makeAutoObservable doesn't work with Object.create

[Cerber-Ursi]

I'm trying to make a little library for specific kind of workflow with Mobx. For this, I attempted to use Object.create to place some functions on the prototype of future store, to be used afterwards as actions; according to the documentation, this should be possible:

All functions on prototype become autoAction.

Intended outcome:
Functions defined on prototype via Object.create are converted to actions, changes to observable state made in them is done without warnings.

Actual outcome:
Prototype of the object is ignored, changing observables inside functions leads to a warning.

How to reproduce the issue:

import { makeAutoObservable, reaction } from "mobx";

const store = Object.create({
  inc() {
    this.value += 1;
  }
});
store.value = 0;

makeAutoObservable(store);
reaction(
  () => store.value,
  () => {}
);

store.inc();

Here's the CodeSandbox, which shows a warning in console on startup.

---

I'm not sure if this is a real error in code. However, the behavior is currently not complying with the documentation, so something probably should be fixed.

[urugator]

Thanks for the report, should be fixed by #3198.

For the time being, you can workaround it by defining constructor on proto:

const store = Object.create({
  constructor() {},
  inc() {
    this.value += 1;
  }
});