Move priorities to separate import to break cycle (#21060)

The event priority constants exports by the reconciler package are
meant to be used by the reconciler (host config) itself. So it doesn't
make sense to export them from a module that requires them.
To break the cycle, we can move them to a separate module and import
that. This looks like a "deep import" of an internal module, which we
try to avoid, but conceptually these are part of the public interface
of the reconciler module. So, no different than importing from the main
`react-reconciler`.
We do need to be careful about not mixing these types of imports with
implementation details. Those are the ones to really avoid.
An unintended benefit of the reconciler fork infra is that it makes
deep imports harder. Any module that we treat as "public", like this
one, needs to account for the `enableNewReconciler` flag and forward
to the correct implementation.

Author: acdlite

packages/react-art/src/ReactARTHostConfig.js

@@ -7,17 +7,11 @@
 
 importTransformfrom'art/core/transform';
 importModefrom'art/modes/current';
-import{enableNewReconciler}from'shared/ReactFeatureFlags';
 importinvariantfrom'shared/invariant';
 
 import{TYPES,EVENT_TYPES,childrenAsString}from'./ReactARTInternals';
 
-import{DefaultLanePriorityasDefaultLanePriority_old}from'react-reconciler/src/ReactFiberLane.old';
-import{DefaultLanePriorityasDefaultLanePriority_new}from'react-reconciler/src/ReactFiberLane.new';
-
-constDefaultLanePriority=enableNewReconciler
- ? DefaultLanePriority_new
- : DefaultLanePriority_old;
+import{DefaultEventPriority}from'react-reconciler/src/ReactEventPriorities';
 
 constpooledTransform=newTransform();
 
@@ -347,7 +341,7 @@ export function shouldSetTextContent(type, props) {
 }
 
 exportfunctiongetCurrentEventPriority(){
-returnDefaultLanePriority;
+returnDefaultEventPriority;
 }
 
 // The ART renderer is secondary to the React DOM renderer.

packages/react-dom/src/client/ReactDOMHostConfig.js

@@ -67,17 +67,11 @@ import {
 enableSuspenseServerRenderer,
 enableCreateEventHandleAPI,
 enableScopeAPI,
-enableNewReconciler,
 }from'shared/ReactFeatureFlags';
 import{HostComponent,HostText}from'react-reconciler/src/ReactWorkTags';
 import{listenToAllSupportedEvents}from'../events/DOMPluginEventSystem';
 
-import{DefaultLanePriorityasDefaultLanePriority_old}from'react-reconciler/src/ReactFiberLane.old';
-import{DefaultLanePriorityasDefaultLanePriority_new}from'react-reconciler/src/ReactFiberLane.new';
-
-constDefaultLanePriority=enableNewReconciler
- ? DefaultLanePriority_new
- : DefaultLanePriority_old;
+import{DefaultEventPriority}from'react-reconciler/src/ReactEventPriorities';
 
 exporttypeType=string;
 exporttypeProps={
@@ -385,7 +379,7 @@ export function createTextInstance(
 exportfunctiongetCurrentEventPriority(): *{
 constcurrentEvent=window.event;
 if(currentEvent===undefined){
-returnDefaultLanePriority;
+returnDefaultEventPriority;
 }
 returngetEventPriority(currentEvent.type);
 }

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

@@ -14,6 +14,7 @@ import type {
 }from'react-reconciler/src/ReactInternalTypes';
 importtype{Container,SuspenseInstance}from'../client/ReactDOMHostConfig';
 importtype{DOMEventName}from'../events/DOMEventNames';
+importtype{LanePriority}from'react-reconciler/src/ReactFiberLane.new';
 
 import{
 isReplayableDiscreteEvent,
@@ -49,18 +50,13 @@ import {
 
 import{
 InputContinuousLanePriorityasInputContinuousLanePriority_old,
-DefaultLanePriorityasDefaultLanePriority_old,
 getCurrentUpdateLanePriorityasgetCurrentUpdateLanePriority_old,
 setCurrentUpdateLanePriorityassetCurrentUpdateLanePriority_old,
 }from'react-reconciler/src/ReactFiberLane.old';
 import{
 InputContinuousLanePriorityasInputContinuousLanePriority_new,
-DefaultLanePriorityasDefaultLanePriority_new,
 getCurrentUpdateLanePriorityasgetCurrentUpdateLanePriority_new,
 setCurrentUpdateLanePriorityassetCurrentUpdateLanePriority_new,
-SyncLanePriority,
-IdleLanePriority,
-NoLanePriority,
 }from'react-reconciler/src/ReactFiberLane.new';
 import{getCurrentPriorityLevelasgetCurrentPriorityLevel_old}from'react-reconciler/src/SchedulerWithReactIntegration.old';
 import{
@@ -71,14 +67,16 @@ import {
 NormalPriorityasNormalSchedulerPriority,
 UserBlockingPriorityasUserBlockingSchedulerPriority,
 }from'react-reconciler/src/SchedulerWithReactIntegration.new';
-importtype{LanePriority}from'react-reconciler/src/ReactFiberLane.new';
+import{
+DiscreteEventPriority,
+ContinuousEventPriority,
+DefaultEventPriority,
+IdleEventPriority,
+}from'react-reconciler/src/ReactEventPriorities';
 
 constInputContinuousLanePriority=enableNewReconciler
  ? InputContinuousLanePriority_new
  : InputContinuousLanePriority_old;
-constDefaultLanePriority=enableNewReconciler
- ? DefaultLanePriority_new
- : DefaultLanePriority_old;
 constgetCurrentUpdateLanePriority=enableNewReconciler
  ? getCurrentUpdateLanePriority_new
  : getCurrentUpdateLanePriority_old;
@@ -94,17 +92,17 @@ function schedulerPriorityToLanePriority(
 ): LanePriority{
 switch(schedulerPriorityLevel){
 caseImmediateSchedulerPriority:
-returnSyncLanePriority;
+returnDiscreteEventPriority;
 caseUserBlockingSchedulerPriority:
-returnInputContinuousLanePriority;
+returnContinuousEventPriority;
 caseNormalSchedulerPriority:
 caseLowSchedulerPriority:
 // TODO: Handle LowSchedulerPriority, somehow. Maybe the same lane as hydration.
-returnDefaultLanePriority;
+returnDefaultEventPriority;
 caseIdleSchedulerPriority:
-returnIdleLanePriority;
+returnIdleEventPriority;
 default:
-returnNoLanePriority;
+returnDefaultEventPriority;
 }
 }
 
@@ -142,13 +140,13 @@ export function createEventListenerWrapperWithPriority(
 consteventPriority=getEventPriority(domEventName);
 letlistenerWrapper;
 switch(eventPriority){
-caseSyncLanePriority:
+caseDiscreteEventPriority:
 listenerWrapper=dispatchDiscreteEvent;
 break;
-caseInputContinuousLanePriority:
+caseContinuousEventPriority:
 listenerWrapper=dispatchContinuousEvent;
 break;
-caseDefaultLanePriority:
+caseDefaultEventPriority:
 default:
 listenerWrapper=dispatchEvent;
 break;
@@ -407,7 +405,7 @@ export function getEventPriority(domEventName: DOMEventName): * {
 case'popstate':
 case'select':
 case'selectstart':
-returnSyncLanePriority;
+returnDiscreteEventPriority;
 case'drag':
 case'dragenter':
 case'dragexit':
@@ -427,7 +425,7 @@ export function getEventPriority(domEventName: DOMEventName): * {
 // eslint-disable-next-line no-fallthrough
 case'mouseenter':
 case'mouseleave':
-returnInputContinuousLanePriority;
+returnContinuousEventPriority;
 case'message': {
 // We might be in the Scheduler callback.
 // Eventually this mechanism will be replaced by a check
@@ -436,6 +434,6 @@ export function getEventPriority(domEventName: DOMEventName): * {
 returnschedulerPriorityToLanePriority(schedulerPriority);
 }
 default:
-returnDefaultLanePriority;
+returnDefaultEventPriority;
 }
 }

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

@@ -21,17 +21,11 @@ import type {
 import{mountSafeCallback_NOT_REALLY_SAFE}from'./NativeMethodsMixinUtils';
 import{create,diff}from'./ReactNativeAttributePayload';
 
-import{enableNewReconciler}from'shared/ReactFeatureFlags';
 importinvariantfrom'shared/invariant';
 
 import{dispatchEvent}from'./ReactFabricEventEmitter';
 
-import{DefaultLanePriorityasDefaultLanePriority_old}from'react-reconciler/src/ReactFiberLane.old';
-import{DefaultLanePriorityasDefaultLanePriority_new}from'react-reconciler/src/ReactFiberLane.new';
-
-constDefaultLanePriority=enableNewReconciler
- ? DefaultLanePriority_new
- : DefaultLanePriority_old;
+import{DefaultEventPriority}from'react-reconciler/src/ReactEventPriorities';
 
 // Modules provided by RN:
 import{
@@ -349,7 +343,7 @@ export function shouldSetTextContent(type: string, props: Props): boolean {
 }
 
 exportfunctiongetCurrentEventPriority(): *{
- return DefaultLanePriority;
+ return DefaultEventPriority;
 }
 
 // The Fabric renderer is secondary to the existing React Native renderer.

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

@@ -10,7 +10,6 @@
 importtype{TouchedViewDataAtPoint}from'./ReactNativeTypes';
 
 importinvariantfrom'shared/invariant';
-import{enableNewReconciler}from'shared/ReactFeatureFlags';
 
 // Modules provided by RN:
 import{
@@ -27,12 +26,7 @@ import {
 }from'./ReactNativeComponentTree';
 importReactNativeFiberHostComponentfrom'./ReactNativeFiberHostComponent';
 
-import{DefaultLanePriorityasDefaultLanePriority_old}from'react-reconciler/src/ReactFiberLane.old';
-import{DefaultLanePriorityasDefaultLanePriority_new}from'react-reconciler/src/ReactFiberLane.new';
-
-constDefaultLanePriority=enableNewReconciler
- ? DefaultLanePriority_new
- : DefaultLanePriority_old;
+import{DefaultEventPriority}from'react-reconciler/src/ReactEventPriorities';
 
 const{get: getViewConfigForType}=ReactNativeViewConfigRegistry;
 
@@ -268,7 +262,7 @@ export function shouldSetTextContent(type: string, props: Props): boolean {
 }
 
 exportfunctiongetCurrentEventPriority(): *{
-returnDefaultLanePriority;
+returnDefaultEventPriority;
 }
 
 // -------------------

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

@@ -27,6 +27,9 @@ import ReactSharedInternals from 'shared/ReactSharedInternals';
 importenqueueTaskfrom'shared/enqueueTask';
 const{IsSomeRendererActing}=ReactSharedInternals;
 
+// TODO: Publish public entry point that exports the event priority constants
+constDefaultEventPriority=8;
+
 typeContainer={
 rootID: string,
 children: Array<Instance|TextInstance>,
@@ -587,7 +590,7 @@ function createReactNoop(reconciler: Function, useMutation: boolean) {
 constroots=newMap();
 constDEFAULT_ROOT_ID='<default>';
 
-letcurrentEventPriority=NoopRenderer.DefaultEventPriority;
+letcurrentEventPriority=DefaultEventPriority;
 
 functionchildToJSX(child,text){
 if(text!==null){

packages/react-reconciler/README.md

@@ -219,10 +219,16 @@ This is a property (not a function) that should be set to `true` if your rendere
 To implement this method, you'll need some constants available on the _returned_`Renderer` object:
 
 ```js
+import {
+DiscreteEventPriority,
+ContinuousEventPriority,
+DefaultEventPriority,
+} from'./ReactFiberReconciler/src/ReactEventPriorities';
+
 constHostConfig= {
 // ...
 getCurrentEventPriority() {
-returnMyRenderer.DefaultEventPriority;
+return DefaultEventPriority;
  },
 // ...
 }
@@ -232,11 +238,11 @@ const MyRenderer = Reconciler(HostConfig);
 
 The constant you return depends on which event, if any, is being handled right now. (In the browser, you can check this using `window.event && window.event.type`).
 
-***Discrete events:** If the active event is _directly caused by the user_ (such as mouse and keyboard events) and _each event in a sequence is intentional_ (e.g. `click`), return `MyRenderer.DiscreteEventPriority`. This tells React that they should interrupt any background work and cannot be batched across time.
+***Discrete events:** If the active event is _directly caused by the user_ (such as mouse and keyboard events) and _each event in a sequence is intentional_ (e.g. `click`), return `DiscreteEventPriority`. This tells React that they should interrupt any background work and cannot be batched across time.
 
-***Continuous events:** If the active event is _directly caused by the user_ but _the user can't distinguish between individual events in a sequence_ (e.g. `mouseover`), return `MyRenderer.ContinuousEventPriority`. This tells React they should interrupt any background work but can be batched across time.
+***Continuous events:** If the active event is _directly caused by the user_ but _the user can't distinguish between individual events in a sequence_ (e.g. `mouseover`), return `ContinuousEventPriority`. This tells React they should interrupt any background work but can be batched across time.
 
-***Other events / No active event:** In all other cases, return `MyRenderer.DefaultEventPriority`. This tells React that this event is considered background work, and interactive events will be prioritized over it.
+***Other events / No active event:** In all other cases, return `DefaultEventPriority`. This tells React that this event is considered background work, and interactive events will be prioritized over it.
 
 You can consult the `getCurrentEventPriority()` implementation in `ReactDOMHostConfig.js` for a reference implementation.
 

packages/react-reconciler/src/ReactEventPriorities.js

@@ -0,0 +1,37 @@
+/**
+ * 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{enableNewReconciler}from'shared/ReactFeatureFlags';
+
+import{
+DiscreteEventPriorityasDiscreteEventPriority_old,
+ContinuousEventPriorityasContinuousEventPriority_old,
+DefaultEventPriorityasDefaultEventPriority_old,
+IdleEventPriorityasIdleEventPriority_old,
+}from'./ReactEventPriorities.old';
+
+import{
+DiscreteEventPriorityasDiscreteEventPriority_new,
+ContinuousEventPriorityasContinuousEventPriority_new,
+DefaultEventPriorityasDefaultEventPriority_new,
+IdleEventPriorityasIdleEventPriority_new,
+}from'./ReactEventPriorities.new';
+
+exportconstDiscreteEventPriority=enableNewReconciler
+ ? DiscreteEventPriority_new
+ : DiscreteEventPriority_old;
+exportconstContinuousEventPriority=enableNewReconciler
+ ? ContinuousEventPriority_new
+ : ContinuousEventPriority_old;
+exportconstDefaultEventPriority=enableNewReconciler
+ ? DefaultEventPriority_new
+ : DefaultEventPriority_old;
+exportconstIdleEventPriority=enableNewReconciler
+ ? IdleEventPriority_new
+ : IdleEventPriority_old;

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

@@ -0,0 +1,15 @@
+/**
+ * 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
+ */
+
+export{
+SyncLanePriorityasDiscreteEventPriority,
+InputContinuousLanePriorityasContinuousEventPriority,
+DefaultLanePriorityasDefaultEventPriority,
+IdleLanePriorityasIdleEventPriority,
+}from'./ReactFiberLane.new';

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

@@ -0,0 +1,15 @@
+/**
+ * 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
+ */
+
+export{
+SyncLanePriorityasDiscreteEventPriority,
+InputContinuousLanePriorityasContinuousEventPriority,
+DefaultLanePriorityasDefaultEventPriority,
+IdleLanePriorityasIdleEventPriority,
+}from'./ReactFiberLane.old';