shouldComponentUpdate() is ignored when Legacy Context and New Context are co-existing

Do you want to request a feature or report a bug?

bug.

What is the current behavior?

In a component tree where legacy context and new context are co-exisiting, when components are placed on tree nodes under the legacy context provider and between new context provider and consumer, components are always rendered even if shouldComponentUpdate() returns false in a parent component.

If the current behavior is a bug, please provide the steps to reproduce and if possible a minimal demo of the problem.

https://jsfiddle.net/fdrgz9c4/15/

The above is the minimal case I’ve created without other dependencies, but first I found this behaviour in my Redux application, which uses legacy style context to map the state in store.

What is the expected behavior?

Should not call render() when shouldComponentUpdate() returns false in parent components, as same as the other cases (it prevents rendering when it is located without legacy context or not between new context provider / consumer tree. See the above fiddle)

Which versions of React, and which browser / OS are affected by this issue? Did this work in previous versions of React?

React 16.5.2, maybe in older versions. No OS/browser dependencies I believe.

[markerikson]

@stomita , @kafein : we’re working on a new React-Redux version 6 that switches to use createContext instead of legacy context. Please see https://github.com/reduxjs/react-redux/pull/995 and https://github.com/reduxjs/react-redux/pull/1000 for our work-in-progress PRs, both of which are available on NPM as tags next-995 and next-1000 respectively. I’ve also been fiddling with some more tweaks that I hope may be worth pushing as updates in the near future.

I’d appreciate it if you could try out those builds and see how well they work overall, and give us feedback in those issues.

[gaearon]

There are a few bugs like this but they are rather difficult to fix and would increase the code size. While this may not be satisfactory our recommendation is to migrate away from legacy context when you can. If you can look into fixing this it would be great though.