Returning Promise<undefined> from getter triggers update

[traed]

Hi!

I don't known if the docs are wrong or if this is not working as intended, but when running this example:

const posts = asyncable(async ($path, $query) => {
    if ($path.toString() === '/posts') {
      const res = await fetch(`/posts?page=${$query.params.page || 1}`);
      return res.json();
    }
  },
  null, 
  [ path, query ]
);

... the store will always be updated. That is because an async function (the getter in this case) will always return a Promise. In this case either the return value of res.json() or a Promise<undefined>. If we instead do this:

const posts = asyncable(($path, $query) => {
    if ($path.toString() === '/posts') {
      return fetch(`/posts?page=${$query.params.page || 1}`).then(res => res.json());
    }
  },
  null, 
  [ path, query ]
);

... it will work as stated in the docs because now the return type is either a Promise or undefined (not Promise<undefined>).

IMO this shouldn't matter. If the getter returns either undefined or Promise<undefined> no update should be triggered.

[PaulMaly]

Hi, I think you're right. Current docs has a mistake about this. Only explicit undefined will stop store update, but probably we can expand this behavior and cover it with a case of Promise<undefined> as well.

[PaulMaly]

Oh, I found that we already discussed this question with community and actually such behavior was implemented in 1.3.0, but already in 1.3.1 it was rolled back with comment:

If getter wants to keep the current value, it should return undefined in an obvious way.

So, probably, I need to think about it more carefully. I'm not sure I remember the reasons of that. For now, I plan to update README to comply with current behavior, while I thinking about it.