Fix running server with Polyfilled fetch

packages/next/server/base-server.ts

@@ -91,10 +91,10 @@ import { parseNextUrl } from '../shared/lib/router/utils/parse-next-url'
 import isError from '../lib/is-error'
 import { getMiddlewareInfo } from './require'
 import { MIDDLEWARE_ROUTE } from '../lib/constants'
-import { NextResponse } from './web/spec-extension/response'
 import { run } from './web/sandbox'
 import { addRequestMeta, getRequestMeta } from './request-meta'
 import { toNodeHeaders } from './web/utils'
+import { relativizeURL } from '../shared/lib/router/utils/relativize-url'
 
 const getCustomRouteMatcher = pathMatch(true)
 
@@ -379,7 +379,13 @@ export default abstract class Server {
         parsedUrl.query = parseQs(parsedUrl.query)
       }
 
-      addRequestMeta(req, '__NEXT_INIT_URL', req.url)
+      // When there are hostname and port we build an absolute URL
+      const initUrl =
+        this.hostname && this.port
+          ? `http://${this.hostname}:${this.port}${req.url}`
+          : req.url
+
+      addRequestMeta(req, '__NEXT_INIT_URL', initUrl)
       addRequestMeta(req, '__NEXT_INIT_QUERY', { ...parsedUrl.query })
 
       const url = parseNextUrl({
@@ -673,6 +679,14 @@ export default abstract class Server {
   }): Promise<FetchEventResult | null> {
     this.middlewareBetaWarning()
 
+    // For middleware to "fetch" we must always provide an absolute URL
+    const url = getRequestMeta(params.request, '__NEXT_INIT_URL')!
+    if (!url.startsWith('http')) {
+      throw new Error(
+        'To use middleware you must provide a `hostname` and `port` to the Next.js Server'
+      )
+    }
+
     const page: { name?: string; params?: { [key: string]: string } } = {}
     if (await this.hasPage(params.parsedUrl.pathname)) {
       page.name = params.parsedUrl.pathname
@@ -687,8 +701,6 @@ export default abstract class Server {
       }
     }
 
-    const subreq = params.request.headers[`x-middleware-subrequest`]
-    const subrequests = typeof subreq === 'string' ? subreq.split(':') : []
     const allHeaders = new Headers()
     let result: FetchEventResult | null = null
 
@@ -708,14 +720,6 @@ export default abstract class Server {
           serverless: this._isLikeServerless,
         })
 
-        if (subrequests.includes(middlewareInfo.name)) {
-          result = {
-            response: NextResponse.next(),
-            waitUntil: Promise.resolve(),
-          }
-          continue
-        }
-
         result = await run({
           name: middlewareInfo.name,
           paths: middlewareInfo.paths,
@@ -727,7 +731,7 @@ export default abstract class Server {
               i18n: this.nextConfig.i18n,
               trailingSlash: this.nextConfig.trailingSlash,
             },
-            url: getRequestMeta(params.request, '__NEXT_INIT_URL')!,
+            url: url,
             page: page,
           },
           useCache: !this.nextConfig.experimental.concurrentFeatures,
@@ -1185,9 +1189,13 @@ export default abstract class Server {
         type: 'route',
         name: 'middleware catchall',
         fn: async (req, res, _params, parsed) => {
-          const fullUrl = getRequestMeta(req, '__NEXT_INIT_URL')
+          if (!this.middleware?.length) {
+            return { finished: false }
+          }
+
+          const initUrl = getRequestMeta(req, '__NEXT_INIT_URL')!
           const parsedUrl = parseNextUrl({
-            url: fullUrl,
+            url: initUrl,
             headers: req.headers,
             nextConfig: {
               basePath: this.nextConfig.basePath,
@@ -1226,6 +1234,18 @@ export default abstract class Server {
             return { finished: true }
           }
 
+          if (result.response.headers.has('x-middleware-rewrite')) {
+            const value = result.response.headers.get('x-middleware-rewrite')!
+            const rel = relativizeURL(value, initUrl)
+            result.response.headers.set('x-middleware-rewrite', rel)
+          }
+
+          if (result.response.headers.has('Location')) {
+            const value = result.response.headers.get('Location')!
+            const rel = relativizeURL(value, initUrl)
+            result.response.headers.set('Location', rel)
+          }
+
           if (
             !result.response.headers.has('x-middleware-rewrite') &&
             !result.response.headers.has('x-middleware-next') &&

packages/next/server/web/adapter.ts

@@ -1,8 +1,9 @@
 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, RequestInit } from './spec-extension/request'
+import { NextRequest } from './spec-extension/request'
 import { NextResponse } from './spec-extension/response'
 import { waitUntilSymbol } from './spec-compliant/fetch-event'
 
@@ -11,13 +12,9 @@ export async function adapter(params: {
   page: string
   request: RequestData
 }): Promise<FetchEventResult> {
-  const url = params.request.url.startsWith('/')
-    ? `https://${params.request.headers.host}${params.request.url}`
-    : params.request.url
-
   const request = new NextRequestHint({
     page: params.page,
-    input: url,
+    input: params.request.url,
     init: {
       geo: params.request.geo,
       headers: fromNodeHeaders(params.request.headers),