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.
Previously, `<Context>` was equivalent to `<Context.Consumer>`. However,
since the introduction of Hooks, the `<Context.Consumer>` API is rarely
used. The goal here is to make the common case cleaner:
```js
const ThemeContext = createContext('light')
function App() {
return (
<ThemeContext value="dark">
...
</ThemeContext>
)
}
function Button() {
const theme = use(ThemeContext)
// ...
}
```
This is technically a breaking change, but we've been warning about
rendering `<Context>` directly for several years by now, so it's
unlikely much code in the wild depends on the old behavior. [Proof that
it warns today (check
console).](https://codesandbox.io/p/sandbox/peaceful-nobel-pdxtfl)
---
**The relevant commit is 5696782b428a5ace96e66c1857e13249b6c07958.** It
switches `createContext` implementation so that `Context.Provider ===
Context`.
The main assumption that changed is that a Provider's fiber type is now
the context itself (rather than an intermediate object). Whereas a
Consumer's fiber type is now always an intermediate object (rather than
it being sometimes the context itself and sometimes an intermediate
object).
My methodology was to start with the relevant symbols, work tags, and
types, and work my way backwards to all usages.
This might break tooling that depends on inspecting React's internal
fields. I've added DevTools support in the second commit. This didn't
need explicit versioning—the structure tells us enough.
This renames Module References to Client References, since they are in
the server->client direction.
I also changed the Proxies exposed from the `node-register` loader to
provide better error messages. Ideally, some of this should be
replicated in the ESM loader too but neither are the source of truth.
We'll replicate this in the static form in the Next.js loaders. cc
@huozhi @shuding
- All references are now functions so that when you call them on the
server, we can yield a better error message.
- References that are themselves already referring to an export name are
now proxies that error when you dot into them.
- `use(...)` can now be used on a client reference to unwrap it server
side and then pass a reference to the awaited value.
* Facebook -> Meta in copyright
rg --files | xargs sed -i 's#Copyright (c) Facebook, Inc. and its affiliates.#Copyright (c) Meta Platforms, Inc. and affiliates.#g'
* Manual tweaks
This was already defeating the XSS issue that Symbols was meant to protect
against. So you were already supposed to use a polyfill for security.
We rely on real Symbol.for in Flight for Server Components so those require
real symbols anyway.
We also don't really support IE without additional polyfills anyway.
- Add Tracing Marker component type to React exports
- Add reconciler work tag
- Add devtools work tag
- Add boilerplate for the cache to render children
No functionality yet
* [Offscreen] Mount/unmount layout effects
Exposes the Offscreen component type and implements basic support for
mount/unmounting layout effects when the visibility is toggled.
Mostly it works the same way as hidden Suspense trees, which use the
same internal fiber type. I had to add an extra bailout, though, that
doesn't apply to the Suspense case but does apply to Offscreen
components: a hidden Offscreen tree will eventually render at low
priority, and when we it does, its `subtreeTag` will have effects
scheduled on it. So I added a check to the layout phase where, if the
subtree is hidden, we skip over the subtree entirely. An alternate
design would be to clear the subtree flags in the render phase, but I
prefer doing it this way since it's harder to mess up.
We also need an API to enable the same thing for passive effects. This
is not yet implemented.
* Add test starting from hidden
Co-authored-by: Rick Hanlon <rickhanlonii@gmail.com>
* Remove Blocks
* Remove Flight Server Runtime
There's no need for this now that the JSResource is part of the bundler
protocol. Might need something for Webpack plugin specifically later.
* Devtools
* Refactor Flight to require a module reference to be brand checked
This exposes a host environment (bundler) specific hook to check if an
object is a module reference. This will be used so that they can be passed
directly into Flight without needing additional wrapper objects.
* Emit module references as a special type of value
We already have JSON and errors as special types of "rows". This encodes
module references as a special type of row value. This was always the
intention because it allows those values to be emitted first in the stream
so that as a large models stream down, we can start preloading as early
as possible.
We preload the module when they resolve but we lazily require them as they
are referenced.
* Emit module references where ever they occur
This emits module references where ever they occur. In blocks or even
directly in elements.
* Don't special case the root row
I originally did this so that a simple stream is also just plain JSON.
However, since we might want to emit things like modules before the root
module in the stream, this gets unnecessarily complicated. We could add
this back as a special case if it's the first byte written but meh.
* Update the protocol
* Add test for using a module reference as a client component
* Relax element type check
Since Flight now accepts a module reference as returned by any bundler
system, depending on the renderer running. We need to drastically relax
the check to include all of them. We can add more as we discover them.
* Move flow annotation
Seems like our compiler is not happy with stripping this.
* Some bookkeeping bug
* Can't use the private field to check
* Expose LegacyHidden type
I will use this internally at Facebook to migrate away from
<div hidden />. The end goal is to migrate to the Offscreen type, but
that has different semantics. This is an incremental step.
* Disable <div hidden /> API in new fork
Migrates to the unstable_LegacyHidden type instead. The old fork does
not support the new component type, so I updated the tests to use an
indirection that picks the correct API. I will remove this once the
LegacyHidden (and/or Offscreen) type has landed in both implementations.
* Add gated warning for `<div hidden />` API
Only exists so we can detect callers in www and migrate them to the new
API. Should not visible to anyone outside React Core team.
* Resolve Server-side Blocks instead of Components
React elements should no longer be used to extract arbitrary data but only
for prerendering trees.
Blocks are used to create asynchronous behavior.
* Resolve Blocks in the Client
* Tests
* Bug fix relay JSON traversal
It's supposed to pass the original object and not the new one.
* Lint
* Move Noop Module Test Helpers to top level entry points
This module has shared state. It needs to be external from builds.
This lets us test the built versions of the Noop renderer.
* Add feature flags
* Add Chunk type and constructor
* Wire up Chunk support in the reconciler
* Update reconciler to reconcile Chunks against the render method
This allows the query and args to be updated.
* Drop the ref. Chunks cannot have refs anyway.
* Add Chunk checks in more missing cases
* Rename secondArg
* Add test and fix lazy chunks
Not really a supported use case but for consistency I guess.
* Fix fragment test
* Add SuspenseList component type
* Push SuspenseContext for SuspenseList
* Force Suspense boundaries into their fallback state
In the "together" mode, we do a second render pass that forces the
fallbacks to stay in place, if not all can unsuspend at once.
* Add test
* Transfer thennables to the SuspenseList
This way, we end up retrying the SuspenseList in case the nested boundary
that just suspended doesn't actually get mounted with this set of
thennables. This happens when the second pass renders the fallback
directly without first attempting to render the content.
* Add warning for unsupported displayOrder
* Add tests for nested sibling boundaries and nested lists
* Fix nested SuspenseList forwarding thennables
* Rename displayOrder to revealOrder
Display order has some "display list" connotations making it sound like
a z-index thing.
Reveal indicates that this isn't really about when something gets rendered
or is ready to be rendered. It's about when content that is already there
gets to be revealed.
* Add test for avoided boundaries
* Make SuspenseList a noop in legacy mode
* Use an explicit suspense list state object
This will be used for more things in the directional case.
Removes support for using arbitrary promises as the type of a React
element. Instead, promises must be wrapped in React.lazy. This gives us
flexibility later if we need to change the protocol.
The reason is that promises do not provide a way to call their
constructor multiple times. For example:
const promiseForA = new Promise(resolve => {
fetchA(a => resolve(a));
});
Given a reference to `promiseForA`, there's no way to call `fetchA`
again. Calling `then` on the promise doesn't run the constructor again;
it only attaches another listener.
In the future we will likely introduce an API like `React.eager` that
is similar to `lazy` but eagerly calls the constructor. That gives us
the ability to call the constructor multiple times. E.g. to increase
the priority, or to retry if the first operation failed.
* pure
A higher-order component version of the `React.PureComponent` class.
During an update, the previous props are compared to the new props. If
they are the same, React will skip rendering the component and
its children.
Unlike userspace implementations, `pure` will not add an additional
fiber to the tree.
The first argument must be a functional component; it does not work
with classes.
`pure` uses shallow comparison by default, like `React.PureComponent`.
A custom comparison can be passed as the second argument.
Co-authored-by: Andrew Clark <acdlite@fb.com>
Co-authored-by: Sophie Alpert <sophiebits@fb.com>
* Warn if first argument is not a functional component
* Accept promise as element type
On the initial render, the element will suspend as if a promise were
thrown from inside the body of the unresolved component. Siblings should
continue rendering and if the parent is a Placeholder, the promise
should be captured by that Placeholder.
When the promise resolves, rendering resumes. If the resolved value
has a `default` property, it is assumed to be the default export of
an ES module, and we use that as the component type. If it does not have
a `default` property, we use the resolved value itself.
The resolved value is stored as an expando on the promise/thenable.
* Use special types of work for lazy components
Because reconciliation is a hot path, this adds ClassComponentLazy,
FunctionalComponentLazy, and ForwardRefLazy as special types of work.
The other types are not supported, but wouldn't be placed into a
separate module regardless.
* Resolve defaultProps for lazy types
* Remove some calls to isContextProvider
isContextProvider checks the fiber tag, but it's typically called after
we've already refined the type of work. We should get rid of it. I
removed some of them in the previous commit, and deleted a few more
in this one. I left a few behind because the remaining ones would
require additional refactoring that feels outside the scope of this PR.
* Remove getLazyComponentTypeIfResolved
* Return baseProps instead of null
The caller compares the result to baseProps to see if anything changed.
* Avoid redundant checks by inlining getFiberTagFromObjectType
* Move tag resolution to ReactFiber module
* Pass next props to update* functions
We should do this with all types of work in the future.
* Refine component type before pushing/popping context
Removes unnecessary checks.
* Replace all occurrences of _reactResult with helper
* Move shared thenable logic to `shared` package
* Check type of wrapper object before resolving to `default` export
* Return resolved tag instead of reassigning
Changed the API to match what we've been using in our latest discussions.
Our tentative plans are for <Placeholder> to automatically hide the timed-out
children, instead of removing them, so their state is not lost. This part is
not yet implemented. We'll likely have a lower level API that does not include
the hiding behavior. This is also not yet implemented.
* Timeout component
Adds Timeout component. If a promise is thrown from inside a Timeout component,
React will suspend the in-progress render from committing. When the promise
resolves, React will retry. If the render is suspended for longer than the
maximum threshold, the Timeout switches to a placeholder state.
The timeout threshold is defined as the minimum of:
- The expiration time of the current render
- The `ms` prop given to each Timeout component in the ancestor path of the
thrown promise.
* Add a test for nested fallbacks
Co-authored-by: Andrew Clark <acdlite@fb.com>
* Resume on promise rejection
React should resume rendering regardless of whether it resolves
or rejects.
* Wrap Suspense code in feature flag
* Children of a Timeout must be strict mode compatible
Async is not required for Suspense, but strict mode is.
* Simplify list of pending work
Some of this was added with "soft expiration" in mind, but now with our revised
model for how soft expiration will work, this isn't necessary.
It would be nice to remove more of this, but I think the list itself is inherent
because we need a way to track the start times, for <Timeout ms={ms} />.
* Only use the Timeout update queue to store promises, not for state
It already worked this way in practice.
* Wrap more Suspense-only paths in the feature flag
* Attach promise listener immediately on suspend
Instead of waiting for commit phase.
* Infer approximate start time using expiration time
* Remove list of pending priority levels
We can replicate almost all the functionality by tracking just five
separate levels: the highest/lowest priority pending levels, the
highest/lowest priority suspended levels, and the lowest pinged level.
We lose a bit of granularity, in that if there are multiple levels of
pending updates, only the first and last ones are known. But in practice
this likely isn't a big deal.
These heuristics are almost entirely isolated to a single module and
can be adjusted later, without API changes, if necessary.
Non-IO-bound work is not affected at all.
* ReactFiberPendingWork -> ReactFiberPendingPriority
* Renaming method names from "pending work" to "pending priority"
* Get rid of SuspenseThenable module
Idk why I thought this was neccessary
* Nits based on Sebastian's feedback
* More naming nits + comments
* Add test for hiding a suspended tree to unblock
* Revert change to expiration time rounding
This means you have to account for the start time approximation
heuristic when writing Suspense tests, but that's going to be
true regardless.
When updating the tests, I also made a fix related to offscreen
priority. We should never timeout inside a hidden tree.
* palceholder -> placeholder
Add a new component type, Profiler, that can be used to collect new render time metrics. Since this is a new, experimental API, it will be exported as React.unstable_Profiler initially.
Most of the functionality for this component has been added behind a feature flag, enableProfileModeMetrics. When the feature flag is disabled, the component will just render its children with no additional behavior. When the flag is enabled, React will also collect timing information and pass it to the onRender function (as described below).
* Add React.isValidElementType()
Per the conversation on #12453, there are a number of third-party
libraries (particularly those that generate higher-order components)
that are performing suboptimal validation of element types.
This commit exposes a function that can perform the desired check
without depending upon React internals.
* Move isValidElementType to shared/
