Redirecting from "getInitialProps" puts the response in html

[JoviDeCroock]

Describe the bug

When deploying an application on netlify with next-on-netlify which uses a page with getInitialProps that's used for redirecting, like the following:

    res.writeHead(302, {
      Location: `en-us`,
    }).end();

It treats this as html, which means that we get to see a html-page which includes:

{"isBase64Encoded":true,"multiValueHeaders":{"Location":["/en-us/"]},"statusCode":302}

rather than actually being redirected to the pages/[locale] handling this, this seems to work correctly when using next dev.

Error in netlify-logs:

ERROR	Unhandled error during request: Error: "Redirect.getInitialProps()" should resolve to an object. But found "undefined" instead.
    at loadGetInitialProps (/var/task/src/web/out_functions/next_index/nextJsPage.js:50131:11)
    at async Function.appGetInitialProps (/var/task/src/web/out_functions/next_index/nextJsPage.js:5470:21)
    at async Function.module.exports.cha2.App.getInitialProps (/var/task/src/web/out_functions/next_index/nextJsPage.js:35698:20)
    at async loadGetInitialProps (/var/task/src/web/out_functions/next_index/nextJsPage.js:50123:17)
    at async renderToHTML (/var/task/src/web/out_functions/next_index/nextJsPage.js:13361:1275)
    at async renderReqToHTML (/var/task/src/web/out_functions/next_index/nextJsPage.js:49246:22)
    at async Module.render (/var/task/src/web/out_functions/next_index/nextJsPage.js:49363:22)

Could this be because of the wrong response-type being detected?

EDIT: adding return {} to getInitialProps makes it work on netlify, trying to figure out why props being undefined is an issue on netlify but not on next dev.

I noticed this piece in the NextPage.js code

function isResSent(res) {
  return res.finished || res.headersSent;
}

When calling res.end() we should set res.finished to true, this is documented here, we also got headersSent but don't know when to set this to true.

To Reproduce

Steps to reproduce:

1. Go to /
2. See html content being the JSON string

Versions

• Next: 10.0.2
• next-on-netlify: 2.6.3

[lindsaylevine]

hm if you're using Next 9.3 or greater (i see you're on Next 10) and the docs recommend using getServerSideProps or getStaticProps over getInitialProps in these later versions. 1. is this an issue using getServerSideProps instead? 2. what's your use case for getInitialProps over getServerSideProps?

[JoviDeCroock]

This issue seems general with both getServerSideProps and getInitialProps. The issue seems to relate to early-termination of the server-side response, in this case a redirect calling res.end() rather than returning an object to be used as props.

the case for getInitialProps is a peculiar one, in librarlies like next-urql a library called react-ssr-prepass is used, the same goes for next-apollo where it's called getDataFromTree. The getInitialProps method allows us to hook into our virtual dom-tree which allows for suspense-traversal. This means that we can use our useQuery hooks to fetch data rather than having to duplicate data-requirements in the getServerSideProps method.

EDIT: getServerSideProps() also seems to validate the object returned from the fn

throw new Error('invariant: getServerSideProps did not return valid props. Please report this.')

[lindsaylevine]

gotcha ok makes sense, thanks for explaining that :) is this something you need hot-fixed out right now or can it wait til our next release?

[JoviDeCroock]

We have a temp-fix in place by returning an empty object for now so it can wait for the next release, thanks for following this up!

[lindsaylevine]

of course!! thanks for investigating and opening a PR, we super appreciate it!!