Example of Apollo Router multiple set-cookie header issue

forward_set_cookie.rhai

// Rhai plugin that forwards set-cookie header from subgraphs to client.
//
// Issue: we override "set-cookie" header, so only the last applies
//   in headers returned to client.

fn process_subgraph_response(response) {
  try {
    let cookie_value = response.headers["set-cookie"];
    if response.context["set-cookie"] == () {
      response.context["set-cookie"] = []
    }
    response.context["set-cookie"] += cookie_value;
  }
  catch(err) {
    log_error(`set-cookie not getting set: ${err}`);
  }
}

fn process_response(response) {
  try {
    if response.context["set-cookie"] != () {
      let cookie_value = response.context["set-cookie"].shift()
      while (cookie_value != ()) {
        // Issue: This currently overrides previous set-cookie header values
        response.headers["set-cookie"] = cookie_value;
        cookie_value = response.context["set-cookie"].shift()
      }
    }
  }
  catch(err) {
    log_error(`set-cookie not created: ${err}`);
  }
}

main.rhai

import "forward_set_cookie" as forward_set_cookie;

fn process_response(response) {
  forward_set_cookie::process_response(response);
}

fn process_subgraph_response(response) {
  forward_set_cookie::process_subgraph_response(response);
}

fn supergraph_service(service) {
  const response_callback = Fn("process_response");
  service.map_response(response_callback);
}

fn subgraph_service(service, subgraph) {
  const response_callback = Fn("process_subgraph_response");
  service.map_response(response_callback);
}