Use object bracket access test for RESERVED_PROPS

[Deraen]

Continuing from #12370 with different solution (ping @gaearon)

• Should be even faster than previous checks using hasOwnProperty (if my benchmark works correctly anyway)
• Google Closure Compiler will optimize away static properties from
  objects if properties aren't accessed dynamically. Using bracket access
  will make Closure to keep these properties in optimized code.

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I thought preserveTypeAnnotations would keep all JSDoc annotations but @nocollapse seems to be different than "general" JSDoc comments, so it is not kept.

After failure with that approach I started looking into why https://github.com/facebook/react/blob/master/packages/shared/isTextInputElement.js#L13-L29 works with Closure optimizations (with externs to keep the property names). The function is transpiled into static object and a function which uses brackets to access the object. Turns out, that because the code is using brackets to access the object Closure doesn't optimize the properties away.

I checked performance difference between hasOwnProperty and brackets, and looks like object bracket access is faster: https://jsperf.com/static-object-check-if-prop-exists/1

[pull-bot]

Details of bundled changes.

Comparing: 00a0e3c...cb8923d

react-is

File	Filesize Diff	Gzip Diff	Prev Size	Current Size	Prev Gzip	Current Gzip	ENV
ReactIs-dev.js	n/a	n/a	0 B	4.13 KB	0 B	1.17 KB	FB_DEV
ReactIs-prod.js	n/a	n/a	0 B	3.3 KB	0 B	932 B	FB_PROD

Generated by 🚫 dangerJS

[gaearon]

I feel hesitant because there might've been some reason it was written this way. For example I think this will have a false positive for hasOwnProperty. And potentially will make adding anything to Object prototype in JS spec a breaking change.

[Deraen]

Oh right. I forgot how JS objects work.

I think I'm out of ideas for fixing #12368 here. I'll check on Closure side if it can be made to understand hasOwnProperty as dynamic access so it can keep the properties like with bracket access.

[gaearon]

Could you give me more details on your strategy in general? Is this the only issue blocking you? It's a bit hard to believe given in how many places we use dot-access.