Issue #2979821 by alexpott, larowlan:...

Issue #2979821 by alexpott, larowlan: \Drupal\config\Form\ConfigSync::processBatch() merges errors incorrectly

core/modules/config/src/Form/ConfigSync.php

@@ -380,7 +380,7 @@ public static function processBatch(ConfigImporter $config_importer, $sync_step,
       if (!isset($context['results']['errors'])) {
         $context['results']['errors'] = [];
       }
-      $context['results']['errors'] += $errors;
+      $context['results']['errors'] = array_merge($context['results']['errors'], $errors);
     }
   }
 

core/modules/config/tests/config_import_test/config_import_test.module

@@ -5,6 +5,8 @@
  * Provides configuration import test helpers.
  */
 
+use Drupal\Core\Config\ConfigImporter;
+
 /**
  * Implements hook_config_import_steps_alter().
  */
@@ -17,9 +19,15 @@ function config_import_test_config_import_steps_alter(&$sync_steps) {
  *
  * @param array $context
  *   The batch context.
+ * @param \Drupal\Core\Config\ConfigImporter $config_importer
+ *   The configuration importer.
  */
-function _config_import_test_config_import_steps_alter(&$context) {
+function _config_import_test_config_import_steps_alter(&$context, ConfigImporter $config_importer) {
   $GLOBALS['hook_config_test']['config_import_steps_alter'] = TRUE;
+  if (\Drupal::state()->get('config_import_steps_alter.error', FALSE)) {
+    $context['results']['errors'][] = '_config_import_test_config_import_steps_alter batch error';
+    $config_importer->logError('_config_import_test_config_import_steps_alter ConfigImporter error');
+  }
   $context['finished'] = 1;
   return;
 }

core/modules/config/tests/src/Functional/ConfigImportUITest.php

@@ -518,4 +518,17 @@ public function testExtensionValidation() {
     $this->assertText('Unable to install the does_not_exist theme since it does not exist.');
   }
 
+  /**
+   * Tests that errors set in the batch and on the ConfigImporter are merged.
+   */
+  public function testBatchErrors() {
+    $new_site_name = 'Config import test ' . $this->randomString();
+    $this->prepareSiteNameUpdate($new_site_name);
+    \Drupal::state()->set('config_import_steps_alter.error', TRUE);
+    $this->drupalPostForm('admin/config/development/configuration', [], t('Import all'));
+    $this->assertSession()->responseContains('_config_import_test_config_import_steps_alter batch error');
+    $this->assertSession()->responseContains('_config_import_test_config_import_steps_alter ConfigImporter error');
+    $this->assertSession()->responseContains('The configuration was imported with errors.');
+  }
+
 }