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Check for store mutations before commit (#22290) 

* [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.
This commit is contained in:
Andrew Clark 2021-09-13 11:07:46 -04:00 committed by GitHub
parent 86c7ca70a9
commit 33226fadaa
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
10 changed files with 745 additions and 199 deletions
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1
packages/react-debug-tools/src/ReactDebugHooks.js vendored
View File

@ -273,7 +273,6 @@ function useSyncExternalStore<T>(
// Advance the current hook index the same number of times
// so that subsequent hooks have the right memoized state.
nextHook(); // SyncExternalStore
nextHook(); // LayoutEffect
nextHook(); // Effect
const value = getSnapshot();
hookLog.push({

54
packages/react-reconciler/src/ReactFiberFlags.js vendored
View File

@ -12,51 +12,53 @@ import {enableCreateEventHandleAPI} from 'shared/ReactFeatureFlags';
export type Flags = number;
// Don't change these two values. They're used by React Dev Tools.
export const NoFlags = /* */ 0b00000000000000000000000;
export const PerformedWork = /* */ 0b00000000000000000000001;
export const NoFlags = /* */ 0b000000000000000000000000;
export const PerformedWork = /* */ 0b000000000000000000000001;
// You can change the rest (and add more).
export const Placement = /* */ 0b00000000000000000000010;
export const Update = /* */ 0b00000000000000000000100;
export const Placement = /* */ 0b000000000000000000000010;
export const Update = /* */ 0b000000000000000000000100;
export const PlacementAndUpdate = /* */ Placement | Update;
export const Deletion = /* */ 0b00000000000000000001000;
export const ChildDeletion = /* */ 0b00000000000000000010000;
export const ContentReset = /* */ 0b00000000000000000100000;
export const Callback = /* */ 0b00000000000000001000000;
export const DidCapture = /* */ 0b00000000000000010000000;
export const Ref = /* */ 0b00000000000000100000000;
export const Snapshot = /* */ 0b00000000000001000000000;
export const Passive = /* */ 0b00000000000010000000000;
export const Hydrating = /* */ 0b00000000000100000000000;
export const Deletion = /* */ 0b000000000000000000001000;
export const ChildDeletion = /* */ 0b000000000000000000010000;
export const ContentReset = /* */ 0b000000000000000000100000;
export const Callback = /* */ 0b000000000000000001000000;
export const DidCapture = /* */ 0b000000000000000010000000;
export const Ref = /* */ 0b000000000000000100000000;
export const Snapshot = /* */ 0b000000000000001000000000;
export const Passive = /* */ 0b000000000000010000000000;
export const Hydrating = /* */ 0b000000000000100000000000;
export const HydratingAndUpdate = /* */ Hydrating | Update;
export const Visibility = /* */ 0b00000000001000000000000;
export const Visibility = /* */ 0b000000000001000000000000;
export const StoreConsistency = /* */ 0b000000000010000000000000;
export const LifecycleEffectMask = Passive | Update | Callback | Ref | Snapshot;
export const LifecycleEffectMask =
Passive | Update | Callback | Ref | Snapshot | StoreConsistency;
// Union of all commit flags (flags with the lifetime of a particular commit)
export const HostEffectMask = /* */ 0b00000000001111111111111;
export const HostEffectMask = /* */ 0b000000000011111111111111;
// These are not really side effects, but we still reuse this field.
export const Incomplete = /* */ 0b00000000010000000000000;
export const ShouldCapture = /* */ 0b00000000100000000000000;
export const ForceUpdateForLegacySuspense = /* */ 0b00000001000000000000000;
export const DidPropagateContext = /* */ 0b00000010000000000000000;
export const NeedsPropagation = /* */ 0b00000100000000000000000;
export const Incomplete = /* */ 0b000000000100000000000000;
export const ShouldCapture = /* */ 0b000000001000000000000000;
export const ForceUpdateForLegacySuspense = /* */ 0b000000010000000000000000;
export const DidPropagateContext = /* */ 0b000000100000000000000000;
export const NeedsPropagation = /* */ 0b000001000000000000000000;
// Static tags describe aspects of a fiber that are not specific to a render,
// e.g. a fiber uses a passive effect (even if there are no updates on this particular render).
// This enables us to defer more work in the unmount case,
// since we can defer traversing the tree during layout to look for Passive effects,
// and instead rely on the static flag as a signal that there may be cleanup work.
export const RefStatic = /* */ 0b00001000000000000000000;
export const LayoutStatic = /* */ 0b00010000000000000000000;
export const PassiveStatic = /* */ 0b00100000000000000000000;
export const RefStatic = /* */ 0b000010000000000000000000;
export const LayoutStatic = /* */ 0b000100000000000000000000;
export const PassiveStatic = /* */ 0b001000000000000000000000;
// These flags allow us to traverse to fibers that have effects on mount
// without traversing the entire tree after every commit for
// double invoking
export const MountLayoutDev = /* */ 0b01000000000000000000000;
export const MountPassiveDev = /* */ 0b10000000000000000000000;
export const MountLayoutDev = /* */ 0b010000000000000000000000;
export const MountPassiveDev = /* */ 0b100000000000000000000000;
// Groups of flags that are used in the commit phase to skip over trees that
// don't contain effects, by checking subtreeFlags.

183
packages/react-reconciler/src/ReactFiberHooks.new.js
View File

@ -44,6 +44,7 @@ import {
SyncLane,
NoLanes,
isSubsetOfLanes,
includesBlockingLane,
mergeLanes,
removeLanes,
intersectLanes,
@ -68,6 +69,7 @@ import {
PassiveStatic as PassiveStaticEffect,
StaticMask as StaticMaskEffect,
Update as UpdateEffect,
StoreConsistency,
} from './ReactFiberFlags';
import {
HasEffect as HookHasEffect,
@ -166,7 +168,15 @@ type StoreInstance<T> = {|
getSnapshot: () => T,
|};
export type FunctionComponentUpdateQueue = {|lastEffect: Effect | null|};
type StoreConsistencyCheck<T> = {|
value: T,
getSnapshot: () => T,
|};
export type FunctionComponentUpdateQueue = {|
lastEffect: Effect | null,
stores: Array<StoreConsistencyCheck<any>> | null,
|};
type BasicStateAction<S> = (S => S) | S;
@ -689,6 +699,7 @@ function updateWorkInProgressHook(): Hook {
function createFunctionComponentUpdateQueue(): FunctionComponentUpdateQueue {
return {
lastEffect: null,
stores: null,
};
}
@ -1256,6 +1267,7 @@ function mountSyncExternalStore<T>(
subscribe: (() => void) => () => void,
getSnapshot: () => T,
): T {
const fiber = currentlyRenderingFiber;
const hook = mountWorkInProgressHook();
// Read the current snapshot from the store on every render. This breaks the
// normal rules of React, and only works because store updates are
@ -1277,13 +1289,45 @@ function mountSyncExternalStore<T>(
getSnapshot,
};
hook.queue = inst;
return useSyncExternalStore(hook, inst, subscribe, getSnapshot, nextSnapshot);
// Schedule an effect to subscribe to the store.
mountEffect(subscribeToStore.bind(null, fiber, inst, subscribe), [subscribe]);
// Schedule an effect to update the mutable instance fields. We will update
// this whenever subscribe, getSnapshot, or value changes. Because there's no
// clean-up function, and we track the deps correctly, we can call pushEffect
// directly, without storing any additional state. For the same reason, we
// don't need to set a static flag, either.
// TODO: We can move this to the passive phase once we add a pre-commit
// consistency check. See the next comment.
fiber.flags |= PassiveEffect;
pushEffect(
HookHasEffect | HookPassive,
updateStoreInstance.bind(null, fiber, inst, nextSnapshot, getSnapshot),
undefined,
null,
);
// Unless we're rendering a blocking lane, schedule a consistency check. Right
// before committing, we will walk the tree and check if any of the stores
// were mutated.
const root: FiberRoot | null = getWorkInProgressRoot();
invariant(
root !== null,
'Expected a work-in-progress root. This is a bug in React. Please file an issue.',
);
if (!includesBlockingLane(root, renderLanes)) {
pushStoreConsistencyCheck(fiber, getSnapshot, nextSnapshot);
}
return nextSnapshot;
}
function updateSyncExternalStore<T>(
subscribe: (() => void) => () => void,
getSnapshot: () => T,
): T {
const fiber = currentlyRenderingFiber;
const hook = updateWorkInProgressHook();
// Read the current snapshot from the store on every render. This breaks the
// normal rules of React, and only works because store updates are
@ -1300,66 +1344,109 @@ function updateSyncExternalStore<T>(
}
}
const prevSnapshot = hook.memoizedState;
if (!is(prevSnapshot, nextSnapshot)) {
const snapshotChanged = !is(prevSnapshot, nextSnapshot);
if (snapshotChanged) {
hook.memoizedState = nextSnapshot;
markWorkInProgressReceivedUpdate();
}
const inst = hook.queue;
return useSyncExternalStore(hook, inst, subscribe, getSnapshot, nextSnapshot);
updateEffect(subscribeToStore.bind(null, fiber, inst, subscribe), [
subscribe,
]);
// Whenever getSnapshot or subscribe changes, we need to check in the
// commit phase if there was an interleaved mutation. In concurrent mode
// this can happen all the time, but even in synchronous mode, an earlier
// effect may have mutated the store.
if (
inst.getSnapshot !== getSnapshot ||
snapshotChanged ||
// Check if the susbcribe function changed. We can save some memory by
// checking whether we scheduled a subscription effect above.
(workInProgressHook !== null &&
workInProgressHook.memoizedState.tag & HookHasEffect)
) {
fiber.flags |= PassiveEffect;
pushEffect(
HookHasEffect | HookPassive,
updateStoreInstance.bind(null, fiber, inst, nextSnapshot, getSnapshot),
undefined,
null,
);
// Unless we're rendering a blocking lane, schedule a consistency check.
// Right before committing, we will walk the tree and check if any of the
// stores were mutated.
const root: FiberRoot | null = getWorkInProgressRoot();
invariant(
root !== null,
'Expected a work-in-progress root. This is a bug in React. Please file an issue.',
);
if (!includesBlockingLane(root, renderLanes)) {
pushStoreConsistencyCheck(fiber, getSnapshot, nextSnapshot);
}
}
return nextSnapshot;
}
function useSyncExternalStore<T>(
hook: Hook,
inst: StoreInstance<T>,
subscribe: (() => void) => () => void,
function pushStoreConsistencyCheck<T>(
fiber: Fiber,
getSnapshot: () => T,
renderedSnapshot: T,
) {
fiber.flags |= StoreConsistency;
const check: StoreConsistencyCheck<T> = {
getSnapshot,
value: renderedSnapshot,
};
let componentUpdateQueue: null | FunctionComponentUpdateQueue = (currentlyRenderingFiber.updateQueue: any);
if (componentUpdateQueue === null) {
componentUpdateQueue = createFunctionComponentUpdateQueue();
currentlyRenderingFiber.updateQueue = (componentUpdateQueue: any);
componentUpdateQueue.stores = [check];
} else {
const stores = componentUpdateQueue.stores;
if (stores === null) {
componentUpdateQueue.stores = [check];
} else {
stores.push(check);
}
}
}
function updateStoreInstance<T>(
fiber: Fiber,
inst: StoreInstance<T>,
nextSnapshot: T,
): T {
const fiber = currentlyRenderingFiber;
const dispatcher = ReactCurrentDispatcher.current;
getSnapshot: () => T,
) {
// These are updated in the passive phase
inst.value = nextSnapshot;
inst.getSnapshot = getSnapshot;
// Track the latest getSnapshot function with a ref. This needs to be updated
// in the layout phase so we can access it during the tearing check that
// happens on subscribe.
// TODO: Circumvent SSR warning
dispatcher.useLayoutEffect(() => {
inst.value = nextSnapshot;
inst.getSnapshot = getSnapshot;
// Something may have been mutated in between render and commit. This could
// have been in an event that fired before the passive effects, or it could
// have been in a layout effect. In that case, we would have used the old
// snapsho and getSnapshot values to bail out. We need to check one more time.
if (checkIfSnapshotChanged(inst)) {
// Force a re-render.
forceStoreRerender(fiber);
}
}
// Whenever getSnapshot or subscribe changes, we need to check in the
// commit phase if there was an interleaved mutation. In concurrent mode
// this can happen all the time, but even in synchronous mode, an earlier
// effect may have mutated the store.
// TODO: Move the tearing checks to an earlier, pre-commit phase so that the
// layout effects always observe a consistent tree.
function subscribeToStore(fiber, inst, subscribe) {
const handleStoreChange = () => {
// The store changed. Check if the snapshot changed since the last time we
// read from the store.
if (checkIfSnapshotChanged(inst)) {
// Force a re-render.
forceStoreRerender(fiber);
}
}, [subscribe, nextSnapshot, getSnapshot]);
dispatcher.useEffect(() => {
const handleStoreChange = () => {
// TODO: Because there is no cross-renderer API for batching updates, it's
// up to the consumer of this library to wrap their subscription event
// with unstable_batchedUpdates. Should we try to detect when this isn't
// the case and print a warning in development?
// The store changed. Check if the snapshot changed since the last time we
// read from the store.
if (checkIfSnapshotChanged(inst)) {
// Force a re-render.
forceStoreRerender(fiber);
}
};
// Check for changes right before subscribing. Subsequent changes will be
// detected in the subscription handler.
handleStoreChange();
// Subscribe to the store and return a clean-up function.
return subscribe(handleStoreChange);
}, [subscribe]);
return nextSnapshot;
};
// Subscribe to the store and return a clean-up function.
return subscribe(handleStoreChange);
}
function checkIfSnapshotChanged(inst) {

183
packages/react-reconciler/src/ReactFiberHooks.old.js
View File

@ -44,6 +44,7 @@ import {
SyncLane,
NoLanes,
isSubsetOfLanes,
includesBlockingLane,
mergeLanes,
removeLanes,
intersectLanes,
@ -68,6 +69,7 @@ import {
PassiveStatic as PassiveStaticEffect,
StaticMask as StaticMaskEffect,
Update as UpdateEffect,
StoreConsistency,
} from './ReactFiberFlags';
import {
HasEffect as HookHasEffect,
@ -166,7 +168,15 @@ type StoreInstance<T> = {|
getSnapshot: () => T,
|};
export type FunctionComponentUpdateQueue = {|lastEffect: Effect | null|};
type StoreConsistencyCheck<T> = {|
value: T,
getSnapshot: () => T,
|};
export type FunctionComponentUpdateQueue = {|
lastEffect: Effect | null,
stores: Array<StoreConsistencyCheck<any>> | null,
|};
type BasicStateAction<S> = (S => S) | S;
@ -689,6 +699,7 @@ function updateWorkInProgressHook(): Hook {
function createFunctionComponentUpdateQueue(): FunctionComponentUpdateQueue {
return {
lastEffect: null,
stores: null,
};
}
@ -1256,6 +1267,7 @@ function mountSyncExternalStore<T>(
subscribe: (() => void) => () => void,
getSnapshot: () => T,
): T {
const fiber = currentlyRenderingFiber;
const hook = mountWorkInProgressHook();
// Read the current snapshot from the store on every render. This breaks the
// normal rules of React, and only works because store updates are
@ -1277,13 +1289,45 @@ function mountSyncExternalStore<T>(
getSnapshot,
};
hook.queue = inst;
return useSyncExternalStore(hook, inst, subscribe, getSnapshot, nextSnapshot);
// Schedule an effect to subscribe to the store.
mountEffect(subscribeToStore.bind(null, fiber, inst, subscribe), [subscribe]);
// Schedule an effect to update the mutable instance fields. We will update
// this whenever subscribe, getSnapshot, or value changes. Because there's no
// clean-up function, and we track the deps correctly, we can call pushEffect
// directly, without storing any additional state. For the same reason, we
// don't need to set a static flag, either.
// TODO: We can move this to the passive phase once we add a pre-commit
// consistency check. See the next comment.
fiber.flags |= PassiveEffect;
pushEffect(
HookHasEffect | HookPassive,
updateStoreInstance.bind(null, fiber, inst, nextSnapshot, getSnapshot),
undefined,
null,
);
// Unless we're rendering a blocking lane, schedule a consistency check. Right
// before committing, we will walk the tree and check if any of the stores
// were mutated.
const root: FiberRoot | null = getWorkInProgressRoot();
invariant(
root !== null,
'Expected a work-in-progress root. This is a bug in React. Please file an issue.',
);
if (!includesBlockingLane(root, renderLanes)) {
pushStoreConsistencyCheck(fiber, getSnapshot, nextSnapshot);
}
return nextSnapshot;
}
function updateSyncExternalStore<T>(
subscribe: (() => void) => () => void,
getSnapshot: () => T,
): T {
const fiber = currentlyRenderingFiber;
const hook = updateWorkInProgressHook();
// Read the current snapshot from the store on every render. This breaks the
// normal rules of React, and only works because store updates are
@ -1300,66 +1344,109 @@ function updateSyncExternalStore<T>(
}
}
const prevSnapshot = hook.memoizedState;
if (!is(prevSnapshot, nextSnapshot)) {
const snapshotChanged = !is(prevSnapshot, nextSnapshot);
if (snapshotChanged) {
hook.memoizedState = nextSnapshot;
markWorkInProgressReceivedUpdate();
}
const inst = hook.queue;
return useSyncExternalStore(hook, inst, subscribe, getSnapshot, nextSnapshot);
updateEffect(subscribeToStore.bind(null, fiber, inst, subscribe), [
subscribe,
]);
// Whenever getSnapshot or subscribe changes, we need to check in the
// commit phase if there was an interleaved mutation. In concurrent mode
// this can happen all the time, but even in synchronous mode, an earlier
// effect may have mutated the store.
if (
inst.getSnapshot !== getSnapshot ||
snapshotChanged ||
// Check if the susbcribe function changed. We can save some memory by
// checking whether we scheduled a subscription effect above.
(workInProgressHook !== null &&
workInProgressHook.memoizedState.tag & HookHasEffect)
) {
fiber.flags |= PassiveEffect;
pushEffect(
HookHasEffect | HookPassive,
updateStoreInstance.bind(null, fiber, inst, nextSnapshot, getSnapshot),
undefined,
null,
);
// Unless we're rendering a blocking lane, schedule a consistency check.
// Right before committing, we will walk the tree and check if any of the
// stores were mutated.
const root: FiberRoot | null = getWorkInProgressRoot();
invariant(
root !== null,
'Expected a work-in-progress root. This is a bug in React. Please file an issue.',
);
if (!includesBlockingLane(root, renderLanes)) {
pushStoreConsistencyCheck(fiber, getSnapshot, nextSnapshot);
}
}
return nextSnapshot;
}
function useSyncExternalStore<T>(
hook: Hook,
inst: StoreInstance<T>,
subscribe: (() => void) => () => void,
function pushStoreConsistencyCheck<T>(
fiber: Fiber,
getSnapshot: () => T,
renderedSnapshot: T,
) {
fiber.flags |= StoreConsistency;
const check: StoreConsistencyCheck<T> = {
getSnapshot,
value: renderedSnapshot,
};
let componentUpdateQueue: null | FunctionComponentUpdateQueue = (currentlyRenderingFiber.updateQueue: any);
if (componentUpdateQueue === null) {
componentUpdateQueue = createFunctionComponentUpdateQueue();
currentlyRenderingFiber.updateQueue = (componentUpdateQueue: any);
componentUpdateQueue.stores = [check];
} else {
const stores = componentUpdateQueue.stores;
if (stores === null) {
componentUpdateQueue.stores = [check];
} else {
stores.push(check);
}
}
}
function updateStoreInstance<T>(
fiber: Fiber,
inst: StoreInstance<T>,
nextSnapshot: T,
): T {
const fiber = currentlyRenderingFiber;
const dispatcher = ReactCurrentDispatcher.current;
getSnapshot: () => T,
) {
// These are updated in the passive phase
inst.value = nextSnapshot;
inst.getSnapshot = getSnapshot;
// Track the latest getSnapshot function with a ref. This needs to be updated
// in the layout phase so we can access it during the tearing check that
// happens on subscribe.
// TODO: Circumvent SSR warning
dispatcher.useLayoutEffect(() => {
inst.value = nextSnapshot;
inst.getSnapshot = getSnapshot;
// Something may have been mutated in between render and commit. This could
// have been in an event that fired before the passive effects, or it could
// have been in a layout effect. In that case, we would have used the old
// snapsho and getSnapshot values to bail out. We need to check one more time.
if (checkIfSnapshotChanged(inst)) {
// Force a re-render.
forceStoreRerender(fiber);
}
}
// Whenever getSnapshot or subscribe changes, we need to check in the
// commit phase if there was an interleaved mutation. In concurrent mode
// this can happen all the time, but even in synchronous mode, an earlier
// effect may have mutated the store.
// TODO: Move the tearing checks to an earlier, pre-commit phase so that the
// layout effects always observe a consistent tree.
function subscribeToStore(fiber, inst, subscribe) {
const handleStoreChange = () => {
// The store changed. Check if the snapshot changed since the last time we
// read from the store.
if (checkIfSnapshotChanged(inst)) {
// Force a re-render.
forceStoreRerender(fiber);
}
}, [subscribe, nextSnapshot, getSnapshot]);
dispatcher.useEffect(() => {
const handleStoreChange = () => {
// TODO: Because there is no cross-renderer API for batching updates, it's
// up to the consumer of this library to wrap their subscription event
// with unstable_batchedUpdates. Should we try to detect when this isn't
// the case and print a warning in development?
// The store changed. Check if the snapshot changed since the last time we
// read from the store.
if (checkIfSnapshotChanged(inst)) {
// Force a re-render.
forceStoreRerender(fiber);
}
};
// Check for changes right before subscribing. Subsequent changes will be
// detected in the subscription handler.
handleStoreChange();
// Subscribe to the store and return a clean-up function.
return subscribe(handleStoreChange);
}, [subscribe]);
return nextSnapshot;
};
// Subscribe to the store and return a clean-up function.
return subscribe(handleStoreChange);
}
function checkIfSnapshotChanged(inst) {

19
packages/react-reconciler/src/ReactFiberLane.new.js
View File

@ -453,27 +453,26 @@ export function includesOnlyTransitions(lanes: Lanes) {
return (lanes & TransitionLanes) === lanes;
}
export function shouldTimeSlice(root: FiberRoot, lanes: Lanes) {
if ((lanes & root.expiredLanes) !== NoLanes) {
// At least one of these lanes expired. To prevent additional starvation,
// finish rendering without yielding execution.
return false;
}
export function includesBlockingLane(root: FiberRoot, lanes: Lanes) {
if (
allowConcurrentByDefault &&
(root.current.mode & ConcurrentUpdatesByDefaultMode) !== NoMode
) {
// Concurrent updates by default always use time slicing.
return true;
return false;
}
const SyncDefaultLanes =
InputContinuousHydrationLane |
InputContinuousLane |
DefaultHydrationLane |
DefaultLane;
return (lanes & SyncDefaultLanes) === NoLanes;
return (lanes & SyncDefaultLanes) !== NoLanes;
}
export function includesExpiredLane(root: FiberRoot, lanes: Lanes) {
// This is a separate check from includesBlockingLane because a lane can
// expire after a render has already started.
return (lanes & root.expiredLanes) !== NoLanes;
}
export function isTransitionLane(lane: Lane) {

19
packages/react-reconciler/src/ReactFiberLane.old.js
View File

@ -453,27 +453,26 @@ export function includesOnlyTransitions(lanes: Lanes) {
return (lanes & TransitionLanes) === lanes;
}
export function shouldTimeSlice(root: FiberRoot, lanes: Lanes) {
if ((lanes & root.expiredLanes) !== NoLanes) {
// At least one of these lanes expired. To prevent additional starvation,
// finish rendering without yielding execution.
return false;
}
export function includesBlockingLane(root: FiberRoot, lanes: Lanes) {
if (
allowConcurrentByDefault &&
(root.current.mode & ConcurrentUpdatesByDefaultMode) !== NoMode
) {
// Concurrent updates by default always use time slicing.
return true;
return false;
}
const SyncDefaultLanes =
InputContinuousHydrationLane |
InputContinuousLane |
DefaultHydrationLane |
DefaultLane;
return (lanes & SyncDefaultLanes) === NoLanes;
return (lanes & SyncDefaultLanes) !== NoLanes;
}
export function includesExpiredLane(root: FiberRoot, lanes: Lanes) {
// This is a separate check from includesBlockingLane because a lane can
// expire after a render has already started.
return (lanes & root.expiredLanes) !== NoLanes;
}
export function isTransitionLane(lane: Lane) {

152
packages/react-reconciler/src/ReactFiberWorkLoop.new.js
View File

@ -13,6 +13,7 @@ import type {Lanes, Lane} from './ReactFiberLane.new';
import type {SuspenseState} from './ReactFiberSuspenseComponent.new';
import type {StackCursor} from './ReactFiberStack.new';
import type {Flags} from './ReactFiberFlags';
import type {FunctionComponentUpdateQueue} from './ReactFiberHooks.new';
import {
warnAboutDeprecatedLifecycles,
@ -34,6 +35,7 @@ import {
} from 'shared/ReactFeatureFlags';
import ReactSharedInternals from 'shared/ReactSharedInternals';
import invariant from 'shared/invariant';
import is from 'shared/objectIs';
import {
// Aliased because `act` will override and push to an internal queue
@ -116,6 +118,7 @@ import {
NoFlags,
Placement,
Incomplete,
StoreConsistency,
HostEffectMask,
Hydrating,
BeforeMutationMask,
@ -140,7 +143,8 @@ import {
includesNonIdleWork,
includesOnlyRetries,
includesOnlyTransitions,
shouldTimeSlice,
includesBlockingLane,
includesExpiredLane,
getNextLanes,
markStarvedLanesAsExpired,
getLanesToRetrySynchronouslyOnError,
@ -769,39 +773,25 @@ function performConcurrentWorkOnRoot(root, didTimeout) {
// TODO: We only check `didTimeout` defensively, to account for a Scheduler
// bug we're still investigating. Once the bug in Scheduler is fixed,
// we can remove this, since we track expiration ourselves.
let exitStatus =
shouldTimeSlice(root, lanes) &&
(disableSchedulerTimeoutInWorkLoop || !didTimeout)
? renderRootConcurrent(root, lanes)
: renderRootSync(root, lanes);
const shouldTimeSlice =
!includesBlockingLane(root, lanes) &&
!includesExpiredLane(root, lanes) &&
(disableSchedulerTimeoutInWorkLoop || !didTimeout);
let exitStatus = shouldTimeSlice
? renderRootConcurrent(root, lanes)
: renderRootSync(root, lanes);
if (exitStatus !== RootIncomplete) {
if (exitStatus === RootErrored) {
const prevExecutionContext = executionContext;
executionContext |= RetryAfterError;
// If an error occurred during hydration,
// discard server response and fall back to client side render.
if (root.hydrate) {
root.hydrate = false;
if (__DEV__) {
errorHydratingContainer(root.containerInfo);
}
clearContainer(root.containerInfo);
}
// If something threw an error, try rendering one more time. We'll render
// synchronously to block concurrent data mutations, and we'll includes
// all pending updates are included. If it still fails after the second
// attempt, we'll give up and commit the resulting tree.
// If something threw an error, try rendering one more time. We'll
// render synchronously to block concurrent data mutations, and we'll
// includes all pending updates are included. If it still fails after
// the second attempt, we'll give up and commit the resulting tree.
const errorRetryLanes = getLanesToRetrySynchronouslyOnError(root);
if (errorRetryLanes !== NoLanes) {
lanes = errorRetryLanes;
exitStatus = renderRootSync(root, errorRetryLanes);
exitStatus = recoverFromConcurrentError(root, errorRetryLanes);
}
executionContext = prevExecutionContext;
}
if (exitStatus === RootFatalErrored) {
const fatalError = workInProgressRootFatalError;
prepareFreshStack(root, NoLanes);
@ -810,9 +800,42 @@ function performConcurrentWorkOnRoot(root, didTimeout) {
throw fatalError;
}
// Check if this render may have yielded to a concurrent event, and if so,
// confirm that any newly rendered stores are consistent.
// TODO: It's possible that even a concurrent render may never have yielded
// to the main thread, if it was fast enough, or if it expired. We could
// skip the consistency check in that case, too.
const renderWasConcurrent = !includesBlockingLane(root, lanes);
const finishedWork: Fiber = (root.current.alternate: any);
if (
renderWasConcurrent &&
!isRenderConsistentWithExternalStores(finishedWork)
) {
// A store was mutated in an interleaved event. Render again,
// synchronously, to block further mutations.
exitStatus = renderRootSync(root, lanes);
// We need to check again if something threw
if (exitStatus === RootErrored) {
const errorRetryLanes = getLanesToRetrySynchronouslyOnError(root);
if (errorRetryLanes !== NoLanes) {
lanes = errorRetryLanes;
exitStatus = recoverFromConcurrentError(root, errorRetryLanes);
// We assume the tree is now consistent because we didn't yield to any
// concurrent events.
}
}
if (exitStatus === RootFatalErrored) {
const fatalError = workInProgressRootFatalError;
prepareFreshStack(root, NoLanes);
markRootSuspended(root, lanes);
ensureRootIsScheduled(root, now());
throw fatalError;
}
}
// We now have a consistent tree. The next step is either to commit it,
// or, if something suspended, wait to commit it after a timeout.
const finishedWork: Fiber = (root.current.alternate: any);
root.finishedWork = finishedWork;
root.finishedLanes = lanes;
finishConcurrentRender(root, exitStatus, lanes);
@ -827,6 +850,27 @@ function performConcurrentWorkOnRoot(root, didTimeout) {
return null;
}
function recoverFromConcurrentError(root, errorRetryLanes) {
const prevExecutionContext = executionContext;
executionContext |= RetryAfterError;
// If an error occurred during hydration, discard server response and fall
// back to client side render.
if (root.hydrate) {
root.hydrate = false;
if (__DEV__) {
errorHydratingContainer(root.containerInfo);
}
clearContainer(root.containerInfo);
}
const exitStatus = renderRootSync(root, errorRetryLanes);
executionContext = prevExecutionContext;
return exitStatus;
}
function finishConcurrentRender(root, exitStatus, lanes) {
switch (exitStatus) {
case RootIncomplete:
@ -939,6 +983,58 @@ function finishConcurrentRender(root, exitStatus, lanes) {
}
}
function isRenderConsistentWithExternalStores(finishedWork: Fiber): boolean {
// Search the rendered tree for external store reads, and check whether the
// stores were mutated in a concurrent event. Intentionally using a iterative
// loop instead of recursion so we can exit early.
let node: Fiber = finishedWork;
while (true) {
if (node.flags & StoreConsistency) {
const updateQueue: FunctionComponentUpdateQueue | null = (node.updateQueue: any);
if (updateQueue !== null) {
const checks = updateQueue.stores;
if (checks !== null) {
for (let i = 0; i < checks.length; i++) {
const check = checks[i];
const getSnapshot = check.getSnapshot;
const renderedValue = check.value;
try {
if (!is(getSnapshot(), renderedValue)) {
// Found an inconsistent store.
return false;
}
} catch (error) {
// If `getSnapshot` throws, return `false`. This will schedule
// a re-render, and the error will be rethrown during render.
return false;
}
}
}
}
}
const child = node.child;
if (node.subtreeFlags & StoreConsistency && child !== null) {
child.return = node;
node = child;
continue;
}
if (node === finishedWork) {
return true;
}
while (node.sibling === null) {
if (node.return === null || node.return === finishedWork) {
return true;
}
node = node.return;
}
node.sibling.return = node.return;
node = node.sibling;
}
// Flow doesn't know this is unreachable, but eslint does
// eslint-disable-next-line no-unreachable
return true;
}
function markRootSuspended(root, suspendedLanes) {
// When suspending, we should always exclude lanes that were pinged or (more
// rarely, since we try to avoid it) updated during the render phase.

152
packages/react-reconciler/src/ReactFiberWorkLoop.old.js
View File

@ -13,6 +13,7 @@ import type {Lanes, Lane} from './ReactFiberLane.old';
import type {SuspenseState} from './ReactFiberSuspenseComponent.old';
import type {StackCursor} from './ReactFiberStack.old';
import type {Flags} from './ReactFiberFlags';
import type {FunctionComponentUpdateQueue} from './ReactFiberHooks.old';
import {
warnAboutDeprecatedLifecycles,
@ -34,6 +35,7 @@ import {
} from 'shared/ReactFeatureFlags';
import ReactSharedInternals from 'shared/ReactSharedInternals';
import invariant from 'shared/invariant';
import is from 'shared/objectIs';
import {
// Aliased because `act` will override and push to an internal queue
@ -116,6 +118,7 @@ import {
NoFlags,
Placement,
Incomplete,
StoreConsistency,
HostEffectMask,
Hydrating,
BeforeMutationMask,
@ -140,7 +143,8 @@ import {
includesNonIdleWork,
includesOnlyRetries,
includesOnlyTransitions,
shouldTimeSlice,
includesBlockingLane,
includesExpiredLane,
getNextLanes,
markStarvedLanesAsExpired,
getLanesToRetrySynchronouslyOnError,
@ -769,39 +773,25 @@ function performConcurrentWorkOnRoot(root, didTimeout) {
// TODO: We only check `didTimeout` defensively, to account for a Scheduler
// bug we're still investigating. Once the bug in Scheduler is fixed,
// we can remove this, since we track expiration ourselves.
let exitStatus =
shouldTimeSlice(root, lanes) &&
(disableSchedulerTimeoutInWorkLoop || !didTimeout)
? renderRootConcurrent(root, lanes)
: renderRootSync(root, lanes);
const shouldTimeSlice =
!includesBlockingLane(root, lanes) &&
!includesExpiredLane(root, lanes) &&
(disableSchedulerTimeoutInWorkLoop || !didTimeout);
let exitStatus = shouldTimeSlice
? renderRootConcurrent(root, lanes)
: renderRootSync(root, lanes);
if (exitStatus !== RootIncomplete) {
if (exitStatus === RootErrored) {
const prevExecutionContext = executionContext;
executionContext |= RetryAfterError;
// If an error occurred during hydration,
// discard server response and fall back to client side render.
if (root.hydrate) {
root.hydrate = false;
if (__DEV__) {
errorHydratingContainer(root.containerInfo);
}
clearContainer(root.containerInfo);
}
// If something threw an error, try rendering one more time. We'll render
// synchronously to block concurrent data mutations, and we'll includes
// all pending updates are included. If it still fails after the second
// attempt, we'll give up and commit the resulting tree.
// If something threw an error, try rendering one more time. We'll
// render synchronously to block concurrent data mutations, and we'll
// includes all pending updates are included. If it still fails after
// the second attempt, we'll give up and commit the resulting tree.
const errorRetryLanes = getLanesToRetrySynchronouslyOnError(root);
if (errorRetryLanes !== NoLanes) {
lanes = errorRetryLanes;
exitStatus = renderRootSync(root, errorRetryLanes);
exitStatus = recoverFromConcurrentError(root, errorRetryLanes);
}
executionContext = prevExecutionContext;
}
if (exitStatus === RootFatalErrored) {
const fatalError = workInProgressRootFatalError;
prepareFreshStack(root, NoLanes);
@ -810,9 +800,42 @@ function performConcurrentWorkOnRoot(root, didTimeout) {
throw fatalError;
}
// Check if this render may have yielded to a concurrent event, and if so,
// confirm that any newly rendered stores are consistent.
// TODO: It's possible that even a concurrent render may never have yielded
// to the main thread, if it was fast enough, or if it expired. We could
// skip the consistency check in that case, too.
const renderWasConcurrent = !includesBlockingLane(root, lanes);
const finishedWork: Fiber = (root.current.alternate: any);
if (
renderWasConcurrent &&
!isRenderConsistentWithExternalStores(finishedWork)
) {
// A store was mutated in an interleaved event. Render again,
// synchronously, to block further mutations.
exitStatus = renderRootSync(root, lanes);
// We need to check again if something threw
if (exitStatus === RootErrored) {
const errorRetryLanes = getLanesToRetrySynchronouslyOnError(root);
if (errorRetryLanes !== NoLanes) {
lanes = errorRetryLanes;
exitStatus = recoverFromConcurrentError(root, errorRetryLanes);
// We assume the tree is now consistent because we didn't yield to any
// concurrent events.
}
}
if (exitStatus === RootFatalErrored) {
const fatalError = workInProgressRootFatalError;
prepareFreshStack(root, NoLanes);
markRootSuspended(root, lanes);
ensureRootIsScheduled(root, now());
throw fatalError;
}
}
// We now have a consistent tree. The next step is either to commit it,
// or, if something suspended, wait to commit it after a timeout.
const finishedWork: Fiber = (root.current.alternate: any);
root.finishedWork = finishedWork;
root.finishedLanes = lanes;
finishConcurrentRender(root, exitStatus, lanes);
@ -827,6 +850,27 @@ function performConcurrentWorkOnRoot(root, didTimeout) {
return null;
}
function recoverFromConcurrentError(root, errorRetryLanes) {
const prevExecutionContext = executionContext;
executionContext |= RetryAfterError;
// If an error occurred during hydration, discard server response and fall
// back to client side render.
if (root.hydrate) {
root.hydrate = false;
if (__DEV__) {
errorHydratingContainer(root.containerInfo);
}
clearContainer(root.containerInfo);
}
const exitStatus = renderRootSync(root, errorRetryLanes);
executionContext = prevExecutionContext;
return exitStatus;
}
function finishConcurrentRender(root, exitStatus, lanes) {
switch (exitStatus) {
case RootIncomplete:
@ -939,6 +983,58 @@ function finishConcurrentRender(root, exitStatus, lanes) {
}
}
function isRenderConsistentWithExternalStores(finishedWork: Fiber): boolean {
// Search the rendered tree for external store reads, and check whether the
// stores were mutated in a concurrent event. Intentionally using a iterative
// loop instead of recursion so we can exit early.
let node: Fiber = finishedWork;
while (true) {
if (node.flags & StoreConsistency) {
const updateQueue: FunctionComponentUpdateQueue | null = (node.updateQueue: any);
if (updateQueue !== null) {
const checks = updateQueue.stores;
if (checks !== null) {
for (let i = 0; i < checks.length; i++) {
const check = checks[i];
const getSnapshot = check.getSnapshot;
const renderedValue = check.value;
try {
if (!is(getSnapshot(), renderedValue)) {
// Found an inconsistent store.
return false;
}
} catch (error) {
// If `getSnapshot` throws, return `false`. This will schedule
// a re-render, and the error will be rethrown during render.
return false;
}
}
}
}
}
const child = node.child;
if (node.subtreeFlags & StoreConsistency && child !== null) {
child.return = node;
node = child;
continue;
}
if (node === finishedWork) {
return true;
}
while (node.sibling === null) {
if (node.return === null || node.return === finishedWork) {
return true;
}
node = node.return;
}
node.sibling.return = node.return;
node = node.sibling;
}
// Flow doesn't know this is unreachable, but eslint does
// eslint-disable-next-line no-unreachable
return true;
}
function markRootSuspended(root, suspendedLanes) {
// When suspending, we should always exclude lanes that were pinged or (more
// rarely, since we try to avoid it) updated during the render phase.

177
packages/react-reconciler/src/__tests__/useSyncExternalStore-test.js vendored Normal file
View File

@ -0,0 +1,177 @@
/**
* Copyright (c) Facebook, Inc. and its affiliates.
*
* This source code is licensed under the MIT license found in the
* LICENSE file in the root directory of this source tree.
*
* @emails react-core
*/
'use strict';
let useSyncExternalStore;
let React;
let ReactNoop;
let Scheduler;
let act;
let useLayoutEffect;
let forwardRef;
let useImperativeHandle;
let useRef;
let startTransition;
// This tests the native useSyncExternalStore implementation, not the shim.
// Tests that apply to both the native implementation and the shim should go
// into useSyncExternalStoreShared-test.js. The reason they are separate is
// because at some point we may start running the shared tests against vendored
// React DOM versions (16, 17, etc) instead of React Noop.
describe('useSyncExternalStore', () => {
beforeEach(() => {
jest.resetModules();
React = require('react');
ReactNoop = require('react-noop-renderer');
Scheduler = require('scheduler');
useLayoutEffect = React.useLayoutEffect;
useImperativeHandle = React.useImperativeHandle;
forwardRef = React.forwardRef;
useRef = React.useRef;
useSyncExternalStore = React.unstable_useSyncExternalStore;
startTransition = React.startTransition;
act = require('jest-react').act;
});
function Text({text}) {
Scheduler.unstable_yieldValue(text);
return text;
}
function createExternalStore(initialState) {
const listeners = new Set();
let currentState = initialState;
return {
set(text) {
currentState = text;
ReactNoop.batchedUpdates(() => {
listeners.forEach(listener => listener());
});
},
subscribe(listener) {
listeners.add(listener);
return () => listeners.delete(listener);
},
getState() {
return currentState;
},
getSubscriberCount() {
return listeners.size;
},
};
}
// @gate supportsNativeUseSyncExternalStore
test(
'detects interleaved mutations during a concurrent read before ' +
'layout effects fire',
async () => {
const store1 = createExternalStore(0);
const store2 = createExternalStore(0);
const Child = forwardRef(({store, label}, ref) => {
const value = useSyncExternalStore(store.subscribe, store.getState);
useImperativeHandle(
ref,
() => {
return value;
},
[],
);
return <Text text={label + value} />;
});
function App({store}) {
const refA = useRef(null);
const refB = useRef(null);
const refC = useRef(null);
useLayoutEffect(() => {
// This layout effect reads children that depend on an external store.
// This demostrates whether the children are consistent when the
// layout phase runs.
const aText = refA.current;
const bText = refB.current;
const cText = refC.current;
Scheduler.unstable_yieldValue(
`Children observed during layout: A${aText}B${bText}C${cText}`,
);
});
return (
<>
<Child store={store} ref={refA} label="A" />
<Child store={store} ref={refB} label="B" />
<Child store={store} ref={refC} label="C" />
</>
);
}
const root = ReactNoop.createRoot();
await act(async () => {
// Start a concurrent render that reads from the store, then yield.
startTransition(() => {
root.render(<App store={store1} />);
});
expect(Scheduler).toFlushAndYieldThrough(['A0', 'B0']);
// During an interleaved event, the store is mutated.
store1.set(1);
// Then we continue rendering.
expect(Scheduler).toFlushAndYield([
// C reads a newer value from the store than A or B, which means they
// are inconsistent.
'C1',
// Before committing the layout effects, React detects that the store
// has been mutated. So it throws out the entire completed tree and
// re-renders the new values.
'A1',
'B1',
'C1',
// The layout effects reads consistent children.
'Children observed during layout: A1B1C1',
]);
});
// Now we're going test the same thing during an update that
// switches stores.
await act(async () => {
startTransition(() => {
root.render(<App store={store2} />);
});
// Start a concurrent render that reads from the store, then yield.
expect(Scheduler).toFlushAndYieldThrough(['A0', 'B0']);
// During an interleaved event, the store is mutated.
store2.set(1);
// Then we continue rendering.
expect(Scheduler).toFlushAndYield([
// C reads a newer value from the store than A or B, which means they
// are inconsistent.
'C1',
// Before committing the layout effects, React detects that the store
// has been mutated. So it throws out the entire completed tree and
// re-renders the new values.
'A1',
'B1',
'C1',
// The layout effects reads consistent children.
'Children observed during layout: A1B1C1',
]);
});
},
);
});

4
scripts/jest/TestFlags.js
View File

@ -84,6 +84,10 @@ function getTestFlags() {
source: !process.env.IS_BUILD,
www,
// This isn't a flag, just a useful alias for tests. Remove once
// useSyncExternalStore lands in the `next` channel.
supportsNativeUseSyncExternalStore: __EXPERIMENTAL__ || www,
// If there's a naming conflict between scheduler and React feature flags, the
// React ones take precedence.
// TODO: Maybe we should error on conflicts? Or we could namespace