Ws: WebSocket objects not assignable to TypeScript WebSocket type because they do not implement the `dispatchEvent` method

[brainkim]

• [x] I've searched for any related issues and avoided creating a duplicate
  issue.

Description

The WebSocket objects which ws uses are not assignable to the typescript WebSocket type because the dispatchEvent method is missing from the implementation.

Reproducible in:

• version: 7.0.0
• Node.js version: 10.16.0
• TypeScript version: 3.4.5
• OS version(s): MacOS 10.14.4

Steps to reproduce:

1. Create a ws server

2. Listen for the connection event

3. Pass the websocket passed to the connection handler to a typescript function which expects a WebSocket object.

Expected result:

No typechecking errors occur

Actual result:

    src/connection/__tests__/socket.ts:104:33 - error TS2345: Argument of type 'WebSocket' is not assignable to parameter of type 'Socket'.
      Property 'dispatchEvent' is missing in type 'WebSocket' but required in type 'WebSocket'.

    104         resolve(new SocketProxy(socket, storage));
                                        ~~~~~~

      ../../node_modules/typescript/lib/lib.dom.d.ts:5226:5
        5226     dispatchEvent(event: Event): boolean;
                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        'dispatchEvent' is declared here.

Attachments:

[lpinca]

There is no TypeScript on this project and there is no dispatchEvent() because we don't fully implement the EventTarget interface.

[brainkim]

There is no TypeScript on this project

Understood! I’m using the types from https://www.npmjs.com/package/@types/ws

there is no dispatchEvent() because we don't fully implement the EventTarget interface.

A stub method which throws a not implemented error would be enough to satisfy the type definition.

[lpinca]

A stub method which throws a not implemented error would be enough to satisfy the type definition.

Please file a PR if you are interested in having it.

[Seairth]

I encountered this issue as well. In my case, I have an interface that contains:

ws: WebSocket;

By default, TS assumes you mean the definition in _lib.dom.d.ts_. Since the only WebSocket I cared about was the class declaration defined in the @types/ws package, I added the following at the top of the file containing my interface:

import WebSocket from 'ws';

This explicit import overrides the "default" one. If you are already importing other stuff from 'ws', you can do:

import WebSocket, { Server /* etc */} from 'ws';

(note: I am using @types/ws version 7.4.0.)