TypeScript type breakage under pnpm / preserveSymlinks=true due to extending Emitter from another package #5411
Description
Is your feature request related to a problem? Please describe.
When using socket.io-client in a symlinked setup (such as pnpm + preserveSymlinks=true or local linking via npm link), TypeScript loses several instance methods (on, emit, etc.) on the Socket class.
This happens because Socket extends the Emitter class from the @socket.io/component-emitter package:
import { Emitter } from "@socket.io/component-emitter";
export class Socket extends Emitter { ... }
Under preserveSymlinks=true, there can be multiple physical copies of @socket.io/component-emitter, resulting in distinct module identities for TypeScript.
As a result, Socket no longer appears to implement the correct emitter API.
This affects:
- pnpm users (the default node_modules structure is symlink-based)
- anyone linking socket.io-client locally (e.g. pnpm link, npm link, or monorepo setups)
Describe the solution you'd like
One of the following would make the types robust against symlinked environments:
- Re-export the emitter types from socket.io-client to unify identity.
- Use composition instead of inheritance for emitter behavior.
- Define an internal interface for the emitter API instead of importing the external class.
Example of a minimal re-export solution:
// socket.io-client/index.ts
import { Emitter } from "@socket.io/component-emitter";
export { Emitter }; // re-export canonical symbol
export class Socket extends Emitter { ... }