Issue #2617152 by Chi, alexpott, dawehner: Single import form needs to handle...

Issue #2617152 by Chi, alexpott, dawehner: Single import form needs to handle invalid YAML correctly and not with an exception

(cherry picked from commit 66320051)

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

@@ -2,6 +2,7 @@
 
 namespace Drupal\config\Form;
 
+use Drupal\Component\Serialization\Exception\InvalidDataTypeException;
 use Drupal\Component\Serialization\Yaml;
 use Drupal\config\StorageReplaceDataWrapper;
 use Drupal\Core\Config\ConfigImporter;
@@ -281,8 +282,13 @@ public function validateForm(array &$form, FormStateInterface $form_state) {
       return;
     }
 
-    // Decode the submitted import.
-    $data = Yaml::decode($form_state->getValue('import'));
+    try {
+      // Decode the submitted import.
+      $data = Yaml::decode($form_state->getValue('import'));
+    }
+    catch (InvalidDataTypeException $e) {
+      $form_state->setErrorByName('import', $this->t('The import failed with the following message: %message', ['%message' => $e->getMessage()]));
+    }
 
     // Validate for config entities.
     if ($form_state->getValue('config_type') !== 'system.simple') {

core/modules/config/src/Tests/ConfigSingleImportExportTest.php

@@ -37,6 +37,16 @@ public function testImport() {
     $uuid = \Drupal::service('uuid');
 
     $this->drupalLogin($this->drupalCreateUser(array('import configuration')));
+
+    // Attempt an import with invalid YAML.
+    $edit = [
+      'config_type' => 'action',
+      'import' => '{{{',
+    ];
+
+    $this->drupalPostForm('admin/config/development/configuration/single/import', $edit, t('Import'));
+    $this->assertText('The import failed with the following message: Malformed inline YAML string ({{{) at line 1 (near "{{{")');
+
     $import = <<<EOD
 label: First
 weight: 0