ensure createTranslator returns default value for undefined translation

Author: lucas-koehler

packages/core/src/i18n/i18nUtil.ts

@@ -65,13 +65,21 @@ export const addI18nKeyToPrefix = (
   return `${i18nKeyPrefix}.${key}`;
 };
 
-export const createTranslator = (
-  fn: (
-    id: string,
-    defaultMessage: string | undefined,
-    values?: any
-  ) => string | undefined
-): Translator => fn as Translator;
+export const createTranslator =
+  (
+    fn: (
+      id: string,
+      defaultMessage: string | undefined,
+      values?: any
+    ) => string | undefined
+  ): Translator =>
+  (id: string, defaultMessage?: string, values?: any) => {
+    const translation = fn(id, defaultMessage, values);
+    if (translation === undefined) {
+      return defaultMessage;
+    }
+    return translation;
+  };
 
 export const defaultTranslator: Translator = createTranslator(
   (_id, defaultMessage) => defaultMessage