React transpiles some of its own `console.error` calls into a helper
that appends component stacks to those calls. However, this doesn't
cover user space `console.error` calls - which includes React helpers
that React has moved into third parties like createClass and prop-types.
The idea is that any user space component can add a warning just like
React can which is why React DevTools adds them too if they don't
already exist. Having them appended in both places is tricky because now
you have to know whether to remove them from React's logs.
Similarly it's often common for server-side frameworks to forget to
cover the `console.error` logs from other sources since React DevTools
isn't active there. However, it's also annoying to get component stacks
clogging the terminal - depending on where the log came from.
In the future `console.createTask()` will cover this use case natively
and when available we don't append them at all.
The new strategy relies on either:
- React DevTools existing to add them to React logs as well as third
parties.
- `console.createTask` being supported and surfaced.
- A third party framework showing the component stack either in an Error
Dialog or appended to terminal output.
For a third party to be able to implement this they need to be able to
get the component stack. To get the component stack from within a
`console.error` call you need to use the `React.captureOwnerStack()`
helper which is only available in `enableOwnerStacks` flag. However,
it's possible to polyfill with parent stacks using internals as a stop
gap. There's a question of whether React 19 should just go out with
`enableOwnerStacks` to expose this but regardless I think it's best it
doesn't include component stacks from the runtime for consistency.
In practice it's not really a regression though because typically either
of the other options exists and error dialogs don't implement
`console.error` overrides anyway yet. SSR terminals might miss them but
they'd only have them in DEV warnings to begin with an a subset of React
warnings. Typically those are either going to happen on the client
anyway or replayed.
Our tests are written to assert that component stacks work in various
scenarios all over the place. To ensure that this keeps working I
implement a "polyfill" that is similar to that expected a server
framework might do - in `assertConsoleErrorDev` and `toErrorDev`.
This PR doesn't yet change www or RN since they have their own forks of
consoleWithStackDev for now.
While the goal is to remove legacy context completely, I think we can
already land the removal of legacy context for function components. I
didn't even know this feature existed until reading the code recently.
The win is just a couple of property lookups on function renders, but it
trims down the API already as the full removal will likely still take a
bit more time.
www: Starting with enabled test renderer and a feature flag for
production rollout.
RN: Not enabled, will follow up on this.
For environments that still have legacy contexts available, this adds a
warning to make the remaining call sites easier to locate and encourage
upgrades.
This marker can then be emitted as a getter. When this object gets
accessed we use a special error to let the user know what is going on.
<img width="1350" alt="Screenshot 2024-07-08 at 10 13 46 PM"
src="https://github.com/facebook/react/assets/63648/e3eb698f-e02d-4394-a051-ba9ac3236480">
When you click the `...`:
<img width="1357" alt="Screenshot 2024-07-08 at 10 13 56 PM"
src="https://github.com/facebook/react/assets/63648/4b8ce1cf-d762-49a4-97b9-aeeb1aa8722c">
I also increased the object limit in console logs. It was arbitrarily
set very low before.
These limits are per message. So if you have a loop of many logs it can
quickly add up a lot of strain on the server memory and the client. This
is trying to find some tradeoff. Unfortunately we don't really do much
deduping in these logs so with cyclic objects it ends up maximizing the
limit and then siblings aren't logged.
Ideally we should be able to lazy load them but that requires a lot of
plumbing to wire up so if we can avoid it we should try to. If we want
to that though one idea is to use the getter to do a sync XHR to load
more data but the server needs to retain the objects in memory for an
unknown amount of time. The client could maybe send a signal to retain
them until a weakref clean up but even then it kind of needs a heartbeat
to let the server know the client is still alive. That's a lot of
complexity. There's probably more we can do to optimize deduping and
other parts of the protocol to make it possible to have even higher
limits.
Component stacks have a similar problem to the problem with keyPath
where we had to move it down and set it late right before recursing.
Currently we work around that by popping exactly one off when something
suspends. That doesn't work with the new server stacks being added which
are more than one. It also meant that we kept having add a single frame
that could be popped when there shouldn't need to be one.
Unlike keyPath component stacks has this weird property that once
something throws we might need the stack that was attempted for errors
or the previous stack if we're going to retry and just recreate it.
I've tried a few different approaches and I didn't like either but this
is the one that seems least problematic.
I first split out renderNodeDestructive into a retryNode helper. During
retries only retryNode is called. When we first discover a node, we pass
through renderNodeDestructive.
Instead of add a component stack frame deep inside renderNodeDestructive
after we've already refined a node, we now add it before in
renderNodeDestructive. That way it's only added once before being
attempted. This is similar to how Fiber works where in ChildFiber we
match the node once to create the instance and then later do we attempt
to actually render it and it's only the second part that's ever retried.
This unfortunately means that we now have to refine the node down to
element/lazy/thenables twice. To avoid refining the type too I move that
to be done lazily.
We already added this for other thrown errors, not just console.errors.
There's a production form of this. We just missed adding this context.
Mainly the best context is the line number though which comes from owner
stacks.
This is the same change as in #30289 but for the main runtime - e.g.
parent stacks in errorInfo.componentStack, appended stacks to
console.error coming from React itself and when we add virtual frames to
owner stacks.
Since we don't add location information these frames look weird to some
stack parsers - such as the native one. This is an existing issue when
you want to use some off-the-shelf parsers to parse production component
stacks for example.
While we won't add Error objects to logs ourselves necessarily, some
third party could want to do the same thing we do in DevTools and so we
should provide the same capability to just take this trace and print it
using an Error object.
Stacked on #30197.
This is similar to #30182 and #21610 in Fizz.
Track the current owner/stack/task on the task. This tracks it for
attribution when serializing child properties.
This lets us provide the right owner and createTask when we
console.error from inside Flight itself. This also affects the way we
print those logs on the client since we need the owner and stack. Now
console.errors that originate on the server gets the right stack on the
client:
<img width="760" alt="Screenshot 2024-07-03 at 6 03 13 PM"
src="https://github.com/facebook/react/assets/63648/913300f8-f364-4e66-a19d-362e8d776c64">
Unfortunately, because we don't track the stack we never pop it so it'll
keep tracking for serializing sibling properties. We rely on "children"
typically being the last property in the common case anyway. However,
this can lead to wrong attribution in some cases where the invalid
property is a next property (without a wrapping element) and there's a
previous element that doesn't. E.g. `<ClientComponent title={<div />}
invalid={nonSerializable} />` would use the div as the attribution
instead of ClientComponent.
I also wrap all of our own console.error, onError and onPostpone in the
context of the parent component. It's annoying to have to remember to do
this though.
We could always wrap the whole rendering in such as context but it would
add more overhead since this rarely actually happens. It might make
sense to track the whole current task instead to lower the overhead.
That's what we do in Fizz. We'd still have to remember to restore the
debug task though. I realize now Fizz doesn't do that neither so the
debug task isn't wrapping the console.errors that Fizz itself logs.
There's something off about that Flight and Fizz implementations don't
perfectly align.
Wire up owner stacks in Flight to the shared internals. This exposes it
to `captureOwnerStack()`.
In this case we install it permanently as we only allow one RSC renderer
which then supports async contexts. Same thing we do for owner.
This also ends up adding it to errors logged by React through
`consoleWithStackDev`. The plan is to eventually remove that but this is
inline with what we do in Fizz and Fiber already.
However, at the same time we've instrumented the console so we need to
strip them back out before sending to the client. This lets the client
control whether to add the stack back in or allowing
`console.createTask` to control it.
This is another reason we shouldn't append them from React but for now
we hack it by removing them after the fact.
It can be efficient to accept raw string chunks to pass through a stream
instead of encoding them into a binary copy first.
Previously our Flight parsers didn't accept receiving string chunks.
That's partly because we sometimes need to encode binary chunks anyway
so string only transport isn't enough but some chunks can be strings.
This adds a partial ability for chunks to be received as strings.
However, accepting strings comes with some downsides. E.g. if the
strings are split up we need to buffer it which compromises the perf for
the common case. If the chunk represents binary data, then we'd need to
encode it back into a typed array which would require a TextEncoder
dependency in the parser. If the string chunk represents a byte length
encoded string we don't know how many unicode characters to read without
measuring them in terms of binary - also requiring a TextEncoder.
This PR is mainly intended for use for pass-through within the same
memory. We can simplify the implementation by assuming that any string
chunk is passed as the original chunk. This requires that the server
stream config doesn't arbitrarily concatenate strings (e.g. large
strings should not be concatenated which is probably a good heuristic
anyway). It also means that this is not suitable to be used with for
example receiving string chunks on the client by passing them through
SSR hydration data - except if the encoding that way was only used with
chunks that were already encoded as strings by Flight.
Web streams mostly just work on binary data anyway so they can't use
this.
In Node.js streams we concatenate precomputed and small strings into
larger buffers. It might make sense to do that using string ropes
instead. However, in the meantime we can at least pass large strings
that are outside our buffer view size as raw strings. There's no benefit
to us eagerly encoding those.
Also, let Node accept string chunks as long as they're following our
expected constraints. This lets us test the mixed protocol using
pass-throughs. This can also be useful when the RSC server is in the
same environment as the SSR server as they don't have to go from strings
to typed arrays back to strings.
Now we can also use this in the pass-through used in renderToMarkup.
This lets us avoid the dependency on TextDecoder/TextEncoder in that
package.
Stacked on #30170.
This lets us track Server Component parent stacks in Fizz which also
lets us track the correct owner stack for lazy.
In Fiber we're careful not to make any DEV only fibers but since the
ReactFizzComponentStack data structures just exist for debug meta data
anyway we can just expand on that.
When we added component stacks to Fizz in prod it severely slowed down
common cases where you intentionally are throwing error for purposes of
client rendering. Our parent component stack generation is very slow
since call components with fake errors to generate them.
Therefore we disabled them in prod but included them in prerenders.
https://github.com/facebook/react/pull/27850
However, we still kept generating data structures for them and the code
still exists there for the prerenders. We could stop generating the data
structures which are not completely free but also not crazy bad.
What we can do instead is just lazily generate the component stacks.
This is in fact what plain stacks do anyway. This doesn't work as well
in Fiber because the data structures are live but on the server they're
immutable so it's fine to do it later as well.
That way you can choose to not read this getter for intentionally thrown
errors - after inspecting the Error object - yet still get component
stacks in prod for other errors.
Stacked on #30142.
This tracks owners and their stacks in DEV in Fizz. We use the
ComponentStackNode as the data structure to track this information -
effectively like ReactComponentInfo (Server) or Fiber (Client). They're
the instance.
I then port them same logic from ReactFiberComponentStack,
ReactFiberOwnerStack and ReactFiberCallUserSpace to Fizz equivalents.
This gets us both owner stacks from `captureOwnerStack()`, as well as
appended to console.errors logged by Fizz, while rendering and in
onError.
We use this to encode the binary length of a large string without
escaping it. This is really kind of optional though. This lets a Server
that can't encode strings but just pass them along able to emit RSC -
albeit a less optimal format.
The only build we have that does that today is react-html but the FB
version of Flight had a similar constraint.
It's still possible to support binary data as long as
byteLengthOfBinaryChunk is implemented which doesn't require a text
encoder. Many streams (including Node streams) support binary OR string
chunks.
Follow up to #30105.
This supports `renderToMarkup` in a non-RSC environment (not the
`react-server` condition).
This is just a Fizz renderer but it errors at runtime when you use
state, effects or event handlers that would require hydration - like the
RSC version would. (Except RSC can give early errors too.)
To do this I have to move the `react-html` builds to a new `markup`
dimension out of the `dom-legacy` dimension so that we can configure
this differently from `renderToString`/`renderToStaticMarkup`.
Eventually that dimension can go away though if deprecated. That also
helps us avoid dynamic configuration and we can just compile in the
right configuration so the split helps anyway.
One consideration is that if a compiler strips out useEffects or inlines
initial state from useState, then it would not get called an the error
wouldn't happen. Therefore to preserve semantics, a compiler would need
to inject some call that can check the current renderer and whether it
should throw.
There is an argument that it could be useful to not error for these
because it's possible to write components that works with SSR but are
just optionally hydrated. However, there's also an argument that doing
that silently is too easy to lead to mistakes and it's better to error -
especially for the e-mail use case where you can't take it back but you
can replay a queue that had failures. There are other ways to
conditionally branch components intentionally. Besides if you want it to
be silent you can still use renderToString (or better yet
renderToReadableStream).
The primary mechanism is the RSC environment and the client-environment
is really the secondary one that's only there to support legacy
environments. So this also ensures parity with the primary environment.
This is all behind the `enableOwnerStacks` flag.
This is a follow up to #29088. In that I moved type validation into the
renderer since that's the one that knows what types are allowed.
However, I only removed it from `React.createElement` and not the JSX
which was an oversight.
However, I also noticed that for invalid types we don't have the right
stack trace for throws because we're not yet inside the JSX element that
itself is invalid. We should use its stack for the stack trace. That's
the reason it's enough to just use the throw now because we can get a
good stack trace from the owner stack. This is fixed by creating a fake
Throw Fiber that gets assigned the right stack.
Additionally, I noticed that for certain invalid types like the most
common one `undefined` we error in Flight so a missing import in RSC
leads to a generic error. Instead of erroring on the Flight side we
should just let anything that's not a Server Component through to the
client and then let the Client renderer determine whether it's a valid
type or not. Since we now have owner stacks through the server too, this
will still be able to provide a good stack trace on the client that
points to the server in that case.
<img width="571" alt="Screenshot 2024-06-25 at 6 46 35 PM"
src="https://github.com/facebook/react/assets/63648/6812c24f-e274-4e09-b4de-21deda9ea1d4">
To get the best stack you have to expand the little icon and the regular
stack is noisy [due to this Chrome
bug](https://issues.chromium.org/issues/345248263) which makes it a
little harder to find but once that's fixed it might be easier.
Name of the package is tbd (straw: `react-html`). It's a new package
separate from `react-dom` though and can be used as a standalone package
- e.g. also from a React Native app.
```js
import {renderToMarkup} from '...';
const html = await renderToMarkup(<Component />);
```
The idea is that this is a helper for rendering HTML that is not
intended to be hydrated. It's primarily intended to support a subset of
HTML that can be used as embedding and not served as HTML documents from
HTTP. For example as e-mails or in RSS/Atom feeds or other
distributions. It's a successor to `renderToStaticMarkup`.
A few differences:
- This doesn't support "Client Components". It can only use the Server
Components subset. No useEffect, no useState etc. since it will never be
hydrated. Use of those are errors.
- You also can't pass Client References so you can't use components
marked with `"use client"`.
- Unlike `renderToStaticMarkup` this does support async so you can
suspend and use data from these components.
- Unlike `renderToReadableStream` this does not support streaming or
Suspense boundaries and any error rejects the promise. Since there's no
feasible way to "client render" or patch up the document.
- Form Actions are not supported since in an embedded environment
there's no place to post back to across versions. You can render plain
forms with fixed URLs though.
- You can't use any resource preloading like `preload()` from
`react-dom`.
## Implementation
This first version in this PR only supports Server Components since
that's the thing that doesn't have an existing API. Might add a Client
Components version later that errors.
We don't want to maintain a completely separate implementation for this
use case so this uses the `dom-legacy` build dimension to wire up a
build that encapsulates a Flight Server -> Flight Client -> Fizz stream
to render Server Components that then get SSR:ed.
There's no problem to use a Flight Client in a Server Component
environment since it's already supported for Server-to-Server. Both of
these use a bundler config that just errors for Client References though
since we don't need any bundling integration and this is just a
standalone package.
Running Fizz in a Server Component environment is a problem though
because it depends on "react" and it needs the client version.
Therefore, for this build we embed the client version of "react" shared
internals into the build. It doesn't need anything to be able to use
those APIs since you can't call the client APIs anyway.
One unfortunate thing though is that since Flight currently needs to go
to binary and back, we need TextEncoder/TextDecoder to be available but
this shouldn't really be necessary. Also since we use the legacy stream
config, large strings that use byteLengthOfChunk errors atm. This needs
to be fixed before shipping. I'm not sure what would be the best
layering though that isn't unnecessarily burdensome to maintain. Maybe
some kind of pass-through protocol that would also be useful in general
- e.g. when Fizz and Flight are in the same process.
---------
Co-authored-by: Sebastian Silbermann <silbermann.sebastian@gmail.com>
When we replay logs we badge them with e.g. `[Server]`. That way it's
easy to identify that the source of the log actually happened on the
Server (RSC). However, when we threw an error we didn't have any such
thing. The error was rethrown on the client and then handled just like
any other client error.
This transfers the `environmentName` in DEV to our restored Error
"sub-class" (conceptually) along with `digest`. That way you can read
`error.environmentName` to print this in your own UI.
I also updated our default for `onCaughtError` (and `onError` in Fizz)
to use the `printToConsole` helper that the Flight Client uses to log it
with the badge format. So by default you get the same experience as
console.error for caught errors:
<img width="810" alt="Screenshot 2024-06-10 at 9 25 12 PM"
src="https://github.com/facebook/react/assets/63648/8490fedc-09f6-4286-9332-fbe6b0faa2d3">
<img width="815" alt="Screenshot 2024-06-10 at 9 39 30 PM"
src="https://github.com/facebook/react/assets/63648/bdcfc554-504a-4b1d-82bf-b717e74975ac">
Unfortunately I can't do the same thing for `onUncaughtError` nor
`onRecoverableError` because they use `reportError` which doesn't have
custom formatting (unless we also prevented default on window.onerror).
However maybe that's ok because 1) you should always have an error
boundary 2) it's not likely that an RSC error can actually recover
because it's not going to be rendered again so shouldn't really happen
outside some parent conditionally rendering maybe.
The other problem with this approach is that the default is no longer
trivial - so reimplementing the default in user space is trickier and
ideally we shouldn't expose our default to be called.
Need to tighten up this a bit.
react-dom isomorphic currently depends on react-reconciler which is
mostly DCE but it's pulled in which makes it hard to make other bundling
changes.
ReactFlightServer can have a hard dependency on the module that imports
its internals since even if other internals are aliased it still always
needs the server one.
This lets the environment name vary within a request by the context a
component, log or error being executed in.
A potentially different API would be something like
`setEnvironmentName()` but we'd have to extend the `ReadableStream` or
something to do that like we do for `.allReady`. As a function though it
has some expansion possibilities, e.g. we could potentially also pass
some information to it for context about what is being asked for.
If it changes before completing a task, we also emit the change so that
we have the debug info for what the environment was before entering a
component and what it was after completing it.
Stacked on #29807.
This lets the nearest Suspense/Error Boundary handle it even if that
boundary is defined by the model itself.
It also ensures that when we have an error during serialization of
properties, those can be associated with the nearest JSX element and
since we have a stack/owner for that element we can use it to point to
the source code of that line. We can't track the source of any nested
arbitrary objects deeper inside since objects don’t track their stacks
but close enough. Ideally we have the property path but we don’t have
that right now. We have a partial in the message itself.
<img width="813" alt="Screenshot 2024-06-09 at 10 08 27 PM"
src="https://github.com/facebook/react/assets/63648/917fbe0c-053c-4204-93db-d68a66e3e874">
Note: The component name (Counter) is lost in the first message because
we don't print it in the Task. We use `"use client"` instead because we
expect the next stack frame to have the name. We also don't include it
in the actual error message because the Server doesn't know the
component name yet. Ideally Client References should be able to have a
name. If the nearest is a Host Component then we do use the name though.
However, it's not actually inside that Component that the error happens
it's in App and that points to the right line number.
An interesting case is that if something that's actually going to be
consumed by the props to a Suspense/Error Boundary or the Client
Component that wraps them fails, then it can't be handled by the
boundary. However, a counter intuitive case might be when that's on the
`children` props. E.g.
`<ErrorBoundary>{clientReferenceOrInvalidSerialization}</ErrorBoundary>`.
This value can be inspected by the boundary so it's not safe to pass it
so if it's errored it is not caught.
## Implementation
The first insight is that this is best solved on the Client rather than
in the Server because that way it also covers Client References that end
up erroring.
The key insight is that while we don't have a true stack when using
`JSON.parse` and therefore no begin/complete we can still infer these
phases for Elements because the first child of an Element is always
`'$'` which is also a leaf. In depth first that's our begin phase. When
the Element itself completes, we have the complete phase. Anything in
between is within the Element.
Using this idea I was able to refactor the blocking tracking mechanism
to stash the blocked information on `initializingHandler` and then on
the way up do we let whatever is nearest handle it - whether that's an
Element or the root Chunk. It's kind of like an Algebraic Effect.
cc @unstubbable This is something you might want to deep dive into to
find more edge cases. I'm sure I've missed something.
---------
Co-authored-by: eps1lon <sebastian.silbermann@vercel.com>
Stacked on #29807.
Conceptually the error's owner/task should ideally be captured when the
Error constructor is called but neither `console.createTask` does this,
nor do we override `Error` to capture our `owner`. So instead, we use
the nearest parent as the owner/task of the error. This is usually the
same thing when it's thrown from the same async component but not if you
await a promise started from a different component/task.
Before this stack the "owner" and "task" of a Lazy that errors was the
nearest Fiber but if the thing erroring is a Server Component, we need
to get that as the owner from the inner most part of debugInfo.
To get the Task for that Server Component, we need to expose it on the
ReactComponentInfo object. Unfortunately that makes the object not
serializable so we need to special case this to exclude it from
serialization. It gets restored again on the client.
Before (Shell):
<img width="813" alt="Screenshot 2024-06-06 at 5 16 20 PM"
src="https://github.com/facebook/react/assets/63648/7da2d4c9-539b-494e-ba63-1abdc58ff13c">
After (App):
<img width="811" alt="Screenshot 2024-06-08 at 12 29 23 AM"
src="https://github.com/facebook/react/assets/63648/dbf40bd7-c24d-4200-81a6-5018bef55f6d">
We know from Fiber that inline objects with more than 16 properties in
V8 turn into dictionaries instead of optimized objects. The trick is to
use a constructor instead of an inline object literal. I don't actually
know if that's still the case or not. I haven't benchmarked/tested the
output. Better safe than sorry.
It's unfortunate that this can have a negative effect for Hermes and JSC
but it's not as bad as it is for V8 because they don't deopt into
dictionaries. The time to construct these objects isn't a concern - the
time to access them frequently is.
We have to beware the Task objects in Fizz. Those are currently on 16
fields exactly so we shouldn't add anymore ideally.
We should ideally have a lint rule against object literals with more
than 16 fields on them. It might not help since sometimes the fields are
conditional.
Stacked on #29491
Previously if you aborted during a render the currently rendering task
would itself be aborted which will cause the entire model to be replaced
by the aborted error rather than just the slot currently being rendered.
This change updates the abort logic to mark currently rendering tasks as
aborted but allowing the current render to emit a partially serialized
model with an error reference in place of the current model.
The intent is to support aborting from rendering synchronously, in
microtasks (after an await or in a .then) and in lazy initializers. We
don't specifically support aborting from things like proxies that might
be triggered during serialization of props
Stacked on #29551
Flight pings much more often than Fizz because async function components
will always take at least a microtask to resolve . Rather than
scheduling this work as a new macrotask Flight now schedules pings in a
microtask. This allows more microtasks to ping before actually doing a
work flush but doesn't force the vm to spin up a new task which is quite
common give n the nature of Server Components
While most builds of Flight and Fizz schedule work in new tasks some do
execute work synchronously. While this is necessary for legacy APIs like
renderToString for modern APIs there really isn't a great reason to do
this synchronously.
We could schedule works as microtasks but we actually want to yield so
the runtime can run events and other things that will unblock additional
work before starting the next work loop.
This change updates all non-legacy uses to be async using the best
availalble macrotask scheduler.
Browser now uses postMessage
Bun uses setTimeout because while it also supports setImmediate the
scheduling is not as eager as the same API in node
the FB build also uses setTimeout
This change required a number of changes to tests which were utilizing
the sync nature of work in the Browser builds to avoid having to manage
timers and tasks. I added a patch to install MessageChannel which is
required by the browser builds and made this patched version integrate
with the Scheduler mock. This way we can effectively use `act` to flush
flight and fizz work similar to how we do this on the client.
This lets us ensure that we use the original V8 format and it lets us
skip source mapping. Source mapping every call can be expensive since we
do it eagerly for server components even if an error doesn't happen.
In the case of an error being thrown we don't actually always do this in
practice because if a try/catch before us touches it or if something in
onError touches it (which the default console.error does), it has
already been initialized. So we have to be resilient to thrown errors
having other formats.
These are not as perf sensitive since something actually threw but if
you want better perf in these cases, you can simply do something like
`onError(error) { console.error(error.message) }` instead.
The server has to be aware whether it's looking up original or compiled
output. I currently use the file:// check to determine if it's referring
to a source mapped file or compiled file in the fixture. A bundled app
can more easily check if it's a bundle or not.
Normally we take the renderClientElement path but this is an internal
fast path.
No tests because we don't run tests with console.createTask (which is
not easy since we test component stacks).
Ideally this would be covered by types but since the types don't
consider flags and DEV it doesn't really help.
We have three kinds of stacks that we send in the RSC protocol:
- The stack trace where a replayed `console.log` was called on the
server.
- The JSX callsite that created a Server Component which then later
called another component.
- The JSX callsite that created a Host or Client Component.
These stack frames disappear in native stacks on the client since
they're executed on the server. This evals a fake file which only has
one call in it on the same line/column as the server. Then we call
through these fake modules to "replay" the callstack. We then replay the
`console.log` within this stack, or call `console.createTask` in this
stack to recreate the stack.
The main concern with this approach is the performance. It adds
significant cost to create all these eval:ed functions but it should
eventually balance out.
This doesn't yet apply source maps to these. With source maps it'll be
able to show the server source code when clicking the links.
I don't love how these appear.
- Because we haven't yet initialized the client module we don't have the
name of the client component we're about to render yet which leads to
the `<...>` task name.
- The `(async)` suffix Chrome adds is still a problem.
- The VMxxxx prefix is used to disambiguate which is noisy. Might be
helped by source maps.
- The continuation of the async stacks end up rooted somewhere in the
bootstrapping of the app. This might be ok when the bootstrapping ends
up ignore listed but it's kind of a problem that you can't clear the
async stack.
<img width="927" alt="Screenshot 2024-05-28 at 11 58 56 PM"
src="https://github.com/facebook/react/assets/63648/1c9d32ce-e671-47c8-9d18-9fab3bffabd0">
<img width="431" alt="Screenshot 2024-05-28 at 11 58 07 PM"
src="https://github.com/facebook/react/assets/63648/52f57518-bbed-400e-952d-6650835ac6b6">
<img width="327" alt="Screenshot 2024-05-28 at 11 58 31 PM"
src="https://github.com/facebook/react/assets/63648/d311a639-79a1-457f-9a46-4f3298d07e65">
<img width="817" alt="Screenshot 2024-05-28 at 11 59 12 PM"
src="https://github.com/facebook/react/assets/63648/3aefd356-acf4-4daa-bdbf-b8c8345f6d4b">
This didn't actually fail before but I'm just adding an extra check.
Currently Client References are always "function" proxies so they never
fall into this branch. However, we do in theory support objects as
client references too depending on environment. We have checks
elsewhere. So this just makes that consistent.
This one should be fully behind the `enableOwnerStacks` flag.
Instead of printing the parent Component stack all the way to the root,
this now prints the owner stack of every JSX callsite. It also includes
intermediate callsites between the Component and the JSX call so it has
potentially more frames. Mainly it provides the line number of the JSX
callsite. In terms of the number of components is a subset of the parent
component stack so it's less information in that regard. This is usually
better since it's more focused on components that might affect the
output but if it's contextual based on rendering it's still good to have
parent stack. Therefore, I still use the parent stack when printing DOM
nesting warnings but I plan on switching that format to a diff view
format instead (Next.js already reformats the parent stack like this).
__Follow ups__
- Server Components show up in the owner stack for client logs but logs
done by Server Components don't yet get their owner stack printed as
they're replayed. They're also not yet printed in the server logs of the
RSC server.
- Server Component stack frames are formatted as the server and added to
the end but this might be a different format than the browser. E.g. if
server is running V8 and browser is running JSC or vice versa. Ideally
we can reformat them in terms of the client formatting.
- This doesn't yet update Fizz or DevTools. Those will be follow ups.
Fizz still prints parent stacks in the server side logs. The stacks
added to user space `console.error` calls by DevTools still get the
parent stacks instead.
- It also doesn't yet expose these to user space so there's no way to
get them inside `onCaughtError` for example or inside a custom
`console.error` override.
- In another follow up I'll use `console.createTask` instead and
completely remove these stacks if it's available.
This is necessary to simplify the component stack handling to make way
for owner stacks. It also solves some hacks that we used to have but
don't quite make sense. It also solves the problem where things like key
warnings get silenced in RSC because they get deduped. It also surfaces
areas where we were missing key warnings to begin with.
Almost every type of warning is issued from the renderer. React Elements
are really not anything special themselves. They're just lazily invoked
functions and its really the renderer that determines there semantics.
We have three types of warnings that previously fired in
JSX/createElement:
- Fragment props validation.
- Type validation.
- Key warning.
It's nice to be able to do some validation in the JSX/createElement
because it has a more specific stack frame at the callsite. However,
that's the case for every type of component and validation. That's the
whole point of enableOwnerStacks. It's also not sufficient to do it in
JSX/createElement so we also have validation in the renderers too. So
this validation is really just an eager validation but also happens
again later.
The problem with these is that we don't really know what types are valid
until we get to the renderer. Additionally, by placing it in the
isomorphic code it becomes harder to do deduping of warnings in a way
that makes sense for that renderer. It also means we can't reuse logic
for managing stacks etc.
Fragment props validation really should just be part of the renderer
like any other component type. This also matters once we add Fragment
refs and other fragment features. So I moved this into Fiber. However,
since some Fragments don't have Fibers, I do the validation in
ChildFiber instead of beginWork where it would normally happen.
For `type` validation we already do validation when rendering. By
leaving it to the renderer we don't have to hard code an extra list.
This list also varies by context. E.g. class components aren't allowed
in RSC but client references are but we don't have an isomorphic way to
identify client references because they're defined by the host config so
the current logic is flawed anyway. I kept the early validation for now
without the `enableOwnerStacks` since it does provide a nicer stack
frame but with that flag on it'll be handled with nice stacks anyway. I
normalized some of the errors to ensure tests pass.
For `key` validation it's the same principle. The mechanism for the
heuristic is still the same - if it passes statically through a parent
JSX/createElement call then it's considered validated. We already did
print the error later from the renderer so this also disables the early
log in the `enableOwnerStacks` flag.
I also added logging to Fizz so that key warnings can print in SSR logs.
Flight is a bit more complex. For elements that end up on the client we
just pass the `validated` flag along to the client and let the client
renderer print the error once rendered. For server components we log the
error from Flight with the server component as the owner on the stack
which will allow us to print the right stack for context. The factoring
of this is a little tricky because we only want to warn if it's in an
array parent but we want to log the error later to get the right debug
info.
Fiber/Fizz has a similar factoring problem that causes us to create a
fake Fiber for the owner which means the logs won't be associated with
the right place in DevTools.
In #29201 a fix was made to ensure we don't "forget" about some
listeners when handling cyclic chunks.
In #29204 another fix was made for a special case when the chunk already
has listeners before it first resolves.
This implements the followup fix for Flight Reply which was originally
missed in #29204
Co-authored-by: Janka Uryga <lolzatu2@gmail.com>
Fixes#29200
The cyclic state might have added listeners that will still need to be
invoked. This happens if we have a cyclic reference AND end up blocked.
We have already cleared these before entering the parsing when we enter
the CYCLIC state so we they already have the right type. If listeners
are added during this phase they should carry over to the blocked state.
---------
Co-authored-by: Hendrik Liebau <mail@hendrik-liebau.de>
This errors on the client normally but in the case the `type` is a
function - i.e. a Server Component - it wouldn't be transferred to error
on the client so you end up with a worse error message. So this just
implements the same check as ChildFiber.
Stacked on #28997.
We can use the technique of referencing an object by its row + property
name path for temporary references - like we do for deduping. That way
we don't need to generate an ID for temporary references. Instead, they
can just be an opaque marker in the slot and it has the implicit ID of
the row + path.
Then we can stash all objects, even the ones that are actually available
to read on the server, as temporary references. Without adding anything
to the payload since the IDs are implicit. If the same object is
returned to the client, it can be referenced by reference instead of
serializing it back to the client. This also helps preserve object
identity.
We assume that the objects are immutable when they pass the boundary.
I'm not sure if this is worth it but with this mechanism, if you return
the `FormData` payload from a `useActionState` it doesn't have to be
serialized on the way back to the client. This is a common pattern for
having access to the last submission as "default value" to the form
fields. However you can still control it by replacing it with another
object if you want. In MPA mode, the temporary references are not
configured and so it needs to be serialized in that case. That's
required anyway for hydration purposes.
I'm not sure if people will actually use this in practice though or if
FormData will always be destructured into some other object like with a
library that turns it into typed data, and back. If so, the object
identity is lost.
Uses the same technique as in #28996 to encode references to already
emitted objects. This now means that Reply can support cyclic objects
too for parity.
Instead of forcing an object to be outlined to be able to refer to it
later we can refer to it by the property path inside another parent
object.
E.g. this encodes such a reference as `'$123:props:children:foo:bar'`.
That way we don't have to preemptively outline object and we can dedupe
after the first time we've found it.
There's no cost on the client if it's not used because we're not storing
any additional information preemptively.
This works mainly because we only have simple JSON objects from the root
reference. Complex objects like Map, FormData etc. are stored as their
entries array in the look up and not the complex object. Other complex
objects like TypedArrays or imports don't have deeply nested objects in
them that can be referenced.
This solves the problem that we only dedupe after the third instance.
This dedupes at the second instance. It also solves the problem where
all nested objects inside deduped instances also are outlined.
The property paths can get pretty large. This is why a test on payload
size increased. We could potentially outline the reference itself at the
first dupe. That way we get a shorter ID to refer to in the third
instance.
