Fix for Next.js POST/PATCH/etc and Server Actions (#122)

As identified in #116 the root cause of the problems with non-get requests in NextJS on Firebase Hosting is that the ExpressJS' readable has been spent on the body-parser middleware. Solution is to create a new Readable from rawBody and pass that to the NextJS request handler.

* Proxy express requests through a new IncomingMessage
* Drop the LRU cache of next apps, no longer needed

---------

Co-authored-by: Leonardo Ortiz <[email protected]>
Co-authored-by: Maximilian Fellner <[email protected]>

packages/firebase-frameworks/src/next.js/index.ts

@@ -1,41 +1,23 @@
 import { parse } from "url";
 import createNextServer from "next";
-import LRU from "lru-cache";
 
 import type { Request } from "firebase-functions/v2/https";
 import type { Response } from "express";
 import type { NextServer } from "next/dist/server/next.js";
+import { incomingMessageFromExpress } from "../utils.js";
 
-const nextAppsLRU = new LRU<string, NextServer>({
-  // TODO tune this
-  max: 3,
-  allowStale: true,
-  updateAgeOnGet: true,
-  dispose: (server) => {
-    server.close();
-  },
+// @ts-expect-error - Next.js doesn't export the custom server function with proper types
+// eslint-disable-next-line @typescript-eslint/no-unsafe-assignment
+const nextApp: NextServer = createNextServer({
+  dev: false,
+  dir: process.cwd(),
+  hostname: "0.0.0.0",
+  port: 443,
 });
 
 export const handle = async (req: Request, res: Response) => {
-  const { hostname, protocol, url } = req;
-  const port = protocol === "https" ? 443 : 80;
-  const key = [hostname, port].join(":");
-  // I wish there was a better way to do this, but it seems like this is the
-  // way to go. Should investigate more if we can get hostname/port to be
-  // dynamic for middleware.
-  let nextApp = nextAppsLRU.get(key);
-  if (!nextApp) {
-    // @ts-expect-error - Next.js doesn't export the custom server function with proper types
-    // eslint-disable-next-line @typescript-eslint/no-unsafe-assignment
-    nextApp = createNextServer({
-      dev: false,
-      dir: process.cwd(),
-      hostname: "0.0.0.0",
-      port,
-    });
-    nextAppsLRU.set(key, nextApp!);
-  }
-  await nextApp!.prepare();
-  const parsedUrl = parse(url, true);
-  nextApp!.getRequestHandler()(req, res, parsedUrl);
+  await nextApp.prepare();
+  const parsedUrl = parse(req.url, true);
+  const incomingMessage = incomingMessageFromExpress(req);
+  await nextApp.getRequestHandler()(incomingMessage, res, parsedUrl);
 };

packages/firebase-frameworks/src/utils.ts

@@ -1,3 +1,7 @@
+import { Request } from "firebase-functions/v2/https";
+import { IncomingMessage } from "node:http";
+import { Socket } from "node:net";
+
 export async function isUsingFirebaseJsSdk() {
   if (!process.env.__FIREBASE_DEFAULTS__) return false;
   try {
@@ -7,3 +11,25 @@ export async function isUsingFirebaseJsSdk() {
     return false;
   }
 }
+
+export function incomingMessageFromExpress(req: Request): IncomingMessage {
+  const socket = new Socket();
+  const incomingMessage = new IncomingMessage(socket);
+
+  incomingMessage.push(req.rawBody);
+  incomingMessage.push(null);
+
+  incomingMessage.headers = req.headers;
+  incomingMessage.headersDistinct = req.headersDistinct;
+  incomingMessage.httpVersion = req.httpVersion;
+  incomingMessage.httpVersionMajor = req.httpVersionMajor;
+  incomingMessage.httpVersionMinor = req.httpVersionMinor;
+  incomingMessage.method = req.method;
+  incomingMessage.rawHeaders = req.rawHeaders;
+  incomingMessage.rawTrailers = req.rawTrailers;
+  incomingMessage.trailers = req.trailers;
+  incomingMessage.trailersDistinct = req.trailersDistinct;
+  incomingMessage.url = req.url;
+
+  return incomingMessage;
+}