Quick update of atom with a previous value is ignored

[lisss]

When you quickly update an atom with a previous value right after updating with a new one - the last change is ignored
The code sample can be found here

[valentyng]

It looks like the issue is here:

• RenderOne https://github.com/grammarly/focal/blob/master/src/react/react.ts#L388-L389
• RenderMany https://github.com/grammarly/focal/blob/master/src/react/react.ts#L487-L488

According to the documentation (https://reactjs.org/docs/react-component.html#setstate):

Think of setState() as a request rather than an immediate command to update the component.

liftedComponent.setState() doesn't update liftedComponent.state immediately.

So, every new renderCache is compared to the initial value, and if they are equal, the state isn't updated.

[valentyng]

A possible solution is moving structEq(liftedComponent.state.renderCache, renderCache) to shouldComponentUpdate (https://github.com/grammarly/focal/blob/master/src/react/react.ts#L116).

However, I'm not sure about the performance here.
@blacktaxi what do you think?

[blacktaxi]

That seems to be a good catch! Let me take some time to debug this. Not sure about moving structEq to shouldComponentUpdate, intuitively it indeed seems to ought to affect performance.

Another obvious solution could be to use the this.setState(prevState => ...) overload and perform the structEq call in the callback.

[oleksiilevzhynskyi]

@blacktaxi this.setState(prevState => prevState) triggers render. It looks like it doesn't make sense to use structEq here. Code - https://codesandbox.io/s/0ol9q3q38w

[blacktaxi]

Added a repro and tracking this in #27 now