refactors the currentUpdatePriority apis to more clearly communicate …

…when you are reading a raw value and when you are getting a resolved value. This allows requestUpdateLane to do a single call into the renderer to get the update priority while still making a reasonable stack based updating of update priorities ergonomic. I had to expose a `peekCurrentUpdatePriority` to satisfy startTransition which needs to set a new priority only if the current one is too low. I tried to stay away from get/set naming to avoid potential issues with whether you are reading the raw value or the derived one that considers window.event

packages/react-art/src/ReactFiberConfigART.js

@@ -343,16 +343,16 @@ export function shouldSetTextContent(type, props) {
 
 let currentUpdatePriority: EventPriority = NoEventPriority;
 
-export function setCurrentUpdatePriority(newPriority: EventPriority) {
+export function setCurrentUpdatePriority(newPriority: EventPriority): void {
   currentUpdatePriority = newPriority;
 }
 
-export function getCurrentUpdatePriority() {
+export function getCurrentUpdatePriority(): EventPriority {
   return currentUpdatePriority;
 }
 
-export function getCurrentEventPriority() {
-  return DefaultEventPriority;
+export function resolveUpdatePriority(): EventPriority {
+  return currentUpdatePriority || DefaultEventPriority;
 }
 
 export function shouldAttemptEagerTransition() {

packages/react-dom-bindings/src/client/ReactDOMUpdatePriority.js

@@ -9,6 +9,12 @@
 
 import type {EventPriority} from 'react-reconciler/src/ReactEventPriorities';
 
+import {getEventPriority} from '../events/ReactDOMEventListener';
+import {
+  NoEventPriority,
+  DefaultEventPriority,
+} from 'react-reconciler/src/ReactEventPriorities';
+
 import ReactDOMSharedInternals from 'shared/ReactDOMSharedInternals';
 const ReactDOMCurrentUpdatePriority =
   ReactDOMSharedInternals.ReactDOMCurrentUpdatePriority;
@@ -21,6 +27,18 @@ export function getCurrentUpdatePriority(): EventPriority {
   return ReactDOMCurrentUpdatePriority.current;
 }
 
+export function resolveUpdatePriority(): EventPriority {
+  const updatePriority = ReactDOMCurrentUpdatePriority.current;
+  if (updatePriority !== NoEventPriority) {
+    return updatePriority;
+  }
+  const currentEvent = window.event;
+  if (currentEvent === undefined) {
+    return DefaultEventPriority;
+  }
+  return getEventPriority(currentEvent.type);
+}
+
 export function runWithPriority<T>(priority: EventPriority, fn: () => T): T {
   const previousPriority = getCurrentUpdatePriority();
   try {

packages/react-dom-bindings/src/client/ReactFiberConfigDOM.js

@@ -7,7 +7,6 @@
  * @flow
  */
 
-import type {EventPriority} from 'react-reconciler/src/ReactEventPriorities';
 import type {DOMEventName} from '../events/DOMEventNames';
 import type {Fiber, FiberRoot} from 'react-reconciler/src/ReactInternalTypes';
 import type {
@@ -29,14 +28,14 @@ import type {
 
 import {NotPending} from 'react-dom-bindings/src/shared/ReactDOMFormActions';
 import {getCurrentRootHostContainer} from 'react-reconciler/src/ReactFiberHostContext';
-import {DefaultEventPriority} from 'react-reconciler/src/ReactEventPriorities';
 
 import hasOwnProperty from 'shared/hasOwnProperty';
 import {checkAttributeStringCoercion} from 'shared/CheckStringCoercion';
 
 export {
   setCurrentUpdatePriority,
   getCurrentUpdatePriority,
+  resolveUpdatePriority,
 } from './ReactDOMUpdatePriority';
 import {
   precacheFiberNode,
@@ -73,7 +72,6 @@ import {
 import {
   isEnabled as ReactBrowserEventEmitterIsEnabled,
   setEnabled as ReactBrowserEventEmitterSetEnabled,
-  getEventPriority,
 } from '../events/ReactDOMEventListener';
 import {SVG_NAMESPACE, MATH_NAMESPACE} from './DOMNamespaces';
 import {
@@ -576,14 +574,6 @@ export function createTextInstance(
   return textNode;
 }
 
-export function getCurrentEventPriority(): EventPriority {
-  const currentEvent = window.event;
-  if (currentEvent === undefined) {
-    return DefaultEventPriority;
-  }
-  return getEventPriority(currentEvent.type);
-}
-
 let currentPopstateTransitionEvent: Event | null = null;
 export function shouldAttemptEagerTransition(): boolean {
   const event = window.event;

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

@@ -117,9 +117,9 @@ function dispatchDiscreteEvent(
   container: EventTarget,
   nativeEvent: AnyNativeEvent,
 ) {
-  const previousPriority = getCurrentUpdatePriority();
   const prevTransition = ReactCurrentBatchConfig.transition;
   ReactCurrentBatchConfig.transition = null;
+  const previousPriority = getCurrentUpdatePriority();
   try {
     setCurrentUpdatePriority(DiscreteEventPriority);
     dispatchEvent(domEventName, eventSystemFlags, container, nativeEvent);
@@ -135,9 +135,9 @@ function dispatchContinuousEvent(
   container: EventTarget,
   nativeEvent: AnyNativeEvent,
 ) {
-  const previousPriority = getCurrentUpdatePriority();
   const prevTransition = ReactCurrentBatchConfig.transition;
   ReactCurrentBatchConfig.transition = null;
+  const previousPriority = getCurrentUpdatePriority();
   try {
     setCurrentUpdatePriority(ContinuousEventPriority);
     dispatchEvent(domEventName, eventSystemFlags, container, nativeEvent);

packages/react-native-renderer/src/ReactFiberConfigFabric.js

@@ -313,17 +313,19 @@ export function shouldSetTextContent(type: string, props: Props): boolean {
 }
 
 let currentUpdatePriority: EventPriority = NoEventPriority;
-export function setCurrentUpdatePriority(
-  newEventPriority: EventPriority,
-): void {
-  currentUpdatePriority = newEventPriority;
+export function setCurrentUpdatePriority(newPriority: EventPriority): void {
+  currentUpdatePriority = newPriority;
 }
 
 export function getCurrentUpdatePriority(): EventPriority {
   return currentUpdatePriority;
 }
 
-export function getCurrentEventPriority(): EventPriority {
+export function resolveUpdatePriority(): EventPriority {
+  if (currentUpdatePriority !== NoEventPriority) {
+    return currentUpdatePriority;
+  }
+
   const currentEventPriority = fabricGetCurrentEventPriority
     ? fabricGetCurrentEventPriority()
     : null;

packages/react-native-renderer/src/ReactFiberConfigNative.js

@@ -263,7 +263,10 @@ export function getCurrentUpdatePriority(): EventPriority {
   return currentUpdatePriority;
 }
 
-export function getCurrentEventPriority(): EventPriority {
+export function resolveUpdatePriority(): EventPriority {
+  if (currentUpdatePriority !== NoEventPriority) {
+    return currentUpdatePriority;
+  }
   return DefaultEventPriority;
 }
 

packages/react-noop-renderer/src/createReactNoop.js

@@ -513,7 +513,10 @@ function createReactNoop(reconciler: Function, useMutation: boolean) {
     setCurrentUpdatePriority,
     getCurrentUpdatePriority,
 
-    getCurrentEventPriority() {
+    resolveUpdatePriority() {
+      if (currentUpdatePriority !== NoEventPriority) {
+        return currentUpdatePriority;
+      }
       return currentEventPriority;
     },
 

packages/react-reconciler/src/ReactEventPriorities.js

@@ -48,6 +48,10 @@ export function isHigherEventPriority(
   return a !== 0 && a < b;
 }
 
+export function eventPriorityToLane(updatePriority: EventPriority): Lane {
+  return updatePriority;
+}
+
 export function lanesToEventPriority(lanes: Lanes): EventPriority {
   const lane = getHighestPriorityLane(lanes);
   if (!isHigherEventPriority(DiscreteEventPriority, lane)) {

packages/react-reconciler/src/ReactFiberReconciler.js

@@ -41,7 +41,7 @@ import getComponentNameFromFiber from 'react-reconciler/src/getComponentNameFrom
 import isArray from 'shared/isArray';
 import {enableSchedulingProfiler} from 'shared/ReactFeatureFlags';
 import ReactSharedInternals from 'shared/ReactSharedInternals';
-import {getPublicInstance, getCurrentUpdatePriority} from './ReactFiberConfig';
+import {getPublicInstance} from './ReactFiberConfig';
 import {
   findCurrentUnmaskedContext,
   processChildContext,
@@ -521,8 +521,6 @@ export function attemptHydrationAtCurrentPriority(fiber: Fiber): void {
   markRetryLaneIfNotHydrated(fiber, lane);
 }
 
-export {getCurrentUpdatePriority};
-
 export {findHostInstance};
 
 export {findHostInstanceWithWarning};

packages/react-reconciler/src/ReactFiberWorkLoop.js

@@ -70,13 +70,13 @@ import {
   cancelTimeout,
   noTimeout,
   afterActiveInstanceBlur,
-  getCurrentEventPriority,
   startSuspendingCommit,
   waitForCommitToBeReady,
   preloadInstance,
   supportsHydration,
-  getCurrentUpdatePriority,
   setCurrentUpdatePriority,
+  getCurrentUpdatePriority,
+  resolveUpdatePriority,
 } from './ReactFiberConfig';
 
 import {createWorkInProgress, resetWorkInProgress} from './ReactFiber';
@@ -161,6 +161,7 @@ import {
   DefaultEventPriority,
   lowerEventPriority,
   lanesToEventPriority,
+  eventPriorityToLane,
 } from './ReactEventPriorities';
 import {requestCurrentTransition} from './ReactFiberTransition';
 import {
@@ -641,25 +642,7 @@ export function requestUpdateLane(fiber: Fiber): Lane {
         requestTransitionLane(transition);
   }
 
-  // Updates originating inside certain React methods, like flushSync, have
-  // their priority set by tracking it with a context variable.
-  //
-  // The opaque type returned by the host config is internally a lane, so we can
-  // use that directly.
-  // TODO: Move this type conversion to the event priority module.
-  const updateLane: Lane = (getCurrentUpdatePriority(): any);
-  if (updateLane !== NoLane) {
-    return updateLane;
-  }
-
-  // This update originated outside React. Ask the host environment for an
-  // appropriate priority, based on the type of event.
-  //
-  // The opaque type returned by the host config is internally a lane, so we can
-  // use that directly.
-  // TODO: Move this type conversion to the event priority module.
-  const eventLane: Lane = (getCurrentEventPriority(): any);
-  return eventLane;
+  return eventPriorityToLane(resolveUpdatePriority());
 }
 
 function requestRetryLane(fiber: Fiber) {
@@ -1446,12 +1429,12 @@ export function getExecutionContext(): ExecutionContext {
 }
 
 export function deferredUpdates<A>(fn: () => A): A {
-  const previousPriority = getCurrentUpdatePriority();
   const prevTransition = ReactCurrentBatchConfig.transition;
 
+  const previousPriority = getCurrentUpdatePriority();
   try {
-    ReactCurrentBatchConfig.transition = null;
     setCurrentUpdatePriority(DefaultEventPriority);
+    ReactCurrentBatchConfig.transition = null;
     return fn();
   } finally {
     setCurrentUpdatePriority(previousPriority);
@@ -1492,11 +1475,11 @@ export function discreteUpdates<A, B, C, D, R>(
   c: C,
   d: D,
 ): R {
-  const previousPriority = getCurrentUpdatePriority();
   const prevTransition = ReactCurrentBatchConfig.transition;
+  const previousPriority = getCurrentUpdatePriority();
   try {
-    ReactCurrentBatchConfig.transition = null;
     setCurrentUpdatePriority(DiscreteEventPriority);
+    ReactCurrentBatchConfig.transition = null;
     return fn(a, b, c, d);
   } finally {
     setCurrentUpdatePriority(previousPriority);
@@ -1533,8 +1516,8 @@ export function flushSync<R>(fn: (() => R) | void): R | void {
   const previousPriority = getCurrentUpdatePriority();
 
   try {
-    ReactCurrentBatchConfig.transition = null;
     setCurrentUpdatePriority(DiscreteEventPriority);
+    ReactCurrentBatchConfig.transition = null;
     if (fn) {
       return fn();
     } else {
@@ -2713,12 +2696,12 @@ function commitRoot(
 ) {
   // TODO: This no longer makes any sense. We already wrap the mutation and
   // layout phases. Should be able to remove.
-  const previousUpdateLanePriority = getCurrentUpdatePriority();
   const prevTransition = ReactCurrentBatchConfig.transition;
 
+  const previousUpdateLanePriority = getCurrentUpdatePriority();
   try {
-    ReactCurrentBatchConfig.transition = null;
     setCurrentUpdatePriority(DiscreteEventPriority);
+    ReactCurrentBatchConfig.transition = null;
     commitRootImpl(
       root,
       recoverableErrors,
@@ -3187,8 +3170,8 @@ export function flushPassiveEffects(): boolean {
     const previousPriority = getCurrentUpdatePriority();
 
     try {
-      ReactCurrentBatchConfig.transition = null;
       setCurrentUpdatePriority(priority);
+      ReactCurrentBatchConfig.transition = null;
       return flushPassiveEffectsImpl();
     } finally {
       setCurrentUpdatePriority(previousPriority);

packages/react-reconciler/src/__tests__/ReactFiberHostContext-test.internal.js

@@ -77,7 +77,10 @@ describe('ReactFiberHostContext', () => {
       getCurrentUpdatePriority: function () {
         return updatePriority;
       },
-      getCurrentEventPriority: function () {
+      resolveUpdatePriority: function () {
+        if (updatePriority !== NoEventPriority) {
+          return updatePriority;
+        }
         return DefaultEventPriority;
       },
       shouldAttemptEagerTransition() {

packages/react-reconciler/src/forks/ReactFiberConfig.custom.js

@@ -67,7 +67,7 @@ export const prepareScopeUpdate = $$$config.prepareScopeUpdate;
 export const getInstanceFromScope = $$$config.getInstanceFromScope;
 export const setCurrentUpdatePriority = $$$config.setCurrentUpdatePriority;
 export const getCurrentUpdatePriority = $$$config.getCurrentUpdatePriority;
-export const getCurrentEventPriority = $$$config.getCurrentEventPriority;
+export const resolveUpdatePriority = $$$config.resolveUpdatePriority;
 export const shouldAttemptEagerTransition =
   $$$config.shouldAttemptEagerTransition;
 export const detachDeletedInstance = $$$config.detachDeletedInstance;

packages/react-test-renderer/src/ReactFiberConfigTestHost.js

@@ -211,7 +211,10 @@ export function getCurrentUpdatePriority(): EventPriority {
   return currentUpdatePriority;
 }
 
-export function getCurrentEventPriority(): EventPriority {
+export function resolveUpdatePriority(): EventPriority {
+  if (currentUpdatePriority !== NoEventPriority) {
+    return currentUpdatePriority;
+  }
   return DefaultEventPriority;
 }
 export function shouldAttemptEagerTransition(): boolean {