Docs: async rewrites examples are not async

[masto]

What is the documentation issue?

Per

next.js/docs/01-app/04-api-reference/05-config/01-next-config-js/rewrites.mdx

Line 39 in a41152e

`rewrites` is an async function that expects to return either an array or an object of arrays (see below) holding objects with `source` and `destination` properties:

and the type definition (

next.js/packages/next/src/server/config-shared.ts

Line 727 in a41152e

rewrites?: () => Promise<

), rewrites is an async function. The examples, however, neither await anything, nor explicitly return a promise.

JavaScript of course wraps the return value in a promise, so this works, but it may be considered bad form. And some of us have our linters turned up to 11.

Is there any context that might help us understand?

I ran an automated installation script for PostHog, which added this configuration and produced an eslint failure, and that led me to noticing this in the Next.js documentation.

I know that it's trivial to work around and I have done so, but I thought it might be worth considering changing the docs.

Does the docs page already exist? Please link to it.

https://nextjs.org/docs/app/api-reference/config/next-config-js/rewrites

[snivels]

In javascript async functions don't need to have an await inside them, like you've said the return value is implicitly wrapped in a promise.

I believe it's an async function because you might want to do something asynchronous before applying the rewrite e.g. getting a users locale from a cookie and rewriting them to the correct localised URL.

I do agree that perhaps an example code snippet using asynchronous behaviour inside the rewrite would reduce confusion, though.

[masto]

Yeah, I'm assuming I am unusual for turning every linter rule up to 11 and enforcing zero warnings in my pre-commit hook (I have a greenfield project so I thought it would be nice to prevent any jank from creeping in). I just changed mine to

return Promise.resolve([...

but I don't know if doing that in the docs would actually confuse more people than it will help.

Anyway, definitely not making any demands or even expressing a strong opinion, just bringing this up in case the maintainers felt like taking it into account.