Adds more scaffolding for experimental event API

packages/react-art/src/ReactARTHostConfig.js

@@ -340,6 +340,10 @@ export function getChildHostContext() {
   return NO_CONTEXT;
 }
 
+export function getChildHostContextForEvent() {
+  return NO_CONTEXT;
+}
+
 export const scheduleTimeout = setTimeout;
 export const cancelTimeout = clearTimeout;
 export const noTimeout = -1;
@@ -440,7 +444,7 @@ export function handleEventComponent(
 }
 
 export function handleEventTarget(
-  type: string,
+  type: Symbol | number,
   props: Props,
   internalInstanceHandle: Object,
 ) {

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

@@ -44,6 +44,12 @@ import dangerousStyleValue from '../shared/dangerousStyleValue';
 
 import type {DOMContainer} from './ReactDOM';
 import type {ReactEventResponder} from 'shared/ReactTypes';
+import {
+  REACT_EVENT_COMPONENT_TYPE,
+  REACT_EVENT_TARGET_TYPE,
+  REACT_EVENT_TARGET_TOUCH_HIT,
+} from 'shared/ReactSymbols';
+import getElementFromTouchHitTarget from 'shared/getElementFromTouchHitTarget';
 
 export type Type = string;
 export type Props = {
@@ -65,6 +71,10 @@ export type PublicInstance = Element | Text;
 type HostContextDev = {
   namespace: string,
   ancestorInfo: mixed,
+  eventData: null | {|
+    isEventComponent?: boolean,
+    isEventTarget?: boolean,
+  |},
 };
 type HostContextProd = string;
 export type HostContext = HostContextDev | HostContextProd;
@@ -73,7 +83,11 @@ export type ChildSet = void; // Unused
 export type TimeoutHandle = TimeoutID;
 export type NoTimeout = -1;
 
-import {enableSuspenseServerRenderer} from 'shared/ReactFeatureFlags';
+import {
+  enableSuspenseServerRenderer,
+  enableEventAPI,
+} from 'shared/ReactFeatureFlags';
+import warning from 'shared/warning';
 
 // Intentionally not named imports because Rollup would
 // use dynamic dispatch for CommonJS interop named imports.
@@ -142,7 +156,7 @@ export function getRootHostContext(
   if (__DEV__) {
     const validatedTag = type.toLowerCase();
     const ancestorInfo = updatedAncestorInfo(null, validatedTag);
-    return {namespace, ancestorInfo};
+    return {namespace, ancestorInfo, eventData: null};
   }
   return namespace;
 }
@@ -159,12 +173,42 @@ export function getChildHostContext(
       parentHostContextDev.ancestorInfo,
       type,
     );
-    return {namespace, ancestorInfo};
+    return {namespace, ancestorInfo, eventData: null};
   }
   const parentNamespace = ((parentHostContext: any): HostContextProd);
   return getChildNamespace(parentNamespace, type);
 }
 
+export function getChildHostContextForEvent(
+  parentHostContext: HostContext,
+  type: Symbol | number,
+): HostContext {
+  if (__DEV__) {
+    const parentHostContextDev = ((parentHostContext: any): HostContextDev);
+    const {namespace, ancestorInfo} = parentHostContextDev;
+    let eventData = null;
+
+    if (type === REACT_EVENT_COMPONENT_TYPE) {
+      eventData = {
+        isEventComponent: true,
+        isEventTarget: false,
+      };
+    } else if (type === REACT_EVENT_TARGET_TYPE) {
+      warning(
+        parentHostContextDev.eventData !== null &&
+          parentHostContextDev.eventData.isEventComponent,
+        'validateDOMNesting: React event targets must be direct children of event components.',
+      );
+      eventData = {
+        isEventComponent: false,
+        isEventTarget: true,
+      };
+    }
+    return {namespace, ancestorInfo, eventData};
+  }
+  return parentHostContext;
+}
+
 export function getPublicInstance(instance: Instance): * {
   return instance;
 }
@@ -296,6 +340,23 @@ export function createTextInstance(
   if (__DEV__) {
     const hostContextDev = ((hostContext: any): HostContextDev);
     validateDOMNesting(null, text, hostContextDev.ancestorInfo);
+    if (enableEventAPI) {
+      const eventData = hostContextDev.eventData;
+      if (eventData !== null) {
+        warning(
+          !eventData.isEventComponent,
+          'validateDOMNesting: React event components cannot have text DOM nodes as children. ' +
+            'Wrap the child text "%s" in an element.',
+          text,
+        );
+        warning(
+          !eventData.isEventTarget,
+          'validateDOMNesting: React event targets cannot have text DOM nodes as children. ' +
+            'Wrap the child text "%s" in an element.',
+          text,
+        );
+      }
+    }
   }
   const textNode: TextInstance = createTextNode(text, rootContainerInstance);
   precacheFiberNode(internalInstanceHandle, textNode);
@@ -804,9 +865,25 @@ export function handleEventComponent(
 }
 
 export function handleEventTarget(
-  type: string,
+  type: Symbol | number,
   props: Props,
   internalInstanceHandle: Object,
 ) {
-  // TODO: add handleEventTarget implementation
+  // Touch target hit slop handling
+  if (type === REACT_EVENT_TARGET_TOUCH_HIT) {
+    // Validates that there is a single element
+    const element = getElementFromTouchHitTarget(internalInstanceHandle);
+    if (element !== null) {
+      // We update the event target state node to be that of the element.
+      // We can then diff this entry to determine if we need to add the
+      // hit slop element, or change the dimensions of the hit slop.
+      const lastElement = internalInstanceHandle.stateNode;
+      if (lastElement !== element) {
+        internalInstanceHandle.stateNode = element;
+        // TODO: Create the hit slop element and attach it to the element
+      } else {
+        // TODO: Diff the left, top, right, bottom props
+      }
+    }
+  }
 }

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

@@ -283,6 +283,14 @@ export function getChildHostContext(
   }
 }
 
+export function getChildHostContextForEvent(
+  parentHostContext: HostContext,
+  type: Symbol | number,
+) {
+  // TODO: add getChildHostContextForEvent implementation
+  return parentHostContext;
+}
+
 export function getPublicInstance(instance: Instance): * {
   return instance.canonical;
 }
@@ -428,7 +436,7 @@ export function handleEventComponent(
 }
 
 export function handleEventTarget(
-  type: string,
+  type: Symbol | number,
   props: Props,
   internalInstanceHandle: Object,
 ) {

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

@@ -206,6 +206,14 @@ export function getChildHostContext(
   }
 }
 
+export function getChildHostContextForEvent(
+  parentHostContext: HostContext,
+  type: Symbol | number,
+) {
+  // TODO: add getChildHostContextForEvent implementation
+  return parentHostContext;
+}
+
 export function getPublicInstance(instance: Instance): * {
   return instance;
 }
@@ -487,7 +495,7 @@ export function handleEventComponent(
 }
 
 export function handleEventTarget(
-  type: string,
+  type: Symbol | number,
   props: Props,
   internalInstanceHandle: Object,
 ) {

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

@@ -21,8 +21,18 @@ import type {ReactNodeList} from 'shared/ReactTypes';
 import * as Scheduler from 'scheduler/unstable_mock';
 import {createPortal} from 'shared/ReactPortal';
 import expect from 'expect';
-import {REACT_FRAGMENT_TYPE, REACT_ELEMENT_TYPE} from 'shared/ReactSymbols';
+import {
+  REACT_FRAGMENT_TYPE,
+  REACT_ELEMENT_TYPE,
+  REACT_EVENT_COMPONENT_TYPE,
+  REACT_EVENT_TARGET_TYPE,
+  REACT_EVENT_TARGET_TOUCH_HIT,
+} from 'shared/ReactSymbols';
 import warningWithoutStack from 'shared/warningWithoutStack';
+import warning from 'shared/warning';
+import getElementFromTouchHitTarget from 'shared/getElementFromTouchHitTarget';
+
+import {enableEventAPI} from 'shared/ReactFeatureFlags';
 
 // for .act's return value
 type Thenable = {
@@ -54,6 +64,8 @@ type HostContext = Object;
 
 const NO_CONTEXT = {};
 const UPPERCASE_CONTEXT = {};
+const EVENT_COMPONENT_CONTEXT = {};
+const EVENT_TARGET_CONTEXT = {};
 const UPDATE_SIGNAL = {};
 if (__DEV__) {
   Object.freeze(NO_CONTEXT);
@@ -250,6 +262,24 @@ function createReactNoop(reconciler: Function, useMutation: boolean) {
       return NO_CONTEXT;
     },
 
+    getChildHostContextForEvent(
+      parentHostContext: HostContext,
+      type: Symbol | number,
+    ) {
+      if (__DEV__ && enableEventAPI) {
+        if (type === REACT_EVENT_COMPONENT_TYPE) {
+          return EVENT_COMPONENT_CONTEXT;
+        } else if (type === REACT_EVENT_TARGET_TYPE) {
+          warning(
+            parentHostContext === EVENT_COMPONENT_CONTEXT,
+            'validateDOMNesting: React event targets must be direct children of event components.',
+          );
+          return EVENT_TARGET_CONTEXT;
+        }
+      }
+      return parentHostContext;
+    },
+
     getPublicInstance(instance) {
       return instance;
     },
@@ -333,6 +363,20 @@ function createReactNoop(reconciler: Function, useMutation: boolean) {
       hostContext: Object,
       internalInstanceHandle: Object,
     ): TextInstance {
+      if (__DEV__ && enableEventAPI) {
+        warning(
+          hostContext !== EVENT_COMPONENT_CONTEXT,
+          'validateDOMNesting: React event components cannot have text DOM nodes as children. ' +
+            'Wrap the child text "%s" in an element.',
+          text,
+        );
+        warning(
+          hostContext !== EVENT_TARGET_CONTEXT,
+          'validateDOMNesting: React event targets cannot have text DOM nodes as children. ' +
+            'Wrap the child text "%s" in an element.',
+          text,
+        );
+      }
       if (hostContext === UPPERCASE_CONTEXT) {
         text = text.toUpperCase();
       }
@@ -363,6 +407,21 @@ function createReactNoop(reconciler: Function, useMutation: boolean) {
 
     isPrimaryRenderer: true,
     supportsHydration: false,
+
+    handleEventComponent() {
+      // NO-OP
+    },
+
+    handleEventTarget(
+      type: Symbol | number,
+      props: Props,
+      internalInstanceHandle: Object,
+    ) {
+      if (type === REACT_EVENT_TARGET_TOUCH_HIT) {
+        // Validates that there is a single element
+        getElementFromTouchHitTarget(internalInstanceHandle);
+      }
+    },
   };
 
   const hostConfig = useMutation