Summary: The essential assumption of the compiler is that if the inputs to a computation have not changed, then the output should not change either--computation that the compiler optimizes is idempotent.
This is, of course, known to be false in practice, because this property rests on requirements (the Rules of React) that are loosely enforced at best. When rolling out the compiler to a codebase that might have rules of react violations, how should developers debug any issues that arise?
This diff attempts one approach to that: when the option is set, rather than simply skipping computation when dependencies haven't changed, we will *still perform the computation*, but will then use a runtime function to compare the original value and the resultant value. The runtime function can be customized, but the idea is that it will perform a structural equality check on the values, and if the values aren't structurally equal, we can report an error, including information about what file and what variable was to blame.
This assists in debugging by narrowing down what specific computation is responsible for a difference in behavior between the uncompiled code and the program after compilation.
ghstack-source-id: 50dad3dacf
Pull Request resolved: https://github.com/facebook/react/pull/29656
The [`files` field](https://docs.npmjs.com/cli/v10/commands/npm-publish#files-included-in-package)
controls what files get included in the published package.
This PR specifies the `files` field on our publishable packages to only
include the `dist` directory, since we don't need to ship any types or
sourcemaps with 3 of them.
react-compiler-runtime is a runtime package which has sourcemaps, so we
also include the `src` directory in the published package.
Also fixes an invalid version range for the react peer dependency in
react-compiler-runtime, tested that it works via https://semver.npmjs.com/
ghstack-source-id: 12b36c203fc9fd8d72a1995fb3fba2312de4aa51
Pull Request resolved: https://github.com/facebook/react-forget/pull/2965
- Updated all directly defined dependencies to the latest React 19 Beta
- `package.json`: used `resolutions` to force React 19 for `react-is` transitive dependency
- `package.json`: postinstall script to patch fbt for the React 19 element Symbol
- Match on the message in Snap to exclude a React 19 warning that `act` should be imported from `react` instead (from inside `@testing-library/react`)
- Some updated snapshots, I think due to now recovering behavior of `useMemoCache`, please review.
In a next step, we can do the following. I excluded it since it from here as it made the PR unreviewable on GitHub.
- Snapshots now use `react/compiler-runtime` as in prod, so the different default in Snap is no longer needed.
Mike Vitousek
Lauren Tan
Jan Kassens
Joe Savona