RTK Query - Setting headers doesn't work

I’m trying to send a POST request and I need to set the ‘content-type’ header to ‘application/json’, I’m using fetchBaseQuery and it’s supposed to automatically do that but it’s not working because when I check the sent request using Chrome Dev Tools and checking the request headers I don’t see ‘content-type’ set to ‘application/json’. I don’t see it at all so I tried to manually do that by either using prepareHeaders like this

// Or from '@reduxjs/toolkit/query' if not using the auto-generated hooks
import { createApi, fetchBaseQuery } from "@reduxjs/toolkit/query/react";

// initialize an empty api service that we'll inject endpoints into later as needed
export const mainApi = createApi({
  reducerPath: "mainApi",
  baseQuery: fetchBaseQuery({
    baseUrl: "http://localhost:5000/api/v1/",
    prepareHeaders: (headers) => {
      headers.set("Content-Type", "application/json");
      console.log(headers);
      return headers;
    },
  }),
  endpoints: () => ({}),
});

it still won’t work, btw console.log(headers) only returns an empty Headers object . I also tried to set the header like this

    addUser: builder.mutation({
      query: (data) => {
        //  console.log(typeof body);
        return {
          url: `auth/signup`,
          method: "POST",
          headers: { "content-type": "application/json" },
          body: JSON.stringify(data),
        };
      },
    }),

I still can’t see the ‘content-type’ header when checking it using browser dev tools.

[anmilleriii]

Thanks for the quick response @phryneas!

I think that your comment here correctly identified this issue (and clarified that it pertains to SuperTokens, not RTK Query).

Therefore I would consider this issue out of scope to RTK query and closable here, (fixing the SuperTokens implementation of their fetch wrapper is now covered by this issue.

[phryneas]

@anmilleriii that looks like that “modified fetch” just does not support getting passed a Request object as the first argument.

The first argument to fetch has to be a RequestInfo which is either a string, or a Request class instance.

Supertokens fails to implement the standard there.