Tidy up React Scope API

[trueadm]

This PR changes the React Scopes (experimental) API, so it's simpler. Previously, you used Scopes like this:

const MyScope = React.unstable_createScope()

function MyComponent() {
  return <MyScope>...</MyScope>
}

With this PR:

const Scope = React.unstable_Scope;

function MyComponent() {
  return <Scope>...</Scope>
}

So they work like Fragment or other common React exports, and can be used directly as the element type.

The reason we have unstable_createScope was because in the older design of the Scopes API, createScope used to take an argument. That specific feature was removed ages ago, so it actually makes no sense to have to do createScope each time.

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[sizebot]

Details of bundled changes.

Comparing: 147179a...86fd780

react-is

File	Filesize Diff	Gzip Diff	Prev Size	Current Size	Prev Gzip	Current Gzip	ENV
react-is.development.js	+1.7%	+4.9%	7.94 KB	8.08 KB	1.98 KB	2.08 KB	UMD_DEV
react-is.production.min.js	-1.8%	-1.5%	2.39 KB	2.34 KB	996 B	981 B	UMD_PROD
react-is.development.js	+1.8%	+4.8%	7.37 KB	7.5 KB	1.9 KB	1.99 KB	NODE_DEV
react-is.production.min.js	-1.8%	-1.5%	2.39 KB	2.35 KB	961 B	947 B	NODE_PROD
ReactIs-dev.js	+16.6%	+20.5%	7.5 KB	8.75 KB	1.91 KB	2.3 KB	FB_WWW_DEV
ReactIs-prod.js	🔺+0.3%	🔺+1.6%	5.56 KB	5.58 KB	1.35 KB	1.37 KB	FB_WWW_PROD

Size changes (experimental)

Generated by 🚫 dangerJS against 86fd780

[sizebot]

Details of bundled changes.

Comparing: 147179a...86fd780

react-is

File	Filesize Diff	Gzip Diff	Prev Size	Current Size	Prev Gzip	Current Gzip	ENV
react-is.development.js	+1.7%	+5.0%	7.93 KB	8.06 KB	1.97 KB	2.07 KB	UMD_DEV
react-is.production.min.js	-1.8%	-1.4%	2.37 KB	2.33 KB	987 B	973 B	UMD_PROD
react-is.development.js	+1.8%	+5.1%	7.35 KB	7.49 KB	1.89 KB	1.99 KB	NODE_DEV
react-is.production.min.js	-1.8%	-1.5%	2.38 KB	2.34 KB	951 B	937 B	NODE_PROD
ReactIs-dev.js	+16.6%	+20.6%	7.5 KB	8.75 KB	1.91 KB	2.31 KB	FB_WWW_DEV
ReactIs-prod.js	🔺+0.3%	🔺+1.6%	5.56 KB	5.58 KB	1.35 KB	1.37 KB	FB_WWW_PROD

Size changes (stable)

Generated by 🚫 dangerJS against 86fd780

[gaearon]

I'm not quite following. Wasn't the idea that you declare separate Scope per piece of functionality, similar to Context? How can you be sure of the type of the exposed scope's refs after this change? Presumably any traversal will now "see" unrelated Scopes, unless I'm missing something.

[trueadm]

@gaearon

Wasn't the idea that you declare separate Scope per piece of functionality, similar to Context? How can you be sure of the type of the exposed scope's refs after this change? Presumably any traversal will now "see" unrelated Scopes, unless I'm missing something.

That's how scopes used to work. They changed a while ago and lost their traversal methods entirely, instead opting to use React Context to traverse up and a method to find child React Context in a sub-tree. This was one of the stems of work we had last year when Sebastian was in London, around making Scopes API "safter" and less super-powered.