Only normalize the hint once.

packages/orm/src/json.ts

@@ -107,20 +107,21 @@ export async function toJSON<T extends Entity, const H extends JsonHint<T>>(
   const entity = Array.isArray(entityOrList) ? entityOrList[0] : entityOrList;
   const loadHint = convertToLoadHint(getMetadata(entity), hint as any, true);
   await entity.em.populate(entityOrList, loadHint);
+  const normHint = normalizeHint(hint as any);
 
   if (Array.isArray(entityOrList)) {
     const list = [] as any;
     await Promise.all(
       entityOrList.map((entity) => {
         const json = {};
         list.push(json);
-        return copyToPayload(json, entity, normalizeHint(hint as any));
+        return copyToPayload(json, entity, normHint);
       }),
     );
     return list;
   } else {
     const json = {};
-    await copyToPayload(json, entity, normalizeHint(hint as any));
+    await copyToPayload(json, entity, normHint);
     return json as any;
   }
 }