react/compiler
Joseph Savona 735e9ac54e
[compiler] enablePreserveExistingMemo memoizes primitive-returning functions (#34343)
`@enablePreserveExistingMemoizationGuarantees` mode currently does not
guarantee memoization of primitive-returning functions. We're often able
to infer that a function returns a primitive based on how its result is
used, for example `foo() + 1` or `object[getIndex()]`, and by default we
do not currently memoize computation that produces a primitive. The
reasoning behind this is that the compiler is primarily focused on
stopping cascading updates — it's fine to recompute a primitive since we
can cheaply compare that primitive and avoid unnecessary downstream
recomputation. But we've gotten a lot of feedback that people find this
surprising, and that sometimes the computation can be expensive enough
that it should be memoized.

This PR changes `@enablePreserveExistingMemoizationGuarantees` mode to
ensure that primitive-returning functions get memoized. Other modes will
not memoize these functions. Separately from this we are considering
enabling this mode by default.

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[//]: # (BEGIN SAPLING FOOTER)
Stack created with [Sapling](https://sapling-scm.com). Best reviewed
with [ReviewStack](https://reviewstack.dev/facebook/react/pull/34343).
* #34347
* #34346
* __->__ #34343
* #34335
2025-09-03 17:45:17 -07:00
..
apps/playground [playground] Upgrade to latest next (#34375) 2025-09-03 13:47:37 -04:00
docs Update DEVELOPMENT_GUIDE.md (#32281) 2025-03-13 11:45:26 -04:00
fixtures [cleanup] Remove compiler runtime-compat fixture library (#31430) 2024-11-05 14:14:39 -05:00
packages [compiler] enablePreserveExistingMemo memoizes primitive-returning functions (#34343) 2025-09-03 17:45:17 -07:00
scripts [compiler] Script to produce markdown of lint rule docs (#34260) 2025-08-22 09:59:28 -07:00
.eslintrc.js [compiler:codegen] Wrap non-ascii characters in JsxExpressionContainer 2024-06-21 10:08:15 -04:00
.gitignore Remove leftover Rust script (#33314) 2025-05-20 12:20:51 -04:00
CHANGELOG.md [compiler] Update changelog for 19.1.0-rc.2 (#33207) 2025-05-15 10:34:11 -04:00
package.json [compiler] Script to produce markdown of lint rule docs (#34260) 2025-08-22 09:59:28 -07:00
README.md Update readme and other docs 2024-05-06 14:53:47 -07:00
yarn.lock [compiler] Aggregate error reporting, separate eslint rules (#34176) 2025-08-21 14:53:34 -07:00

React Compiler

React Compiler is a compiler that optimizes React applications, ensuring that only the minimal parts of components and hooks will re-render when state changes. The compiler also validates that components and hooks follow the Rules of React.

More information about the design and architecture of the compiler are covered in the Design Goals.

More information about developing the compiler itself is covered in the Development Guide.