Add isRootDehydrated function

Currently this does nothing except read a boolean field, but I'm about
to change this logic.

Since this is accessed by React DOM, too, I put the function in a
separate module that can be deep imported. Previously, it was accessing
the FiberRoot directly. The reason it's a separate module is to break a
circular dependency between React DOM and the reconciler.

packages/react-dom/src/events/ReactDOMEventListener.js

@@ -53,6 +53,7 @@ import {
   setCurrentUpdatePriority,
 } from 'react-reconciler/src/ReactEventPriorities';
 import ReactSharedInternals from 'shared/ReactSharedInternals';
+import {isRootDehydrated} from 'react-reconciler/src/ReactFiberShellHydration';
 
 const {ReactCurrentBatchConfig} = ReactSharedInternals;
 
@@ -386,7 +387,7 @@ export function findInstanceBlockingEvent(
         targetInst = null;
       } else if (tag === HostRoot) {
         const root: FiberRoot = nearestMounted.stateNode;
-        if (root.isDehydrated) {
+        if (isRootDehydrated(root)) {
           // If this happens during a replay something went wrong and it might block
           // the whole system.
           return getContainerFromFiber(nearestMounted);

packages/react-dom/src/events/ReactDOMEventReplaying.js

@@ -39,6 +39,7 @@ import {
 } from '../client/ReactDOMComponentTree';
 import {HostRoot, SuspenseComponent} from 'react-reconciler/src/ReactWorkTags';
 import {isHigherEventPriority} from 'react-reconciler/src/ReactEventPriorities';
+import {isRootDehydrated} from 'react-reconciler/src/ReactFiberShellHydration';
 
 let _attemptSynchronousHydration: (fiber: Object) => void;
 
@@ -414,7 +415,7 @@ function attemptExplicitHydrationTarget(
         }
       } else if (tag === HostRoot) {
         const root: FiberRoot = nearestMounted.stateNode;
-        if (root.isDehydrated) {
+        if (isRootDehydrated(root)) {
           queuedTarget.blockedOn = getContainerFromFiber(nearestMounted);
           // We don't currently have a way to increase the priority of
           // a root other than sync.

packages/react-reconciler/src/ReactFiberBeginWork.new.js

@@ -223,6 +223,7 @@ import {
   createOffscreenHostContainerFiber,
   isSimpleFunctionComponent,
 } from './ReactFiber.new';
+import {isRootDehydrated} from './ReactFiberShellHydration';
 import {
   retryDehydratedSuspenseBoundary,
   scheduleUpdateOnFiber,
@@ -1351,7 +1352,7 @@ function updateHostRoot(current, workInProgress, renderLanes) {
     resetHydrationState();
     return bailoutOnAlreadyFinishedWork(current, workInProgress, renderLanes);
   }
-  if (root.isDehydrated && enterHydrationState(workInProgress)) {
+  if (isRootDehydrated(root) && enterHydrationState(workInProgress)) {
     // If we don't have any current children this might be the first pass.
     // We always try to hydrate. If this isn't a hydration pass there won't
     // be any children to hydrate which is effectively the same thing as

packages/react-reconciler/src/ReactFiberBeginWork.old.js

@@ -223,6 +223,7 @@ import {
   createOffscreenHostContainerFiber,
   isSimpleFunctionComponent,
 } from './ReactFiber.old';
+import {isRootDehydrated} from './ReactFiberShellHydration';
 import {
   retryDehydratedSuspenseBoundary,
   scheduleUpdateOnFiber,
@@ -1351,7 +1352,7 @@ function updateHostRoot(current, workInProgress, renderLanes) {
     resetHydrationState();
     return bailoutOnAlreadyFinishedWork(current, workInProgress, renderLanes);
   }
-  if (root.isDehydrated && enterHydrationState(workInProgress)) {
+  if (isRootDehydrated(root) && enterHydrationState(workInProgress)) {
     // If we don't have any current children this might be the first pass.
     // We always try to hydrate. If this isn't a hydration pass there won't
     // be any children to hydrate which is effectively the same thing as

packages/react-reconciler/src/ReactFiberCommitWork.new.js

@@ -82,6 +82,7 @@ import {
   Visibility,
 } from './ReactFiberFlags';
 import getComponentNameFromFiber from 'react-reconciler/src/getComponentNameFromFiber';
+import {isRootDehydrated} from './ReactFiberShellHydration';
 import {
   resetCurrentFiber as resetCurrentDebugFiberInDEV,
   setCurrentFiber as setCurrentDebugFiberInDEV,
@@ -1878,7 +1879,7 @@ function commitWork(current: Fiber | null, finishedWork: Fiber): void {
       case HostRoot: {
         if (supportsHydration) {
           const root: FiberRoot = finishedWork.stateNode;
-          if (root.isDehydrated) {
+          if (isRootDehydrated(root)) {
             // We've just hydrated. No need to hydrate again.
             root.isDehydrated = false;
             commitHydratedContainer(root.containerInfo);
@@ -1986,7 +1987,7 @@ function commitWork(current: Fiber | null, finishedWork: Fiber): void {
     case HostRoot: {
       if (supportsHydration) {
         const root: FiberRoot = finishedWork.stateNode;
-        if (root.isDehydrated) {
+        if (isRootDehydrated(root)) {
           // We've just hydrated. No need to hydrate again.
           root.isDehydrated = false;
           commitHydratedContainer(root.containerInfo);

packages/react-reconciler/src/ReactFiberCommitWork.old.js

@@ -82,6 +82,7 @@ import {
   Visibility,
 } from './ReactFiberFlags';
 import getComponentNameFromFiber from 'react-reconciler/src/getComponentNameFromFiber';
+import {isRootDehydrated} from './ReactFiberShellHydration';
 import {
   resetCurrentFiber as resetCurrentDebugFiberInDEV,
   setCurrentFiber as setCurrentDebugFiberInDEV,
@@ -1878,7 +1879,7 @@ function commitWork(current: Fiber | null, finishedWork: Fiber): void {
       case HostRoot: {
         if (supportsHydration) {
           const root: FiberRoot = finishedWork.stateNode;
-          if (root.isDehydrated) {
+          if (isRootDehydrated(root)) {
             // We've just hydrated. No need to hydrate again.
             root.isDehydrated = false;
             commitHydratedContainer(root.containerInfo);
@@ -1986,7 +1987,7 @@ function commitWork(current: Fiber | null, finishedWork: Fiber): void {
     case HostRoot: {
       if (supportsHydration) {
         const root: FiberRoot = finishedWork.stateNode;
-        if (root.isDehydrated) {
+        if (isRootDehydrated(root)) {
           // We've just hydrated. No need to hydrate again.
           root.isDehydrated = false;
           commitHydratedContainer(root.containerInfo);

packages/react-reconciler/src/ReactFiberCompleteWork.new.js

@@ -160,6 +160,7 @@ import {
   includesSomeLane,
   mergeLanes,
 } from './ReactFiberLane.new';
+import {isRootDehydrated} from './ReactFiberShellHydration';
 import {resetChildFibers} from './ReactChildFiber.new';
 import {createScopeInstance} from './ReactFiberScope.new';
 import {transferActualDuration} from './ReactProfilerTimer.new';
@@ -890,7 +891,7 @@ function completeWork(
           // If we hydrated, then we'll need to schedule an update for
           // the commit side-effects on the root.
           markUpdate(workInProgress);
-        } else if (!fiberRoot.isDehydrated) {
+        } else if (!isRootDehydrated(fiberRoot)) {
           // Schedule an effect to clear this container at the start of the next commit.
           // This handles the case of React rendering into a container with previous children.
           // It's also safe to do for updates too, because current.child would only be null

packages/react-reconciler/src/ReactFiberCompleteWork.old.js

@@ -160,6 +160,7 @@ import {
   includesSomeLane,
   mergeLanes,
 } from './ReactFiberLane.old';
+import {isRootDehydrated} from './ReactFiberShellHydration';
 import {resetChildFibers} from './ReactChildFiber.old';
 import {createScopeInstance} from './ReactFiberScope.old';
 import {transferActualDuration} from './ReactProfilerTimer.old';
@@ -890,7 +891,7 @@ function completeWork(
           // If we hydrated, then we'll need to schedule an update for
           // the commit side-effects on the root.
           markUpdate(workInProgress);
-        } else if (!fiberRoot.isDehydrated) {
+        } else if (!isRootDehydrated(fiberRoot)) {
           // Schedule an effect to clear this container at the start of the next commit.
           // This handles the case of React rendering into a container with previous children.
           // It's also safe to do for updates too, because current.child would only be null

packages/react-reconciler/src/ReactFiberReconciler.new.js

@@ -48,6 +48,7 @@ import {
   isContextProvider as isLegacyContextProvider,
 } from './ReactFiberContext.new';
 import {createFiberRoot} from './ReactFiberRoot.new';
+import {isRootDehydrated} from './ReactFiberShellHydration';
 import {
   injectInternals,
   markRenderScheduled,
@@ -411,7 +412,7 @@ export function attemptSynchronousHydration(fiber: Fiber): void {
   switch (fiber.tag) {
     case HostRoot:
       const root: FiberRoot = fiber.stateNode;
-      if (root.isDehydrated) {
+      if (isRootDehydrated(root)) {
         // Flush the first scheduled "update".
         const lanes = getHighestPriorityPendingLanes(root);
         flushRoot(root, lanes);

packages/react-reconciler/src/ReactFiberReconciler.old.js

@@ -48,6 +48,7 @@ import {
   isContextProvider as isLegacyContextProvider,
 } from './ReactFiberContext.old';
 import {createFiberRoot} from './ReactFiberRoot.old';
+import {isRootDehydrated} from './ReactFiberShellHydration';
 import {
   injectInternals,
   markRenderScheduled,
@@ -411,7 +412,7 @@ export function attemptSynchronousHydration(fiber: Fiber): void {
   switch (fiber.tag) {
     case HostRoot:
       const root: FiberRoot = fiber.stateNode;
-      if (root.isDehydrated) {
+      if (isRootDehydrated(root)) {
         // Flush the first scheduled "update".
         const lanes = getHighestPriorityPendingLanes(root);
         flushRoot(root, lanes);

packages/react-reconciler/src/ReactFiberShellHydration.js

@@ -0,0 +1,17 @@
+/**
+ * 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.
+ *
+ * @flow
+ */
+
+import type {FiberRoot} from './ReactInternalTypes';
+
+// This is imported by the event replaying implementation in React DOM. It's
+// in a separate file to break a circular dependency between the renderer and
+// the reconciler.
+export function isRootDehydrated(root: FiberRoot) {
+  return root.isDehydrated;
+}

packages/react-reconciler/src/ReactFiberWorkLoop.new.js

@@ -88,6 +88,7 @@ import {
   createWorkInProgress,
   assignFiberPropertiesInDEV,
 } from './ReactFiber.new';
+import {isRootDehydrated} from './ReactFiberShellHydration';
 import {NoMode, ProfileMode, ConcurrentMode} from './ReactTypeOfMode';
 import {
   HostRoot,
@@ -581,7 +582,7 @@ export function scheduleUpdateOnFiber(
       }
     }
 
-    if (root.isDehydrated && root.tag !== LegacyRoot) {
+    if (isRootDehydrated(root) && root.tag !== LegacyRoot) {
       // This root's shell hasn't hydrated yet. Revert to client rendering.
       if (workInProgressRoot === root) {
         // If this happened during an interleaved event, interrupt the
@@ -1016,7 +1017,7 @@ function performConcurrentWorkOnRoot(root, didTimeout) {
 function recoverFromConcurrentError(root, errorRetryLanes) {
   // If an error occurred during hydration, discard server response and fall
   // back to client side render.
-  if (root.isDehydrated) {
+  if (isRootDehydrated(root)) {
     root.isDehydrated = false;
     if (__DEV__) {
       errorHydratingContainer(root.containerInfo);

packages/react-reconciler/src/ReactFiberWorkLoop.old.js

@@ -88,6 +88,7 @@ import {
   createWorkInProgress,
   assignFiberPropertiesInDEV,
 } from './ReactFiber.old';
+import {isRootDehydrated} from './ReactFiberShellHydration';
 import {NoMode, ProfileMode, ConcurrentMode} from './ReactTypeOfMode';
 import {
   HostRoot,
@@ -581,7 +582,7 @@ export function scheduleUpdateOnFiber(
       }
     }
 
-    if (root.isDehydrated && root.tag !== LegacyRoot) {
+    if (isRootDehydrated(root) && root.tag !== LegacyRoot) {
       // This root's shell hasn't hydrated yet. Revert to client rendering.
       if (workInProgressRoot === root) {
         // If this happened during an interleaved event, interrupt the
@@ -1016,7 +1017,7 @@ function performConcurrentWorkOnRoot(root, didTimeout) {
 function recoverFromConcurrentError(root, errorRetryLanes) {
   // If an error occurred during hydration, discard server response and fall
   // back to client side render.
-  if (root.isDehydrated) {
+  if (isRootDehydrated(root)) {
     root.isDehydrated = false;
     if (__DEV__) {
       errorHydratingContainer(root.containerInfo);