Promise may not be fulfilled with 'undefined' when statusCode is not 204

[milesj]

Environment

react-native 0.64.2
@callstack/repack 2.5.1

Description

I seem to get this error a lot and I'm not sure why, as there's no other information. It only happens when bundling ios, not android. Here's the full console log.

ℹ [21:46:13.025Z][DevServerProxy] Starting compiler worker { platform: 'ios', port: 64743 }
ℹ [21:46:13.074Z][DevServerProxy] Hermes device connected { deviceId: 2 }
ℹ [21:46:14.087Z][DevServer@ios] Server listening at http://[::]:64743
ℹ [21:46:14.088Z][DevServerProxy] fetching from remote server {
  source: 'http://localhost:64743/index.bundle?platform=ios&dev=true&minify=false&modulesOnly=false&runModule=true&app=com.coinbase.OnboardingMobile'
}
ℹ [21:46:14.094Z][DevServerProxy] fetching from remote server { source: 'http://localhost:64743/api/dashboard/stats?platform=ios' }
ℹ [21:46:14.129Z][webpack-dev-middleware] wait until bundle finished: /index.bundle?platform=ios&dev=true&minify=false&modulesOnly=false&runModule=true&app=com.coinbase.OnboardingMobile
ℹ [21:46:14.130Z][DevServer@ios] Dashboard client connected { clientId: 'client#0' }
ℹ [21:46:14.132Z][webpack-dev-middleware] wait until bundle finished: /api/dashboard/stats?platform=ios
✖ [21:47:13.971Z][DevServerProxy] Promise may not be fulfilled with 'undefined' when statusCode is not 204 {
  err: {
    type: 'FastifyError',
    message: "Promise may not be fulfilled with 'undefined' when statusCode is not 204",
    stack: "FastifyError: Promise may not be fulfilled with 'undefined' when statusCode is not 204\n" +
      '    at /Users/milesjohnson/Projects/react-native/node_modules/fastify/lib/wrapThenable.js:30:30',
    name: 'FastifyError',
    code: 'FST_ERR_PROMISE_NOT_FULFILLED',
    statusCode: 500
  }
}

Reproducible Demo

[zamotany]

Does this happen on a fresh project as well?

[milesj]

No, just ours. I think our project may be too big. With metro, our bundle is 25mb+. When trying to use repack, our bundle is about 50mb, and almost always runs out of memory while trying to bundle.

[roshan-lmi]

Also happening in one of my project. The bundle size is big for me too.

[geroale]

Same issue here

[andreszuluaga-wolox]

me too, I refresh the project and this run ok

[mahi8813]

Any clue on how ti solve this bug.? Any help would be appreciated

[zamotany]

Unfortunately, I don't have any clues. Unless someone provides a reproduction project and I can use, the chances of fixing it are slim.

[tom-sherman]

This happens to me also on our relatively large project but I don't run out of memory. It seems like a timeout is being hit in the dev server as the build process continues (as seen in the dashboard). When I wait for the build to finish and reload the app everything is "fine". (quotes because I have issues with some modules, will create a separate issue for these)

This case might be simple to fix by removing/extending a timeout?

[zamotany]

This case might be simple to fix by removing/extending a timeout?

It's worth a shot. I can provide a diff what to edit and alter the timeout and I'd appreciate if someone can apply it and see if the issue still persists.

[tom-sherman]

Sure, I can try this on our codebase 👍

Just to note tho, we're not currently running repack in production. It's only implemented on a WIP/POC branch right now.

[zamotany]

Ok I think I found a solution.

I've checked the code and the timeout is set for 5mins so it's not the timeout inside Re.Pack than might be causing the issue, but then I've added short timeout to the request for a bundle: curl "http://localhost:8081/index.bundle?platform=ios" --max-time 10 - the bundle compilation takes around 20+s in TesterApp so curl should terminate the connection due to timeout and it did and I was finally able to see the infamous Promise may not be fulfilled with 'undefined' when statusCode is not 204.

As for the solution:
Could someone add return reply; to the end of the forwardRequest (line 234) function inside node_modules/@callstack/repack/dist/server/DevServerProxy.js:

  async forwardRequest(platform, request, reply) {
    if (!this.workers[platform]) {
      await this.runWorker(platform);
    }

    const {
      port
    } = await this.workers[platform];
    const host = request.headers[':authority'] || request.headers.host;
    const url = request.headers[':path'] || request.raw.url;

    if (!url || !host) {
      reply.code(500).send();
    } else {
      const compilerWorkerUrl = `http://localhost:${port}${url}`;
      this.fastify.log.debug({
        msg: 'Fetching from worker',
        url: compilerWorkerUrl,
        method: request.method,
        body: request.body
      });
      reply.from(compilerWorkerUrl);
    }
+   return reply;
  }