Error: Couldn't find your server instance. Did you write `module.exports = app`?

[ryanditjia]

Hi, I’m getting an error that seems like a false negative.

The error is:

This is now-sapper, your Vercel builder. Turns out we couldn't find your server instance. Did you write module.exports = app?

Read the docs or create an issue: https://github.com/thgh/now-sapper

My server.js looks as follows.

const app = polka() // You can also use Express
// …

export default app

[ryanditjia]

Looks like this was it.

This problem happens if the server portion of your rollup.config.js you have preserveEntrySignatures set to false.

[thgh]

For future reference:

// Is NOT preserved when preserveEntrySignatures: false
export default app

// Is preserved when preserveEntrySignatures: 'strict'
export default app

// Is preserved when preserveEntrySignatures: false
module.exports = app

// Is preserved when preserveEntrySignatures: 'strict'
module.exports = app