Allow reading request bodies in middlewares

packages/next/server/base-http/node.ts

@@ -7,6 +7,11 @@ import { NEXT_REQUEST_META, RequestMeta } from '../request-meta'
 
 import { BaseNextRequest, BaseNextResponse } from './index'
 
+type Req = IncomingMessage & {
+  [NEXT_REQUEST_META]?: RequestMeta
+  cookies?: NextApiRequestCookies
+}
+
 export class NodeNextRequest extends BaseNextRequest<Readable> {
   public headers = this._req.headers;
 
@@ -21,12 +26,11 @@ export class NodeNextRequest extends BaseNextRequest<Readable> {
     return this._req
   }
 
-  constructor(
-    private _req: IncomingMessage & {
-      [NEXT_REQUEST_META]?: RequestMeta
-      cookies?: NextApiRequestCookies
-    }
-  ) {
+  set originalRequest(value: Req) {
+    this._req = value
+  }
+
+  constructor(private _req: Req) {
     super(_req.method!.toUpperCase(), _req.url!, _req)
   }
 

packages/next/server/body-streams.ts

@@ -0,0 +1,87 @@
+import type { IncomingMessage } from 'http'
+import { Readable } from 'stream'
+import { TransformStream } from 'next/dist/compiled/web-streams-polyfill'
+
+type BodyStream = ReadableStream<Uint8Array>
+
+/**
+ * Creates a ReadableStream from a Node.js HTTP request
+ */
+function requestToBodyStream(request: IncomingMessage): BodyStream {
+  const transform = new TransformStream<Uint8Array, Uint8Array>({
+    start(controller) {
+      request.on('data', (chunk) => controller.enqueue(chunk))
+      request.on('end', () => controller.terminate())
+      request.on('error', (err) => controller.error(err))
+    },
+  })
+
+  return transform.readable as unknown as ReadableStream<Uint8Array>
+}
+
+function bodyStreamToNodeStream(bodyStream: BodyStream): Readable {
+  const reader = bodyStream.getReader()
+  return Readable.from(
+    (async function* () {
+      while (true) {
+        const { done, value } = await reader.read()
+        if (done) {
+          return
+        }
+        yield value
+      }
+    })()
+  )
+}
+
+function replaceRequestBody<T extends IncomingMessage>(
+  base: T,
+  stream: Readable
+): T {
+  for (const key in stream) {
+    let v = stream[key as keyof Readable] as any
+    if (typeof v === 'function') {
+      v = v.bind(stream)
+    }
+    base[key as keyof T] = v
+  }
+
+  return base
+}
+
+/**
+ * An interface that encapsulates body stream cloning
+ * of an incoming request.
+ */
+export function clonableBodyForRequest<T extends IncomingMessage>(
+  incomingMessage: T
+) {
+  let bufferedBodyStream: BodyStream | null = null
+
+  return {
+    /**
+     * Replaces the original request body if necessary.
+     * This is done because once we read the body from the original request,
+     * we can't read it again.
+     */
+    finalize(): void {
+      if (bufferedBodyStream) {
+        replaceRequestBody(
+          incomingMessage,
+          bodyStreamToNodeStream(bufferedBodyStream)
+        )
+      }
+    },
+    /**
+     * Clones the body stream
+     * to pass into a middleware
+     */
+    cloneBodyStream(): BodyStream {
+      const originalStream =
+        bufferedBodyStream ?? requestToBodyStream(incomingMessage)
+      const [stream1, stream2] = originalStream.tee()
+      bufferedBodyStream = stream1
+      return stream2
+    },
+  }
+}

packages/next/server/next-server.ts

@@ -38,7 +38,7 @@ import { PagesManifest } from '../build/webpack/plugins/pages-manifest-plugin'
 import { recursiveReadDirSync } from './lib/recursive-readdir-sync'
 import { format as formatUrl, UrlWithParsedQuery } from 'url'
 import compression from 'next/dist/compiled/compression'
-import Proxy from 'next/dist/compiled/http-proxy'
+import HttpProxy from 'next/dist/compiled/http-proxy'
 import { route } from './router'
 import { run } from './web/sandbox'
 
@@ -73,6 +73,7 @@ import { loadEnvConfig } from '@next/env'
 import { getCustomRoute } from './server-route-utils'
 import { urlQueryToSearchParams } from '../shared/lib/router/utils/querystring'
 import ResponseCache from '../server/response-cache'
+import { clonableBodyForRequest } from './body-streams'
 
 export * from './base-server'
 
@@ -485,7 +486,7 @@ export default class NextNodeServer extends BaseServer {
     parsedUrl.search = stringifyQuery(req, query)
 
     const target = formatUrl(parsedUrl)
-    const proxy = new Proxy({
+    const proxy = new HttpProxy({
       target,
       changeOrigin: true,
       ignorePath: true,
@@ -1236,6 +1237,11 @@ export default class NextNodeServer extends BaseServer {
 
     const allHeaders = new Headers()
     let result: FetchEventResult | null = null
+    const method = (params.request.method || 'GET').toUpperCase()
+    let originalBody =
+      method !== 'GET' && method !== 'HEAD'
+        ? clonableBodyForRequest(params.request.body)
+        : undefined
 
     for (const middleware of this.middleware || []) {
       if (middleware.match(params.parsedUrl.pathname)) {
@@ -1245,7 +1251,6 @@ export default class NextNodeServer extends BaseServer {
         }
 
         await this.ensureMiddleware(middleware.page, middleware.ssr)
-
         const middlewareInfo = this.getMiddlewareInfo(middleware.page)
 
         result = await run({
@@ -1254,14 +1259,15 @@ export default class NextNodeServer extends BaseServer {
           env: middlewareInfo.env,
           request: {
             headers: params.request.headers,
-            method: params.request.method || 'GET',
+            method,
             nextConfig: {
               basePath: this.nextConfig.basePath,
               i18n: this.nextConfig.i18n,
               trailingSlash: this.nextConfig.trailingSlash,
             },
             url: url,
             page: page,
+            body: originalBody?.cloneBodyStream(),
           },
           useCache: !this.nextConfig.experimental.runtime,
           onWarning: (warning: Error) => {
@@ -1298,6 +1304,8 @@ export default class NextNodeServer extends BaseServer {
       }
     }
 
+    originalBody?.finalize()
+
     return result
   }
 

packages/next/server/web/adapter.ts

@@ -16,6 +16,7 @@ export async function adapter(params: {
     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,

packages/next/server/web/types.ts

@@ -39,6 +39,7 @@ export interface RequestData {
     params?: { [key: string]: string }
   }
   url: string
+  body?: ReadableStream<Uint8Array>
 }
 
 export interface FetchEventResult {

test/production/reading-request-body-in-middleware/index.test.ts

@@ -0,0 +1,144 @@
+import { createNext } from 'e2e-utils'
+import { NextInstance } from 'test/lib/next-modes/base'
+import { fetchViaHTTP } from 'next-test-utils'
+
+describe('reading request body in middleware', () => {
+  let next: NextInstance
+
+  beforeAll(async () => {
+    next = await createNext({
+      files: {
+        'pages/_middleware.js': `
+          const { NextResponse } = require('next/server');
+
+          export default async function middleware(request) {
+            if (!request.body) {
+              return new Response('No body', { status: 400 });
+            }
+
+            const json = await request.json();
+
+            if (request.nextUrl.searchParams.has("next")) {
+              const res = NextResponse.next();
+              res.headers.set('x-from-root-middleware', '1');
+              return res;
+            }
+
+            return new Response(JSON.stringify({
+              root: true,
+              ...json,
+            }), {
+              status: 200,
+              headers: {
+                'content-type': 'application/json',
+              },
+            })
+          }
+        `,
+
+        'pages/nested/_middleware.js': `
+          const { NextResponse } = require('next/server');
+
+          export default async function middleware(request) {
+            if (!request.body) {
+              return new Response('No body', { status: 400 });
+            }
+
+            const json = await request.json();
+
+            return new Response(JSON.stringify({
+              root: false,
+              ...json,
+            }), {
+              status: 200,
+              headers: {
+                'content-type': 'application/json',
+              },
+            })
+          }
+        `,
+
+        'pages/api/hi.js': `
+          export default function hi(req, res) {
+            res.json({
+              ...req.body,
+              api: true,
+            })
+          }
+        `,
+      },
+      dependencies: {},
+    })
+  })
+  afterAll(() => next.destroy())
+
+  it('rejects with 400 for get requests', async () => {
+    const response = await fetchViaHTTP(next.url, '/')
+    expect(response.status).toEqual(400)
+  })
+
+  it('returns root: true for root calls', async () => {
+    const response = await fetchViaHTTP(
+      next.url,
+      '/',
+      {},
+      {
+        method: 'POST',
+        body: JSON.stringify({
+          foo: 'bar',
+        }),
+      }
+    )
+    expect(response.status).toEqual(200)
+    expect(await response.json()).toEqual({
+      foo: 'bar',
+      root: true,
+    })
+  })
+
+  it('reads the same body on both middlewares', async () => {
+    const response = await fetchViaHTTP(
+      next.url,
+      '/nested/hello',
+      {
+        next: '1',
+      },
+      {
+        method: 'POST',
+        body: JSON.stringify({
+          foo: 'bar',
+        }),
+      }
+    )
+    expect(response.status).toEqual(200)
+    expect(await response.json()).toEqual({
+      foo: 'bar',
+      root: false,
+    })
+  })
+
+  it('passes the body to the api endpoint', async () => {
+    const response = await fetchViaHTTP(
+      next.url,
+      '/api/hi',
+      {
+        next: '1',
+      },
+      {
+        method: 'POST',
+        headers: {
+          'content-type': 'application/json',
+        },
+        body: JSON.stringify({
+          foo: 'bar',
+        }),
+      }
+    )
+    expect(response.status).toEqual(200)
+    expect(await response.json()).toEqual({
+      foo: 'bar',
+      api: true,
+    })
+    expect(response.headers.get('x-from-root-middleware')).toEqual('1')
+  })
+})

yarn.lock

@@ -20812,8 +20812,7 @@ [email protected]:
     source-list-map "^2.0.0"
     source-map "~0.6.1"
 
-"webpack-sources3@npm:[email protected]", webpack-sources@^3.2.3:
-  name webpack-sources3
+"webpack-sources3@npm:[email protected]", webpack-sources@^3.2.2, webpack-sources@^3.2.3:
   version "3.2.3"
   resolved "https://registry.yarnpkg.com/webpack-sources/-/webpack-sources-3.2.3.tgz#2d4daab8451fd4b240cc27055ff6a0c2ccea0cde"
   integrity sha512-/DyMEOrDgLKKIG0fmvtz+4dUX/3Ghozwgm6iPp8KRhvn+eQf9+Q7GWxVNMk3+uCPWfdXYC4ExGBckIXdFEfH1w==