Fabric: Coupling Tag inside TargetEventEmitter

Summary: Now instead of passing `reactTag` through the whole event pipeline, we store it inside `EventTargetWrapper` (and it does not leave `UIManagerBinding`). It helps with reducing the complexity of `EventEmitter` and will help us in migrating to JSI.

Reviewed By: sahrens

Differential Revision: D13123045

fbshipit-source-id: aa9ee94d5660ff3090369c1e55cf748d2e72b987

ReactCommon/fabric/events/EventEmitter.cpp

@@ -40,7 +40,6 @@ EventEmitter::EventEmitter(
     WeakEventDispatcher eventDispatcher)
     : eventTarget_(std::move(eventTarget)),
       weakEventTarget_({}),
-      tag_(tag),
       eventDispatcher_(std::move(eventDispatcher)) {}
 
 void EventEmitter::dispatchEvent(
@@ -48,19 +47,14 @@ void EventEmitter::dispatchEvent(
     const folly::dynamic &payload,
     const EventPriority &priority) const {
   SystraceSection s("EventEmitter::dispatchEvent");
+
   auto eventDispatcher = eventDispatcher_.lock();
   if (!eventDispatcher) {
     return;
   }
 
-  // Mixing `target` into `payload`.
-  assert(payload.isObject());
-  folly::dynamic extendedPayload = folly::dynamic::object("target", tag_);
-  extendedPayload.merge_patch(payload);
-
   eventDispatcher->dispatchEvent(
-      RawEvent(normalizeEventType(type), extendedPayload, eventTarget_),
-      priority);
+      RawEvent(normalizeEventType(type), payload, eventTarget_), priority);
 }
 
 void EventEmitter::enable() const {

ReactCommon/fabric/events/EventEmitter.h

@@ -84,7 +84,6 @@ class EventEmitter {
 
   mutable SharedEventTarget eventTarget_;
   mutable WeakEventTarget weakEventTarget_;
-  Tag tag_;
   WeakEventDispatcher eventDispatcher_;
   mutable int enableCounter_{0};
 };

ReactCommon/fabric/uimanager/UIManagerBinding.cpp

@@ -71,6 +71,7 @@ void UIManagerBinding::dispatchEvent(
   SystraceSection s("UIManagerBinding::dispatchEvent");
 
   auto eventTargetValue = jsi::Value::null();
+  folly::dynamic extendedPayload;
 
   if (eventTarget) {
     auto &eventTargetWrapper =
@@ -79,6 +80,13 @@ void UIManagerBinding::dispatchEvent(
     if (eventTargetValue.isUndefined()) {
       return;
     }
+
+    // Mixing `target` into `payload`.
+    assert(payload.isObject());
+    extendedPayload = folly::dynamic::object("target", eventTargetWrapper.tag);
+    extendedPayload.merge_patch(payload);
+  } else {
+    extendedPayload = payload;
   }
 
   auto &eventHandlerWrapper =
@@ -87,7 +95,7 @@ void UIManagerBinding::dispatchEvent(
       runtime,
       {std::move(eventTargetValue),
        jsi::String::createFromUtf8(runtime, type),
-       jsi::valueFromDynamic(runtime, payload)});
+       jsi::valueFromDynamic(runtime, extendedPayload)});
 }
 
 void UIManagerBinding::invalidate() const {
@@ -119,7 +127,7 @@ jsi::Value UIManagerBinding::get(
                   componentNameFromValue(runtime, arguments[1]),
                   surfaceIdFromValue(runtime, arguments[2]),
                   rawPropsFromValue(runtime, arguments[3]),
-                  eventTargetFromValue(runtime, arguments[4])));
+                  eventTargetFromValue(runtime, arguments[4], arguments[0])));
         });
   }
 

ReactCommon/fabric/uimanager/primitives.h

@@ -31,10 +31,11 @@ inline RawProps rawPropsFromDynamic(const folly::dynamic object) noexcept {
 }
 
 struct EventTargetWrapper : public EventTarget {
-  EventTargetWrapper(jsi::WeakObject instanceHandle)
-      : instanceHandle(std::move(instanceHandle)) {}
+  EventTargetWrapper(jsi::WeakObject instanceHandle, Tag tag)
+      : instanceHandle(std::move(instanceHandle)), tag(tag) {}
 
   mutable jsi::WeakObject instanceHandle;
+  mutable Tag tag;
 };
 
 struct EventHandlerWrapper : public EventHandler {
@@ -97,9 +98,11 @@ inline static RawProps rawPropsFromValue(
 
 inline static SharedEventTarget eventTargetFromValue(
     jsi::Runtime &runtime,
-    const jsi::Value &value) {
+    const jsi::Value &eventTargetValue,
+    const jsi::Value &tagValue) {
   return std::make_shared<EventTargetWrapper>(
-      jsi::WeakObject(runtime, value.getObject(runtime)));
+      jsi::WeakObject(runtime, eventTargetValue.getObject(runtime)),
+      tagValue.getNumber());
 }
 
 inline static Tag tagFromValue(jsi::Runtime &runtime, const jsi::Value &value) {