Fixes #2527: Source language for `app` message category was always `en` no…

framework/CHANGELOG.md

@@ -48,6 +48,7 @@ Yii Framework 2 Change Log
 - Bug #2399: Fixed the bug that AssetBundle did not handle relative URLs correctly (qiangxue)
 - Bug #2502: Unclear error message when `$_SERVER['DOCUMENT_ROOT']` is empty (samdark)
 - Bug #2519: MessageSource removed translation messages when event handler was bound to `missingTranslation`-event (cebe)
+- Bug #2527: Source language for `app` message category was always `en` no matter which application `sourceLanguage` was used (samdark)
 - Bug: Fixed `Call to a member function registerAssetFiles() on a non-object` in case of wrong `sourcePath` for an asset bundle (samdark)
 - Bug: Fixed incorrect event name for `yii\jui\Spinner` (samdark)
 - Bug: Json::encode() did not handle objects that implement JsonSerializable interface correctly (cebe)

framework/i18n/I18N.php

@@ -65,7 +65,7 @@ class I18N extends Component
 		if (!isset($this->translations['app'])) {
 			$this->translations['app'] = [
 				'class' => 'yii\i18n\PhpMessageSource',
-				'sourceLanguage' => 'en',
+				'sourceLanguage' => Yii::$app->sourceLanguage,
 				'basePath' => '@app/messages',
 			];
 		}