A Flow upgrade removed the bundled library definitinos for
SynthaticEvent and we probably want to use our internal definitions.
Those are not properly typed at this point yet, but we can look into
that as a followup.
This update was a bit more involved.
- `React$Component` was removed, I replaced it with Flow component
types.
- Flow removed shipping the standard library. This adds the environment
libraries back from `flow-typed` which seemed to have changed slightly
(probably got more precise and less `any`s). Suppresses some new type
errors.
After an easy couple version with #34252, this version is less flexible
(and safer) on inferring exported types mainly.
We require to annotate some exported types to differentiate between
`boolean` and literal `true` types, etc.
This is intended to be used by various client side resources where the
transfer size is interesting to know how it'll perform in various
network conditions. Not intended to be added by the server.
For now it's only added internally by DevTools itself on img/css but
I'll add it from Flight Client too in a follow up.
This now shows this as the "transfer size" which is the encoded body
size + headers/overhead. Where as the "fileSize" that I add to images is
the decoded body size, like what you'd see on disk. This is what Chrome
shows so it's less confusing if you compare Network tab and this view.
We currently only track the reason something might suspend in
development mode through debug info but this excludes some cases. As a
result we can end up with boundary that suspends but has no cause. This
tries to detect that and show a notice for why that might be. I'm also
trying to make it work with old React versions to cover everything.
In production we don't track any of this meta data like `_debugInfo`,
`_debugThenable` etc. so after resolution there's no information to take
from. Except suspensey images / css which we can track in prod too. We
could track lazy component types already. We'd have to add something
that tracks after the fact if something used a lazy child, child as a
promise, hooks, etc. which doesn't exist today. So that's not backwards
compatible and might add some perf/memory cost. However, another
strategy is also to try to replay the components after the fact which
could be backwards compatible. That's tricky for child position since
there's so many rules for how to do that which would have to be
replicated.
If you're in development you get a different error. Given that we've
added instrumentation very recently. If you're on an older development
version of React, then you get a different error. Unfortunately I think
my feature test is not quite perfect because it's tricky to test for the
instrumentation I just added.
https://github.com/facebook/react/pull/34146 So I think for some
prereleases that has `_debugOwner` but doesn't have that you'll get a
misleading error.
Finally, if you're in a modern development environment, the only reason
we should have any gaps is because of throw-a-Promise. This will
highlight it as missing. We can detect that something threw if a
Suspense boundary commits with a RetryCache but since it's a WeakSet we
can't look into it to see anything about what it might have been. I
don't plan on doing anything to improve this since it would only apply
to new versions of React anyway and it's just inherently flawed. So just
deprecate it #34032.
Note that nothing in here can detect that we suspended Transition. So
throwing at the root or in an update won't show that anywhere.
This computes a min and max range for the whole suspense boundary even
when selecting a single component so that each component in a boundary
has a consistent range.
The start of this range is the earliest start of I/O in that boundary or
the end of the previous suspense boundary, whatever is earlier. If the
end of the previous boundary would make the range large, then we cap it
since it's likely that the other boundary was just an independent
render.
The end of the range is the latest end of I/O in that boundary. If this
is smaller than the end of the previous boundary plus the 300ms
throttle, then we extend the end. This visualizes what throttling could
potentially do if the previous boundary committed right at its end. Ofc,
it might not have committed exactly at that time in this render. So this
is just showing a potential throttle that could happen. To see actual
throttle, you look in the Performance Track.
<img width="661" height="353" alt="Screenshot 2025-08-14 at 12 41 43 AM"
src="https://github.com/user-attachments/assets/b0155e5e-a83f-400c-a6b9-5c38a9d8a34f"
/>
We could come up with some annotation to highlight that this is eligible
to be throttled in this case. If the lines don't extend to the edge,
then it's likely it was throttled.
Same as #34166 but for Suspensey images.
The trick here is to check the `SuspenseyImagesMode` since not all
versions of React and not all subtrees will have Suspensey images
enabled yet.
The other trick is to read back from `currentSrc` to get the image url
we actually resolved to in this case. Similar to how for Suspensey CSS
we check if the media query would've matched.
<img width="591" height="205" alt="Screenshot 2025-08-11 at 9 32 56 PM"
src="https://github.com/user-attachments/assets/ac98785c-d3e0-407c-84e0-c27f86c0ecac"
/>
The skeletons right now are too jarring because they're visually heavier
than the content that comes in later. This makes them draw attention to
themselves as flashing things.
A good skeleton and loading indicator should ideally start as invisible
as possible and then gradually become more visible the longer time
passes so that if it loads quickly then it was never much visible at
all.
Even at its max it should never be heavier weight than the final content
so that it visually reverts into lesser. Another rule of thumb is that
it should be as close as possible to the final content in size but if
it's unknown it should always be smaller than the final content so that
the content grows into its slot rather than the slot contracting.
This makes the skeleton fade from invisible into the dimmest color just
as a subtle hint that something is still loading.
I also added a missing skeleton since the stack traces in rendered by
can now suspend while source mapping.
The other tweak I did is use disabled buttons in all the cases where we
load the ability to enable a button. This is more subtle and if you
hover over you can see why it's still disabled. Rather than flashing the
button each time you change element.
We need to track that Suspensey CSS (Host Resources) can contribute to
the loading state. We can pick up the start/end time from the
Performance Observer API since we know which resource was loaded.
If DOM nodes are not filtered there's a link to the `<link>` instance.
The `"awaited by"` stack is the callsite of the JSX creating the
`<link>`.
<img width="591" height="447" alt="Screenshot 2025-08-11 at 1 35 21 AM"
src="https://github.com/user-attachments/assets/63af0ca9-de8d-4c74-a797-af0a009b5d73"
/>
Inspecting the link itself:
<img width="592" height="344" alt="Screenshot 2025-08-11 at 1 31 43 AM"
src="https://github.com/user-attachments/assets/89603dbc-6721-4bbf-8b58-6010719b29e3"
/>
In this approach I only include it if the page currently matches the
media query. It might contribute in some other scenario but we're not
showing every possible state but every possible scenario that might
suspend if timing changes in the current state.
Stacked on #34148.
This picks up the stack for the await from the `use()` Hook if one was
used to get this async info.
When you select a component that used hooks, we already collect this
information.
If you select a Suspense boundary, this lazily invokes the first
component that awaited this data to inspects its hooks and produce a
stack trace for the use().
When all we have for the name is "Promise" I also use the name of the
first callsite in the stack trace if there's more than one. Which in
practice will be the name of the custom Hook that called it. Ideally
we'd use source mapping and ignore listing for this but that would
require suspending the display. We could maybe make the SuspendedByRow
wrapped in a Suspense boundary for this case.
<img width="438" height="401" alt="Screenshot 2025-08-10 at 10 07 55 PM"
src="https://github.com/user-attachments/assets/2a68917d-c27b-4c00-84aa-0ceb51c4e541"
/>
Similar to #34144 but for `use()`.
`use()` dependencies don't get added to the `fiber._debugInfo` set
because that just models the things blocking the children, and not the
Fiber component itself. This picks up any debug info from the thenable
state that we stashed onto `_debugThenableState` so that we know it used
`use()`.
<img width="593" height="425" alt="Screenshot 2025-08-09 at 4 03 40 PM"
src="https://github.com/user-attachments/assets/c7e06884-4efd-47fa-a76b-132935db6ddc"
/>
Without #34146 this doesn't pick up uninstrumented promises but after
it, it'll pick those up as well. An instrumented promise that doesn't
have anything in its debug info is not picked up. For example, if it
didn't depend on any I/O on the server.
This doesn't yet pick up the stack trace of the `use()` call. That
information is in the Hooks information but needs a follow up to extract
it.
E.g. if the owner is null or the same as current component and no stack.
This happens for example when you return a plain Promise in the child
position and inspect the component it was returned in since there's no
hook stack and the owner is the same as the instance itself so there's
nothing new to link to.
Before:
<img width="267" height="99" alt="Screenshot 2025-08-10 at 10 28 32 PM"
src="https://github.com/user-attachments/assets/23341ab2-2888-457d-a1d1-128f3e0bd5ec"
/>
After:
<img width="253" height="91" alt="Screenshot 2025-08-10 at 10 29 04 PM"
src="https://github.com/user-attachments/assets/b33bb38b-891a-4f46-bc16-15604b033cdb"
/>
Normally, we pick up debug info from instrumented Promise or React.Lazy
while we're reconciling in ReactChildFiber when they appear in the child
position. We add those to the `_debugInfo` of the Fiber.
However, we don't do that for for Lazy in the Component type position.
Instead, we have to pick up the debug info from it explicitly in
DevTools. Likely this is the info added by #34137. Older versions
wouldn't be covered by this particular mechanism but more generally from
throwing a Promise.
<img width="592" height="449" alt="Screenshot 2025-08-08 at 11 32 33 PM"
src="https://github.com/user-attachments/assets/87211c64-a7df-47b7-a784-5cdc7c5fae16"
/>
The name prop will be used in the Suspense tab to help identity a
boundary. Activity will also allow names. A custom component can be
identified by the name of the component but built-ins doesn't have that.
This PR adds it to the Components Tree View as well since otherwise you
only have the key to go on. Normally we don't add all the props to avoid
making this view too noisy but this is an exception along with key to
help identify a boundary quickly in the tree.
Unlike the SuspenseNode store, this wouldn't ever have a name inferred
by owner since that kind of context already exists in this view.
<img width="600" height="161" alt="Screenshot 2025-08-08 at 1 20 36 PM"
src="https://github.com/user-attachments/assets/fe50d624-887a-4b9d-9186-75f131f83195"
/>
I also made both the key and name prop searchable.
<img width="608" height="206" alt="Screenshot 2025-08-08 at 1 32 27 PM"
src="https://github.com/user-attachments/assets/d3502d9c-7614-45fc-b973-57f06dd9cddc"
/>
This shows the stack trace of the JSX at each level so now you can also
jump to the code location for the JSX callsite. The visual is similar to
the owner stacks with `createTask` except when you click the `<...>` you
jump to the Instance in the Components panel.
<img width="593" height="450" alt="Screenshot 2025-08-08 at 12 19 21 AM"
src="https://github.com/user-attachments/assets/dac35faf-9d99-46ce-8b41-7c6fe24625d2"
/>
I'm not sure it's really necessary to have all the JSX stacks of every
owner. We could just have it for the current component and then the rest
of the owners you could get to if you just click that owner instance.
As a bonus, I also use the JSX callsite as the fallback for the "View
Source" button. This is primarily useful for built-ins like `<div>` and
`<Suspense>` that don't have any implementation to jump to anyway. It's
useful to be able to jump to where a boundary was defined.
With RSC it's common to get React.lazy objects in the children position.
This first formats them nicely.
Then it adds introspection support for both lazy and elements.
Unfortunately because of quirks with the hydration mechanism we have to
expose it under the name `_payload` instead of something direct. Also
because the name "type" is taken we can't expose the type field on an
element neither. That whole algorithm could use a rewrite.
<img width="422" height="137" alt="Screenshot 2025-08-07 at 11 37 03 PM"
src="https://github.com/user-attachments/assets/a6f65f58-dbc4-4b8f-928b-d7f629fc51b2"
/>
<img width="516" height="275" alt="Screenshot 2025-08-07 at 11 36 36 PM"
src="https://github.com/user-attachments/assets/650bafdb-a633-4d78-9487-a750a18074ce"
/>
For JSX an alternative or additional feature might be instead to jump to
the first Instance that was rendered using that JSX. We know that based
on the equality of the memoizedProps on the Fiber. It's just a matter of
whether we do that eagerly or more lazily when you click but you may not
have a match so would be nice to indicate that before you click.
