Generic type for userData in WebSocket for Typescript

[yelliver]

In C++ version, uWebSockets has getUserData() while uWebSockets .js has [key: string]: any;
But their types are any & is not recommended in Typescript. What about this:

interface WebSocket<T> 
{ 
    userData: T;
}

We will have the consistent API between C++ & js versions as well as maintain the static type definition for Typescript.
We can also keep the [key: string]: any; for who want the convenience of weak typing

[SuspiciousLookingOwl]

Consider following changes.

Usage:

import { App } from "uWebSockets.js";

interface UserData {
	id: number;
	name: string;
}

const app = App<UserData>();

app.ws("/*", {
	open: (ws) => {
		ws.userData = {
			id: 0,
			name: "Owl",
		};
	},
	message: (ws) => {
		ws.userData.id; // number
		ws.userData.name; // string
		
		ws.userData.id = "Hello"; // TypeScript compilation error because `id` supposed to be `number`, not `string`
	},
});

---

I think this is a neat feature, temporary work around (that I use) is to create a .d.ts file on your project:

import "uWebSockets.js";

interface UserData {
	id: number;
	name: string;
}

declare module "uWebSockets.js" {
	interface WebSocket {
		userData: UserData;
	}
}

then you can use it just like the example above (without the generic type when calling App())

[ghost]

It's a known problem. TS is a separate layer above JS -> whatever happens in TS, we can't know about or control. We only know about and can change V8/JS. So making template functions that take type UserData is impossible since that information only exists in TS (which is not part of V8/JS). So you can't really implement a typed interface like that.

[SuspiciousLookingOwl]

I think what @yelliver suggested is to add generic type for ws.userData just for better development experience when using TypeScript. Instead of dealing with any type when accessing ws.userData, developers can provide its own typing for ws.userData so they get that sweet auto code completion when dealing with ws.userData

[yelliver]

@alexhultman-2fa can you please check @SuspiciousLookingOwl code above, it is what I want