Issue #3409088: Translation source language resets to English on import

Closes #3409088

src/Normalizer/ContentEntityNormalizer.php

@@ -11,6 +11,7 @@ use Drupal\Core\Entity\Plugin\DataType\EntityReference;
 use Drupal\Core\Extension\ModuleHandlerInterface;
 use Drupal\Core\Field\FieldItemInterface;
 use Drupal\Core\Installer\InstallerKernel;
+use Drupal\Core\Language\LanguageInterface;
 use Drupal\Core\Language\LanguageManagerInterface;
 use Drupal\Core\TypedData\DataReferenceTargetDefinition;
 use Drupal\Core\TypedData\Plugin\DataType\Uri;
@@ -496,7 +497,10 @@ class ContentEntityNormalizer implements ContentEntityNormalizerInterface {
     // During the installer, when installing with an alternative language,
     // EN is still when modules are installed so check the default language
     // instead.
-    if (!$this->languageManager->getLanguage($data['_meta']['default_langcode']) || (InstallerKernel::installationAttempted() && $this->languageManager->getDefaultLanguage()->getId() != $data['_meta']['default_langcode'])) {
+    if ($this->languageManager->getLanguage($data['_meta']['default_langcode']) instanceof LanguageInterface) {
+      return $data;
+    }
+    if ((InstallerKernel::installationAttempted() && $this->languageManager->getDefaultLanguage()->getId() != $data['_meta']['default_langcode'])) {
       $use_default = TRUE;
       if (isset($data['translations'])) {
         foreach ($data['translations'] as $langcode => $translation_data) {