API routes return CloudFront 503 on `next` `12.0.9`

(I think this is a feature request, more than a bug 🤔)

Is your feature request related to a problem? Please describe.

When upgrading next from 12.0.8 to 12.0.9, API routes started to return a generic 503 from CloudFront.

• Update: I’m seeing the same error message that @jakubriedl posted ^1

TypeError: Cannot read property 'headers' of undefined
    at Object.apiResolver (/var/task/chunks/89.js:10564:43)
    at Module.<anonymous> (/var/task/chunks/89.js:6094:34)

A barebones API route (/api/health.ts) would return a generic 503 CloudFront error

import { NextApiHandler } from "next";

const handler: NextApiHandler = async (req, res) => {
  return res.status(200).send("OK");
};

export default handler;

Describe the solution you’d like

For these to just work with next >= 12.0.9 🙏

    "@sls-next/cdk-construct": "3.7.0-alpha.7",
    "@sls-next/lambda-at-edge": "3.7.0-alpha.7",

Describe alternatives you’ve considered

Pin next to 12.0.8

Additional context

https://github.com/vercel/next.js/compare/v12.0.8...v12.0.9

[Knufle]

Hi everybody, I was having the 503 error today after setting up a pretty standard nextjs project using serverless-next.js 3.6.0, I thought it was a Lambda permission issue so I created a new role/policy but the error persisted, I’m using next 12.1.0 btw. Reading through the comments I saw some people mention the alpha pre-release so I tested 3.7.0-alpha.10 and boom, the default api that comes in the example project (api/hello) started working! I even removed the policy/role that I created and everything is still working just fine, I hope this helps someone too.

[traianturcu]

I apologize if this is not the right place to ask this question, but do you happen to know if AWS Amplify uses serverless-nextjs for deploying Next.js apps? When using Amplify to deploy our app I encounter the same issue (unless I switch to Next 12.0.8)