must provide query string error

query-ppx.re

[%%raw {|require('isomorphic-fetch')|}];
open Js.Promise;

module FilmQuery = [%graphql {|
  {
    allFilms {
      films {
        id
        title
        releaseDate
      }
    }
  }
|}];

exception Graphql_error(string);

/* Construct a "packaged" query; FilmQuery takes no arguments: */
let filmQuery = FilmQuery.make();

/* Send this query string to the server */
let query = filmQuery##query;

let sendQuery = (q) =>
  Fetch.(
    fetchWithInit(
        "http://swapi.apis.guru/",
        RequestInit.make(
        ~method_=Post,
        ~body=
          Js.Dict.fromList([("query", Js.Json.string(q##query)), ("variables", q##variables)])
          |> Js.Json.object_
          |> Js.Json.stringify
          |> BodyInit.make,
        ~credentials=Include,
        ~headers=HeadersInit.makeWithArray([|("content-type", "application/json")|]),
        ()
      )
    )
    |> Js.Promise.then_(json => Response.json(json) |> resolve)
    |> Js.Promise.then_(data => Js.log(data) |> resolve)
    |> Js.Promise.catch(err => resolve(Js.log(err)))
  );
Js.log(query);
sendQuery(query);
/* 
- error
[bucklescript]
This has type:
  string
But somewhere wanted:
  Js.t({.. query : string, variables : Js.Json.t })
string

*/