NextJS API routes are missing from Vercel's build outputs when folder contains index.js/ts

[angusryer]

I'm using NextJS /api routes and deploying to Vercel.

It seems that wherever I have an index.ts file located within the /api folder structure, Vercel will replace the contents of its containing folder (including /api itself) with a single file. All of the sibling route files will be ignored.

Oddly enough, the folder that contains the index file will remain--but without contents.

Ex:

/api/index.ts
/api/mock1/index.ts
/api/mock1/mock1-endpoint.ts
/api/mock2/index.ts
/api/mock2/mock2-endpoint.ts

This will produce an output of:

/api // empty folder
λ api

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• Note: you'll have to deploy this code to see the output in Vercel's dashboard

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Reproducible code: https://github.com/angusryer/missing-lambdas-vercel-nextjs

Deployed example: https://missing-lambdas-vercel-nextjs.vercel.app/

The api routes are visible as seen in the 'source' tab of the production deployment:

But they are not available in the 'output' tab:

Does anyone know why this happens and ways to get around it?

[Pieparker]

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