add <TracingMarker> component boilerplate

- Add Tracing Marker component type to React exports
- Add reconciler work tag
- Add devtools work tag
- Add boilerplate for the cache to render children

No functionality yet

packages/react-devtools-shared/src/backend/renderer.js

@@ -24,6 +24,7 @@ import {
   ElementTypeRoot,
   ElementTypeSuspense,
   ElementTypeSuspenseList,
+  ElementTypeTracingMarker,
   StrictMode,
 } from 'react-devtools-shared/src/types';
 import {
@@ -247,6 +248,8 @@ export function getInternalReactConstants(
       SimpleMemoComponent: 15,
       SuspenseComponent: 13,
       SuspenseListComponent: 19, // Experimental
+      TracingMarkerComponent: 25, // Experimental - This is technically in 18 but we don't
+      // want to fork again so we're adding it here instead
       YieldComponent: -1, // Removed
     };
   } else if (gte(version, '17.0.0-alpha')) {
@@ -277,6 +280,7 @@ export function getInternalReactConstants(
       SimpleMemoComponent: 15,
       SuspenseComponent: 13,
       SuspenseListComponent: 19, // Experimental
+      TracingMarkerComponent: -1, // Doesn't exist yet
       YieldComponent: -1, // Removed
     };
   } else if (gte(version, '16.6.0-beta.0')) {
@@ -307,6 +311,7 @@ export function getInternalReactConstants(
       SimpleMemoComponent: 15,
       SuspenseComponent: 13,
       SuspenseListComponent: 19, // Experimental
+      TracingMarkerComponent: -1, // Doesn't exist yet
       YieldComponent: -1, // Removed
     };
   } else if (gte(version, '16.4.3-alpha')) {
@@ -337,6 +342,7 @@ export function getInternalReactConstants(
       SimpleMemoComponent: -1, // Doesn't exist yet
       SuspenseComponent: 16,
       SuspenseListComponent: -1, // Doesn't exist yet
+      TracingMarkerComponent: -1, // Doesn't exist yet
       YieldComponent: -1, // Removed
     };
   } else {
@@ -367,6 +373,7 @@ export function getInternalReactConstants(
       SimpleMemoComponent: -1, // Doesn't exist yet
       SuspenseComponent: 16,
       SuspenseListComponent: -1, // Doesn't exist yet
+      TracingMarkerComponent: -1, // Doesn't exist yet
       YieldComponent: 9,
     };
   }
@@ -405,6 +412,7 @@ export function getInternalReactConstants(
     SimpleMemoComponent,
     SuspenseComponent,
     SuspenseListComponent,
+    TracingMarkerComponent,
   } = ReactTypeOfWork;
 
   function resolveFiberType(type: any) {
@@ -484,6 +492,8 @@ export function getInternalReactConstants(
         return 'SuspenseList';
       case Profiler:
         return 'Profiler';
+      case TracingMarkerComponent:
+        return 'TracingMarker';
       default:
         const typeSymbol = getTypeSymbol(type);
 
@@ -583,6 +593,7 @@ export function attach(
     SimpleMemoComponent,
     SuspenseComponent,
     SuspenseListComponent,
+    TracingMarkerComponent,
   } = ReactTypeOfWork;
   const {
     ImmediatePriority,
@@ -1044,6 +1055,8 @@ export function attach(
         return ElementTypeSuspense;
       case SuspenseListComponent:
         return ElementTypeSuspenseList;
+      case TracingMarkerComponent:
+        return ElementTypeTracingMarker;
       default:
         const typeSymbol = getTypeSymbol(type);
 

packages/react-devtools-shared/src/backend/types.js

@@ -53,6 +53,7 @@ export type WorkTagMap = {|
   SimpleMemoComponent: WorkTag,
   SuspenseComponent: WorkTag,
   SuspenseListComponent: WorkTag,
+  TracingMarkerComponent: WorkTag,
   YieldComponent: WorkTag,
 |};
 

packages/react-devtools-shared/src/types.js

@@ -32,11 +32,12 @@ export const ElementTypeProfiler = 10;
 export const ElementTypeRoot = 11;
 export const ElementTypeSuspense = 12;
 export const ElementTypeSuspenseList = 13;
+export const ElementTypeTracingMarker = 14;
 
 // Different types of elements displayed in the Elements tree.
 // These types may be used to visually distinguish types,
 // or to enable/disable certain functionality.
-export type ElementType = 1 | 2 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13;
+export type ElementType = 1 | 2 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14;
 
 // WARNING
 // The values below are referenced by ComponentFilters (which are saved via localStorage).

packages/react-devtools-shared/src/utils.js

@@ -22,7 +22,10 @@ import {
   StrictMode,
   Suspense,
 } from 'react-is';
-import {REACT_SUSPENSE_LIST_TYPE as SuspenseList} from 'shared/ReactSymbols';
+import {
+  REACT_SUSPENSE_LIST_TYPE as SuspenseList,
+  REACT_TRACING_MARKER_TYPE as TracingMarker,
+} from 'shared/ReactSymbols';
 import {
   TREE_OPERATION_ADD,
   TREE_OPERATION_REMOVE,
@@ -684,6 +687,8 @@ export function getDisplayNameForReactElement(
       return 'Suspense';
     case SuspenseList:
       return 'SuspenseList';
+    case TracingMarker:
+      return 'TracingMarker';
     default:
       const {type} = element;
       if (typeof type === 'string') {

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

@@ -25,6 +25,7 @@ import {
   enableScopeAPI,
   enableSyncDefaultUpdates,
   allowConcurrentByDefault,
+  enableTransitionTracing,
 } from 'shared/ReactFeatureFlags';
 import {
   supportsPersistence,
@@ -56,6 +57,7 @@ import {
   OffscreenComponent,
   LegacyHiddenComponent,
   CacheComponent,
+  TracingMarkerComponent,
 } from './ReactWorkTags';
 import getComponentNameFromFiber from 'react-reconciler/src/getComponentNameFromFiber';
 
@@ -91,6 +93,7 @@ import {
   REACT_OFFSCREEN_TYPE,
   REACT_LEGACY_HIDDEN_TYPE,
   REACT_CACHE_TYPE,
+  REACT_TRACING_MARKER_TYPE,
 } from 'shared/ReactSymbols';
 
 export type {Fiber};
@@ -521,6 +524,11 @@ export function createFiberFromTypeAndProps(
           return createFiberFromCache(pendingProps, mode, lanes, key);
         }
       // eslint-disable-next-line no-fallthrough
+      case REACT_TRACING_MARKER_TYPE:
+        if (enableTransitionTracing) {
+          return createFiberFromTracingMarker(pendingProps, mode, lanes, key);
+        }
+      // eslint-disable-next-line no-fallthrough
       default: {
         if (typeof type === 'object' && type !== null) {
           switch (type.$$typeof) {
@@ -746,6 +754,18 @@ export function createFiberFromCache(
   return fiber;
 }
 
+export function createFiberFromTracingMarker(
+  pendingProps: any,
+  mode: TypeOfMode,
+  lanes: Lanes,
+  key: null | string,
+) {
+  const fiber = createFiber(TracingMarkerComponent, pendingProps, key, mode);
+  fiber.elementType = REACT_TRACING_MARKER_TYPE;
+  fiber.lanes = lanes;
+  return fiber;
+}
+
 export function createFiberFromText(
   content: string,
   mode: TypeOfMode,

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

@@ -25,6 +25,7 @@ import {
   enableScopeAPI,
   enableSyncDefaultUpdates,
   allowConcurrentByDefault,
+  enableTransitionTracing,
 } from 'shared/ReactFeatureFlags';
 import {
   supportsPersistence,
@@ -56,6 +57,7 @@ import {
   OffscreenComponent,
   LegacyHiddenComponent,
   CacheComponent,
+  TracingMarkerComponent,
 } from './ReactWorkTags';
 import getComponentNameFromFiber from 'react-reconciler/src/getComponentNameFromFiber';
 
@@ -91,6 +93,7 @@ import {
   REACT_OFFSCREEN_TYPE,
   REACT_LEGACY_HIDDEN_TYPE,
   REACT_CACHE_TYPE,
+  REACT_TRACING_MARKER_TYPE,
 } from 'shared/ReactSymbols';
 
 export type {Fiber};
@@ -521,6 +524,11 @@ export function createFiberFromTypeAndProps(
           return createFiberFromCache(pendingProps, mode, lanes, key);
         }
       // eslint-disable-next-line no-fallthrough
+      case REACT_TRACING_MARKER_TYPE:
+        if (enableTransitionTracing) {
+          return createFiberFromTracingMarker(pendingProps, mode, lanes, key);
+        }
+      // eslint-disable-next-line no-fallthrough
       default: {
         if (typeof type === 'object' && type !== null) {
           switch (type.$$typeof) {
@@ -746,6 +754,18 @@ export function createFiberFromCache(
   return fiber;
 }
 
+export function createFiberFromTracingMarker(
+  pendingProps: any,
+  mode: TypeOfMode,
+  lanes: Lanes,
+  key: null | string,
+) {
+  const fiber = createFiber(TracingMarkerComponent, pendingProps, key, mode);
+  fiber.elementType = REACT_TRACING_MARKER_TYPE;
+  fiber.lanes = lanes;
+  return fiber;
+}
+
 export function createFiberFromText(
   content: string,
   mode: TypeOfMode,

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

@@ -61,6 +61,7 @@ import {
   OffscreenComponent,
   LegacyHiddenComponent,
   CacheComponent,
+  TracingMarkerComponent,
 } from './ReactWorkTags';
 import {
   NoFlags,
@@ -93,6 +94,7 @@ import {
   enableSuspenseLayoutEffectSemantics,
   enableSchedulingProfiler,
   enablePersistentOffscreenHostContainer,
+  enableTransitionTracing,
 } from 'shared/ReactFeatureFlags';
 import isArray from 'shared/isArray';
 import shallowEqual from 'shared/shallowEqual';
@@ -898,6 +900,21 @@ function updateCacheComponent(
   return workInProgress.child;
 }
 
+// This should only be called if the name changes
+function updateTracingMarkerComponent(
+  current: Fiber | null,
+  workInProgress: Fiber,
+  renderLanes: Lanes,
+) {
+  if (!enableTransitionTracing) {
+    return null;
+  }
+
+  const nextChildren = workInProgress.pendingProps.children;
+  reconcileChildren(current, workInProgress, nextChildren, renderLanes);
+  return workInProgress.child;
+}
+
 function updateFragment(
   current: Fiber | null,
   workInProgress: Fiber,
@@ -3900,6 +3917,16 @@ function beginWork(
       }
       break;
     }
+    case TracingMarkerComponent: {
+      if (enableTransitionTracing) {
+        return updateTracingMarkerComponent(
+          current,
+          workInProgress,
+          renderLanes,
+        );
+      }
+      break;
+    }
   }
 
   throw new Error(

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

@@ -61,6 +61,7 @@ import {
   OffscreenComponent,
   LegacyHiddenComponent,
   CacheComponent,
+  TracingMarkerComponent,
 } from './ReactWorkTags';
 import {
   NoFlags,
@@ -93,6 +94,7 @@ import {
   enableSuspenseLayoutEffectSemantics,
   enableSchedulingProfiler,
   enablePersistentOffscreenHostContainer,
+  enableTransitionTracing,
 } from 'shared/ReactFeatureFlags';
 import isArray from 'shared/isArray';
 import shallowEqual from 'shared/shallowEqual';
@@ -898,6 +900,21 @@ function updateCacheComponent(
   return workInProgress.child;
 }
 
+// This should only be called if the name changes
+function updateTracingMarkerComponent(
+  current: Fiber | null,
+  workInProgress: Fiber,
+  renderLanes: Lanes,
+) {
+  if (!enableTransitionTracing) {
+    return null;
+  }
+
+  const nextChildren = workInProgress.pendingProps.children;
+  reconcileChildren(current, workInProgress, nextChildren, renderLanes);
+  return workInProgress.child;
+}
+
 function updateFragment(
   current: Fiber | null,
   workInProgress: Fiber,
@@ -3900,6 +3917,16 @@ function beginWork(
       }
       break;
     }
+    case TracingMarkerComponent: {
+      if (enableTransitionTracing) {
+        return updateTracingMarkerComponent(
+          current,
+          workInProgress,
+          renderLanes,
+        );
+      }
+      break;
+    }
   }
 
   throw new Error(

packages/react-reconciler/src/ReactWorkTags.js

@@ -32,7 +32,8 @@ export type WorkTag =
   | 21
   | 22
   | 23
-  | 24;
+  | 24
+  | 25;
 
 export const FunctionComponent = 0;
 export const ClassComponent = 1;
@@ -58,3 +59,4 @@ export const ScopeComponent = 21;
 export const OffscreenComponent = 22;
 export const LegacyHiddenComponent = 23;
 export const CacheComponent = 24;
+export const TracingMarkerComponent = 25;

packages/react-reconciler/src/getComponentNameFromFiber.js

@@ -34,6 +34,7 @@ import {
   OffscreenComponent,
   LegacyHiddenComponent,
   CacheComponent,
+  TracingMarkerComponent,
 } from 'react-reconciler/src/ReactWorkTags';
 import getComponentNameFromType from 'shared/getComponentNameFromType';
 import {REACT_STRICT_MODE_TYPE} from 'shared/ReactSymbols';
@@ -103,7 +104,8 @@ export default function getComponentNameFromFiber(fiber: Fiber): string | null {
       return 'Suspense';
     case SuspenseListComponent:
       return 'SuspenseList';
-
+    case TracingMarkerComponent:
+      return 'TracingMarker';
     // The display name for this tags come from the user-provided type:
     case ClassComponent:
     case FunctionComponent:

packages/react/index.js

@@ -58,6 +58,7 @@ export {
   unstable_LegacyHidden,
   unstable_Offscreen,
   unstable_Scope,
+  unstable_TracingMarker,
   unstable_getCacheSignal,
   unstable_getCacheForType,
   unstable_useCacheRefresh,