There's two problems. The biggest one is that it turns out that Chrome
is throttling looping timers that we're using both while polling and for
batching bridge traffic. This means that bridge traffic a lot of the
time just slows down to 1 second at a time. No wonder it feels sluggish.
The only solution is to not use timers for this.
Even when it doesn't like in Firefox the batching into 100ms still feels
too sluggish.
The fix I use is to batch using a microtask instead so we can still
batch multiple commands sent in a single event but we never artificially
slow down an interaction.
I don't think we've reevaluated this for a long time since this was in
the initial commit of DevTools to this repo. If it causes other issues
we can follow up on those.
We really shouldn't use timers for debouncing and such. In fact, React
itself recommends against it because we have a better technique with
scheduling in Concurrent Mode. The correct way to implement this in the
bridge is using a form of back-pressure where we don't keep sending
messages until we get a message back and only send the last one that
matters. E.g. when moving the cursor over a the elements tab we
shouldn't let the backend one-by-one move the DOM node to each one we
have ever passed. We should just move to the last one we're currently
hovering over. But this can't be done at the bridge layer since it
doesn't know if it's a last-one-wins or imperative operation where each
one needs to be sent. It needs to be done higher. I'm not currently
seeing any perf problems with this new approach but I'm curious on React
Native or some thing. RN might need the back-pressure approach. That can
be a follow up if we ever find a test case.
Finally, the other problem is that we use a Suspense boundary around the
Element Inspection. Suspense boundaries are for things that are expected
to take a long time to load. This shows a loading state immediately. To
avoid flashing when it ends up being fast, React throttles the reveal to
200ms. This means that we take a minimum of 200ms to show the props. The
way to show fast async data in React is using a Transition (either using
startTransition or useDeferredValue). This lets the old value remaining
in place while we're loading the next one.
We already implement this using `inspectedElementID` which is the async
one. It would be more idiomatic to implement this with useDeferredValue
rather than the reducer we have now but same principle. We were just
using the wrong ID in a few places so when it synchronously updated they
suspended. So I just made them use the inspectedElementID instead.
Then I can simply remove the Suspense boundary. Now the selection
updates in the tree view synchronously and the sidebar lags a frame or
two but it feels instant. It doesn't flash to white between which is
key.
Stacked on #30491.
When going from DOM Node to select a component or highlight a component
we find the nearest mounted ancestor. However, when multiple renderers
are nested there can be multiple ancestors. The original fix#24665 did
this by taking the inner renderer if it was an exact match but if it
wasn't it just took the first renderer.
Instead, we can track the inner most node we've found so far. Then get
the ID from that node (which will be fast since it's now a perfect
match). This is a better match.
However, the main reason I'm doing this is because the old mechanism
leaked the `Fiber` type outside the `RendererInterface` which is
supposed to abstract all of that. With the new algorithm this doesn't
leak.
I've tested this with a new build against the repro in the old issue
#24539 and it seems to work.
Stacked on #30427.
Most hooks and such are called inside renders which already have these
on the stack but life-cycles that call out on them are useful to cut off
too.
Typically we don't create JSX in here so they wouldn't be part of owner
stacks anyway but they can be apart of plain stacks such as the ones
prefixes to console logs or printed by error dialogs.
This lets us cut off any React internals below. This should really be
possible using just ignore listing too ideally.
At this point we should maybe just build a Babel plugin that lets us
annotate a function to need to have this name.
The current stack is available in the native UI but that's hidden by
default so you don't see the actual current component on the stack.
This is unlike the native async stacks UI where they're all together.
So we prefix the stack with the current stack first.
<img width="279" alt="Screenshot 2024-07-22 at 10 05 13 PM"
src="https://github.com/user-attachments/assets/8f568fda-6493-416d-a0be-661caf44d808">
---------
Co-authored-by: Ruslan Lesiutin <rdlesyutin@gmail.com>
Stacked on #30410.
Use "owner stacks" as the appended component stack if it is available on
the Fiber. This will only be available if the enableOwnerStacks flag is
on. Otherwise it fallback to parent stacks. In prod, there's no owner so
it's never added there.
I was going back and forth on whether to inject essentially
`captureOwnerStack` as part of the DevTools hooks or replicate the
implementation but decided to replicate the implementation.
The DevTools needs all the same information from internals to implement
owner views elsewhere in the UI anyway so we're not saving anything in
terms of the scope of internals. Additionally, we really need this
information for non-current components as well like "rendered by" views
of the currently selected component.
It can also be useful if we need to change the format after the fact
like we did for parent stacks in:
https://github.com/facebook/react/pull/30289
Injecting the implementation would lock us into specifics both in terms
of what the core needs to provide and what the DevTools can use.
The implementation depends on the technique used in #30369 which tags
frames to strip out with `react-stack-bottom-frame`. That's how the
implementation knows how to materialize the error if it hasn't already.
Firefox:
<img width="487" alt="Screenshot 2024-07-21 at 11 33 37 PM"
src="https://github.com/user-attachments/assets/d3539b53-4578-4fdd-af25-25698b2bcc7d">
Follow up: One thing about this view is that it doesn't include the
current actual synchronous stack. When I used to append these I would
include both the real current stack and the owner stack. That's because
the owner stack doesn't include the name of the currently executing
component. I'll probably inject the current stack too in addition to the
owner stack. This is similar to how native Async Stacks are basically
just appended onto the current stack rather than its own.
Before:
<img width="844" alt="Screenshot 2024-07-04 at 3 20 34 PM"
src="https://github.com/facebook/react/assets/63648/0fd8a53f-538a-4429-a4cf-c22f85a09aa8">
After:
<img width="845" alt="Screenshot 2024-07-05 at 6 08 28 PM"
src="https://github.com/facebook/react/assets/63648/7b9da13a-fa97-4581-9899-06de6fface65">
Firefox:
<img width="1338" alt="Screenshot 2024-07-05 at 6 09 50 PM"
src="https://github.com/facebook/react/assets/63648/f2eb9f2a-2251-408f-86d0-b081279ba378">
The first log doesn't get a stack because it's logged before DevTools
boots up and connects which is unfortunate.
The second log already has a stack printed by React (this is on stable)
it gets replaced by our object now.
The third and following logs don't have a stack and get one appended.
I only turn the stack into an error object if it matches what we would
emit from DevTools anyway. Otherwise we assume it's not React. Since I
had to change the format slightly to make this work, I first normalize
the stack slightly before doing a comparison since it won't be 1:1.
<!--
Thanks for submitting a pull request!
We appreciate you spending the time to work on these changes. Please
provide enough information so that others can review your pull request.
The three fields below are mandatory.
Before submitting a pull request, please make sure the following is
done:
1. Fork [the repository](https://github.com/facebook/react) and create
your branch from `main`.
2. Run `yarn` in the repository root.
3. If you've fixed a bug or added code that should be tested, add tests!
4. Ensure the test suite passes (`yarn test`). Tip: `yarn test --watch
TestName` is helpful in development.
5. Run `yarn test --prod` to test in the production environment. It
supports the same options as `yarn test`.
6. If you need a debugger, run `yarn test --debug --watch TestName`,
open `chrome://inspect`, and press "Inspect".
7. Format your code with
[prettier](https://github.com/prettier/prettier) (`yarn prettier`).
8. Make sure your code lints (`yarn lint`). Tip: `yarn linc` to only
check changed files.
9. Run the [Flow](https://flowtype.org/) type checks (`yarn flow`).
10. If you haven't already, complete the CLA.
Learn more about contributing:
https://reactjs.org/docs/how-to-contribute.html
-->
## Summary
Fix how devtools handles URLs. It
- cannot handle relative source map URLs `//# sourceMappingURL=x.map`
- cannot recognize Windows style URLs
## How did you test this change?
works on my side
## Summary
This is the pre-requisite for
https://github.com/facebook/react/pull/29231.
Current implementation of profiling hooks is only using
`performance.mark` and then makes `performance.clearMarks` call right
after it to free the memory. We've been relying on this assumption in
the tests that every mark is cleared by the time we check something.
https://github.com/facebook/react/pull/29231 adds `performance.measure`
calls and the `start` mark is not cleared until the corresponding `stop`
one is registered, and then they are cleared together.
## How did you test this change?
To test against React from source:
```
yarn test --build --project=devtools -r=experimental --ci
```
To test against React 18:
```
./scripts/circleci/download_devtools_regression_build.js 18.0 --replaceBuild
node ./scripts/jest/jest-cli.js --build --project devtools --release-channel=experimental --reactVersion 18.0 --ci
```
Stacked on https://github.com/facebook/react/pull/29869.
## Summary
When using ANSI escape sequences, we construct a message in the
following way: `console.<method>('\x1b...%s\x1b[0m',
userspaceArgument1?, userspaceArgument2?, userspaceArgument3?, ...)`.
This won't dim all arguments, if user had something like `console.log(1,
2, 3)`, we would only apply it to `1`, since this is the first
arguments, so we need to:
- inline everything whats possible into a single string, while
preserving console substitutions defined by the user
- omit css and object substitutions, since we can't really inline them
and will delegate in to the environment
## How did you test this change?
Added some tests, manually inspected that it works well for web and
native cases.
Basically make `console.error` and `console.warn` behave like normal -
when a component stack isn't appended. I need this because I need to be
able to print rich logs with the component stack option and to be able
to disable instrumentation completely in `console.createTask`
environments that don't need it.
Currently we can't print logs with richer objects because they're
toString:ed first. In practice, pretty much all arguments we log are
already toString:ed so it's not necessary anyway. Some might be like a
number. So it would only be a problem if some environment can't handle
proper consoles but then it's up to that environment to toString it
before logging.
The `Warning: ` prefix is historic and is both noisy and confusing. It's
mostly unnecessary since the UI surrounding `console.error` and
`console.warn` tend to have visual treatment around it anyway. However,
it's actively misleading when `console.error` gets prefixed with a
Warning that we consider an error level. There's an argument to be made
that some of our `console.error` don't make the bar for an error but
then the argument is to downgrade each of those to `console.warn` - not
to brand all our actual error logging with `Warning: `.
Apparently something needs to change in React Native before landing this
because it depends on the prefix somehow which probably doesn't make
sense already.
## Overview
Updates `eslint-plugin-jest` and enables the recommended rules with some
turned off that are unhelpful.
The main motivations is:
a) we have a few duplicated tests, which this found an I deleted
b) making sure we don't accidentally commit skipped tests
This refactors key warning to happen inline after we've matched a Fiber.
I didn't want to do that originally because it was riskier. But it turns
out to be straightforward enough.
This lets us use that Fiber as the source of the warning which matters
to DevTools because then DevTools can associate it with the right
component after it mounts.
We can also associate the duplicate key warning with this Fiber. That
way we'll get the callsite with the duplicate key on the stack and can
associate this warning with the child that had the duplicate.
I kept the forked DevTools tests because the warning now is counted on
the Child instead of the Parent (18 behavior).
However, this won't be released in 19.0.0 so I only test this in
whatever the next version is.
Doesn't seem worth it to have a test for just the 19.0.0 behavior.
## Summary
The test started to fail after
https://github.com/facebook/react/pull/29088.
Fork the test and the expected store state for:
- React 18.x, to represent the previous behavior
- React >= 19, to represent the current RDT behavior, where error can't
be connected to the fiber, because it was not yet mounted and shared
with DevTools.
Ideally, DevTools should start keeping track of such fibers, but also
distinguish them from some that haven't mounted due to Suspense or error
boundaries.
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.
This lets us expose the component stack to the error reporting that
happens here as `console.error` patching. Now if you just call
`console.error` in the error handlers it'll get the component stack
added to the end by React DevTools.
However, unfortunately this happens a little too late so the Fiber will
be disconnected with its `.return` pointer set to null already. So it'll
be too late to extract a parent component stack from but you can at
least get the stack from source to error boundary. To work around this I
manually add the parent component stack in our default handlers when
owner stacks are off. We could potentially fix this but you can also
just include it yourself if you're calling `console.error` and it's not
a problem for owner stacks.
This is not a problem for owner stacks because we'll still have those
and so for those just calling `console.error` just works. However, the
main feature is that by letting React add them, we can switch to using
native error stacks when available.
We previously had two slightly different concepts for "current fiber".
There's the "owner" which is set inside of class components in prod if
string refs are enabled, and sometimes inside function components in DEV
but not other contexts.
Then we have the "current fiber" which is only set in DEV for various
warnings but is enabled in a bunch of contexts.
This unifies them into a single "current fiber".
The concept of string refs shouldn't really exist so this should really
be a DEV only concept. In the meantime, this sets the current fiber
inside class render only in prod, however, in DEV it's now enabled in
more contexts which can affect the string refs. That was already the
case that a string ref in a Function component was only connecting to
the owner in prod. Any string ref associated with any non-class won't
work regardless so that's not an issue. The practical change here is
that an element with a string ref created inside a life-cycle associated
with a class will work in DEV but not in prod. Since we need the current
fiber to be available in more contexts in DEV for the debugging
purposes. That wouldn't affect any old code since it would have a broken
ref anyway. New code shouldn't use string refs anyway.
The other implication is that "owner" doesn't necessarily mean
"rendering" since we need the "owner" to track other debug information
like stacks - in other contexts like useEffect, life cycles, etc.
Internally we have a separate `isRendering` flag that actually means
we're rendering but even that is a very overloaded concept. So anything
that uses "owner" to imply rendering might be wrong with this change.
This is a first step to a larger refactor for tracking current rendering
information.
---------
Co-authored-by: Sebastian Silbermann <silbermann.sebastian@gmail.com>
This PR reorganizes the `react-dom` entrypoint to only pull in code that
is environment agnostic. Previously if you required anything from this
entrypoint in any environment the entire client reconciler was loaded.
In a prior release we added a server rendering stub which you could
alias in server environments to omit this unecessary code. After landing
this change this entrypoint should not load any environment specific
code.
While a few APIs are truly client (browser) only such as createRoot and
hydrateRoot many of the APIs you import from this package are only
useful in the browser but could concievably be imported in shared code
(components running in Fizz or shared components as part of an RSC app).
To avoid making these require opting into the client bundle we are
keeping them in the `react-dom` entrypoint and changing their
implementation so that in environments where they are not particularly
useful they do something benign and expected.
#### Removed APIs
The following APIs are being removed in the next major. Largely they
have all been deprecated already and are part of legacy rendering modes
where concurrent features of React are not available
* `render`
* `hydrate`
* `findDOMNode`
* `unmountComponentAtNode`
* `unstable_createEventHandle`
* `unstable_renderSubtreeIntoContainer`
* `unstable_runWithPrioirty`
#### moved Client APIs
These APIs were available on both `react-dom` (with a warning) and
`react-dom/client`. After this change they are only available on
`react-dom/client`
* `createRoot`
* `hydrateRoot`
#### retained APIs
These APIs still exist on the `react-dom` entrypoint but have normalized
behavior depending on which renderers are currently in scope
* `flushSync`: will execute the function (if provided) inside the
flushSync implemention of FlightServer, Fizz, and Fiber DOM renderers.
* `unstable_batchedUpdates`: This is a noop in concurrent mode because
it is now the only supported behavior because there is no legacy
rendering mode
* `createPortal`: This just produces an object. It can be called from
anywhere but since you will probably not have a handle on a DOM node to
pass to it it will likely warn in environments other than the browser
* preloading APIS such as `preload`: These methods will execute the
preload across all renderers currently in scope. Since we resolve the
Request object on the server using AsyncLocalStorage or the current
function stack in practice only one renderer should act upon the
preload.
In addition to these changes the server rendering stub now just rexports
everything from `react-dom`. In a future minor we will add a warning
when using the stub and in the next major we will remove the stub
altogether
We have changed the shape (and the runtime) of React Elements. To help
avoid precompiled or inlined JSX having subtle breakages or deopting
hidden classes, I renamed the symbol so that we can early error if
private implementation details are used or mismatching versions are
used.
Why "transitional"? Well, because this is not the last time we'll change
the shape. This is just a stepping stone to removing the `ref` field on
the elements in the next version so we'll likely have to do it again.
Follow up to #28783 and #28786.
Since we've changed the implementations of these we can rename them to
something a bit more descriptive while we're at it, since anyone
depending on them will need to upgrade their code anyway.
"react" with no condition:
`__CLIENT_INTERNALS_DO_NOT_USE_OR_WARN_USERS_THEY_CANNOT_UPGRADE`
"react" with "react-server" condition:
`__SERVER_INTERNALS_DO_NOT_USE_OR_WARN_USERS_THEY_CANNOT_UPGRADE`
"react-dom":
`__DOM_INTERNALS_DO_NOT_USE_OR_WARN_USERS_THEY_CANNOT_UPGRADE`
This implements the concept of a DEV-only "owner" for Server Components.
The owner concept isn't really super useful. We barely use it anymore,
but we do have it as a concept in DevTools in a couple of cases so this
adds it for parity. However, this is mainly interesting because it could
be used to wire up future owner-based stacks.
I do this by outlining the DebugInfo for a Server Component
(ReactComponentInfo). Then I just rely on Flight deduping to refer to
that. I refer to the same thing by referential equality so that we can
associate a Server Component parent in DebugInfo with an owner.
If you suspend and replay a Server Component, we have to restore the
same owner. To do that, I did a little ugly hack and stashed it on the
thenable state object. Felt unnecessarily complicated to add a stateful
wrapper for this one dev-only case.
The owner could really be anything since it could be coming from a
different implementation. Because this is the first time we have an
owner other than Fiber, I have to fix up a bunch of places that assumes
Fiber. I mainly did the `typeof owner.tag === 'number'` to assume it's a
Fiber for now.
This also doesn't actually add it to DevTools / RN Inspector yet. I just
ignore them there for now.
Because Server Components can be async the owner isn't tracked after an
await. We need per-component AsyncLocalStorage for that. This can be
done in a follow up.
## Summary
Based on
- https://github.com/facebook/react/pull/27903
This PR
- Silence warning in React tests
- Turn on flag
We want to finish cleaning up internal RTR usage, but let's prioritize
the deprecation process. We do this by silencing the internal warning
for now.
## How did you test this change?
`yarn build`
`yarn test ReactHooksInspectionIntegration -b`
## Overview
The error messages that say:
> ReactDOM.hydrate is no longer supported in React 18
Don't make sense in the React 19 release. Instead, they should say:
> ReactDOM.hydrate was removed in React 19.
For legacy mode, they should say:
> ReactDOM.hydrate has not been supported since React 18.
Reverting some of https://github.com/facebook/react/pull/27804 which
renamed this option to stable. This PR just replaces internal usage to
make upcoming PRs cleaner.
Keeping isConcurrent unstable for the next major release in order to
enable a broader deprecation of RTR and be consistent with concurrent
rendering everywhere for next major.
(https://github.com/facebook/react/pull/28498)
- Next major will use concurrent root
- The old behavior (legacy root by default, concurrent root with
unstable option) will be preserved for React Native until new
architecture is fully shipped.
- Flag and legacy root usage can be removed after RN dependency is
unblocked without an additional breaking change
We broke the ability to "break on uncaught exceptions" by adding a
try/catch higher up in the scheduling. We're giving up on fixing that so
we can remove the replay trick inside an event handler.
The issue with that approach is that we end up double logging a lot of
errors in DEV since they get reported to the page.
It's also a lot of complexity around this feature.
`_debugSource` was removed in
https://github.com/facebook/react/pull/28265.
This PR migrates DevTools to define `source` for Fiber based on
component stacks. This will be done lazily for inspected elements, once
user clicks on the element in the tree.
`DevToolsComponentStackFrame.js` was just copy-pasted from the
implementation in `ReactComponentStackFrame`.
Symbolication part is done in
https://github.com/facebook/react/pull/28471 and stacked on this commit.
Adds a flag to disable legacy mode. Currently this flag is used to cause
legacy mode apis like render and hydrate to throw. This change also
removes render, hydrate, unmountComponentAtNode, and
unstable_renderSubtreeIntoContainer from the experiemntal entrypoint.
Right now for Meta builds this flag is off (legacy mode is still
supported). In OSS builds this flag matches __NEXT_MAJOR__ which means
it currently is on in experiemental. This means that after merging
legacy mode is effectively removed from experimental builds. While this
is a breaking change, experimental builds are not stable and users can
pin to older versions or update their use of react-dom to no longer use
legacy mode APIs.
I'm a bit ambivalent about this one because it's not the main strategy
that I plan on pursuing. I plan on replacing most DEV-only specific
stacks like `console.error` stacks with a new take on owner stacks and
native stacks. The future owner stacks may or may not be exposed to
error boundaries in DEV but if they are they'd be a new errorInfo
property since they're owner based and not available in prod.
The use case in `console.error` mostly goes away in the future so this
PR is mainly for error boundaries. It doesn't hurt to have it in there
while I'm working on the better stacks though.
The `componentStack` property exposed to error boundaries is more like
production behavior similar to `new Error().stack` (which even in DEV
won't ever expose owner stacks because `console.createTask` doesn't
affect these). I'm not sure it's worth adding server components in DEV
(this PR) because then you have forked behavior between dev and prod.
However, since even in the future there won't be any other place to get
the *parent* stack, maybe this can be useful information even if it's
only dev. We could expose a third property on errorInfo that's DEV only
and parent stack but including server components. That doesn't seem
worth it over just having the stack differ in dev and prod.
I don't plan on adding line/column number to these particular stacks.
A follow up could be to add this to Fizz prerender too but only in DEV.
Depends on:
- #28317
- #28320
---
Changes the behavior of the JSX runtime to pass through `ref` as a
normal prop, rather than plucking it from the props object and storing
on the element.
This is a breaking change since it changes the type of the receiving
component. However, most code is unaffected since it's unlikely that a
component would have attempted to access a `ref` prop, since it was not
possible to get a reference to one.
`forwardRef` _will_ still pluck `ref` from the props object, though,
since it's extremely common for users to spread the props object onto
the inner component and pass `ref` as a differently named prop. This is
for maximum compatibility with existing code — the real impact of this
change is that `forwardRef` is no longer required.
Currently, refs are resolved during child reconciliation and stored on
the fiber. As a result of this change, we can move ref resolution to
happen only much later, and only for components that actually use them.
Then we can remove the `ref` field from the Fiber type. I have not yet
done that in this step, though.
Depends on:
- #28317
---
There's a ton of overlap between the createElement implementation and
the JSX implementation, so I combined them into a single module.
In the actual build output, the shared code between JSX and
createElement will get duplicated anyway, because react/jsx-runtime and
react (where createElement lives) are separate, flat build artifacts.
So this is more about code organization — with a few key exceptions, the
implementations of createElement and jsx are highly coupled.
Alternative to #28295.
Instead of stashing all of the Usables eagerly, we can extract them by
replaying the render when we need them like we do with any other hook.
We already had an implementation of `use()` but it wasn't quite
complete.
These can also include further DebugInfo on them such as what Server
Component rendered the Promise or async debug info. This is nice just to
see which use() calls were made in the side-panel but it can also be
used to gather everything that might have suspended.
Together with https://github.com/facebook/react/pull/28286 we cover the
case when a Promise was used a child and if it was unwrapped with use().
Notably we don't cover a Promise that was thrown (although we do support
that in a Server Component which maybe we shouldn't). Throwing a Promise
isn't officially supported though and that use case should move to the
use() Hook.
The pattern of conditionally suspending based on cache also isn't really
supported with the use() pattern. You should always call use() if you
previously called use() with the same input. This also ensures that we
can track what might have suspended rather than what actually did.
One limitation of this strategy is that it's hard to find all the places
something might suspend in a tree without rerendering all the fibers
again. So we might need to still add something to the tree to indicate
which Fibers may have further debug info / thenables.
Along with all the places using it like the `_debugSource` on Fiber.
This still lets them be passed into `createElement` (and JSX dev
runtime) since those can still be used in existing already compiled code
and we don't want that to start spreading to DOM attributes.
We used to have a DEV mode that compiles the source location of JSX into
the compiled output. This was nice because we could get the actual call
site of the JSX (instead of just somewhere in the component). It had a
bunch of issues though:
- It only works with JSX.
- The way this source location is compiled is different in all the
pipelines along the way. It relies on this transform being first and the
source location we want to extract but it doesn't get preserved along
source maps and don't have a way to be connected to the source hosted by
the source maps. Ideally it should just use the mechanism other source
maps use.
- Since it's expensive it only works in DEV so if it's used for
component stacks it would vary between dev and prod.
- It only captures the callsite of the JSX and not the stack between the
component and that callsite. In the happy case it's in the component but
not always.
Instead, we have another zero-cost trick to extract the call site of
each component lazily only if it's needed. This ensures that component
stacks are the same in DEV and PROD. At the cost of worse line number
information.
The better way to get the JSX call site would be to get it from `new
Error()` or `console.createTask()` inside the JSX runtime which can
capture the whole stack in a consistent way with other source mappings.
We might explore that in the future.
This removes source location info from React DevTools and React Native
Inspector. The "jump to source code" feature or inspection can be made
lazy instead by invoking the lazy component stack frame generation. That
way it can be made to work in prod too. The filtering based on file path
is a bit trickier.
When redesigned this UI should ideally also account for more than one
stack frame.
With this change the DEV only Babel transforms are effectively
deprecated since they're not necessary for anything.
