Custom Server with bodyParser, don't parse body again in API Route (#…

…16169)

## Why

Some users prefer to use a custom server implementation that handles body parsing. If they do this, they have no way to opt out of all body parsing in API Routes. Requests with bodies die if next's `bodyParser` is not disabled. Requests just hang forever.

Instead of adding [this config](https://nextjs.org/docs/api-routes/api-middlewares#custom-config) to every API Route, we do a simple check to avoid parsing the body twice.

Fixes #8315
Fixes #7960

packages/next/next-server/server/api-utils.ts

@@ -56,7 +56,7 @@ export async function apiResolver(
     )
 
     // Parsing of body
-    if (bodyParser) {
+    if (bodyParser && !apiReq.body) {
       apiReq.body = await parseBody(
         apiReq,
         config.api && config.api.bodyParser && config.api.bodyParser.sizeLimit

test/integration/api-body-parser/pages/api/index.js

@@ -0,0 +1,5 @@
+export default ({ method, body }, res) => {
+  if (method === 'POST') {
+    res.status(200).json(body)
+  }
+}

test/integration/api-body-parser/server.js

@@ -0,0 +1,28 @@
+const next = require('next')
+const bodyParser = require('body-parser')
+const express = require('express')
+
+const dev = process.env.NODE_ENV !== 'production'
+const dir = __dirname
+const port = process.env.PORT || 3000
+
+const app = next({ dev, dir })
+const handleNextRequests = app.getRequestHandler()
+
+app.prepare().then(() => {
+  const server = express()
+
+  server.use(bodyParser.json({ limit: '5mb' }))
+
+  server.all('*', (req, res) => {
+    handleNextRequests(req, res)
+  })
+
+  server.listen(port, (err) => {
+    if (err) {
+      throw err
+    }
+
+    console.log(`> Ready on http://localhost:${port}`)
+  })
+})

test/integration/api-body-parser/test/index.test.js

@@ -0,0 +1,72 @@
+/* eslint-env jest */
+
+import { join } from 'path'
+import {
+  killApp,
+  findPort,
+  launchApp,
+  fetchViaHTTP,
+  initNextServerScript,
+} from 'next-test-utils'
+import clone from 'clone'
+import getPort from 'get-port'
+
+jest.setTimeout(1000 * 60 * 2)
+const appDir = join(__dirname, '../')
+let appPort
+
+let app
+let server
+jest.setTimeout(1000 * 60 * 2)
+
+const context = {}
+
+function runTests() {
+  it('should parse JSON body', async () => {
+    appPort = await findPort()
+    app = await launchApp(appDir, appPort, {})
+    const data = await makeRequest()
+    expect(data).toEqual([{ title: 'Nextjs' }])
+    killApp(app)
+  })
+
+  it('should not throw if request body is already parsed in custom middleware', async () => {
+    await startServer()
+    const data = await makeRequest()
+    expect(data).toEqual([{ title: 'Nextjs' }])
+    killApp(server)
+  })
+}
+
+async function makeRequest() {
+  const data = await fetchViaHTTP(appPort, '/api', null, {
+    method: 'POST',
+    headers: {
+      'Content-Type': 'application/json; charset=utf-8',
+    },
+    body: JSON.stringify([{ title: 'Nextjs' }]),
+  }).then((res) => res.ok && res.json())
+
+  return data
+}
+
+const startServer = async (optEnv = {}, opts) => {
+  const scriptPath = join(appDir, 'server.js')
+  context.appPort = appPort = await getPort()
+  const env = Object.assign(
+    {},
+    clone(process.env),
+    { PORT: `${appPort}` },
+    optEnv
+  )
+
+  server = await initNextServerScript(
+    scriptPath,
+    /ready on/i,
+    env,
+    /ReferenceError: options is not defined/,
+    opts
+  )
+}
+
+runTests()