Bug: Actor<T> cannot be assigned to ActorRef<T>. The options also seem wrongly typed.

[phcoliveira]

XState version

XState version 5

Description

I am using the latest xstate package: 5.15.0.

There are two issues.

This is the main issue. From the docs, I expected to assign the value returned from createActor<T> to a variable declared as ActorRefFrom<T>. But it is not possible.

This is the second, less important issue. I used to pass an inspect function to createActor(logic, {inspect}). Now I can't do it and I can't make sense of the options' type.

Expected result

I expected to assign createActor<T> to ActorRefFrom<T>.

I also expected to pass an inspect function.

Actual result

I can't do them. There are typing issues.

Reproduction

https://codesandbox.io/p/sandbox/actor-t-can-not-be-assigned-to-actorref-t-nkwptq?file=%2Fsrc%2Findex.ts%3A22%2C50

Additional context

https://discord.com/channels/795785288994652170/1265313261805502585/1266061251658649762

https://discord.com/channels/795785288994652170/1265729221305696307/1265729221305696307

[phcoliveira]

@Andarist, in the code sandbox above, It seems possible to pass the inspect function, which is the second, and not the most important, problem.

I am trying to figure out what I can't do it on my project.

In any case, the first problem is reproducible in the code sandbox.

[phcoliveira]

[davidkpiano]

This is likely because of the ConditionalRequired<…> complex type that we have, where we require the input if the logic requires the input, and there's no way of being able to "predict" that. The input and logic being in two separate places makes this harder.

cc. @Andarist

---

Future note: if createMachine(…) returned a function that must always be called to create actor logic, we can avoid this problem pretty nicely:

const machineFn = createMachine(...);
const actor = createActor(machineFn(someInput));

// @ts-expect-error if input is required
const actor = createActor(machineFn());

// same with other types of logic
const promiseFn = fromPromise(...);

const actor = createActor(promiseFn(someInput));

[davidkpiano]

As a workaround, I recommend using ActorRefFromLogic, which is introduced in #5011 (not released yet) but is just this:

export type ActorRefFromLogic<T extends AnyActorLogic> = ActorRef<
  SnapshotFrom<T>,
  EventFromLogic<T>,
  EmittedFrom<T>
>;

Then, this will work as expected:

  const logic = createMachine({});

  class ActorThing<T extends AnyActorLogic> {
    actorRef: ActorRefFromLogic<T>;
    constructor(actorLogic: T) {
      const actor = createActor(actorLogic);

      actor satisfies ActorRefFromLogic<typeof actorLogic>;
      this.actorRef = actor;
    }
  }

  new ActorThing(logic);

[phcoliveira]

Thank you, @davidkpiano. I will check it out.