Unable to set optimistic data

[emaborsa]

Hi all,
I am trying to set optimistic data in React, before calling my api, here is my code:

  const insertAdminCarTask = useCallback(
    async (carId: string, body: UpsertCarTask, optimisticData: CarTask[]): Promise<void> => {
      const url = `/admin/cars/${carId}/tasks`;

      const options = { optimisticData: [...optimisticData] };

      await mutate(url, undefined, options);
      await api.postNoResult<UpsertCarTask>(url, body);
    },
    [api]
  );

I must confess, I did't get rid how to properly set optimistic data in order that React re-renders the data without SWR callling the api. I mutate the key with optimistic data (options) but without data (undefined), because the endpoint returns NO_CONTENT. However, React does not re-renders the optimistic data. Any hints?