feat: support waitUntil

Author: ascorbic

src/run/handlers/server.ts

@@ -16,6 +16,7 @@ import { nextResponseProxy } from '../revalidate.js'
 
 import { createRequestContext, getLogger, getRequestContext } from './request-context.cjs'
 import { getTracer } from './tracer.cjs'
+import { setWaitUntil } from './wait-until.cjs'
 
 const nextImportPromise = import('../next.cjs')
 
@@ -52,7 +53,7 @@ interface FutureContext extends Context {
 
 export default async (request: Request, context: FutureContext) => {
   const tracer = getTracer()
-
+  setWaitUntil(context)
   if (!nextHandler) {
     await tracer.withActiveSpan('initialize next server', async () => {
       // set the server config

src/run/handlers/wait-until.cts

@@ -0,0 +1,28 @@
+/**
+ *  @see https://github.com/vercel/next.js/blob/canary/packages/next/src/server/after/builtin-request-context.ts
+ */
+const NEXT_REQUEST_CONTEXT_SYMBOL = Symbol.for('@next/request-context')
+
+export type NextJsRequestContext = {
+  get(): { waitUntil?: (promise: Promise<unknown>) => void } | undefined
+}
+
+type GlobalThisWithRequestContext = typeof globalThis & {
+  [NEXT_REQUEST_CONTEXT_SYMBOL]?: NextJsRequestContext
+}
+
+/**
+ * Registers a `waitUntil` to be used by Next.js for next/after
+ */
+
+export function setWaitUntil({ waitUntil }: { waitUntil?: (promise: Promise<unknown>) => void }) {
+  if (!waitUntil) {
+    return
+  }
+  // eslint-disable-next-line @typescript-eslint/no-extra-semi
+  ;(globalThis as GlobalThisWithRequestContext)[NEXT_REQUEST_CONTEXT_SYMBOL] = {
+    get() {
+      return { waitUntil }
+    },
+  }
+}