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`
50 lines
1.5 KiB
TypeScript
50 lines
1.5 KiB
TypeScript
import { createNext } from 'e2e-utils'
|
|
import { NextInstance } from 'test/lib/next-modes/base'
|
|
import { fetchViaHTTP } from 'next-test-utils'
|
|
|
|
describe('middleware environment variables in node server reflect the usage inference', () => {
|
|
let next: NextInstance
|
|
|
|
beforeAll(() => {
|
|
process.env.CAN_BE_INFERRED = 'can-be-inferred'
|
|
process.env.X_CUSTOM_HEADER = 'x-custom-header'
|
|
process.env.IGNORED_ENV_VAR = 'ignored-env-var'
|
|
})
|
|
|
|
beforeAll(async () => {
|
|
next = await createNext({
|
|
files: {
|
|
'pages/index.js': `
|
|
export default function () { return <div>Hello, world!</div> }
|
|
`,
|
|
'middleware.js': `
|
|
export default function middleware() {
|
|
return new Response(null, {
|
|
headers: {
|
|
data: JSON.stringify({
|
|
canBeInferred: process.env.CAN_BE_INFERRED,
|
|
rest: process.env
|
|
}),
|
|
'X-Custom-Header': process.env.X_CUSTOM_HEADER,
|
|
}
|
|
})
|
|
}
|
|
`,
|
|
},
|
|
dependencies: {},
|
|
})
|
|
})
|
|
afterAll(() => next.destroy())
|
|
|
|
it('limits process.env to only contain env vars that are inferred from usage', async () => {
|
|
const response = await fetchViaHTTP(next.url, '/test')
|
|
expect(JSON.parse(response.headers.get('data'))).toEqual({
|
|
canBeInferred: 'can-be-inferred',
|
|
rest: {
|
|
CAN_BE_INFERRED: 'can-be-inferred',
|
|
X_CUSTOM_HEADER: 'x-custom-header',
|
|
NEXT_RUNTIME: 'edge',
|
|
},
|
|
})
|
|
})
|
|
})
|