fix(typings): accept string | undefined as init argument

Related: https://github.com/socketio/socket.io/issues/4873

lib/index.ts

@@ -28,11 +28,7 @@ function lookup(
   opts?: Partial<ManagerOptions & SocketOptions>
 ): Socket;
 function lookup(
-  uri: string | Partial<ManagerOptions & SocketOptions>,
-  opts?: Partial<ManagerOptions & SocketOptions>
-): Socket;
-function lookup(
-  uri: string | Partial<ManagerOptions & SocketOptions>,
+  uri?: string | Partial<ManagerOptions & SocketOptions>,
   opts?: Partial<ManagerOptions & SocketOptions>
 ): Socket {
   if (typeof uri === "object") {

test/support/util.ts

@@ -10,8 +10,8 @@
  * @see https://webdriver.io/docs/frameworks/#using-mocha
  * @param fn
  */
-export function wrap(fn) {
-  return new Promise((resolve) => fn(resolve));
+export function wrap(fn: (done: (err?: Error) => void) => void) {
+  return new Promise<Error>((resolve) => fn(resolve));
 }
 
 export function success(done, socket) {

test/typed-events.test-d.ts

@@ -1,10 +1,21 @@
 import { io, Socket } from "..";
 import type { DefaultEventsMap } from "@socket.io/component-emitter";
 import { expectError, expectType } from "tsd";
-import { createServer } from "http";
 
 // This file is run by tsd, not mocha.
 
+describe("init", () => {
+  io();
+  io("https://example.com");
+  io({
+    forceNew: true,
+  });
+  io("https://example.com", {
+    forceNew: true,
+  });
+  io(process.env.NODE_ENV === "production" ? "https://example.com" : undefined);
+});
+
 describe("typed events", () => {
   describe("no event map", () => {
     describe("on", () => {