Webpack 5, API functions and Vercel error

What version of Next.js are you using?

10.2.2

What version of Node.js are you using?

14

What browser are you using?

Chrome

What operating system are you using?

macOS

How are you deploying your application?

Vercel

Describe the Bug

What is happening? As soon as we enable webpack5, some of our endpoints break.

Which endpoints? Those that share using a function that uses fs.readFile. If it’s a single endpoint using that function, it works just fine. As soon as we add a second endpoint, they both break.

What’s the error?

Where does this happen>? This only happens on Vercel, it works fine locally while doing next build && next start.

Expected Behavior

We should be able to enable webpack5 and not have endpoints breaking under the description listed above.

To Reproduce

Check it out this repo. Here are the two endpoints sharing a single external function.

Also, we have Vercel deployments to verify:

• Here’s a deployment with a single endpoint where everything works just fine.
• Here’s a deployment with an extra endpoint where they break.
• Here’s the diff between those two deployments, in order to fully verify the issue.

[ijjk]

@marbiano I opened a PR here which should address the above issue, thanks for the reproduction!

[ijjk]

Hi, this has been updated and can now be tested in v11.1.1-canary.14 of Next.js by adding the below config to your next.config.js and re-deploying. Please update and give it a try!

module.exports = {
  experimental: {
    nftTracing: true
  }
}