causing a billing redirect loop

[maneko00]

Issue summary

When I try to redirect the billing url for the app, a loop occurs and status code 302 is returned.
I used redirectOutOfApp function

It works in the development environment, but when the app is deployed to Heroku, it enters a redirect loop and does not proceed to the billing screen.

• @shopify/shopify-api version:7.3.1
• Node version:18.15.0
• Operating system:M1 Mac

// @ts-check
import { join } from "path";
import { readFileSync } from "fs";
import express from "express";
import serveStatic from "serve-static";

import shopify from "./shopify.js";
import GDPRWebhookHandlers from "./gdpr.js";
import { requestBilling } from "./billing.js";

const PORT = parseInt(
  process.env.BACKEND_PORT || process.env.PORT || "3000",
  10
);

const STATIC_PATH =
  process.env.NODE_ENV === "production"
    ? `${process.cwd()}/frontend/dist`
    : `${process.cwd()}/frontend/`;

const app = express();

// Set up Shopify authentication and webhook handling
app.get(shopify.config.auth.path, shopify.auth.begin());
app.get(
  shopify.config.auth.callbackPath,
  shopify.auth.callback(),
  requestBilling,
  shopify.redirectToShopifyOrAppRoot()
);
app.post(
  shopify.config.webhooks.path,
  shopify.processWebhooks({ webhookHandlers: GDPRWebhookHandlers })
);

app.use("/api/*", shopify.validateAuthenticatedSession());

app.use(express.json());

app.use(shopify.cspHeaders());
app.use(serveStatic(STATIC_PATH, { index: false }));

app.use("/*", shopify.ensureInstalledOnShop(),
  requestBilling,
  async (_req, res, _next) => {
  return res
    .status(200)
    .set("Content-Type", "text/html")
    .send(readFileSync(join(STATIC_PATH, "index.html")));
});

app.listen(PORT);

billing.js

import shopify, { billingConfig } from "./shopify.js";


export const requestBilling = async (req, res, next) => {
  console.debug('Start checking billing');

  const plans = Object.keys(billingConfig);
  let session = res.locals.shopify?.session;
  const isAuth = !session ? false : true;

  if(!isAuth) {
    session = await getRequestShopSession(
      shopify.api,
      shopify.config,
      req,
      res
    );
  }

  const isTest = process.env.NODE_ENV !== 'production';

  const hasPayment = await shopify.api.billing.check({session, plans, isTest});
${shopInfo.planDisplayName}`);

  if (hasPayment) {
    next();
  } else {
    const redirectUri = await shopify.api.billing.request({session, plan: plans[0], isTest});
    if(isAuth) {
      res.redirect(redirectUri);
    }
    else {
      shopify.redirectOutOfApp({
        req,
        res,
        redirectUri: redirectUri,
        shop: shopify.api.utils.sanitizeShop(req.query.shop),
      });
    }
  }
};

const getRequestShopSession = async(api, config, req, res) => {
  const shop = shopify.api.utils.sanitizeShop(req.query.shop);
  if (!shop) {
    return undefined;
  }
  config.logger.debug('Checking if shop has installed the app', {
    shop
  });
  const sessionId = api.session.getOfflineId(shop);
  const session = await config.sessionStorage.loadSession(sessionId);
  return session;
}

Expected behavior

Actual behavior

Steps to reproduce the problem

1. Create a new shopify/cli node app template.
2. Add the billing process and deploy the app
3. Install the application and cancel the billing.
4. When you open the application again, you will be redirected to the billing page.

[maneko00]

Changed to redirect from frontend.