fix: shim require("node:buffer") (#233)

* chore: repro aws middleware build failure

repro for https://linear.app/netlify/issue/FRA-248/edge-function-middleware-error-on-next-runtime-v5-beta

* fix: shim require("node:buffer")

* chore: comment

* chore: add more shims

Author: Skn0tt

edge-runtime/shim/index.js

@@ -3,9 +3,36 @@
 // application.
 import { AsyncLocalStorage } from 'node:async_hooks'
 import process from 'node:process'
+import * as BufferCompat from 'node:buffer'
+import * as EventsCompat from 'node:events'
+import * as AsyncHooksCompat from 'node:async_hooks'
+import * as AssertCompat from 'node:assert'
+import * as UtilCompat from 'node:util'
 
 globalThis.process = process
 
 globalThis.AsyncLocalStorage = AsyncLocalStorage
 
+// next.js generates require("node:buffer") statemenents:
+// https://github.com/vercel/next.js/blob/89e68377baf3ea6d2bf09e0ae694f57ec5c8ea93/packages/next/src/build/webpack-config.ts#L1677-L1684
+// we need to shim them, because require doesn't work on Deno
+// we've also added a few more shims that Next.js also shims in their own sandbox:
+// https://github.com/vercel/next.js/blob/55b472b5fc8da9a97ffca0070befa80ae431217f/packages/next/src/server/web/sandbox/context.ts#L177
+globalThis.require = function nextRuntimeMinimalRequireShim(name) {
+  switch (name.replace(/^node:/, '')) {
+    case 'buffer':
+      return BufferCompat
+    case 'events':
+      return EventsCompat
+    case 'async_hooks':
+      return AsyncHooksCompat
+    case 'assert':
+      return AssertCompat
+    case 'util':
+      return UtilCompat
+    default:
+      throw new ReferenceError(`require is not defined`)
+  }
+}
+
 var _ENTRIES = {}

tests/e2e/edge-middleware.test.ts

@@ -31,3 +31,9 @@ test('Does not run edge middleware at the origin', async ({ page }) => {
   const h1 = page.locator('h1')
   await expect(h1).toHaveText('Message from middleware: hello')
 })
+
+test('Supports CJS dependencies in Edge Middleware', async ({ page }) => {
+  const res = await page.goto(`${ctx.url}/test/next`)
+
+  expect(await res?.headerValue('x-cjs-module-works')).toEqual("true")
+})

tests/fixtures/middleware/middleware.ts

@@ -1,12 +1,24 @@
 import type { NextRequest } from 'next/server'
 import { NextResponse } from 'next/server'
+import { createServerRunner } from '@aws-amplify/adapter-nextjs'
 
-export function middleware(request: NextRequest) {
+export const { runWithAmplifyServerContext } = createServerRunner({
+  config: {},
+})
+
+export async function middleware(request: NextRequest) {
   const response = getResponse(request)
 
   response.headers.append('Deno' in globalThis ? 'x-deno' : 'x-node', Date.now().toString())
   response.headers.set('x-hello-from-middleware-res', 'hello')
 
+  await runWithAmplifyServerContext({
+    nextServerContext: { request, response },
+    operation: async () => {
+      response.headers.set('x-cjs-module-works', 'true')
+    },
+  })
+
   return response
 }
 

tests/fixtures/middleware/package-lock.json

@@ -8,6 +8,7 @@
     "build": "next build"
   },
   "dependencies": {
+    "@aws-amplify/adapter-nextjs": "^1.0.13",
     "next": "^14.0.4",
     "react": "18.2.0",
     "react-dom": "18.2.0"