Update to Drupal 8.1.8. For more information, see https://www.drupal.org/project/drupal/releases/8.1.8

core/modules/migrate/tests/modules/migrate_external_translated_test/migrate_external_translated_test.info.yml

@@ -0,0 +1,8 @@
+name: 'Migration external translated test'
+type: module
+package: Testing
+version: VERSION
+core: 8.x
+dependencies:
+  - node
+  - migrate

core/modules/migrate/tests/modules/migrate_external_translated_test/migrations/migrate.migration.external_translated_test_node.yml

@@ -0,0 +1,19 @@
+id: external_translated_test_node
+label: External translated content
+source:
+  plugin: migrate_external_translated_test
+  default_lang: true
+  constants:
+    type: external_test
+process:
+  type: constants/type
+  title: title
+  langcode:
+    plugin: static_map
+    source: lang
+    map:
+      English: en
+      French: fr
+      Spanish: es
+destination:
+  plugin: entity:node

core/modules/migrate/tests/modules/migrate_external_translated_test/migrations/migrate.migration.external_translated_test_node_translation.yml

@@ -0,0 +1,27 @@
+id: external_translated_test_node_translation
+label: External translated content translations
+source:
+  plugin: migrate_external_translated_test
+  default_lang: false
+  constants:
+    type: external_test
+process:
+  nid:
+    plugin: migration
+    source: name
+    migration: external_translated_test_node
+  type: constants/type
+  title: title
+  langcode:
+    plugin: static_map
+    source: lang
+    map:
+      English: en
+      French: fr
+      Spanish: es
+destination:
+  plugin: entity:node
+  translations: true
+migration_dependencies:
+  required:
+    - external_translated_test_node

core/modules/migrate/tests/modules/migrate_external_translated_test/src/Plugin/migrate/source/MigrateExternalTranslatedTestSource.php

@@ -0,0 +1,77 @@
+<?php
+
+namespace Drupal\migrate_external_translated_test\Plugin\migrate\source;
+
+use Drupal\migrate\Plugin\migrate\source\SourcePluginBase;
+
+/**
+ * A simple migrate source for our tests.
+ *
+ * @MigrateSource(
+ *   id = "migrate_external_translated_test"
+ * )
+ */
+class MigrateExternalTranslatedTestSource extends SourcePluginBase {
+
+  /**
+   * The data to import.
+   *
+   * @var array
+   */
+  protected $import = [
+    ['name' => 'cat', 'title' => 'Cat', 'lang' => 'English'],
+    ['name' => 'cat', 'title' => 'Chat', 'lang' => 'French'],
+    ['name' => 'cat', 'title' => 'Gato', 'lang' => 'Spanish'],
+    ['name' => 'dog', 'title' => 'Dog', 'lang' => 'English'],
+    ['name' => 'dog', 'title' => 'Chien', 'lang' => 'French'],
+    ['name' => 'monkey', 'title' => 'Monkey', 'lang' => 'English'],
+  ];
+
+  /**
+   * {@inheritdoc}
+   */
+  public function fields() {
+    return [
+      'name' => $this->t('Unique name'),
+      'title' => $this->t('Title'),
+      'lang' => $this->t('Language'),
+    ];
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function __toString() {
+    return '';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getIds() {
+    $ids['name']['type'] = 'string';
+    if (!$this->configuration['default_lang']) {
+      $ids['lang']['type'] = 'string';
+    }
+    return $ids;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function initializeIterator() {
+    $data = [];
+
+    // Keep the rows with the right languages.
+    $want_default = $this->configuration['default_lang'];
+    foreach ($this->import as $row) {
+      $is_english = $row['lang'] == 'English';
+      if ($want_default == $is_english) {
+        $data[] = $row;
+      }
+    }
+
+    return new \ArrayIterator($data);
+  }
+
+}