Implements general-purpose function outlining. Specifically, anonymous function expressions which have no dependencies/context variables are extracted into named top-level functions. The original function expression is replaced with a `LoadGlobal` of the generated name.
Note that the architecture is designed to allow very general purpose forms of outlining, though we currently are very conservative in what we outline. Specifically, the outlining allows annotating functions with an optional ReactiveFunctionType, which if set will cause the outlined function to get compiled as that type. So we could for example outline a helper hook or helper component, set the type, and then have the hook/component get memoized as well. For now though we just outline with no type set, and generate the function as-is without running it through compilation.
ghstack-source-id: 2a7da6c8e85c3f8becb22d3869d9b6200f7db126
Pull Request resolved: https://github.com/facebook/react/pull/30331
Summary: In change-detection mode, we previously were spreading the contents of the computation block into the result twice. Other babel passes that cause in-place mutations of the AST would then be causing action at a distance and breaking the overall transform result. This pr creates clones of the nodes instead, so that mutations aren't reflected in both places where the block is used.
ghstack-source-id: b78def8d8d1b8f9978df0a231f64fdeda786a3a3
Pull Request resolved: https://github.com/facebook/react/pull/30148
This PR extends the previous logic added in #29141 to also account for
other kinds of non-ascii characters such as `\n`. Because these control
characters are individual special characters (and not 2 characters `\`
and `n`) we match based on unicode which was already being checked for
non-Latin characters.
This allows control characters to continue to be compiled equivalently
to its original source if it was provided in a JsxExpressionContainer.
However note that this PR does not convert JSX attributes that are
StringLiterals to JsxExpressionContainer, to preserve the original
source code as it was written.
Alternatively we could always emit a JsxExpressionContainer if it was
used in the source and not try to down level it to some other node
kind. But since we already do this I opted to keep this behavior.
Partially addresses #29648.
ghstack-source-id: ecc61c9f0bece90d18623b3c570fea05fbcd811a
Pull Request resolved: https://github.com/facebook/react/pull/29997
There are two cases where it's legit/intended to remove scopes, and we can inline the scope rather than reify a "pruned" scope:
* Scopes that contain a single instruction with a hook call. The fact that we create a scope in this case at all is just an artifact of it being simpler to do this and remove the scope later rather than try to avoid creating it in the first place. So for these scopes, we can just inline them.
* Scopes that are provably non-escaping. Removing the scope is an optimization, not a case of us having to prune away something that should be there. So again, its fine to inline in this case.
I found this from syncing the stack internally and looking at differences in compiled output. The latter case was most common but the first case is just an obvious improvement.
ghstack-source-id: 80610ddafad65eb837d0037e2692dd74bc548088
Pull Request resolved: https://github.com/facebook/react/pull/29820
Adds additional information to the CompileSuccess LoggerEvent:
* `prunedMemoBlocks` is the number of reactive scopes that were pruned for some reason.
* `prunedMemoValues` is the number of unique _values_ produced by those scopes.
Both numbers exclude blocks that are just a hook call - ie although we create and prune a scope for eg `useState()`, that's just an artifact of the sequencing of our pipeline. So what this metric is counting is cases of _other_ values that go unmemoized. See the new fixture, which takes advantage of improvements in the snap runner to optionally emit the logger events in the .expect.md file if you include the "logger" pragma in a fixture.
ghstack-source-id: c2015bb5565746d07427587526b71e23685279c2
Pull Request resolved: https://github.com/facebook/react/pull/29810
There's a category of bug currently where pruned reactive scopes whose outputs are non-reactive can have their code end up inlining into another scope, moving the location of the instruction. Any value that had a scope assigned has to have its order of evaluation preserved, despite the fact that it got pruned, so naively we could just force every pruned scope to have its declarations promoted to named variables.
However, that ends up assigning names to _tons_ of scope declarations that don't really need to be promoted. For example, a scope with just a hook call ends up with:
```
const x = useFoo();
=>
scope {
$t0 = Call read useFoo$ (...);
}
$t1 = StoreLocal 'x' = read $t0;
```
Where t0 doesn't need to be promoted since it's used immediately to assign to another value which is a non-temporary.
So the idea of this PR is that we can track outputs of pruned scopes which are directly referenced from inside a later scope. This fixes one of the two cases of the above pattern. We'll also likely have to consider values from pruned scopes as always reactive, i'll do that in the next PR.
ghstack-source-id: b37fb9a7cb1430b7c35ec5946269ce5a886a486a
Pull Request resolved: https://github.com/facebook/react/pull/29789
There are a few places where we want to check whether a value actually got memoized, and we currently have to infer this based on values that "should" have a scope and whether a corresponding scope actually exists. This PR adds a new ReactiveStatement variant to model a reactive scope block that was pruned for some reason, and updates all the passes that prune scopes to instead produce this new variant.
ghstack-source-id: aea6dab469acb1f20058b85cb6f9aafab5d167cd
Pull Request resolved: https://github.com/facebook/react/pull/29781
## Summary
See #29737
## How did you test this change?
As the feature requires module support and the test runner does
currently not support running tests as modules, I could only test it via
playground.
Summary: Using the change detection code to debug codebases that violate the rules of react is a lot easier when we have a source location corresponding to the value that has changed inappropriately. I didn't see an easy way to track that information in the existing data structures at the point of codegen, so this PR adds locations to identifiers and reactive scopes (the location of a reactive scope is the range of the locations of its included identifiers).
I'm interested if there's a better way to do this that I missed!
ghstack-source-id: aed5f7edda
Pull Request resolved: https://github.com/facebook/react/pull/29658
Summary: This PR expands the analysis from the previous in the stack in order to also capture when a value can incorrectly change within a single render, rather than just changing between two renders. In the case where dependencies have changed and so a new value is being computed, we now compute the value twice and compare the results. This would, for example, catch when we call Math.random() in render.
The generated code is a little convoluted, because we don't want to have to traverse the generated code and substitute variable names with new ones. Instead, we save the initial value to the cache as normal, then run the computation block again and compare the resulting values to the cached ones. Then, to make sure that the cached values are identical to the computed ones, we reassign the cached values into the output variables.
ghstack-source-id: d0f11a4cb2
Pull Request resolved: https://github.com/facebook/react/pull/29657
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
Summary: This adds a debugging mode to the compiler that simply adds a `|| true` to the guard on all memoization blocks, which results in the generated code never using memoized values and always recomputing them. This is designed as a validation tool for the compiler's correctness--every program *should* behave exactly the same with this option enabled as it would with it disabled, and so any difference in behavior should be investigated as either a compiler bug or a pipeline issue.
(We add `|| true` rather than dropping the conditional block entirely because we still want to exercise the guard tests, in case the guards themselves are the source of an error, like reading a property from undefined in a guard.)
ghstack-source-id: 955a47ec16
Pull Request resolved: https://github.com/facebook/react/pull/29655
We currently use `LoadGlobal` and `StoreGlobal` to represent any read (or write) of a variable defined outside the component or hook that is being compiled. This is mostly fine, but for a lot of things we want to do going forward (resolving types across modules, for example) it helps to understand the actual source of a variable.
This PR is an incremental step in that direction. We continue to use LoadGlobal/StoreGlobal, but LoadGlobal now has a `binding:NonLocalBinding` instead of just the name of the global. The NonLocalBinding type tells us whether it was an import (and which kind, the source module name etc), a module-local binding, or a true global. By keeping the LoadGlobal/StoreGlobal instructions, most code that deals with "anything not declared locally" doesn't have to care about the difference. However, code that _does_ want to know the source of the value can figure it out.
ghstack-source-id: e701d4ebc0fb5681a0197198ac2c2a03b3e8aae9
Pull Request resolved: https://github.com/facebook/react/pull/29188
Babel doesn't seem to properly preserve escaping of HTML entities when emitting JSX text children, so this commit works around the issue by emitting a JsxExpressionContainer for JSX children that contain ">", "<", or "&" characters.
Closes#29100
ghstack-source-id: 2d0622397cc067c6336f3635073e07daef854084
Pull Request resolved: https://github.com/facebook/react/pull/29143
Workaround for a bug in older versions of Babel, where strings with unicode are incorrectly escaped when emitted as JSX attributes, causing double-escaping by later processing.
Closes#29120Closes#29124
ghstack-source-id: 065440d4fb97e164beb8a8f15f252f372a59c5a0
Pull Request resolved: https://github.com/facebook/react/pull/29141
Adds supports for hot module reloading (HMR) by resetting the cache if a hash of the source file changes. This is enabled via a compiler flag, but also enabled automatically via the babel plugin when NODE_ENV=development.
ghstack-source-id: 5cd1ad5c89
Pull Request resolved: https://github.com/facebook/react-forget/pull/2951
