fix: serve handler error with 0 arguments (#23652)

Fixes #23651

Co-authored-by: Satya Rohith <[email protected]>

Author: 2 people

ext/http/00_serve.ts

@@ -793,9 +793,9 @@ internals.serveHttpOnConnection = serveHttpOnConnection;
 
 function registerDeclarativeServer(exports) {
   if (ObjectHasOwn(exports, "fetch")) {
-    if (typeof exports.fetch !== "function" || exports.fetch.length !== 1) {
+    if (typeof exports.fetch !== "function") {
       throw new TypeError(
-        "Invalid type for fetch: must be a function with a single parameter",
+        "Invalid type for fetch: must be a function with a single or no parameter",
       );
     }
     return ({ servePort, serveHost }) => {

tests/testdata/serve/no_args.ts

@@ -0,0 +1,5 @@
+export default {
+  fetch() {
+    return new Response("deno serve with no args in fetch() works!");
+  },
+};