Replace SuspenseConfig object with an integer (#19706)

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.
2026-02-24 04:33:04 +00:00 · 2020-08-28 12:52:56 -05:00
parent b754caaaf2
commit 92fcd46cc7
15 changed files with 80 additions and 108 deletions
--- a/packages/react-debug-tools/src/ReactDebugHooks.js
+++ b/packages/react-debug-tools/src/ReactDebugHooks.js
@@ -20,7 +20,7 @@ import type {
 } from 'react-reconciler/src/ReactInternalTypes';
 import type {OpaqueIDType} from 'react-reconciler/src/ReactFiberHostConfig';

-import type {SuspenseConfig} from 'react-reconciler/src/ReactFiberSuspenseConfig';
+import type {SuspenseConfig} from 'react-reconciler/src/ReactFiberTransition';
 import {NoMode} from 'react-reconciler/src/ReactTypeOfMode';

 import ErrorStackParser from 'error-stack-parser';
--- a/packages/react-dom/src/server/ReactPartialRendererHooks.js
+++ b/packages/react-dom/src/server/ReactPartialRendererHooks.js
@@ -15,7 +15,7 @@ import type {
  MutableSourceSubscribeFn,
  ReactContext,
 } from 'shared/ReactTypes';
-import type {SuspenseConfig} from 'react-reconciler/src/ReactFiberSuspenseConfig';
+import type {SuspenseConfig} from 'react-reconciler/src/ReactFiberTransition';
 import type PartialRenderer from './ReactPartialRenderer';

 import {validateContextBounds} from './ReactPartialRendererContext';
--- a/packages/react-reconciler/src/ReactFiberClassComponent.new.js
+++ b/packages/react-reconciler/src/ReactFiberClassComponent.new.js
@@ -56,7 +56,6 @@ import {
  requestUpdateLane,
  scheduleUpdateOnFiber,
 } from './ReactFiberWorkLoop.new';
-import {requestCurrentSuspenseConfig} from './ReactFiberSuspenseConfig';
 import {logForceUpdateScheduled, logStateUpdateScheduled} from './DebugTracing';

 import {disableLogs, reenableLogs} from 'shared/ConsolePatchingDev';
@@ -196,8 +195,7 @@ const classComponentUpdater = {
  enqueueSetState(inst, payload, callback) {
    const fiber = getInstance(inst);
    const eventTime = requestEventTime();
-    const suspenseConfig = requestCurrentSuspenseConfig();
-    const lane = requestUpdateLane(fiber, suspenseConfig);
+    const lane = requestUpdateLane(fiber);

    const update = createUpdate(eventTime, lane);
    update.payload = payload;
@@ -227,8 +225,7 @@ const classComponentUpdater = {
  enqueueReplaceState(inst, payload, callback) {
    const fiber = getInstance(inst);
    const eventTime = requestEventTime();
-    const suspenseConfig = requestCurrentSuspenseConfig();
-    const lane = requestUpdateLane(fiber, suspenseConfig);
+    const lane = requestUpdateLane(fiber);

    const update = createUpdate(eventTime, lane);
    update.tag = ReplaceState;
@@ -260,8 +257,7 @@ const classComponentUpdater = {
  enqueueForceUpdate(inst, callback) {
    const fiber = getInstance(inst);
    const eventTime = requestEventTime();
-    const suspenseConfig = requestCurrentSuspenseConfig();
-    const lane = requestUpdateLane(fiber, suspenseConfig);
+    const lane = requestUpdateLane(fiber);

    const update = createUpdate(eventTime, lane);
    update.tag = ForceUpdate;
--- a/packages/react-reconciler/src/ReactFiberClassComponent.old.js
+++ b/packages/react-reconciler/src/ReactFiberClassComponent.old.js
@@ -56,7 +56,6 @@ import {
  requestUpdateLane,
  scheduleUpdateOnFiber,
 } from './ReactFiberWorkLoop.old';
-import {requestCurrentSuspenseConfig} from './ReactFiberSuspenseConfig';
 import {logForceUpdateScheduled, logStateUpdateScheduled} from './DebugTracing';

 import {disableLogs, reenableLogs} from 'shared/ConsolePatchingDev';
@@ -196,8 +195,7 @@ const classComponentUpdater = {
  enqueueSetState(inst, payload, callback) {
    const fiber = getInstance(inst);
    const eventTime = requestEventTime();
-    const suspenseConfig = requestCurrentSuspenseConfig();
-    const lane = requestUpdateLane(fiber, suspenseConfig);
+    const lane = requestUpdateLane(fiber);

    const update = createUpdate(eventTime, lane);
    update.payload = payload;
@@ -227,8 +225,7 @@ const classComponentUpdater = {
  enqueueReplaceState(inst, payload, callback) {
    const fiber = getInstance(inst);
    const eventTime = requestEventTime();
-    const suspenseConfig = requestCurrentSuspenseConfig();
-    const lane = requestUpdateLane(fiber, suspenseConfig);
+    const lane = requestUpdateLane(fiber);

    const update = createUpdate(eventTime, lane);
    update.tag = ReplaceState;
@@ -260,8 +257,7 @@ const classComponentUpdater = {
  enqueueForceUpdate(inst, callback) {
    const fiber = getInstance(inst);
    const eventTime = requestEventTime();
-    const suspenseConfig = requestCurrentSuspenseConfig();
-    const lane = requestUpdateLane(fiber, suspenseConfig);
+    const lane = requestUpdateLane(fiber);

    const update = createUpdate(eventTime, lane);
    update.tag = ForceUpdate;
--- a/packages/react-reconciler/src/ReactFiberHooks.new.js
+++ b/packages/react-reconciler/src/ReactFiberHooks.new.js
@@ -16,7 +16,7 @@ import type {
 import type {Fiber, Dispatcher} from './ReactInternalTypes';
 import type {Lanes, Lane} from './ReactFiberLane';
 import type {HookEffectTag} from './ReactHookEffectTags';
-import type {SuspenseConfig} from './ReactFiberSuspenseConfig';
+import type {SuspenseConfig} from './ReactFiberTransition';
 import type {ReactPriorityLevel} from './ReactInternalTypes';
 import type {FiberRoot} from './ReactInternalTypes';
 import type {OpaqueIDType} from './ReactFiberHostConfig';
@@ -70,7 +70,6 @@ import invariant from 'shared/invariant';
 import getComponentName from 'shared/getComponentName';
 import is from 'shared/objectIs';
 import {markWorkInProgressReceivedUpdate} from './ReactFiberBeginWork.new';
-import {requestCurrentSuspenseConfig} from './ReactFiberSuspenseConfig';
 import {
  UserBlockingPriority,
  NormalPriority,
@@ -1003,8 +1002,7 @@ function useMutableSource<Source, Snapshot>(
      if (!is(snapshot, maybeNewSnapshot)) {
        setSnapshot(maybeNewSnapshot);

-        const suspenseConfig = requestCurrentSuspenseConfig();
-        const lane = requestUpdateLane(fiber, suspenseConfig);
+        const lane = requestUpdateLane(fiber);
        markRootMutableRead(root, lane);
      }
      // If the source mutated between render and now,
@@ -1024,8 +1022,7 @@ function useMutableSource<Source, Snapshot>(
        latestSetSnapshot(latestGetSnapshot(source._source));

        // Record a pending mutable source update with the same expiration time.
-        const suspenseConfig = requestCurrentSuspenseConfig();
-        const lane = requestUpdateLane(fiber, suspenseConfig);
+        const lane = requestUpdateLane(fiber);

        markRootMutableRead(root, lane);
      } catch (error) {
@@ -1441,12 +1438,12 @@ function mountDeferredValue<T>(
 ): T {
  const [prevValue, setValue] = mountState(value);
  mountEffect(() => {
-    const previousConfig = ReactCurrentBatchConfig.suspense;
-    ReactCurrentBatchConfig.suspense = config === undefined ? null : config;
+    const prevTransition = ReactCurrentBatchConfig.transition;
+    ReactCurrentBatchConfig.transition = 1;
    try {
      setValue(value);
    } finally {
-      ReactCurrentBatchConfig.suspense = previousConfig;
+      ReactCurrentBatchConfig.transition = prevTransition;
    }
  }, [value, config]);
  return prevValue;
@@ -1458,12 +1455,12 @@ function updateDeferredValue<T>(
 ): T {
  const [prevValue, setValue] = updateState(value);
  updateEffect(() => {
-    const previousConfig = ReactCurrentBatchConfig.suspense;
-    ReactCurrentBatchConfig.suspense = config === undefined ? null : config;
+    const prevTransition = ReactCurrentBatchConfig.transition;
+    ReactCurrentBatchConfig.transition = 1;
    try {
      setValue(value);
    } finally {
-      ReactCurrentBatchConfig.suspense = previousConfig;
+      ReactCurrentBatchConfig.transition = prevTransition;
    }
  }, [value, config]);
  return prevValue;
@@ -1475,12 +1472,12 @@ function rerenderDeferredValue<T>(
 ): T {
  const [prevValue, setValue] = rerenderState(value);
  updateEffect(() => {
-    const previousConfig = ReactCurrentBatchConfig.suspense;
-    ReactCurrentBatchConfig.suspense = config === undefined ? null : config;
+    const prevTransition = ReactCurrentBatchConfig.transition;
+    ReactCurrentBatchConfig.transition = 1;
    try {
      setValue(value);
    } finally {
-      ReactCurrentBatchConfig.suspense = previousConfig;
+      ReactCurrentBatchConfig.transition = prevTransition;
    }
  }, [value, config]);
  return prevValue;
@@ -1509,8 +1506,8 @@ function startTransition(setPending, config, callback) {
    runWithPriority(
      priorityLevel > NormalPriority ? NormalPriority : priorityLevel,
      () => {
-        const previousConfig = ReactCurrentBatchConfig.suspense;
-        ReactCurrentBatchConfig.suspense = config === undefined ? null : config;
+        const prevTransition = ReactCurrentBatchConfig.transition;
+        ReactCurrentBatchConfig.transition = 1;
        try {
          setPending(false);
          callback();
@@ -1518,7 +1515,7 @@ function startTransition(setPending, config, callback) {
          if (decoupleUpdatePriorityFromScheduler) {
            setCurrentUpdateLanePriority(previousLanePriority);
          }
-          ReactCurrentBatchConfig.suspense = previousConfig;
+          ReactCurrentBatchConfig.transition = prevTransition;
        }
      },
    );
@@ -1535,13 +1532,13 @@ function startTransition(setPending, config, callback) {
    runWithPriority(
      priorityLevel > NormalPriority ? NormalPriority : priorityLevel,
      () => {
-        const previousConfig = ReactCurrentBatchConfig.suspense;
-        ReactCurrentBatchConfig.suspense = config === undefined ? null : config;
+        const prevTransition = ReactCurrentBatchConfig.transition;
+        ReactCurrentBatchConfig.transition = 1;
        try {
          setPending(false);
          callback();
        } finally {
-          ReactCurrentBatchConfig.suspense = previousConfig;
+          ReactCurrentBatchConfig.transition = prevTransition;
        }
      },
    );
@@ -1685,8 +1682,7 @@ function dispatchAction<S, A>(
  }

  const eventTime = requestEventTime();
-  const suspenseConfig = requestCurrentSuspenseConfig();
-  const lane = requestUpdateLane(fiber, suspenseConfig);
+  const lane = requestUpdateLane(fiber);

  const update: Update<S, A> = {
    lane,
--- a/packages/react-reconciler/src/ReactFiberHooks.old.js
+++ b/packages/react-reconciler/src/ReactFiberHooks.old.js
@@ -16,7 +16,7 @@ import type {
 import type {Fiber, Dispatcher} from './ReactInternalTypes';
 import type {Lanes, Lane} from './ReactFiberLane';
 import type {HookEffectTag} from './ReactHookEffectTags';
-import type {SuspenseConfig} from './ReactFiberSuspenseConfig';
+import type {SuspenseConfig} from './ReactFiberTransition';
 import type {ReactPriorityLevel} from './ReactInternalTypes';
 import type {FiberRoot} from './ReactInternalTypes';
 import type {OpaqueIDType} from './ReactFiberHostConfig';
@@ -69,7 +69,6 @@ import invariant from 'shared/invariant';
 import getComponentName from 'shared/getComponentName';
 import is from 'shared/objectIs';
 import {markWorkInProgressReceivedUpdate} from './ReactFiberBeginWork.old';
-import {requestCurrentSuspenseConfig} from './ReactFiberSuspenseConfig';
 import {
  UserBlockingPriority,
  NormalPriority,
@@ -1002,8 +1001,7 @@ function useMutableSource<Source, Snapshot>(
      if (!is(snapshot, maybeNewSnapshot)) {
        setSnapshot(maybeNewSnapshot);

-        const suspenseConfig = requestCurrentSuspenseConfig();
-        const lane = requestUpdateLane(fiber, suspenseConfig);
+        const lane = requestUpdateLane(fiber);
        markRootMutableRead(root, lane);
      }
      // If the source mutated between render and now,
@@ -1023,8 +1021,7 @@ function useMutableSource<Source, Snapshot>(
        latestSetSnapshot(latestGetSnapshot(source._source));

        // Record a pending mutable source update with the same expiration time.
-        const suspenseConfig = requestCurrentSuspenseConfig();
-        const lane = requestUpdateLane(fiber, suspenseConfig);
+        const lane = requestUpdateLane(fiber);

        markRootMutableRead(root, lane);
      } catch (error) {
@@ -1440,12 +1437,12 @@ function mountDeferredValue<T>(
 ): T {
  const [prevValue, setValue] = mountState(value);
  mountEffect(() => {
-    const previousConfig = ReactCurrentBatchConfig.suspense;
-    ReactCurrentBatchConfig.suspense = config === undefined ? null : config;
+    const prevTransition = ReactCurrentBatchConfig.transition;
+    ReactCurrentBatchConfig.transition = 1;
    try {
      setValue(value);
    } finally {
-      ReactCurrentBatchConfig.suspense = previousConfig;
+      ReactCurrentBatchConfig.transition = prevTransition;
    }
  }, [value, config]);
  return prevValue;
@@ -1457,12 +1454,12 @@ function updateDeferredValue<T>(
 ): T {
  const [prevValue, setValue] = updateState(value);
  updateEffect(() => {
-    const previousConfig = ReactCurrentBatchConfig.suspense;
-    ReactCurrentBatchConfig.suspense = config === undefined ? null : config;
+    const prevTransition = ReactCurrentBatchConfig.transition;
+    ReactCurrentBatchConfig.transition = 1;
    try {
      setValue(value);
    } finally {
-      ReactCurrentBatchConfig.suspense = previousConfig;
+      ReactCurrentBatchConfig.transition = prevTransition;
    }
  }, [value, config]);
  return prevValue;
@@ -1474,12 +1471,12 @@ function rerenderDeferredValue<T>(
 ): T {
  const [prevValue, setValue] = rerenderState(value);
  updateEffect(() => {
-    const previousConfig = ReactCurrentBatchConfig.suspense;
-    ReactCurrentBatchConfig.suspense = config === undefined ? null : config;
+    const prevTransition = ReactCurrentBatchConfig.transition;
+    ReactCurrentBatchConfig.transition = 1;
    try {
      setValue(value);
    } finally {
-      ReactCurrentBatchConfig.suspense = previousConfig;
+      ReactCurrentBatchConfig.transition = prevTransition;
    }
  }, [value, config]);
  return prevValue;
@@ -1508,8 +1505,8 @@ function startTransition(setPending, config, callback) {
    runWithPriority(
      priorityLevel > NormalPriority ? NormalPriority : priorityLevel,
      () => {
-        const previousConfig = ReactCurrentBatchConfig.suspense;
-        ReactCurrentBatchConfig.suspense = config === undefined ? null : config;
+        const prevTransition = ReactCurrentBatchConfig.transition;
+        ReactCurrentBatchConfig.transition = 1;
        try {
          setPending(false);
          callback();
@@ -1517,7 +1514,7 @@ function startTransition(setPending, config, callback) {
          if (decoupleUpdatePriorityFromScheduler) {
            setCurrentUpdateLanePriority(previousLanePriority);
          }
-          ReactCurrentBatchConfig.suspense = previousConfig;
+          ReactCurrentBatchConfig.transition = prevTransition;
        }
      },
    );
@@ -1534,13 +1531,13 @@ function startTransition(setPending, config, callback) {
    runWithPriority(
      priorityLevel > NormalPriority ? NormalPriority : priorityLevel,
      () => {
-        const previousConfig = ReactCurrentBatchConfig.suspense;
-        ReactCurrentBatchConfig.suspense = config === undefined ? null : config;
+        const prevTransition = ReactCurrentBatchConfig.transition;
+        ReactCurrentBatchConfig.transition = 1;
        try {
          setPending(false);
          callback();
        } finally {
-          ReactCurrentBatchConfig.suspense = previousConfig;
+          ReactCurrentBatchConfig.transition = prevTransition;
        }
      },
    );
@@ -1683,8 +1680,7 @@ function dispatchAction<S, A>(
  }

  const eventTime = requestEventTime();
-  const suspenseConfig = requestCurrentSuspenseConfig();
-  const lane = requestUpdateLane(fiber, suspenseConfig);
+  const lane = requestUpdateLane(fiber);

  const update: Update<S, A> = {
    lane,
--- a/packages/react-reconciler/src/ReactFiberReconciler.new.js
+++ b/packages/react-reconciler/src/ReactFiberReconciler.new.js
@@ -83,7 +83,6 @@ import {
  getCurrentUpdateLanePriority,
  setCurrentUpdateLanePriority,
 } from './ReactFiberLane';
-import {requestCurrentSuspenseConfig} from './ReactFiberSuspenseConfig';
 import {
  scheduleRefresh,
  scheduleRoot,
@@ -266,8 +265,7 @@ export function updateContainer(
      warnIfNotScopedWithMatchingAct(current);
    }
  }
-  const suspenseConfig = requestCurrentSuspenseConfig();
-  const lane = requestUpdateLane(current, suspenseConfig);
+  const lane = requestUpdateLane(current);

  if (enableSchedulingProfiler) {
    markRenderScheduled(lane);
@@ -427,7 +425,7 @@ export function attemptHydrationAtCurrentPriority(fiber: Fiber): void {
    return;
  }
  const eventTime = requestEventTime();
-  const lane = requestUpdateLane(fiber, null);
+  const lane = requestUpdateLane(fiber);
  scheduleUpdateOnFiber(fiber, lane, eventTime);
  markRetryLaneIfNotHydrated(fiber, lane);
 }
--- a/packages/react-reconciler/src/ReactFiberReconciler.old.js
+++ b/packages/react-reconciler/src/ReactFiberReconciler.old.js
@@ -83,7 +83,6 @@ import {
  getCurrentUpdateLanePriority,
  setCurrentUpdateLanePriority,
 } from './ReactFiberLane';
-import {requestCurrentSuspenseConfig} from './ReactFiberSuspenseConfig';
 import {
  scheduleRefresh,
  scheduleRoot,
@@ -266,8 +265,7 @@ export function updateContainer(
      warnIfNotScopedWithMatchingAct(current);
    }
  }
-  const suspenseConfig = requestCurrentSuspenseConfig();
-  const lane = requestUpdateLane(current, suspenseConfig);
+  const lane = requestUpdateLane(current);

  if (enableSchedulingProfiler) {
    markRenderScheduled(lane);
@@ -427,7 +425,7 @@ export function attemptHydrationAtCurrentPriority(fiber: Fiber): void {
    return;
  }
  const eventTime = requestEventTime();
-  const lane = requestUpdateLane(fiber, null);
+  const lane = requestUpdateLane(fiber);
  scheduleUpdateOnFiber(fiber, lane, eventTime);
  markRetryLaneIfNotHydrated(fiber, lane);
 }
--- a/packages/react-reconciler/src/ReactFiberSuspenseConfig.js
+++ b/packages/react-reconciler/src/ReactFiberSuspenseConfig.js
@@ -9,18 +9,22 @@

 import ReactSharedInternals from 'shared/ReactSharedInternals';

-const {ReactCurrentBatchConfig} = ReactSharedInternals;
-
+// Deprecated
 export type SuspenseConfig = {|
  timeoutMs: number,
  busyDelayMs?: number,
  busyMinDurationMs?: number,
 |};

+// Deprecated
 export type TimeoutConfig = {|
  timeoutMs: number,
 |};

-export function requestCurrentSuspenseConfig(): null | SuspenseConfig {
-  return ReactCurrentBatchConfig.suspense;
+const {ReactCurrentBatchConfig} = ReactSharedInternals;
+
+export const NoTransition = 0;
+
+export function requestCurrentTransition(): number {
+  return ReactCurrentBatchConfig.transition;
 }
--- a/packages/react-reconciler/src/ReactFiberWorkLoop.new.js
+++ b/packages/react-reconciler/src/ReactFiberWorkLoop.new.js
@@ -12,7 +12,6 @@ import type {Fiber, FiberRoot} from './ReactInternalTypes';
 import type {Lanes, Lane} from './ReactFiberLane';
 import type {ReactPriorityLevel} from './ReactInternalTypes';
 import type {Interaction} from 'scheduler/src/Tracing';
-import type {SuspenseConfig} from './ReactFiberSuspenseConfig';
 import type {SuspenseState} from './ReactFiberSuspenseComponent.new';
 import type {StackCursor} from './ReactFiberStack.new';
 import type {FunctionComponentUpdateQueue} from './ReactFiberHooks.new';
@@ -188,6 +187,7 @@ import {
  schedulerPriorityToLanePriority,
  lanePriorityToSchedulerPriority,
 } from './ReactFiberLane';
+import {requestCurrentTransition, NoTransition} from './ReactFiberTransition';
 import {beginWork as originalBeginWork} from './ReactFiberBeginWork.new';
 import {completeWork} from './ReactFiberCompleteWork.new';
 import {unwindWork, unwindInterruptedWork} from './ReactFiberUnwindWork.new';
@@ -402,10 +402,7 @@ export function getCurrentTime() {
  return now();
 }

-export function requestUpdateLane(
-  fiber: Fiber,
-  suspenseConfig: SuspenseConfig | null,
-): Lane {
+export function requestUpdateLane(fiber: Fiber): Lane {
  // Special cases
  const mode = fiber.mode;
  if ((mode & BlockingMode) === NoMode) {
@@ -449,10 +446,8 @@ export function requestUpdateLane(
    currentEventWipLanes = workInProgressRootIncludedLanes;
  }

-  if (suspenseConfig !== null) {
-    // Use the size of the timeout as a heuristic to prioritize shorter
-    // transitions over longer ones.
-    // TODO: This will coerce numbers larger than 31 bits to 0.
+  const isTransition = requestCurrentTransition() !== NoTransition;
+  if (isTransition) {
    if (currentEventPendingLanes !== NoLanes) {
      currentEventPendingLanes =
        mostRecentlyUpdatedRoot !== null
--- a/packages/react-reconciler/src/ReactFiberWorkLoop.old.js
+++ b/packages/react-reconciler/src/ReactFiberWorkLoop.old.js
@@ -12,7 +12,6 @@ import type {Fiber, FiberRoot} from './ReactInternalTypes';
 import type {Lanes, Lane} from './ReactFiberLane';
 import type {ReactPriorityLevel} from './ReactInternalTypes';
 import type {Interaction} from 'scheduler/src/Tracing';
-import type {SuspenseConfig} from './ReactFiberSuspenseConfig';
 import type {SuspenseState} from './ReactFiberSuspenseComponent.old';
 import type {Effect as HookEffect} from './ReactFiberHooks.old';
 import type {StackCursor} from './ReactFiberStack.old';
@@ -174,6 +173,7 @@ import {
  schedulerPriorityToLanePriority,
  lanePriorityToSchedulerPriority,
 } from './ReactFiberLane';
+import {requestCurrentTransition, NoTransition} from './ReactFiberTransition';
 import {beginWork as originalBeginWork} from './ReactFiberBeginWork.old';
 import {completeWork} from './ReactFiberCompleteWork.old';
 import {unwindWork, unwindInterruptedWork} from './ReactFiberUnwindWork.old';
@@ -390,10 +390,7 @@ export function getCurrentTime() {
  return now();
 }

-export function requestUpdateLane(
-  fiber: Fiber,
-  suspenseConfig: SuspenseConfig | null,
-): Lane {
+export function requestUpdateLane(fiber: Fiber): Lane {
  // Special cases
  const mode = fiber.mode;
  if ((mode & BlockingMode) === NoMode) {
@@ -437,10 +434,8 @@ export function requestUpdateLane(
    currentEventWipLanes = workInProgressRootIncludedLanes;
  }

-  if (suspenseConfig !== null) {
-    // Use the size of the timeout as a heuristic to prioritize shorter
-    // transitions over longer ones.
-    // TODO: This will coerce numbers larger than 31 bits to 0.
+  const isTransition = requestCurrentTransition() !== NoTransition;
+  if (isTransition) {
    if (currentEventPendingLanes !== NoLanes) {
      currentEventPendingLanes =
        mostRecentlyUpdatedRoot !== null
--- a/packages/react-reconciler/src/ReactInternalTypes.js
+++ b/packages/react-reconciler/src/ReactInternalTypes.js
@@ -27,7 +27,7 @@ import type {RootTag} from './ReactRootTags';
 import type {TimeoutHandle, NoTimeout} from './ReactFiberHostConfig';
 import type {Wakeable} from 'shared/ReactTypes';
 import type {Interaction} from 'scheduler/src/Tracing';
-import type {SuspenseConfig, TimeoutConfig} from './ReactFiberSuspenseConfig';
+import type {SuspenseConfig, TimeoutConfig} from './ReactFiberTransition';

 export type ReactPriorityLevel = 99 | 98 | 97 | 96 | 95 | 90;

--- a/packages/react/src/ReactBatchConfig.js
+++ b/packages/react/src/ReactBatchConfig.js
@@ -7,17 +7,21 @@
 * @flow
 */

-import type {SuspenseConfig} from 'react-reconciler/src/ReactFiberSuspenseConfig';
+import type {SuspenseConfig} from 'react-reconciler/src/ReactFiberTransition';

 import ReactCurrentBatchConfig from './ReactCurrentBatchConfig';

-// Within the scope of the callback, mark all updates as being allowed to suspend.
+// This is a copy of startTransition, except if null or undefined is passed,
+// then updates inside the scope are opted-out of the outer transition scope.
+// TODO: Deprecated. Remove in favor of startTransition. Figure out how scopes
+// should nest, and whether we need an API to opt-out nested scopes.
 export function withSuspenseConfig(scope: () => void, config?: SuspenseConfig) {
-  const previousConfig = ReactCurrentBatchConfig.suspense;
-  ReactCurrentBatchConfig.suspense = config === undefined ? null : config;
+  const prevTransition = ReactCurrentBatchConfig.transition;
+  ReactCurrentBatchConfig.transition =
+    config === undefined || config === null ? 0 : 1;
  try {
    scope();
  } finally {
-    ReactCurrentBatchConfig.suspense = previousConfig;
+    ReactCurrentBatchConfig.transition = prevTransition;
  }
 }
--- a/packages/react/src/ReactCurrentBatchConfig.js
+++ b/packages/react/src/ReactCurrentBatchConfig.js
@@ -7,14 +7,12 @@
 * @flow
 */

-import type {SuspenseConfig} from 'react-reconciler/src/ReactFiberSuspenseConfig';
-
 /**
 * Keeps track of the current batch's configuration such as how long an update
 * should suspend for if it needs to.
 */
 const ReactCurrentBatchConfig = {
-  suspense: (null: null | SuspenseConfig),
+  transition: (0: number),
 };

 export default ReactCurrentBatchConfig;
--- a/packages/react/src/ReactStartTransition.js
+++ b/packages/react/src/ReactStartTransition.js
@@ -9,16 +9,12 @@

 import ReactCurrentBatchConfig from './ReactCurrentBatchConfig';

-// Default to an arbitrarily large timeout. Effectively, this is infinite. The
-// eventual goal is to never timeout when refreshing already visible content.
-const IndefiniteTimeoutConfig = {timeoutMs: 100000};
-
 export function startTransition(scope: () => void) {
-  const previousConfig = ReactCurrentBatchConfig.suspense;
-  ReactCurrentBatchConfig.suspense = IndefiniteTimeoutConfig;
+  const prevTransition = ReactCurrentBatchConfig.transition;
+  ReactCurrentBatchConfig.transition = 1;
  try {
    scope();
  } finally {
-    ReactCurrentBatchConfig.suspense = previousConfig;
+    ReactCurrentBatchConfig.transition = prevTransition;
  }
 }