From b3b72bbdcfe296a369e06f5564f7aa398842a520 Mon Sep 17 00:00:00 2001
From: Valentin Shergin <shergin@fb.com>
Date: Tue, 29 May 2018 14:54:52 -0700
Subject: [PATCH] Fabric: Using types `EventTarget`, `EventHandler` & co.
 instead of `void *` everywhere

Summary:
Nothing actually changed besides type names... which actually helps me found an issue in FabricUIManager!
Now there is no a single `void *` in Fabric/C++ and JavaScript bindings. Yay!

Reviewed By: fkgozali

Differential Revision: D8191420

fbshipit-source-id: b1eb60b6bc34dd25ab200aab854ffbd7ccf5b15d
---
 .../fabric/core/events/EventPrimitives.h       | 14 +++++++++-----
 .../fabric/core/primitives/ReactPrimitives.h   |  2 +-
 .../fabric/uimanager/FabricUIManager.cpp       | 14 +++++++-------
 ReactCommon/fabric/uimanager/FabricUIManager.h | 18 +++++++++---------
 4 files changed, 26 insertions(+), 22 deletions(-)

diff --git a/ReactCommon/fabric/core/events/EventPrimitives.h b/ReactCommon/fabric/core/events/EventPrimitives.h
index 46b715796..5dc5cb5d6 100644
--- a/ReactCommon/fabric/core/events/EventPrimitives.h
+++ b/ReactCommon/fabric/core/events/EventPrimitives.h
@@ -22,11 +22,15 @@ enum class EventPriority {
   Deferred = AsynchronousBatched,
 };
 
-// `InstanceHandler`, `EventTarget`, and `EventHandler` are all opaque
-// raw pointers. We use `struct {} *` trick to differentiate them in compiler's
-// eyes to ensure type safety.
-using EventTarget = struct {} *;
-using EventHandler = struct {} *;
+/* `InstanceHandler`, `EventTarget`, and `EventHandler` are all opaque
+ * raw pointers. We use `struct {} *` trick to differentiate them in compiler's
+ * eyes to ensure type safety.
+ * These structs must have names (and the names must be exported)
+ * to allow consistent template (e.g. `std::function`) instantiating
+ * across different modules.
+ */
+using EventTarget = struct EventTargetDummyStruct {} *;
+using EventHandler = struct EventHandlerDummyStruct {} *;
 
 } // namespace react
 } // namespace facebook
diff --git a/ReactCommon/fabric/core/primitives/ReactPrimitives.h b/ReactCommon/fabric/core/primitives/ReactPrimitives.h
index 0b5004ab2..c81f0ac93 100644
--- a/ReactCommon/fabric/core/primitives/ReactPrimitives.h
+++ b/ReactCommon/fabric/core/primitives/ReactPrimitives.h
@@ -19,7 +19,7 @@ namespace react {
  * `Tag` and `InstanceHandle` are used to address React Native components.
  */
 using Tag = int32_t;
-using InstanceHandle = void *;
+using InstanceHandle = struct InstanceHandleDummyStruct {} *;
 
 /*
  * `RawProps` represents untyped map with props comes from JavaScript side.
diff --git a/ReactCommon/fabric/uimanager/FabricUIManager.cpp b/ReactCommon/fabric/uimanager/FabricUIManager.cpp
index 94b630c74..7bedbfc8e 100644
--- a/ReactCommon/fabric/uimanager/FabricUIManager.cpp
+++ b/ReactCommon/fabric/uimanager/FabricUIManager.cpp
@@ -78,7 +78,7 @@ FabricUIManager::FabricUIManager(SharedComponentDescriptorRegistry componentDesc
 
 FabricUIManager::~FabricUIManager() {
   if (eventHandler_) {
-    releaseEventTargetFunction_(eventHandler_);
+    releaseEventHandlerFunction_(eventHandler_);
   }
 }
 
@@ -106,11 +106,11 @@ void FabricUIManager::setReleaseEventHandlerFunction(std::function<ReleaseEventH
   releaseEventHandlerFunction_ = releaseEventHandlerFunction;
 }
 
-void *FabricUIManager::createEventTarget(void *instanceHandle) {
+EventTarget FabricUIManager::createEventTarget(const InstanceHandle &instanceHandle) const {
   return createEventTargetFunction_(instanceHandle);
 }
 
-void FabricUIManager::dispatchEvent(void *eventTarget, const std::string &type, const folly::dynamic &payload) {
+void FabricUIManager::dispatchEvent(const EventTarget &eventTarget, const std::string &type, const folly::dynamic &payload) const {
   dispatchEventFunction_(
     eventHandler_,
     eventTarget,
@@ -119,12 +119,12 @@ void FabricUIManager::dispatchEvent(void *eventTarget, const std::string &type,
   );
 }
 
-void FabricUIManager::releaseEventTarget(void *eventTarget) {
+void FabricUIManager::releaseEventTarget(const EventTarget &eventTarget) const {
   releaseEventTargetFunction_(eventTarget);
 }
 
 SharedShadowNode FabricUIManager::createNode(int tag, std::string viewName, int rootTag, folly::dynamic props, InstanceHandle instanceHandle) {
-  isLoggingEnabled && LOG(INFO) << "FabricUIManager::createNode(tag: " << tag << ", name: " << viewName << ", rootTag" << rootTag << ", props: " << props << ")";
+  isLoggingEnabled && LOG(INFO) << "FabricUIManager::createNode(tag: " << tag << ", name: " << viewName << ", rootTag: " << rootTag << ", props: " << props << ")";
 
   ComponentName componentName = componentNameByReactViewName(viewName);
   const SharedComponentDescriptor &componentDescriptor = (*componentDescriptorRegistry_)[componentName];
@@ -251,8 +251,8 @@ void FabricUIManager::completeRoot(int rootTag, const SharedShadowNodeUnsharedLi
   }
 }
 
-void FabricUIManager::registerEventHandler(void *eventHandler) {
-  isLoggingEnabled && LOG(INFO) << "FabricUIManager::registerEventHandler(eventHandler)";
+void FabricUIManager::registerEventHandler(const EventHandler &eventHandler) {
+  isLoggingEnabled && LOG(INFO) << "FabricUIManager::registerEventHandler(eventHandler: " << eventHandler << ")";
   eventHandler_ = eventHandler;
 }
 
diff --git a/ReactCommon/fabric/uimanager/FabricUIManager.h b/ReactCommon/fabric/uimanager/FabricUIManager.h
index 54d1b8340..ca0987a08 100644
--- a/ReactCommon/fabric/uimanager/FabricUIManager.h
+++ b/ReactCommon/fabric/uimanager/FabricUIManager.h
@@ -18,10 +18,10 @@
 namespace facebook {
 namespace react {
 
-using CreateEventTargetFunction = void *(void *instanceHandle);
-using DispatchEventFunction = void (void *eventHandler, void *eventTarget, std::string type, folly::dynamic payload);
-using ReleaseEventTargetFunction = void (void *eventTarget);
-using ReleaseEventHandlerFunction = void (void *eventHandler);
+using CreateEventTargetFunction = EventTarget (InstanceHandle instanceHandle);
+using DispatchEventFunction = void (EventHandler eventHandler, EventTarget eventTarget, std::string type, folly::dynamic payload);
+using ReleaseEventTargetFunction = void (EventTarget eventTarget);
+using ReleaseEventHandlerFunction = void (EventHandler eventHandler);
 
 class FabricUIManager {
 public:
@@ -51,9 +51,9 @@ public:
 
 #pragma mark - Native-facing Interface
 
-  void *createEventTarget(void *instanceHandle);
-  void dispatchEvent(void *eventTarget, const std::string &type, const folly::dynamic &payload);
-  void releaseEventTarget(void *eventTarget);
+  EventTarget createEventTarget(const InstanceHandle &instanceHandle) const;
+  void dispatchEvent(const EventTarget &eventTarget, const std::string &type, const folly::dynamic &payload) const;
+  void releaseEventTarget(const EventTarget &eventTarget) const;
 
 #pragma mark - JavaScript/React-facing Interface
 
@@ -66,13 +66,13 @@ public:
   SharedShadowNodeUnsharedList createChildSet(Tag rootTag);
   void appendChildToSet(const SharedShadowNodeUnsharedList &childSet, const SharedShadowNode &childNode);
   void completeRoot(Tag rootTag, const SharedShadowNodeUnsharedList &childSet);
-  void registerEventHandler(void *eventHandler);
+  void registerEventHandler(const EventHandler &eventHandler);
 
 private:
 
   SharedComponentDescriptorRegistry componentDescriptorRegistry_;
   UIManagerDelegate *delegate_;
-  void *eventHandler_;
+  EventHandler eventHandler_;
   std::function<CreateEventTargetFunction> createEventTargetFunction_;
   std::function<DispatchEventFunction> dispatchEventFunction_;
   std::function<ReleaseEventTargetFunction> releaseEventTargetFunction_;