[wip] warn for setState in render on initial mount

[rickhanlonii]

TODO

• Fizz
• Update server tests

[react-sizebot]

Comparing: 5a9921b...1225093

Critical size changes

Includes critical production bundles, as well as any change greater than 2%:

Name	+/-	Base	Current	+/- gzip	Base gzip	Current gzip
oss-stable/react-dom/cjs/react-dom.production.js	=	6.68 kB	6.68 kB	=	1.83 kB	1.83 kB
oss-stable/react-dom/cjs/react-dom-client.production.js	=	608.07 kB	608.07 kB	=	107.68 kB	107.69 kB
oss-experimental/react-dom/cjs/react-dom.production.js	=	6.69 kB	6.69 kB	=	1.83 kB	1.83 kB
oss-experimental/react-dom/cjs/react-dom-client.production.js	=	665.99 kB	665.99 kB	=	117.39 kB	117.39 kB
facebook-www/ReactDOM-prod.classic.js	=	693.36 kB	693.36 kB	=	122.02 kB	122.02 kB
facebook-www/ReactDOM-prod.modern.js	=	683.78 kB	683.78 kB	=	120.40 kB	120.40 kB

Significant size changes

Includes any change greater than 0.2%:

Expand to show

Name	+/-	Base	Current	+/- gzip	Base gzip	Current gzip
test_utils/ReactAllWarnings.js	+0.32%	66.51 kB	66.73 kB	+0.23%	16.74 kB	16.78 kB

Generated by 🚫 dangerJS against 1225093

[gaearon]

Maybe “during the initial render”? Set state “on mount” usually refers to doing it in an effect which isn’t what this seems to be about.

Also, “this behavior is deprecated” maybe could be “this is deprecated, pass the initial value to useState instead” or something like that so it’s clear how to fix it.