[compiler runtime] repro: infinite render with useMemoCache + render phase updates

[mofeiZ]

Repro for an infinite render bug we found when testing internally. See equivalent codesandbox repro here.

When render phase updates cause a re-render, useMemoCache arrays for the fiber are cleared and recreated on every retry while hook state is preserved.

This pattern (queuing re-renders on the current fiber during render) is perfectly valid. I believe this is a bug as React compiler currently replaces useMemos with useMemoCache calls and inlined instructions, taking care to preserve existing memoization dependencies. This should be the identity transform, but runtime implementation differences mean that uncompiled code behaves as expected (no infinite render) while compiled code fails to render.

[vercel]

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Name	Status	Preview	Comments	Updated (UTC)
react-compiler-playground	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Aug 29, 2024 9:18pm

[react-sizebot]

Comparing: 61739a8...c173745

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	+0.05%	1.83 kB	1.83 kB
oss-stable/react-dom/cjs/react-dom-client.production.js	=	501.40 kB	501.40 kB	=	89.99 kB	89.99 kB
oss-experimental/react-dom/cjs/react-dom.production.js	=	6.69 kB	6.69 kB	+0.05%	1.83 kB	1.83 kB
oss-experimental/react-dom/cjs/react-dom-client.production.js	=	508.52 kB	508.52 kB	=	91.16 kB	91.16 kB
facebook-www/ReactDOM-prod.classic.js	=	596.16 kB	596.16 kB	=	105.70 kB	105.70 kB
facebook-www/ReactDOM-prod.modern.js	=	572.44 kB	572.44 kB	=	101.88 kB	101.88 kB

Significant size changes

Includes any change greater than 0.2%:

(No significant changes)

Generated by 🚫 dangerJS against 6a1722d

[josephsavona]

thanks for the repro! let's land and we can work on a fix