next
Version:
The React Framework
34 lines (33 loc) • 2.35 kB
TypeScript
import { type ReadonlyHeaders } from '../web/spec-extension/adapters/headers';
/**
* In this version of Next.js `headers()` returns a Promise however you can still reference the properties of the underlying Headers instance
* synchronously to facilitate migration. The `UnsafeUnwrappedHeaders` type is added to your code by a codemod that attempts to automatically
* updates callsites to reflect the new Promise return type. There are some cases where `headers()` cannot be automatically converted, namely
* when it is used inside a synchronous function and we can't be sure the function can be made async automatically. In these cases we add an
* explicit type case to `UnsafeUnwrappedHeaders` to enable typescript to allow for the synchronous usage only where it is actually necessary.
*
* You should should update these callsites to either be async functions where the `headers()` value can be awaited or you should call `headers()`
* from outside and await the return value before passing it into this function.
*
* You can find instances that require manual migration by searching for `UnsafeUnwrappedHeaders` in your codebase or by search for a comment that
* starts with `@next-codemod-error`.
*
* In a future version of Next.js `headers()` will only return a Promise and you will not be able to access the underlying Headers instance
* without awaiting the return value first. When this change happens the type `UnsafeUnwrappedHeaders` will be updated to reflect that is it no longer
* usable.
*
* This type is marked deprecated to help identify it as target for refactoring away.
*
* @deprecated
*/
export type UnsafeUnwrappedHeaders = ReadonlyHeaders;
/**
* This function allows you to read the HTTP incoming request headers in
* [Server Components](https://nextjs.org/docs/app/building-your-application/rendering/server-components),
* [Server Actions](https://nextjs.org/docs/app/building-your-application/data-fetching/server-actions-and-mutations),
* [Route Handlers](https://nextjs.org/docs/app/building-your-application/routing/route-handlers) and
* [Middleware](https://nextjs.org/docs/app/building-your-application/routing/middleware).
*
* Read more: [Next.js Docs: `headers`](https://nextjs.org/docs/app/api-reference/functions/headers)
*/
export declare function headers(): Promise<ReadonlyHeaders>;