fix(30724): clear "x-middleware-next" header when chaining middlewares (

#30866)

* fix(30724): clear "x-middleware-next" header when chaining middlewares

* refactor: do not accumulate "x-middleware-next" header

* test: fix grammar of test case title

* Update packages/next/server/next-server.ts

Co-authored-by: Javi Velasco <javier.velasco86@gmail.com>

packages/next/server/next-server.ts

@@ -700,7 +700,9 @@ export default class Server {
         })
 
         for (let [key, value] of result.response.headers) {
-          allHeaders.append(key, value)
+          if (key !== 'x-middleware-next') {
+            allHeaders.append(key, value)
+          }
         }
 
         if (!this.renderOpts.dev) {

test/integration/middleware/core/pages/responses/deep/_middleware.js

@@ -1,6 +1,9 @@
 import { NextResponse } from 'next/server'
 
 export async function middleware(request, _event) {
+  if (request.nextUrl.searchParams.get('deep-intercept') === 'true') {
+    return new NextResponse('intercepted!')
+  }
   const next = NextResponse.next()
   next.headers.set('x-deep-header', 'valid')
   next.headers.append('x-append-me', 'deep')

test/integration/middleware/core/test/index.test.js

@@ -341,6 +341,14 @@ function responseTests(locale = '') {
       'foo=oatmeal',
     ])
   })
+
+  it(`${locale} should be intercepted by deep middleware`, async () => {
+    const res = await fetchViaHTTP(
+      context.appPort,
+      `${locale}/responses/deep?deep-intercept=true`
+    )
+    expect(await res.text()).toBe('intercepted!')
+  })
 }
 
 function interfaceTests(locale = '') {