fix(next): Do not display message when middleware is removed on dev m…

…ode (#39604)

Fixes #39532

## Bug

- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Errors have helpful link attached, see `contributing.md`

packages/next/server/next-server.ts

@@ -1636,7 +1636,6 @@ export default class NextNodeServer extends BaseServer {
       return { finished: false }
     }
     if (!(await this.hasMiddleware(middleware.page))) {
-      console.warn(`The Edge Function for ${middleware.page} was not found`)
       return { finished: false }
     }
 

test/integration/middleware-dev-update/middleware.js

@@ -0,0 +1,9 @@
+import { NextResponse } from 'next/server'
+
+export function middleware(request) {
+  if (request.nextUrl.pathname.startsWith('/_next/')) return
+
+  const res = NextResponse.rewrite(new URL('/', request.url))
+  res.headers.set('X-From-Middleware', 'true')
+  return res
+}

test/integration/middleware-dev-update/pages/index.js

@@ -0,0 +1,9 @@
+export default (props) => <div id="from-middleware">{props.fromMiddleware}</div>
+
+export async function getServerSideProps({ res }) {
+  return {
+    props: {
+      fromMiddleware: res.getHeader('x-from-middleware') || '',
+    },
+  }
+}

test/integration/middleware-dev-update/test/index.test.js

@@ -0,0 +1,125 @@
+import {
+  fetchViaHTTP,
+  File,
+  findPort,
+  killApp,
+  launchApp,
+  retry,
+} from 'next-test-utils'
+import { join } from 'path'
+import webdriver from 'next-webdriver'
+
+const context = {
+  appDir: join(__dirname, '../'),
+  logs: { output: '', stdout: '', stderr: '' },
+  middleware: new File(join(__dirname, '../middleware.js')),
+}
+
+describe('Middleware development errors', () => {
+  beforeEach(async () => {
+    context.logs = { output: '', stdout: '', stderr: '' }
+    context.appPort = await findPort()
+    context.app = await launchApp(context.appDir, context.appPort, {
+      onStdout(msg) {
+        context.logs.output += msg
+        context.logs.stdout += msg
+      },
+      onStderr(msg) {
+        context.logs.output += msg
+        context.logs.stderr += msg
+      },
+    })
+  })
+
+  afterEach(() => {
+    context.middleware.restore()
+    if (context.app) {
+      killApp(context.app)
+    }
+  })
+
+  async function assertMiddlewareFetch(hasMiddleware, path = '/') {
+    const res = await fetchViaHTTP(context.appPort, path)
+    expect(res.status).toBe(200)
+    expect(res.headers.get('x-from-middleware')).toBe(
+      hasMiddleware ? 'true' : null
+    )
+  }
+
+  async function assertMiddlewareRender(hasMiddleware, path = '/') {
+    const browser = await webdriver(context.appPort, path)
+    const fromMiddleware = await browser.elementById('from-middleware').text()
+    expect(fromMiddleware).toBe(hasMiddleware ? 'true' : '')
+  }
+
+  describe('when middleware is removed', () => {
+    beforeEach(async () => {
+      await assertMiddlewareFetch(true)
+      context.middleware.delete()
+    })
+
+    it('sends response correctly', async () => {
+      await assertMiddlewareFetch(false)
+      await assertMiddlewareRender(false)
+
+      // assert no extra message on stderr
+      expect(context.logs.stderr).toBe('')
+    })
+  })
+
+  describe('when middleware is removed and re-added', () => {
+    beforeEach(async () => {
+      await assertMiddlewareFetch(true)
+      context.middleware.delete()
+      await assertMiddlewareFetch(false)
+      context.middleware.restore()
+    })
+
+    it('sends response correctly', async () => {
+      await assertMiddlewareFetch(true)
+      await assertMiddlewareRender(true)
+    })
+  })
+
+  describe('when middleware is added', () => {
+    beforeEach(async () => {
+      context.middleware.delete()
+      await assertMiddlewareFetch(false)
+      context.middleware.restore()
+    })
+
+    it('sends response correctly', async () => {
+      await retry(() => assertMiddlewareFetch(true))
+      await assertMiddlewareRender(true)
+    })
+  })
+
+  describe('when matcher is added', () => {
+    beforeEach(async () => {
+      context.middleware.write(
+        context.middleware.originalContent +
+          `
+        export const config = {
+          matcher: '/',
+        }
+      `
+      )
+
+      await assertMiddlewareFetch(true)
+
+      context.middleware.write(
+        context.middleware.originalContent +
+          `
+        export const config = {
+          matcher: '/asdf',
+        }
+      `
+      )
+    })
+
+    it('sends response correctly', async () => {
+      await retry(() => assertMiddlewareFetch(true, '/asdf'))
+      await retry(() => assertMiddlewareRender(true, '/asdf'))
+    })
+  })
+})