update observable inside autorun/observable won't trigger render

[roeycohen]

Seems like updating an observable inside a rendering function will not behave nicely:

const testMap = observable.map({a: 1});
autorun(() =>
{
	console.log(testMap.toJS());
	if (!testMap.has('b'))
	{
		testMap.set('b', 2); //won't trigger autorun function again (and prevent following lines execution?)
		// setTimeout(() => testMap.set('b', 2), 0); //works
	}
});

Is it possible that this is by design to prevent infinite rendering?
If so, maybe this scenario is worth mentioning in the documentation pitfalls...

[BATCOH]

IDK about details of current implementation, but in general changing observables within an autorun\reaction is not recommended by the docs:
https://mobx.js.org/reactions.html#use-reactions-sparingly

[roeycohen]

1oq @BATCOH

[kubk]

Consider using a simple setter without any autorun / reactions:

...
setMap(key, value) {
  this.testMap.set(key, value);
  if (!testMap.has('b')) {
    this.testMap.set('b', 2);
  }
} 

[roeycohen]

but the problem @kubk occur when inside reactions, and not in a simple function :)

[urugator]

Possibly same as #2346, not entirely sure