Cannot augment WebSocket interface in TypeScript #1877
Description
when adding a method sendAsync to WebSocket, i have to augment the interface of WebSocket
// promisify.ts
export function promisifySend(socket: WebSocket): void {
socket.sendAsync = function (/*......*/): Promise<void> {
/*......*/
}
}
declare module 'ws' {
export default interface Websocket { // default export
sendAsync(/*......*/): Promise<void>;
}
}
//1.ts
import WebSocket from 'ws'; // import a default export
import { promisifySend } from './promisify.ts';but this syntax above is illegal in TS, see microsoft/TypeScript#14080
TS only allows to augment a interface which is a named export, for example
// promisify.ts
export function promisifySend(socket: WebSocket): void {
socket.sendAsync = function (/*......*/): Promise<void> {
/*......*/
}
}
declare module 'ws' {
export interface Websocket { // named export
sendAsync(/*......*/): Promise<void>;
}
}
// 1.ts
import { WebSocket } from 'ws'; // import a named export
import { promisifySend } from './promisify.ts';this requires WebSocket is not default export but a named export.
obviously, this is a bug of TS, not of ws. but you cannot look forward to TS fixing its bug. so i recommend ws exports a WebSocket within WebSocket, like
// index.js
const WebSocket = require('./lib/websocket');
WebSocket.WebSocket = WebSocket;
module.exports = WebSocket;