How should I handle optional exposed methods in TypeScript?

[vicary]

I would like to expose a common interface for all my workers like this:

export interface WrappedWorker {
  foo?: () => void;
}

And one of my workers implements it like this:

import * as Comlink from "comlink";
import type { WrappedWorker } from "./WrappedWorker.ts";

export class FooWorker implements WrappedWorker {
  foo: () => "bar"
}

Comlink.expose(new FooWorker());

In my main thread, the wrapped worker will expose foo as Remote<() => string> | Promise<undefined>, this causes two problems:

1. await fooWorker?.foo(); causes lint error for when foo is Promise<undefined>.
2. If I resolve the method getter promise before actually calling, comlink proxy will try to .apply() to undefined and throws. Option 1 throws this one too if foo is actually undefined at runtime.

const worker = new Worker("./WrappedWorker.ts");
const fooWorker = Comlink.wrap(worker);

// 1. Not all constituents of type 'Promise<undefined> | Remote<() => Promisable<void>>' are callable.
await fooWorker?.foo();

// 2. TypeError: Cannot read properties of undefined (reading 'apply')
const fooMethod = await fooWorker.foo;
await fooMethod?.();