Ensure src/middleware handles correctly (#75702)

This is a follow-up to #75624
which ensures middleware behaves correctly in the `src/` directory. This
previously wasn't an issue since edge runtime output location isn't
picky since it's just output in the middleware-manifest although with
node runtime it is particular.

packages/next/src/build/entries.ts

@@ -714,7 +714,7 @@ export async function createEntrypoints(
                 isDev: false,
               })
           } else if (isMiddlewareFile(page)) {
-            server[serverBundlePath] = getEdgeServerEntry({
+            server[serverBundlePath.replace('src/', '')] = getEdgeServerEntry({
               ...params,
               rootDir,
               absolutePagePath: absolutePagePath,

packages/next/src/export/index.ts

@@ -33,6 +33,7 @@ import {
   SERVER_REFERENCE_MANIFEST,
   APP_PATH_ROUTES_MANIFEST,
   ROUTES_MANIFEST,
+  FUNCTIONS_CONFIG_MANIFEST,
 } from '../shared/lib/constants'
 import loadConfig from '../server/config'
 import type { ExportPathMap } from '../server/config-shared'
@@ -476,7 +477,13 @@ async function exportAppImpl(
         join(distDir, SERVER_DIRECTORY, MIDDLEWARE_MANIFEST)
       ) as MiddlewareManifest
 
-      hasMiddleware = Object.keys(middlewareManifest.middleware).length > 0
+      const functionsConfigManifest = require(
+        join(distDir, SERVER_DIRECTORY, FUNCTIONS_CONFIG_MANIFEST)
+      )
+
+      hasMiddleware =
+        Object.keys(middlewareManifest.middleware).length > 0 ||
+        Boolean(functionsConfigManifest.functions?.['/_middleware'])
     } catch {}
 
     // Warn if the user defines a path for an API page

packages/next/src/server/dev/on-demand-entry-handler.ts

@@ -418,7 +418,7 @@ export async function findPagePathData(
     let bundlePath = normalizedPagePath
     let pageKey = posix.normalize(pageUrl)
 
-    if (isInstrumentation) {
+    if (isInstrumentation || isMiddlewareFile(normalizedPagePath)) {
       bundlePath = bundlePath.replace('/src', '')
       pageKey = page.replace('/src', '')
     }

test/integration/middleware-src-node/next.config.js

@@ -0,0 +1,5 @@
+module.exports = {
+  experimental: {
+    nodeMiddleware: true,
+  },
+}

test/integration/middleware-src-node/src/middleware.js

@@ -0,0 +1,11 @@
+import { NextResponse } from 'next/server'
+
+export const config = {
+  runtime: 'nodejs',
+}
+
+export default function () {
+  const response = NextResponse.next()
+  response.headers.set('X-From-Src-Middleware', 'true')
+  return response
+}

test/integration/middleware-src-node/src/middleware.ts

@@ -0,0 +1,11 @@
+import { NextResponse } from 'next/server'
+
+export const config = {
+  runtime: 'nodejs',
+}
+
+export default function () {
+  const response = NextResponse.next()
+  response.headers.set('X-From-Src-Middleware-TS', 'true')
+  return response
+}

test/integration/middleware-src-node/src/pages/index.js

@@ -0,0 +1,2 @@
+const Page = () => <h1>Hi from SRC</h1>
+export default Page

test/integration/middleware-src-node/test/index.test.js

@@ -0,0 +1,130 @@
+/* eslint-env jest */
+
+import fs from 'fs-extra'
+import { join } from 'path'
+import {
+  fetchViaHTTP,
+  File,
+  findPort,
+  launchApp,
+  killApp,
+  nextBuild,
+} from 'next-test-utils'
+
+let app
+let appPort
+const appDir = join(__dirname, '../')
+const nextConfig = new File(join(appDir, 'next.config.js'))
+const srcHeader = 'X-From-Src-Middleware'
+const rootHeader = 'X-From-Root-Middleware'
+const rootMiddlewareJSFile = join(appDir, 'middleware.js')
+const rootMiddlewareTSFile = join(appDir, 'middleware.ts')
+
+function runSingleMiddlewareTests() {
+  it('loads an runs src middleware', async () => {
+    const response = await fetchViaHTTP(appPort, '/post-1')
+    expect(response.headers.has(srcHeader)).toBe(false)
+    expect(response.headers.has(`${srcHeader}-TS`)).toBe(true)
+  })
+}
+
+function runDoubleMiddlewareTests() {
+  it('loads and runs only root middleware', async () => {
+    const response = await fetchViaHTTP(appPort, '/post-1')
+    expect(response.headers.has(srcHeader)).toBe(false)
+    expect(response.headers.has(`${srcHeader}-TS`)).toBe(false)
+    expect(response.headers.has(rootHeader)).toBe(false)
+    expect(response.headers.has(`${rootHeader}-TS`)).toBe(true)
+  })
+}
+
+async function writeRootMiddleware() {
+  await fs.copy(join(appDir, 'src/pages'), join(appDir, 'pages'), {
+    force: true,
+    recursive: true,
+  })
+  await fs.writeFile(
+    rootMiddlewareJSFile,
+    `
+import { NextResponse } from 'next/server'
+
+export default function () {
+const response = NextResponse.next()
+response.headers.set('${rootHeader}', 'true')
+return response
+}`
+  )
+  await fs.writeFile(
+    rootMiddlewareTSFile,
+    `
+import { NextResponse } from 'next/server'
+
+export default function () {
+const response = NextResponse.next()
+response.headers.set('${rootHeader}-TS', 'true')
+return response
+}`
+  )
+}
+
+async function removeRootMiddleware() {
+  await fs.remove(rootMiddlewareJSFile, { force: true })
+  await fs.remove(rootMiddlewareTSFile, { force: true })
+  await fs.remove(join(appDir, 'pages'), { force: true, recursive: true })
+}
+
+describe.each([
+  {
+    title: 'Middleware in src/ folder',
+    setup() {},
+    teardown() {},
+    runTest: runSingleMiddlewareTests,
+  },
+  {
+    title: 'Middleware in src/ and / folders',
+    setup: writeRootMiddleware,
+    teardown: removeRootMiddleware,
+    runTest: runDoubleMiddlewareTests,
+  },
+])('$title', ({ setup, teardown, runTest }) => {
+  beforeAll(() => setup())
+  afterAll(() => teardown())
+  ;(process.env.TURBOPACK_BUILD ? describe.skip : describe)(
+    'development mode',
+    () => {
+      beforeAll(async () => {
+        appPort = await findPort()
+        app = await launchApp(appDir, appPort)
+      })
+      afterAll(() => killApp(app))
+
+      runTest()
+    }
+  )
+  ;(process.env.TURBOPACK_DEV ? describe.skip : describe)(
+    'production mode',
+    () => {
+      let exportOutput = ''
+
+      beforeAll(async () => {
+        nextConfig.write(`module.exports = { output: 'export' }`)
+        const result = await nextBuild(appDir, [], {
+          stderr: true,
+          stdout: true,
+        })
+
+        const outdir = join(__dirname, '..', 'out')
+        await fs.remove(outdir).catch(() => {})
+
+        exportOutput = result.stderr + result.stdout
+      })
+      afterAll(() => nextConfig.restore())
+
+      it('should warn about middleware on export', async () => {
+        expect(exportOutput).toContain(
+          'Statically exporting a Next.js application via `next export` disables API routes and middleware.'
+        )
+      })
+    }
+  )
+})