Bug: shouldComponentUpdate() doesn't being called while using this.context

[BiosBoy]

Well, guys, I've read this post by @gaearon #2517 and still didn't figure out - does new context API is compatible with shouldComponentUpdate() since React v.16?

As far as I tested today shouldComponentUpdate is not callable at all while using this.context on the child component.

React version:

React & ReactDOM: v.16.13.1

Steps To Reproduce

1. Create a basic wrapper component with its child like: <MyContext.Provider value={store}>{child}</MyContext.Provider>
2. Set context on the child: static contextType = MyContext.
3. Try to call at least some console.log() inside ShouldComponentUpdate(), 100% the last one won't event being called.

The current behavior

Child component re-renders every time, shouldComponentUpdate even don't call at all.

The expected behavior

shouldComponentUpdate should be callable while used along with this.context on the child components.

UPD

I found shouldComponentUpdate working while using context on the child through <MyContext.Consumer> via HOC? That's the magic or a real bug...

[aweary]

Hey @BiosBoy! It's exepcted that shouldComponentUpdate isn't called when context is updated. This is noted in the context docs:

The propagation from Provider to its descendant consumers (including .contextType and useContext) is not subject to the shouldComponentUpdate method, so the consumer is updated even when an ancestor component skips an update.

Hope that helps clear things up!

[Zhell1]

I am having the same issue, I have react automatically rendering too much stuff when I update the context, where sometime only 1 consumer has changed. Is there any way to prevent propagation to consumers in some cases ?
update: answer is yes, see #15156