This adds plumbing for opening a stream from the Flight Client to the
Flight Server so it can ask for more data on-demand. In this mode, the
Flight Server keeps the connection open as long as the client is still
alive and there's more objects to load. It retains any depth limited
objects so that they can be asked for later. In this first PR it just
releases the object when it's discovered on the server and doesn't
actually lazy load it yet. That's coming in a follow up.
This strategy is built on the model that each request has its own
channel for this. Instead of some global registry. That ensures that
referential identity is preserved within a Request and the Request can
refer to previously written objects by reference.
The fixture implements a WebSocket per request but it doesn't have to be
done that way. It can be multiplexed through an existing WebSocket for
example. The current protocol is just a Readable(Stream) on the server
and WritableStream on the client. It could even be sent through a HTTP
request body if browsers implemented full duplex (which they don't).
This PR only implements the direction of messages from Client to Server.
However, I also plan on adding Debug Channel in the other direction to
allow debug info (optionally) be sent from Server to Client through this
channel instead of through the main RSC request. So the `debugChannel`
option will be able to take writable or readable or both.
---------
Co-authored-by: Hendrik Liebau <mail@hendrik-liebau.de>
This frees some memory that will be even more important in a follow up.
Currently, all `ReactPromise` instances hold onto their original
`Response`. The `Response` holds onto all objects that were in that
response since they're needed in case the parsed content ends up
referring to an existing object. If everything you retain are plain
objects then that's fine and the `Response` gets GC:ed, but if you're
retaining a `Promise` itself then it holds onto the whole `Response`.
The only thing that needs this reference at all is a
`ResolvedModelChunk` since it will lazily initialize e.g. by calling
`.then` on itself and so we need to know where to find any sibling
chunks it may refer to. However, we can just store the `Response` on the
`reason` field for this particular state.
That way when all lazy values are touched and initialized the `Response`
is freed. We also free up some memory by getting rid of the extra field.
It wasn't immediately obvious to me, that all the exports here are
related to legacy context, so renaming for clarity.
Modern context lives in `ReactFiberNewContext` which we could probably
also raname in a separate step to just Context.
Stacked on #33588, #33589 and #33590.
This lets us automatically show the resolved value in the UI.
<img width="863" alt="Screenshot 2025-06-22 at 12 54 41 AM"
src="https://github.com/user-attachments/assets/a66d1d5e-0513-4767-910c-5c7169fc2df4"
/>
We can also show rejected I/O that may or may not have been handled with
the error message.
<img width="838" alt="Screenshot 2025-06-22 at 12 55 06 AM"
src="https://github.com/user-attachments/assets/e0a8b6ae-08ba-46d8-8cc5-efb60956a1d1"
/>
To get this working we need to keep the Promise around for longer so
that we can access it once we want to emit an async sequence. I do this
by storing the WeakRefs but to ensure that the Promise doesn't get
garbage collected, I keep a WeakMap of Promise to the Promise that it
depended on. This lets the VM still clean up any Promise chains that
have leaves that are cleaned up. So this makes Promises live until the
last Promise downstream is done. At that point we can go back up the
chain to read the values out of them.
Additionally, to get the best possible value we don't want to get a
Promise that's used by internals of a third-party function. We want the
value that the first party gets to observe. To do this I had to change
the logic for which "await" to use, to be the one that is the first
await that happened in user space. It's not enough that the await has
any first party at all on the stack - it has to be the very first frame.
This is a little sketchy because it relies on the `.then()` call or
`await` call not having any third party wrappers. But it gives the best
object since it hides all the internals. For example when you call
`fetch()` we now log that actual `Response` object.
This adds better support for serializing class instances as Debug
values.
It adds a new marker on the object `{ "": "$P...", ... }` which
indicates which constructor's prototype to use for this object's
prototype. It doesn't encode arbitrary prototypes and it doesn't encode
any of the properties on the prototype. It might get some of the
properties from the prototype by virtue of `toString` on a `class`
constructor will include the whole class's body.
This will ensure that the instance gets the right name in logs.
Additionally, this now also invokes getters if they're enumerable on the
prototype. This lets us reify values that can only be read from native
classes.
---------
Co-authored-by: Hendrik Liebau <mail@hendrik-liebau.de>
We already support serializing the values of instrumented Promises as
debug values such as in console logs. However, we don't support plain
native promises.
This waits a microtask to see if we can read the value within a
microtask and if so emit it. This is so that we can still close the
connection.
Otherwise, we emit a "halted" row into its row id which replaces the old
"Infinite Promise" reference.
We could potentially wait until the end of the render before cancelling
so that if it resolves before we exit we can still include its value but
that would require a bit more work. Ideally we'd have a way to get these
lazily later anyway.
It turns out this was being compiled to a `_defineProperty` helper by
Babel or Closure. We're supposed to have it error the build when we use
features like this that might get compiled.
We should stick to simple ES5 features.
There's a memory leak in DebugNode where the `Error` objects that we
instantiate retains their callstacks which can have Promises on them. In
fact, it's very likely since the current callsite has the "resource" on
it which is the Promise itself. If those Promises are retained then
their `destroy` async hook is never fired which doesn't clean up our map
which can contains the `Error` object. Creating a cycle that can't be
cleaned up.
This fix is just eagerly reifying and parsing the stacks.
I totally expect this to be crazy slow since there's so many Promises
that we end up not needing to visit otherwise. We'll need to optimize it
somehow. Perhaps by being smarter about which ones we might need stacks
for. However, at least it doesn't leak indefinitely.
Stacked on #33539.
Stores dedupes of `renderConsoleValue` in a separate set. This allows us
to dedupe objects safely since we can't write objects using this
algorithm if they might also be referenced by the "real" serialization.
Also renamed it to `renderDebugModel` since it's not just for console
anymore.
On pages that have a high number of server components (e.g. common when
doing syntax highlighting), the debug outlining can produce extremely
large RSC payloads. For example a documentation page I was working on
had a 13.8 MB payload. I noticed that a majority of this was the source
code for the same function components repeated over and over again (over
4000 times) within `$E()` eval commands.
This PR deduplicates the same functions by serializing by reference,
similar to what is already done for objects. Doing this reduced the
payload size of my page from 13.8 MB to 4.6 MB, and resulted in only 31
evals instead of over 4000. As a result it reduced development page load
and hydration time from 4 seconds to 1.5 seconds. It also means the
deserialized functions will have reference equality just as they did on
the server.
## Summary
Make this flag dynamic, so it can be controlled internally.
## How did you test this change?
Build, observe that `console.timeStamp` is only present in FB artifacts
and `enableComponentPerformanceTrack` is referenced.
Ensures that effects are well-formed with respect to the rules:
* For a given instruction, each place is only initialized once (w one of
Create, CreateFrom, Assign)
* Ensures that Alias targets are already initialized within the same
instruction (should have a Create before them)
* Preserves Create and similar instructions
* Avoids duplicate instructions when inferring effects of function
expressions
---
[//]: # (BEGIN SAPLING FOOTER)
Stack created with [Sapling](https://sapling-scm.com). Best reviewed
with [ReviewStack](https://reviewstack.dev/facebook/react/pull/33558).
* #33571
* __->__ #33558
* #33547
Adds some typed helpers to represent aliasing, assign, capture,
createfrom, and mutate effects along with representative runtime
behavior, and then adds tests to demonstrate that we model
capture->createfrom and createfrom->capture correctly.
There is one case (createfrom->capture in a lambda) where we infer a
less precise effect, but in the more conservative direction (we include
more code/deps than necesssary rather than fewer).
---
[//]: # (BEGIN SAPLING FOOTER)
Stack created with [Sapling](https://sapling-scm.com). Best reviewed
with [ReviewStack](https://reviewstack.dev/facebook/react/pull/33543).
* #33571
* #33558
* #33547
* __->__ #33543
Now that we have support for defining aliasing signatures in
moduleTypeProvider, which uses string names for
receiver/args/returns/etc, we can reuse that same form for builtin
declarations. The declarations are written in the unparsed form and than
parsed/validated when registered (in the addFunction/addHook call).
This also required flushing out configs/schemas for more effect types.
---
[//]: # (BEGIN SAPLING FOOTER)
Stack created with [Sapling](https://sapling-scm.com). Best reviewed
with [ReviewStack](https://reviewstack.dev/facebook/react/pull/33530).
* #33571
* #33558
* #33547
* #33543
* #33533
* #33532
* __->__ #33530
In comparing compilation output of the old/new inference models I found
this case (heavily distilled into a fixture). Roughly speaking the
scenario is:
* Create a mutable object `x`
* Extract part of that object and pass it to a hook/jsx so that _part_
becomes frozen
* Mutate `x`, even indirectly.
In the old model we can still independently memoize the value from the
middle step, since we assume that part of the larger value is not
changing. In the new model, the mutation from the later step effectively
overrides the freeze effect in step 2, and considers the value to have
changed later anyway.
We've already rolled out and vetted the previous behavior, confirming
that the heuristic of "that part of the mutable object is fozen now" is
generally safe. I'll fix in a follow-up.
---
[//]: # (BEGIN SAPLING FOOTER)
Stack created with [Sapling](https://sapling-scm.com). Best reviewed
with [ReviewStack](https://reviewstack.dev/facebook/react/pull/33522).
* #33571
* #33558
* #33547
* #33543
* #33533
* #33532
* #33530
* #33526
* __->__ #33522
* #33518
The previous error for hoisting violations pointed only to the variable
declaration, but didn't show where the value was accessed before that
declaration. We now track where each hoisted variable is first accessed
and report two errors, one for the reference and one for the
declaration. When we improve our diagnostic infra to support reporting
errors at multiple locations we can merge these into a single conceptual
error.
---
[//]: # (BEGIN SAPLING FOOTER)
Stack created with [Sapling](https://sapling-scm.com). Best reviewed
with [ReviewStack](https://reviewstack.dev/facebook/react/pull/33514).
* #33571
* #33558
* #33547
* #33543
* #33533
* #33532
* #33530
* #33526
* #33522
* #33518
* __->__ #33514
* #33573
The previous error message was generic, because the old style function
signature didn't support a way to specify a reason alongside a freeze
effect. This meant we could only say why a value was frozen for
instructions, but not hooks which use function signatures. By defining a
new aliasing signature for custom hooks we can specify a reason and
provide a better error message.
---
[//]: # (BEGIN SAPLING FOOTER)
Stack created with [Sapling](https://sapling-scm.com). Best reviewed
with [ReviewStack](https://reviewstack.dev/facebook/react/pull/33513).
* #33571
* #33558
* #33547
* #33543
* #33533
* #33532
* #33530
* #33526
* #33522
* #33518
* #33514
* __->__ #33513
AnalyzeFunctions had logic to reset the mutable ranges of context
variables after visiting inner function expressions. However, there was
a bug in that logic: InferReactiveScopeVariables makes all the
identifiers in a scope point to the same mutable range instance. That
meant that it was possible for a later function expression to indirectly
cause an earlier function expressions' context variables to get a
non-zero mutable range.
The fix is to not just reset start/end of context var ranges, but assign
a new range instance. Thanks for the help on debugging, @mofeiz!
---
[//]: # (BEGIN SAPLING FOOTER)
Stack created with [Sapling](https://sapling-scm.com). Best reviewed
with [ReviewStack](https://reviewstack.dev/facebook/react/pull/33500).
* #33571
* #33558
* #33547
* #33543
* #33533
* #33532
* #33530
* #33526
* #33522
* #33518
* #33514
* #33513
* #33512
* #33504
* __->__ #33500
* #33497
* #33496
Squashed, review-friendly version of the stack from
https://github.com/facebook/react/pull/33488.
This is new version of our mutability and inference model, designed to
replace the core algorithm for determining the sets of instructions
involved in constructing a given value or set of values. The new model
replaces InferReferenceEffects, InferMutableRanges (and all of its
subcomponents), and parts of AnalyzeFunctions. The new model does not
use per-Place effect values, but in order to make this drop-in the end
_result_ of the inference adds these per-Place effects.
I'll write up a larger document on the model, first i'm doing some
housekeeping to rebase the PR.
---
[//]: # (BEGIN SAPLING FOOTER)
Stack created with [Sapling](https://sapling-scm.com). Best reviewed
with [ReviewStack](https://reviewstack.dev/facebook/react/pull/33494).
* #33571
* #33558
* #33547
* #33543
* #33533
* #33532
* #33530
* #33526
* #33522
* #33518
* #33514
* #33513
* #33512
* #33504
* #33500
* #33497
* #33496
* #33495
* __->__ #33494
* #33572
This was really meant to be there from the beginning. A `cache()`:ed
entry has a life time. On the server this ends when the render finishes.
On the client this ends when the cache of that scope gets refreshed.
When a cache is no longer needed, it should be possible to abort any
outstanding network requests or other resources. That's what
`cacheSignal()` gives you. It returns an `AbortSignal` which aborts when
the cache lifetime is done based on the same execution scope as a
`cache()`ed function - i.e. `AsyncLocalStorage` on the server or the
render scope on the client.
```js
import {cacheSignal} from 'react';
async function Component() {
await fetch(url, { signal: cacheSignal() });
}
```
For `fetch` in particular, a patch should really just do this
automatically for you. But it's useful for other resources like database
connections.
Another reason it's useful to have a `cacheSignal()` is to ignore any
errors that might have triggered from the act of being aborted. This is
just a general useful JavaScript pattern if you have access to a signal:
```js
async function getData(id, signal) {
try {
await queryDatabase(id, { signal });
} catch (x) {
if (!signal.aborted) {
logError(x); // only log if it's a real error and not due to cancellation
}
return null;
}
}
```
This just gets you a convenient way to get to it without drilling
through so a more idiomatic code in React might look something like.
```js
import {cacheSignal} from "react";
async function getData(id) {
try {
await queryDatabase(id);
} catch (x) {
if (!cacheSignal()?.aborted) {
logError(x);
}
return null;
}
}
```
If it's called outside of a React render, we normally treat any cached
functions as uncached. They're not an error call. They can still load
data. It's just not cached. This is not like an aborted signal because
then you couldn't issue any requests. It's also not like an infinite
abort signal because it's not actually cached forever. Therefore,
`cacheSignal()` returns `null` when called outside of a React render
scope.
Notably the `signal` option passed to `renderToReadableStream` in both
SSR (Fizz) and RSC (Flight Server) is not the same instance that comes
out of `cacheSignal()`. If you abort the `signal` passed in, then the
`cacheSignal()` is also aborted with the same reason. However, the
`cacheSignal()` can also get aborted if the render completes
successfully or fatally errors during render - allowing any outstanding
work that wasn't used to clean up. In the future we might also expand on
this to give different
[`TaskSignal`](https://developer.mozilla.org/en-US/docs/Web/API/TaskSignal)
to different scopes to pass different render or network priorities.
On the client version of `"react"` this exposes a noop (both for
Fiber/Fizz) due to `disableClientCache` flag but it's exposed so that
you can write shared code.
As discussed in chat, this is a simple fix to stop introducing labels
inside expressions.
The useMemo-with-optional test was added in
d70b2c2c4e
and crashes for the same reason- an unexpected label as a value block
terminal.
---
[//]: # (BEGIN SAPLING FOOTER)
Stack created with [Sapling](https://sapling-scm.com). Best reviewed
with [ReviewStack](https://reviewstack.dev/facebook/react/pull/33548).
* __->__ #33548
* #33546
Previously the experimental workflow relied on the canary one running
first to avoid race conditions. However, I didn't account for the fact
that the canary one can now be skipped.
It may be useful at times to publish only specific packages as an
experimental tag. For example, if we need to cherry pick some fixes for
an old release, we can first do so by creating that as an experimental
release just for that package to allow for quick testing by downstream
projects.
Similar to .github/workflows/runtime_releases_from_npm_manual.yml I
added three options (`dry`, `only_packages`, `skip_packages`) to
`runtime_prereleases.yml` which both the manual and nightly workflows
reuse. I also added a discord notification when the manual workflow is
run.
## Summary
The devtools Components tab's component tree view currently has a
behavior where the indentation of each level of the tree scales based on
the available width of the view. If the view is narrow or component
names are long, all indentation showing the hierarchy of the tree scales
down with the view width until there is no indentation at all. This
makes it impossible to see the nesting of the tree, making the tree view
much less useful. With long component names and deep hierarchies this
issue is particularly egregious. For comparison, the Chrome Dev Tools
Elements panel uses a fixed indentation size, so it doesn't suffer from
this issue.
This PR adds a minimum pixel value for the indentation width, so that
even when the window is narrow some indentation will still be visible,
maintaining the visual representation of the component tree hierarchy.
Alternatively, we could match the behavior of the Chrome Dev Tools and
just use a constant indentation width.
## How did you test this change?
- tests (yarn test-build-devtools)
- tested in browser:
- added an alternate left/right split pane layout to
react-devtools-shell to test with
(https://github.com/facebook/react/pull/33516)
- tested resizing the tree view in different layout modes
### before this change:
https://github.com/user-attachments/assets/470991f1-dc05-473f-a2cb-4f7333f6bae4
with a long component name:
https://github.com/user-attachments/assets/1568fc64-c7d7-4659-bfb1-9bfc9592fb9d
### after this change:
https://github.com/user-attachments/assets/f60bd7fc-97f6-4680-9656-f0db3d155411
with a long component name:
https://github.com/user-attachments/assets/6ac3f58c-42ea-4c5a-9a52-c3b397f37b45
## Summary
This PR adds a 'Layout' selector to the devtools shell main example, as
well as a resizable split pane, allowing more realistic testing of how
the devtools behaves when used in a vertical or horizontal layout and at
different sizes (e.g. when resizing the Chrome Dev Tools pane).
## How did you test this change?
https://github.com/user-attachments/assets/81179413-7b46-47a9-bc52-4f7ec414e8be
This bug was reported via our wg and appears to only affect values
created as a ref.
Currently, postfix operators used in a callback gets compiled to:
```js
modalId.current = modalId.current + 1; // 1
const id = modalId.current; // 1
return id;
```
which is semantically incorrect. The postfix increment operator should
return the value before incrementing. In other words something like this
should have been compiled instead:
```js
const id = modalId.current; // 0
modalId.current = modalId.current + 1; // 1
return id;
```
This bug does not trigger when the incremented value is a plain
primitive, instead there is a TODO bailout.
