* Add useId to dispatcher
* Initial useId implementation
Ids are base 32 strings whose binary representation corresponds to the
position of a node in a tree.
Every time the tree forks into multiple children, we add additional bits
to the left of the sequence that represent the position of the child
within the current level of children.
00101 00010001011010101
╰─┬─╯ ╰───────┬───────╯
Fork 5 of 20 Parent id
The leading 0s are important. In the above example, you only need 3 bits
to represent slot 5. However, you need 5 bits to represent all the forks
at the current level, so we must account for the empty bits at the end.
For this same reason, slots are 1-indexed instead of 0-indexed.
Otherwise, the zeroth id at a level would be indistinguishable from
its parent.
If a node has only one child, and does not materialize an id (i.e. does
not contain a useId hook), then we don't need to allocate any space in
the sequence. It's treated as a transparent indirection. For example,
these two trees produce the same ids:
<> <>
<Indirection> <A />
<A /> <B />
</Indirection> </>
<B />
</>
However, we cannot skip any materializes an id. Otherwise, a parent id
that does not fork would be indistinguishable from its child id. For
example, this tree does not fork, but the parent and child must have
different ids.
<Parent>
<Child />
</Parent>
To handle this scenario, every time we materialize an id, we allocate a
new level with a single slot. You can think of this as a fork with only
one prong, or an array of children with length 1.
It's possible for the the size of the sequence to exceed 32 bits, the
max size for bitwise operations. When this happens, we make more room by
converting the right part of the id to a string and storing it in an
overflow variable. We use a base 32 string representation, because 32 is
the largest power of 2 that is supported by toString(). We want the base
to be large so that the resulting ids are compact, and we want the base
to be a power of 2 because every log2(base) bits corresponds to a single
character, i.e. every log2(32) = 5 bits. That means we can lop bits off
the end 5 at a time without affecting the final result.
* Incremental hydration
Stores the tree context on the dehydrated Suspense boundary's state
object so it resume where it left off.
* Add useId to react-debug-tools
* Add selective hydration test
Demonstrates that selective hydration works and ids are preserved even
after subsequent client updates.
* Hoist error codes import to module scope
When this code was written, the error codes map (`codes.json`) was
created on-the-fly, so we had to lazily require from inside the visitor.
Because `codes.json` is now checked into source, we can import it a
single time in module scope.
* Minify error constructors in production
We use a script to minify our error messages in production. Each message
is assigned an error code, defined in `scripts/error-codes/codes.json`.
Then our build script replaces the messages with a link to our
error decoder page, e.g. https://reactjs.org/docs/error-decoder.html/?invariant=92
This enables us to write helpful error messages without increasing the
bundle size.
Right now, the script only works for `invariant` calls. It does not work
if you throw an Error object. This is an old Facebookism that we don't
really need, other than the fact that our error minification script
relies on it.
So, I've updated the script to minify error constructors, too:
Input:
Error(`A ${adj} message that contains ${noun}`);
Output:
Error(formatProdErrorMessage(ERR_CODE, adj, noun));
It only works for constructors that are literally named Error, though we
could add support for other names, too.
As a next step, I will add a lint rule to enforce that errors written
this way must have a corresponding error code.
* Minify "no fallback UI specified" error in prod
This error message wasn't being minified because it doesn't use
invariant. The reason it didn't use invariant is because this particular
error is created without begin thrown — it doesn't need to be thrown
because it's located inside the error handling part of the runtime.
Now that the error minification script supports Error constructors, we
can minify it by assigning it a production error code in
`scripts/error-codes/codes.json`.
To support the use of Error constructors more generally, I will add a
lint rule that enforces each message has a corresponding error code.
* Lint rule to detect unminified errors
Adds a lint rule that detects when an Error constructor is used without
a corresponding production error code.
We already have this for `invariant`, but not for regular errors, i.e.
`throw new Error(msg)`. There's also nothing that enforces the use of
`invariant` besides convention.
There are some packages where we don't care to minify errors. These are
packages that run in environments where bundle size is not a concern,
like react-pg. I added an override in the ESLint config to ignore these.
* Temporarily add invariant codemod script
I'm adding this codemod to the repo temporarily, but I'll revert it
in the same PR. That way we don't have to check it in but it's still
accessible (via the PR) if we need it later.
* [Automated] Codemod invariant -> Error
This commit contains only automated changes:
npx jscodeshift -t scripts/codemod-invariant.js packages --ignore-pattern="node_modules/**/*"
yarn linc --fix
yarn prettier
I will do any manual touch ups in separate commits so they're easier
to review.
* Remove temporary codemod script
This reverts the codemod script and ESLint config I added temporarily
in order to perform the invariant codemod.
* Manual touch ups
A few manual changes I made after the codemod ran.
* Enable error code transform per package
Currently we're not consistent about which packages should have their
errors minified in production and which ones should.
This adds a field to the bundle configuration to control whether to
apply the transform. We should decide what the criteria is going
forward. I think it's probably a good idea to minify any package that
gets sent over the network. So yes to modules that run in the browser,
and no to modules that run on the server and during development only.
Recoil uses useMutableSource behind a flag. I thought this was fine
because Recoil isn't used in any concurrent roots, so the behavior
would be the same, but it turns out that it is used by concurrent
roots in a few places.
I'm not expecting it to be hard to migrate to useSyncExternalStore, but
to de-risk the change I'm going to roll it out gradually with a flag. In
the meantime, I've added back the useMutableSource API.
Adds a third argument called `getServerSnapshot`.
On the server, React calls this one instead of the normal `getSnapshot`.
We also call it during hydration.
So it represents the snapshot that is used to generate the initial,
server-rendered HTML. The purpose is to avoid server-client mismatches.
What we render during hydration needs to match up exactly with what we
render on the server.
The pattern is for the server to send down a serialized copy of the
store that was used to generate the initial HTML. On the client, React
will call either `getSnapshot` or `getServerSnapshot` on the client as
appropriate, depending on whether it's currently hydrating.
The argument is optional for fully client rendered use cases. If the
user does attempt to omit `getServerSnapshot`, and the hook is called
on the server, React will abort that subtree on the server and
revert to client rendering, up to the nearest Suspense boundary.
For the userspace shim, we will need to use a heuristic (canUseDOM)
to determine whether we are in a server environment. I'll do that in
a follow up.
* [useSyncExternalStore] Remove extra hook object
Because we already track `getSnapshot` and `value` on the store
instance, we don't need to also track them as effect dependencies. And
because the effect doesn't require any clean-up, we don't need to track
a `destroy` function.
So, we don't need to store any additional state for this effect. We can
call `pushEffect` directly, and only during renders where something
has changed.
This saves some memory, but my main motivation is because I plan to use
this same logic to schedule a pre-commit consistency check. (See the
inline comments for more details.)
* Split shouldTimeSlice into two separate functions
Lanes that are blocking (SyncLane, and DefaultLane inside a blocking-
by-default root) are always blocking for a given root. Whereas expired
lanes can expire while the render phase is already in progress.
I want to check if a lane is blocking without checking whether it
expired, so I split `shouldTimeSlice` into two separate functions.
I'll use this in the next step.
* Check for store mutations before commit
When a store is read for the first time, or when `subscribe` or
`getSnapshot` changes, during a concurrent render, we have to check
at the end of the render phase whether the store was mutated by
an concurrent event.
In the userspace shim, we perform this check in a layout effect, and
patch up any inconsistencies by scheduling another render + commit.
However, even though we patch them up in the next render, the parent
layout effects that fire in the original render will still observe an
inconsistent tree.
In the native implementation, we can instead check for inconsistencies
right after the root is completed, before entering the commit phase. If
we do detect a mutaiton, we can discard the tree and re-render before
firing any effects. The re-render is synchronous to block further
concurrent mutations (which is also what we do to recover from tearing
bugs that result in an error). After the synchronous re-render, we can
assume the tree the tree is consistent and continue with the normal
algorithm for finishing a completed root (i.e. either suspend
or commit).
The result is that layout effects will always observe a consistent tree.
Adds support for useSyncExternalStore to react-debug-tools, which in
turn adds support for React Devtools.
Test plan: I added a test to ReactHooksInspectionIntegration, based on
existing one for useMutableSource.
We added this unstable feature a few years ago, as a way to opt out of
context updates, but it didn't prove useful in practice.
We have other proposals for how to address the same problem, like
context selectors.
Since it was prefixed with `unstable_`, we should be able to remove it
without consequence. The hook API already warned if you used it.
Even if someone is using it somewhere, it's meant to be an optimization
only, so if they are using the API properly, it should not have any
semantic impact.
* Remove react/unstable_cache
We're probably going to make it available via the dispatcher. Let's remove this for now.
* Add readContext() to the dispatcher
On the server, it will be per-request.
On the client, there will be some way to shadow it.
For now, I provide it on the server, and throw on the client.
* Use readContext() from react-fetch
This makes it work on the server (but not on the client until we implement it there.)
Updated the test to use Server Components. Now it passes.
* Fixture: Add fetch from a Server Component
* readCache -> getCacheForType<T>
* Add React.unstable_getCacheForType
* Add a feature flag
* Fix Flow
* Add react-suspense-test-utils and port tests
* Remove extra Map lookup
* Unroll async/await because build system
* Add some error coverage and retry
* Add unstable_getCacheForType to Flight entry
* 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
And `useDeferredValue`.
The options were already disabled in previous commits, so this doesn't
change any behavior. I upated type signatures and cleaned up the hook
implementation a bit — no longer have to wrap the `start` method with
`useCallback`, because its only remaining dependency is a `setState`
method, which never changes. Instead, we can store the `start` method
on a ref.
Now that the options in SuspenseConfig are no longer supported, the
only thing we use it for is to track whether an update is part of
a transition.
I've renamed `ReactCurrentBatchConfig.suspense` to
`ReactCurrentBatchConfig.transition`, and changed the type to a number.
The number is always either 0 or 1. I could have made it a boolean;
however, most likely this will eventually be either a Lane or an
incrementing identifier.
The `withSuspenseConfig` export still exists until we've removed
all the callers from www.
* Add "unstbale_" prefix to mutable source APIs
* DebugHooks no longer calls useMutableSource() on init
This was causing an observable behavioral difference between experimental DEV and PROD builds.
We don't initialize stack position for other composite hooks (e.g. useDeferredValue, useTransition, useOpaqueIdentifier). If we did, it would cause the same obesrvable behavioral difference.
Some of our internal reconciler types have leaked into other packages.
Usually, these types are treated as opaque; we don't read and write
to its fields. This is good.
However, the type is often passed back to a reconciler method. For
example, React DOM creates a FiberRoot with `createContainer`, then
passes that root to `updateContainer`. It doesn't do anything with the
root except pass it through, but because `updateContainer` expects a
full FiberRoot, React DOM is still coupled to all its fields.
I don't know if there's an idiomatic way to handle this in Flow. Opaque
types are simlar, but those only work within a single file. AFAIK,
there's no way to use a package as the boundary for opaqueness.
The immediate problem this presents is that the reconciler refactor will
involve changes to our internal data structures. I don't want to have to
fork every single package that happens to pass through a Fiber or
FiberRoot, or access any one of its fields. So my current plan is to
share the same Flow type across both forks. The shared type will be a
superset of each implementation's type, e.g. Fiber will have both an
`expirationTime` field and a `lanes` field. The implementations will
diverge, but not the types.
To do this, I lifted the type definitions into a separate module.
* Add useOpaqueIdentifier Hook
We currently use unique IDs in a lot of places. Examples are:
* `<label for="ID">`
* `aria-labelledby`
This can cause some issues:
1. If we server side render and then hydrate, this could cause an
hydration ID mismatch
2. If we server side render one part of the page and client side
render another part of the page, the ID for one part could be
different than the ID for another part even though they are
supposed to be the same
3. If we conditionally render something with an ID , this might also
cause an ID mismatch because the ID will be different on other
parts of the page
This PR creates a new hook `useUniqueId` that generates a different
unique ID based on whether the hook was called on the server or client.
If the hook is called during hydration, it generates an opaque object
that will rerender the hook so that the IDs match.
Co-authored-by: Andrew Clark <git@andrewclark.io>
* Enable prefer-const rule
Stylistically I don't like this but Closure Compiler takes advantage of
this information.
* Auto-fix lints
* Manually fix the remaining callsites
* Revert "ReactDOM.useEvent: enable on internal www and add inspection test (#18395)"
This reverts commit e0ab1a429d.
* Revert "ReactDOM.useEvent: Add support for experimental scopes API (#18375)"
This reverts commit a16b349745.
* ReactDOM.useEvent: Add support for experimental scopes API
* Rename lower case isomorphic default exports modules to upper case named exports
We're somewhat inconsistent here between e.g. ReactLazy and memo.
Let's pick one.
This also moves the responder, fundamental, scope creators from shared
since they're isomorphic and same as the other creators.
* Move some files that are specific to the react-reconciler from shared
Individual renderers are allowed to deep require into the reconciler.
* Move files specific to react-dom from shared
react-interactions is right now dom specific (it wasn't before) so we can
type check it together with other dom stuff. Avoids the need for
a shared ReactDOMTypes to be checked by RN for example.
* Move ReactWorkTags to the reconciler
* Move createPortal to export from reconciler
Otherwise Noop can't access it since it's not allowed deep requires.
useMutableSource hook
useMutableSource() enables React components to safely and efficiently read from a mutable external source in Concurrent Mode. The API will detect mutations that occur during a render to avoid tearing and it will automatically schedule updates when the source is mutated.
RFC: reactjs/rfcs#147
The useState hook has always composed the useReducer hook. 1:1 composition like this is fine.
But some more recent hooks (e.g. useTransition, useDeferredValue) compose multiple hooks internally. This breaks react-debug-tools because it causes off-by-N errors when the debug tools re-renders the function.
For example, if a component were to use the useTransition and useMemo hooks, the normal hooks dispatcher would create a list of first state, then callback, then memo hooks, but the debug tools package would expect a list of transition then memo. This can break user code and cause runtime errors in both the react-debug-tools package and in product code.
This PR fixes the currently broken hooks by updating debug tools to be aware of the composite hooks (how many times it should call nextHook essentially) and adds tests to make sure they don't get out of sync again. We'll need to add similar tests for future composite hooks (like useMutableSource #18000).
* Update Flow to 0.84
* Fix violations
* Use inexact object syntax in files from fbsource
* Fix warning extraction to use a modern parser
* Codemod inexact objects to new syntax
* Tighten types that can be exact
* Revert unintentional formatting changes from codemod
* 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
* ReactDebugHooks identifies State and Reducer hooks as editable
* Inject overrideHookState() method to DevTools to support editing in DEV builds
* Added an integration test for React DevTools, react-debug-tools, and overrideHookState
* Restrict effect return type to a function or nothing
We already warn in dev if the wrong type is returned. This updates the
Flow type.
* Restrict return type further
* Assume Effect hook returns either a function or undefined
* Tweak warning message
* Improve Reducer Hook's lazy init API
* Use generic type for initilizer input
Still requires an `any` cast in the case where `init` function is
not provided.
* Move DEV-only function right above where it's used
I don't like looking at this top-level function #petty
* Use different dispatchers for functions & classes
Classes support readContext, but not any of the other dispatcher
methods. Function support all methods.
This is a more robust version of our previous strategy of checking
whether `currentlyRenderingFiber` is null.
As a next step, we can use a separate dispatcher for each phase of the
render cycle (mount versus update).
* Use separate dispatchers for mount and update
* Remove mount code from update path
Deletes mount-specific code from the update path, since it should be
unreachable. To continue supporting progressive enhancement (mounting
new hooks at the end of the list), we detect when there are no more
current hooks and switch back to the mount dispatcher. Progressive
enhancement isn't officially supported yet, so it will continue to warn.
* Factoring nits
* Fix Flow
Had to cheat more than I would like
* More Flow nits
* Switch back to using a special dispatcher for nested hooks in DEV
In order for this strategy to work, I had to revert progressive
enhancement support (appending hooks to the end). It was previously a
warning but now it results in an error. We'll reconsider later.
* Always pass args to updateState and updateReducer
Even though the extra args are only used on mount, to ensure
type consistency.
