100644
--- a/core/modules/config/lib/Drupal/config/Tests/ConfigUpgradeTest.php
+++ b/core/modules/config/lib/Drupal/config/Tests/ConfigUpgradeTest.php
@@ -98,5 +98,26 @@ function testConfigurationUpdate() {
     catch (ConfigException $e) {
       $this->pass('Exception was thrown on missing default module configuration file.');
     }
+
+    // For this test it is essential that update_variables_to_config has already
+    // run on the config object.
+    config('config_upgrade.test')
+      ->set('numeric_keys.403', '')
+      ->set('numeric_keys.404', '')
+      ->save();
+
+    db_insert('variable')
+      ->fields(array('name', 'value'))
+      ->values(array('config_upgrade_403', serialize('custom403')))
+      ->values(array('config_upgrade_404', serialize('custom404')))
+      ->execute();
+
+    // Perform migration.
+    update_variables_to_config('config_upgrade.test', array(
+      'config_upgrade_403' => 'numeric_keys.403',
+      'config_upgrade_404' => 'numeric_keys.404',
+    ));
+
+    $this->assertIdentical(config('config_upgrade.test')->get('numeric_keys'), array(403 => 'custom403', 404 => 'custom404'));
   }
 }
diff --git a/core/modules/system/tests/modules/config_upgrade/config/config_upgrade.test.yml b/core/modules/system/tests/modules/config_upgrade/config/config_upgrade.test.yml
index c921534..fc448c1 100644
--- a/core/modules/system/tests/modules/config_upgrade/config/config_upgrade.test.yml
+++ b/core/modules/system/tests/modules/config_upgrade/config/config_upgrade.test.yml
@@ -2,3 +2,6 @@ parent:
   bar: Bar
   baz: Baz
 foo: Foo
+numeric_keys:
+  403: ''
+  404: ''