Shallow renderer: subsequent setState calls inside componentWillMount discard the previous ones

[Hypnosphi]

What is the current behavior?

If componentWillMount has multiple setState calls, only the last one works in shallow renderer

If the current behavior is a bug, please provide the steps to reproduce and if possible a minimal demo of the problem
https://www.webpackbin.com/bins/-Kw11Ya_ZJ1BcL0rpDKj

Here, DOM renderer correctly renders "Hello, world" while test shallow renderer renders "undefined, world".

Which versions of React, and which browser / OS are affected by this issue? Did this work in previous versions of React?
Issue is introduced in React 16.

The reason must be those lines, replacing publicInstance.state with this._renderer._newState should fix it:

react/src/renderers/testing/ReactShallowRendererEntry.js

Lines 212 to 215 in e932ad6

	this._renderer._newState = {
	...publicInstance.state,
	...partialState,
	};

[gaearon]

Want to send a PR?

[Hypnosphi]

Sure, will do

[gaearon]

Fixed by #11167.

[gaearon]

React 16.1.0-beta has been released. Please update react, react-dom, and react-test-renderer (if you use it) to this version and let us know if it solved the issue! We’d appreciate if you could test before Monday when we plan to get 16.1.0 out.