import { FileRef, nextTestSetup } from 'e2e-utils' import { createSandbox } from 'development-sandbox' import path from 'path' import { outdent } from 'outdent' const middlewarePath = 'middleware.js' const middlewareWarning = `A middleware can not alter response's body` describe('middlewares', () => { const { next } = nextTestSetup({ files: new FileRef( path.join(__dirname, '..', 'acceptance', 'fixtures', 'default-template') ), skipStart: true, }) it.each([ { title: 'returning response with literal string', code: outdent` export default function middleware() { return new Response('this is not allowed'); } `, }, { title: 'returning response with literal number', code: outdent` export default function middleware() { return new Response(10); } `, }, { title: 'returning response with JSON.stringify', code: outdent` export default function middleware() { return new Response(JSON.stringify({ foo: 'this is not allowed' })); } `, }, { title: 'populating response with a value', code: outdent` export default function middleware(request) { const body = JSON.stringify({ foo: 'this should not be allowed, but hard to detect with AST' }) return new Response(body); } `, }, { title: 'populating response with a function call', code: outdent` function buildBody() { return 'this should not be allowed, but hard to detect with AST' } export default function middleware(request) { return new Response(buildBody()); } `, }, { title: 'populating response with an async function call', code: outdent` export default async function middleware(request) { return new Response(await fetch('https://example.vercel.sh')); } `, }, ])('does not warn when $title', async ({ code }) => { await using _sandbox = await createSandbox( next, new Map([[middlewarePath, code]]) ) expect(next.cliOutput).not.toMatch(middlewareWarning) }) it.each([ { title: 'returning null reponse body', code: outdent` export default function middleware() { return new Response(null); } `, }, { title: 'returning undefined response body', code: outdent` export default function middleware() { return new Response(undefined); } `, }, ])('does not warn when $title', async ({ code }) => { await using _sandbox = await createSandbox( next, new Map([[middlewarePath, code]]) ) expect(next.cliOutput).not.toMatch(middlewareWarning) }) })