How does work specifying map of annotations?

[dSalieri]

I am trying to sort out how annotations work in makeObservable function.

For example we have the next:

import { makeObservable, observable, action } from '/mobx.js';
makeObservable({
  counter: 0, 
  inc() {
    this.counter++;
  }
}, {
  counter: observable,
  inc: action
})

observable and action are functions and they must be called as I expected. But they have not been invoked. How does actually work makeObservable if it doesn't use functions from annotations map?

[urugator]

When you use these functions as annotations, you should think of them as symbols, like so:

if (annotation === observable) {
  // some logic that defines observable prop
}

In the actual implementation, there are extra props defined on these functions that are being used by makeObservable, but that's an implementation detail. You can't implement your own annotation, there is no public Annotation interface.