Vercel Serverless - astro build fails with "Cannot use import statement outside a module"

[ref-thomasledoux1]

What version of astro are you using?

2.0.14

Are you using an SSR adapter? If so, which one?

Vercel

What package manager are you using?

npm

What operating system are you using?

Mac

Describe the Bug

I recently switched from the Edge Vercel adapter to the Serverless Vercel adapter, and I notice the astro build command is now failing.
The error seems to happen during the prerendering phase.
The stacktrace points to dist/index.js, which is a generated file by Astro I suppose, so not sure how this can be fixed.

(node:30558) Warning: To load an ES module, set "type": "module" in the package.json or use the .mjs extension.
(Use `node --trace-warnings ...` to show where the warning was created)
error   Cannot use import statement outside a module
/Users/thomas_ledoux/Documents/Projects/website-thomas-astro/dist/entry.js:1
import { performance } from 'node:perf_hooks';
^^^^^^

SyntaxError: Cannot use import statement outside a module
   at internalCompileFunction (node:internal/vm:73:18)
   at wrapSafe (node:internal/modules/cjs/loader:1176:20)
   at Module._compile (node:internal/modules/cjs/loader:1218:27)
   at Module._extensions..js (node:internal/modules/cjs/loader:1308:10)
   at Module.load (node:internal/modules/cjs/loader:1117:32)
   at Module._load (node:internal/modules/cjs/loader:958:12)
   at ModuleWrap.<anonymous> (node:internal/modules/esm/translators:169:29)
   at ModuleJob.run (node:internal/modules/esm/module_job:194:25)

My codesandbox didn't want to work when sharing it, so I just added the Github link to the right branch.

Link to Minimal Reproducible Example

https://github.com/thomasledoux1/website-thomas-astro/tree/feature/add-auth-comment-overview

Participation

• I am willing to submit a pull request for this issue.

[ref-thomasledoux1]

Extra info: switched to Netlify adaptor and issue doesn’t occur anymore. So had something to do with Vercel Serverless adaptor

[wbjohn]

Did you try adding "type": "module" in your package.json?

[thomasledoux1]

Weirdly, this did fix the issue.
I wonder why it does work with the exact same setup with the Netlify adaptor though?
Maybe this should be added to the docs if it would really be necessary to add this line to your package.json?