Type issues with wrapping around EventEmitter since v4.0.1

[Marcel Beumer]

Since 4.0.1 we have the the following typing issues with EventEmitter that we did not have with 4.0.0. We think it probably has something to do with e84ca51#diff-b52768974e6bc0faccb7d4b75b162c99R122.

Please see code below. Works on 4.0.0, gives type errors on 4.0.1.

Thank you!

import EventEmitter from "eventemitter3";

export enum EventFoo {
  ERROR = "error",
  PLAY = "play",
}

export enum EventBar {
  AD_LOADED = "adLoaded",
  AD_STARTED = "adStarted",
}

interface PayloadFoo {
  [EventFoo.ERROR]: [{ error: Error }];
  [EventFoo.PLAY]: [{}];
}

interface PayloadBar {
  [EventBar.AD_LOADED]: [{}];
  [EventBar.AD_STARTED]: [{}];
}

type Payload = PayloadFoo & PayloadBar;

const emitter = new EventEmitter<Payload>();

emitter.emit(EventFoo.ERROR, { error: new Error() });
emitter.on(EventFoo.ERROR, (payload) => {
  console.log(payload.error);
});

type WrappedApi = {
  on<K extends keyof Payload>(name: K, fn: (...args: Payload[K]) => void): void;
};

const api: WrappedApi = {
  on(name, fn) {
    // TYPE ERROR: Argument of type '(...args: Payload[K]) => void' is not assignable to parameter of type 'K extends EventFoo | EventBar.AD_LOADED ? Handler<Payload[K], void> : never'.ts(2345)
    emitter.on(name, fn);
    return emitter;
  },
};

(Object.keys(EventFoo) as [keyof typeof EventFoo]).forEach((eventName) => {
  api.on(EventFoo[eventName], (payload) => {
    console.log(payload);
  });
});

(Object.keys(EventFoo) as [keyof typeof EventFoo]).forEach((eventName) => {
  // TYPE ERROR: Parameter 'payload' implicitly has an 'any' type.ts(7006)
  emitter.on(EventFoo[eventName], (payload) => {
    console.log(payload);
  });
});

[Frédérique Mittelstaedt]

I've addressed a bug with that commit, just now. Will check now if the PR fixes that.

[Luigi Pinca]

Should be fixed by #223.

[Frédérique Mittelstaedt]

@marcelbeumer I've tested my fix locally and it works for me. Can you verify that 4.0.3 fixes all issues for you?

[Marcel Beumer]

@gfmio: yes also works for me. Thanks for the super quick fix!