compiler: fixture for suboptimal jsx sibling memo block merging

[josephsavona]

Stack from ghstack (oldest at bottom):

• 29197

• 29157

• 29156

• -> #29155

React Compiler attempts to merge consecutive reactive scopes in order to reduce overhead. The basic idea is that if two consecutive scopes would always invalidate together then we should merge them. It gets more complicated, though, because values produced by the earlier scope may not always invalidate when their inputs do. For example, a scope that produces fn(x) may not invalidate on all changes to x if the function is Math.max(x, 10) (changing x from 8 to 9 won't change the output).

Previously we were conservative and only merged if either:

• the two scopes had the same dependencies
• the second scope's deps exactly matched the previous scope's outputs.

You can see this in the new fixture, where the second <button> gets its own scope, which happens because the preceding scope has an extra output that isn't a dep of the <button>'s scope.

[vercel[bot]]

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Name	Status	Preview	Comments	Updated (UTC)
react-compiler-playground	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	May 21, 2024 0:16am

[react-sizebot]

Comparing: bf046e86531141d0eb9ffc1165f775a57ffb00f5...9c54058a5f4b4df576226079a999f27b1f40b918

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	=	6.66 kB	6.66 kB	=	1.82 kB	1.82 kB
oss-stable/react-dom/cjs/react-dom-client.production.js	=	495.71 kB	495.71 kB	=	88.78 kB	88.78 kB
oss-experimental/react-dom/cjs/react-dom.production.js	=	6.67 kB	6.67 kB	=	1.83 kB	1.83 kB
oss-experimental/react-dom/cjs/react-dom-client.production.js	=	500.51 kB	500.51 kB	=	89.47 kB	89.47 kB
facebook-www/ReactDOM-prod.classic.js	=	592.86 kB	592.86 kB	=	104.28 kB	104.28 kB
facebook-www/ReactDOM-prod.modern.js	=	569.08 kB	569.08 kB	=	100.69 kB	100.69 kB
__test_utils__/ReactAllWarnings.js	Deleted	64.35 kB	0.00 kB	Deleted	16.05 kB	0.00 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](https://react-builds.vercel.app/commits/9c54058a5f4b4df576226079a999f27b1f40b918/files/__test_utils__/ReactAllWarnings.js?compare=bf046e86531141d0eb9ffc1165f775a57ffb00f5) | **Deleted** | 64.35 kB | 0.00 kB | Deleted | 16.05 kB | 0.00 kB

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