bf089562c7
_Hello Next.js team! First PR here, I hope I've followed the right practices._ ### What's in there? It has been decided to only support the following uses cases in Next.js' middleware: - rewrite the URL (`x-middleware-rewrite` response header) - redirect to another URL (`Location` response header) - pass on to the next piece in the request pipeline (`x-middleware-next` response header) 1. during development, a warning on console tells developers when they are returning a response (either with `Response` or `NextResponse`). 2. at build time, this warning becomes an error. 3. at run time, returning a response body will trigger a 500 HTTP error with a JSON payload containing the detailed error. All returned/thrown errors contain a link to the documentation. This is a breaking feature compared to the _beta_ middleware implementation, and also removes `NextResponse.json()` which makes no sense any more. ### How to try it? - runtime behavior: `HEADLESS=true yarn jest test/integration/middleware/core` - build behavior : `yarn jest test/integration/middleware/build-errors` - development behavior: `HEADLESS=true yarn jest test/development/middleware-warnings` ### Notes to reviewers The limitation happens in next's web adapter. ~The initial implementation was to check `response.body` existence, but it turns out [`Response.redirect()`](https://github.com/vercel/next.js/blob/canary/packages/next/server/web/spec-compliant/response.ts#L42-L53) may set the response body (https://github.com/vercel/next.js/pull/31886). Hence why the proposed implementation specifically looks at response headers.~ `Response.redirect()` and `NextResponse.redirect()` do not need to include the final location in their body: it is handled by next server https://github.com/vercel/next.js/blob/canary/packages/next/server/next-server.ts#L1142 Because this is a breaking change, I had to adjust several tests cases, previously returning JSON/stream/text bodies. When relevant, these middlewares are returning data using response headers. About DevEx: relying on AST analysis to detect forbidden use cases is not as good as running the code. Such cases are easy to detect: ```js new Response('a text value') new Response(JSON.stringify({ /* whatever */ }) ``` But these are false-positive cases: ```js function returnNull() { return null } new Response(returnNull()) function doesNothing() {} new Response(doesNothing()) ``` However, I see no good reasons to let users ship middleware such as the one above, hence why the build will fail, even if _technically speaking_, they are not setting the response body. ## Feature - [x] Implements an existing feature request or RFC. Make sure the feature request has been accepted for implementation before opening a PR. - [ ] Related issues linked using `fixes #number` - [x] Integration tests added - [x] Documentation added - [ ] Telemetry added. In case of a feature if it's used or not. - [x] Errors have helpful link attached, see `contributing.md` ## Documentation / Examples - [x] Make sure the linting passes by running `yarn lint`
83 lines
2.2 KiB
TypeScript
83 lines
2.2 KiB
TypeScript
import type { NextMiddleware, RequestData, FetchEventResult } from './types'
|
|
import type { RequestInit } from './spec-extension/request'
|
|
import { DeprecationError } from './error'
|
|
import { fromNodeHeaders } from './utils'
|
|
import { NextFetchEvent } from './spec-extension/fetch-event'
|
|
import { NextRequest } from './spec-extension/request'
|
|
import { NextResponse } from './spec-extension/response'
|
|
import { waitUntilSymbol } from './spec-compliant/fetch-event'
|
|
|
|
export async function adapter(params: {
|
|
handler: NextMiddleware
|
|
page: string
|
|
request: RequestData
|
|
}): Promise<FetchEventResult> {
|
|
const request = new NextRequestHint({
|
|
page: params.page,
|
|
input: params.request.url,
|
|
init: {
|
|
body: params.request.body,
|
|
geo: params.request.geo,
|
|
headers: fromNodeHeaders(params.request.headers),
|
|
ip: params.request.ip,
|
|
method: params.request.method,
|
|
nextConfig: params.request.nextConfig,
|
|
page: params.request.page,
|
|
},
|
|
})
|
|
|
|
const event = new NextFetchEvent({ request, page: params.page })
|
|
const response = await params.handler(request, event)
|
|
|
|
return {
|
|
response: response || NextResponse.next(),
|
|
waitUntil: Promise.all(event[waitUntilSymbol]),
|
|
}
|
|
}
|
|
|
|
export function blockUnallowedResponse(
|
|
promise: Promise<FetchEventResult>
|
|
): Promise<FetchEventResult> {
|
|
return promise.then((result) => {
|
|
if (result.response?.body) {
|
|
console.error(
|
|
new Error(
|
|
`A middleware can not alter response's body. Learn more: https://nextjs.org/docs/messages/returning-response-body-in-middleware`
|
|
)
|
|
)
|
|
return {
|
|
...result,
|
|
response: new Response('Internal Server Error', {
|
|
status: 500,
|
|
statusText: 'Internal Server Error',
|
|
}),
|
|
}
|
|
}
|
|
return result
|
|
})
|
|
}
|
|
|
|
class NextRequestHint extends NextRequest {
|
|
sourcePage: string
|
|
|
|
constructor(params: {
|
|
init: RequestInit
|
|
input: Request | string
|
|
page: string
|
|
}) {
|
|
super(params.input, params.init)
|
|
this.sourcePage = params.page
|
|
}
|
|
|
|
get request() {
|
|
throw new DeprecationError({ page: this.sourcePage })
|
|
}
|
|
|
|
respondWith() {
|
|
throw new DeprecationError({ page: this.sourcePage })
|
|
}
|
|
|
|
waitUntil() {
|
|
throw new DeprecationError({ page: this.sourcePage })
|
|
}
|
|
}
|