Server action called from client component is invoked but return data is always undefined (even though network response has data in it)

[RahulBirCodes]

Server action called from client component is invoked but return data is always undefined (even though network response has data in it)

[caioalmeida12]

Hello, Rahul.

Just tried to run your code and, apparently, the error does not occur on my machine (i dont know why)

[RahulBirCodes]

@ztanner Works on my project, thanks a lot!

[RahulBirCodes]

@caioalmeida12 That's because you ran localhost:3000/test without adding the subdomain in front. As per my reproduction steps you need to navigate to demo.localhost:3000/test. I will update the repo to return 404s without subdomain

[dfltr]

Check your network panel for a CORS error. Having a request/response mysteriously zero itself out is a smell that usually points to a CORS violation, as the browser will ditch the body of the request without any other indication that something went wrong.

[RahulBirCodes]

@dfltr Route handlers work though and don't see anything, does the code work when you run it locally?

[RahulBirCodes]

Update on this: regular server actions used in

elements return undefined as well even though the action is being performed. This is a pretty critical bug hope it can be resolved or touched upon

[ztanner]

It looks like your middleware is rewriting the IPC call that powers the server action on the /test page. The fetch call associated with your server action is only bundled with the /[domain]/test route and it's being rewritten to /localhost:3000/[domain]/test.

I'm not 100% following your middleware logic but you can avoid rewriting the action handlers by ensuring the rewrite isn't called for requests that contain the next-action header.

[RahulBirCodes]

Ahhh that makes sense, thank you @ztanner for the quick response!

What Im trying to do in the middleware is take any subdomain request like test.localhost:3000/ and in the middleware add the domain as a slug that I can use to support multi tenancy. Majority of this middleware code is from the Vercel Platforms Starter Kit. I think this is something that needs to be addressed in the starter kit then since server actions come undefined there as well.

Would there be another way you'd suggest to go about this?

[RahulBirCodes]

Hey @ztanner, can't get redirects within server actions to work even though Im excluding it on the middleware. If I put an absolute url in the redirect as well it'll show a 404 and then upon refresh go to the right place :/ It seems like redirects also include the next-action header so when I exclude it, it doesn't do the redirection properly.

[ztanner]

Hey @RahulBirCodes -- I took a closer look and realized the rewrite actually isn't the inherent problem, so you can ignore that suggestion. I think what's happening is that the middleware is causing the content-type header that we would normally set on the action to get lost on the response. Could you try something like this in your middleware and let me know if it works for you?

  if (req.headers.get('next-action')) {
    newHeaders.set('content-type', 'text/x-component')
  }

(I don't expect this to be something you have to worry about in your code, just wanting to identify the root cause)

[RahulBirCodes]

Hey @ztanner, just tested and got the following error on the client: ⨯ SyntaxError: No number after minus sign in JSON at position 1 (line 1 column 2)
at JSON.parse ()
digest: "837905482"

[ztanner]

Hey @ztanner, just tested and got the following error on the client: ⨯ SyntaxError: No number after minus sign in JSON at position 1 (line 1 column 2) at JSON.parse () digest: "837905482"

Does that happen in your repro, or do you have different code that's causing that behavior? If so could you update your repro?

[RahulBirCodes]

@ztanner just pushed to my repro. It's throwing the json error as well now. i updated it to mimic my actual project a little bit so when you're testing go to demo.localhost:3000/login instead.

[ztanner]

@ztanner just pushed to my repro. It's throwing the json error as well now. i updated it to mimic my actual project a little bit so when you're testing go to demo.localhost:3000/login instead.

Thanks for the repro. I've traced it to when you attempt to pass new headers into NextResponse.rewrite. If you don't override the rewrite headers it appears to function properly. I'll dig in on the Next.js side to see why that's happening.

[ztanner]

Hey @RahulBirCodes upon digging further into it, I think this is expected behavior.

In your reproduction you're taking request headers, adding a new property, and then sending to the client as response headers. However those request headers aren't meant to be sent to the client, as they overwrite things like content-type etc.

If you're wanting to add the x-url response header, you can do so on a new Headers object, rather than cloning the headers from the request. I confirmed that worked as expected, so I'm going to close this out!

[github-actions]

This closed issue has been automatically locked because it had no new activity for 2 weeks. If you are running into a similar issue, please create a new issue with the steps to reproduce. Thank you.