Support Vercel's Express in "inngest/express" serve handler (#290)

## Summary
<!-- Succinctly describe your change, providing context, what you've
changed, and why. -->

Adds support for Vercel's Node Express server, which has differing
reported types from the `express` package.

## Checklist
<!-- Tick these items off as you progress. -->
<!-- If an item isn't applicable, ideally please strikeout the item by
wrapping it in "~~"" and suffix it with "N/A My reason for skipping
this." -->
<!-- e.g. "- [ ] ~~Added tests~~ N/A Only touches docs" -->

- [ ] ~~Added a [docs PR](https://github.com/inngest/website) that
references this PR~~ N/A Bug fix
- [x] Added unit/integration tests
- [x] Added changesets if applicable

## Related
<!-- A space for any related links, issues, or PRs. -->
<!-- Linear issues are autolinked. -->
<!-- e.g. - INN-123 -->
<!-- GitHub issues/PRs can be linked using shorthand. -->
<!-- e.g. "- inngest/inngest#123" -->
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links.-->
- Supersedes #288
- Closes inngest/inngest#553

.changeset/pink-impalas-change.md

@@ -0,0 +1,5 @@
+---
+"inngest": patch
+---
+
+Support Vercel's Express (`@vercel/node`) in `"inngest/express"` serve handler

packages/inngest/package.json

@@ -71,6 +71,7 @@
     "@types/sha.js": "^2.4.0",
     "@typescript-eslint/eslint-plugin": "^5.47.0",
     "@typescript-eslint/parser": "^5.47.0",
+    "@vercel/node": "^2.15.9",
     "concurrently": "^7.4.0",
     "eslint": "^8.30.0",
     "eslint-config-prettier": "^8.5.0",

packages/inngest/src/express.test.ts

@@ -1,9 +1,25 @@
 import { InngestCommHandler } from "@local/components/InngestCommHandler";
 import * as ExpressHandler from "@local/express";
+import { type VercelRequest, type VercelRequestQuery } from "@vercel/node";
 import { createClient, testFramework } from "./test/helpers";
 
 testFramework("Express", ExpressHandler);
 
+testFramework("Express (Vercel)", ExpressHandler, {
+  transformReq: (expressReq, res) => {
+    const req: Partial<VercelRequest> = {
+      // eslint-disable-next-line @typescript-eslint/no-unsafe-assignment
+      body: expressReq.body,
+      headers: expressReq.headers,
+      query: expressReq.query as VercelRequestQuery,
+      method: expressReq.method,
+      url: expressReq.url,
+    };
+
+    return [req, res];
+  },
+});
+
 describe("InngestCommHandler", () => {
   describe("registerBody", () => {
     it("Includes correct base URL for functions", () => {

packages/inngest/src/express.ts

@@ -1,9 +1,11 @@
+import { type VercelRequest, type VercelResponse } from "@vercel/node";
 import { type Request, type Response } from "express";
 import {
   InngestCommHandler,
   type ServeHandler,
 } from "./components/InngestCommHandler";
 import { headerKeys, queryKeys } from "./helpers/consts";
+import { type Either } from "./helpers/types";
 import { type SupportedFrameworkName } from "./types";
 
 export const name: SupportedFrameworkName = "express";
@@ -20,10 +22,21 @@ export const serve: ServeHandler = (nameOrInngest, fns, opts) => {
     nameOrInngest,
     fns,
     opts,
-    (req: Request, _res: Response) => {
-      const hostname = req.get("host") || req.headers["host"];
-      const protocol = hostname?.includes("://") ? "" : `${req.protocol}://`;
-      const url = new URL(req.originalUrl, `${protocol}${hostname || ""}`);
+    (
+      req: Either<Request, VercelRequest>,
+      _res: Either<Response, VercelResponse>
+    ) => {
+      // `req.hostname` can filter out port numbers; beware!
+      const hostname = req.headers["host"] || opts?.serveHost;
+
+      const protocol = hostname?.includes("://")
+        ? ""
+        : `${req.protocol || "https"}://`;
+
+      const url = new URL(
+        req.originalUrl || req.url || "",
+        `${protocol}${hostname || ""}`
+      );
 
       return {
         url,

packages/inngest/src/helpers/types.ts

@@ -186,3 +186,9 @@ export type ObjectAssign<TArr, TAcc = {}> = TArr extends [
 export type ExclusiveKeys<T, Keys1 extends keyof T, Keys2 extends keyof T> =
   | (Omit<T, Keys1> & { [K in Keys1]?: never })
   | (Omit<T, Keys2> & { [K in Keys2]?: never });
+
+/**
+ * A type that represents either `A` or `B`. Shared properties retain their
+ * types and unique properties are marked as optional.
+ */
+export type Either<A, B> = Partial<A> & Partial<B> & (A | B);