SuspenseList progressively renders items even if the list is CPU bound,
i.e. it isn't waiting for missing data. It does this by showing a
fallback for the remaining items, committing the items in that have
already finished, then starting a new render to continue working on
the rest.
When it schedules that subsequent render, it uses a slightly lower
priority than the current render: `renderExpirationTime - 1`.
This commit changes it to reschedule at `renderExpirationTime` instead.
I don't know what the original motivation was for bumping the expiration
time slightly lower. The comment says that the priorities of the two
renders are the same (which makes sense to me) so I imagine it was
motivated by some implementation detail. I don't think it's necessary
anymore, though perhaps it was when it was originally written. If it is
still necessary, we should write a test case that illustrates why.
Changes the internal fiber structure of the Suspense component. When a
Suspense boundary can't finish rendering and switches to a fallback, we
wrap the "primary" tree in a Fragment fiber and hide all its DOM nodes.
Then we mount the fallback tree into a separate Fragment fiber. Both
trees will render into the same parent DOM node (since React fragments
aren't part of the host tree), but the wrappers ensure that the children
in each tree are reconciled separately.
The old implementation would try to be clever and only add the fragment
wrapper when the fallback was in place, to save memory. This "worked"
but was prone to regressions, since this is the only such place in the
codebase where we wrap existing nodes in a new node. (In other words,
it's a form of reparenting, which we don't implement elsewhere).
Since the original implementation, we've also added lots of additional
requirements to the Suspense component that have led to an explosion in
complexity, like limited support in Legacy Mode (with very different
semantics) and progressive hydration.
We're planning to add even more features to the Suspense boundary, so
we're going to sacrifice a bit more memory for a simpler implementation
that is less prone to regressions.
This ended up removing a lot of weird hacks and edge cases, but there
are still plenty left over. Most of the remaining complexity is related
to Legacy mode. That's the next thing we should aim to drop support for.
Because this is a risky change, I've only changed this in the new
reconciler. It blocks some other features, but as of now we're not
planning to implement those in the old reconciler. If that changes, this
should cherry-pick to the other implementation without much effort.
* Add LanePriority type
React's internal scheduler has more priority levels than the external
Scheduler package. Let's use React as the source of truth for tracking
the priority of updates so we have more control. We'll still fall back
to Scheduler in the default case. In the future, we should consider
removing `runWithPriority` from Scheduler and replacing the valid use
cases with React-specific APIs.
This commit adds a new type, called a LanePriority to disambiguate from
the Scheduler one.
("Lane" refers to another type that I'm planning. It roughly translates
to "thread." Each lane will have a priority associated with it.)
I'm not actually using the lane anywhere, yet. Only setting stuff up.
* Remove expiration times train model
In the old reconciler, expiration times are computed by applying an
offset to the current system time. This has the effect of increasing
the priority of updates as time progresses. Because we also use
expiration times as a kind of "thread" identifier, it turns out this
is quite limiting because we can only flush work sequentially along
the timeline.
The new model will use a bitmask to represent parallel threads that
can be worked on in any combination and in any order.
In this commit, expiration times and the linear timeline are still in
place, but they are no longer based on a timestamp. Effectively, they
are constants based on their priority level.
* Stop using ExpirationTime to represent timestamps
Follow up to the previous commit. This converts the remaining places
where we were using the ExpirationTime type to represent a timestamp,
like Suspense timeouts.
* Fork Dependencies and PendingInteractionMap types
These contain expiration times
* Make ExpirationTime an opaque type
ExpirationTime is currently just an alias for the `number` type, for a
few reasons. One is that it predates Flow's opaque type feature. Another
is that making it opaque means we have to move all our comparisons and
number math to the ExpirationTime module, and use utility functions
everywhere else.
However, this is actually what we want in the new system, because the
Lanes type that will replace ExpirationTime is a bitmask with a
particular layout, and performing operations on it will involve more
than just number comparisions and artihmetic. I don't want this logic to
spread ad hoc around the whole codebase.
The utility functions get inlined by Closure so it doesn't matter
performance-wise.
I automated most of the changes with JSCodeshift, with only a few manual
tweaks to stuff like imports. My goal was to port the logic exactly to
prevent subtle mistakes, without trying to simplify anything in the
process. I'll likely need to audit many of these sites again when I
replace them with the new type, though, especially the ones
in ReactFiberRoot.
I added the codemods I used to the `scripts` directory. I won't merge
these to master. I'll remove them in a subsequent commit. I'm only
committing them here so they show up in the PR for future reference.
I had a lot of trouble getting Flow to pass. Somehow it was not
inferring the correct type of the constants exported from the
ExpirationTime module, despite being annotated correctly.
I tried converting them them to constructor functions — `NoWork`
becomes `NoWork()` — and that made it work. I used that to unblock me,
and fixed all the other type errors. Once there were no more type
errors, I tried converting the constructors back to constants. Started
getting errors again.
Then I added a type constraint everywhere a constant was referenced.
That fixed it. I also figured out that you only have to add a constraint
when the constant is passed to another function, even if the function is
annotated. So this indicates to me that it's probably a Flow bug. I'll
file an issue with Flow.
* Delete temporary codemods used in previous commit
I only added these to the previous commit so that I can easily run it
again when rebasing. When the stack is squashed, it will be as if they
never existed.
This could be used to do custom formatting of the stack trace in a way
that isn't compatible with how we use it. So we disable it while we use
it.
In theory we could call this ourselves with the result of our stack.
It would be a lot of extra production code though. My personal opinion
is that this should always be done server side instead of on the client.
We could expose a custom parser that converts it and passes it through
prepareStackTrace as structured data. That way it's external and doesn't
have to be built-in to React.
We currently use the stack to dedupe warnings in a couple of places.
This is a very heavy weight way of computing that a warning doesn't need
to be fired.
This uses parent component name as a heuristic for deduping. It's not
perfect but as soon as you fix one you'll uncover the next. It might be a
little annoying but having many logs is also annoying.
We now have no special cases for stacks. The only thing that uses stacks in
dev is the console.error and dev tools. This means that we could
externalize this completely to an console.error patching module and drop
it from being built-in to react.
The only prod/dev behavior is the one we pass to error boundaries or the
error we throw if you don't have an error boundary.
* Remove priority field from tracing
* Remove DebugTracing mode from new reconciler (temporarily)
* Run DebugTracing tests in the *other* variant so it's no on for new reconciler
* DevTools console override handles new component stack format
DevTools does not attempt to mimic the default browser console format for its component stacks but it does properly detect the new format for Chrome, Firefox, and Safari.
* Detect double stacks in the new format in tests
* Remove unnecessary uses of getStackByFiberInDevAndProd
These all execute in the right execution context already.
* Set the debug fiber around the cases that don't have an execution context
* Remove stack detection in our console log overrides
We never pass custom stacks as part of the args anymore.
* Bonus: Don't append getStackAddendum to invariants
We print component stacks for every error anyway so this is just duplicate
information.
* Upgrade fbjs-scripts
This script takes into account the NODE_ENV as part of jest cache keys.
This avoids flaky tests since we depend on different transforms in prod
and dev.
* Upgrade Fresh test to Babel 7 transform
* test: Add failing case for dangerouslySetInnerHtml=undefined
* fix: skip dangerouslySetInnerHtml warning if it's undefined
* test: add similar test that should trigger the warning
* chore: Remove redundant nullish check
* Poke yarn_test_www_variant which timed out
* test: Add smaller test for innerHTML=string to innerHTML=undefined
* Fix incorrect unmounted state update warning
We detach fibers (which nulls the field) when we commit a deletion, so any state updates scheduled between that point and when we eventually flush passive effect destroys won't have a way to check if there is a pending passive unmount effect scheduled for its alternate unless we also explicitly track this for both the current and the alternate.
This commit adds a new DEV-only effect type, `PendingPassiveUnmountDev`, to handle this case.
We typecheck the reconciler against each one of our host configs.
`yarn flow dom` checks it against the DOM renderer, `yarn flow native`
checks it against the native renderer, and so on.
To do this, we generate separate flowconfig files.
Currently, there is no root-level host config, so running Flow
directly via `flow` CLI doesn't work. You have to use the `yarn flow`
command and pick a specific renderer.
A drawback of this design, though, is that our Flow setup doesn't work
with other tooling. Namely, editor integrations.
I think the intent of this was maybe so you don't run Flow against a
renderer than you intended, see it pass, and wrongly think you fixed
all the errors. However, since they all run in CI, I don't think this
is a big deal. In practice, I nearly always run Flow against the same
renderer (DOM), and I'm guessing that's the most common workflow for
others, too.
So what I've done in this commit is modify the `yarn flow` command to
copy the generated `.flowconfig` file into the root directory. The
editor integration will pick this up and show Flow information for
whatever was the last renderer you checked.
Everything else about the setup is the same, and all the renderers will
continue to be checked by CI.
* Failing test for #18657
* Remove incorrect priority check
I think this was just poor factoring on my part in #18411. Honestly it
doesn't make much sense to me, but my best guess is that I must have
thought that when `baseTime > currentChildExpirationTime`, the function
would fall through to the
`currentChildExpirationTime < renderExpirationTime` branch below.
Really I think just made an oopsie.
Regardless, this logic is galaxy brainéd. A goal of the Lanes refactor
I'm working on is to make these types of checks -- is there remaining
work in this tree? -- a lot easier to think about. Hopefully.
Nick Reiley
Sebastian Markbåge
Andrew Clark
Luna Ruan
Chang Yan
Dominic Gannaway
Brian Vaughn
Naman Goel
Sebastian Silbermann
Nicolas Gallagher
dependabot[bot]
Dan Abramov
Boris Serdiuk
Thomas Brown