Remove legacy Hermes C++ code and HERMES_V1_ENABLED compile definition (#56731)

Summary:

  - Remove all dead C++ code behind `!defined(HERMES_V1_ENABLED)` guards in `HermesExecutorFactory.cpp` and `HermesInstance.cpp`
  - Delete `Registration.h`, `Registration.cpp`, `ConnectionDemux.h`, `ConnectionDemux.cpp`, and `ConnectionDemuxTests.cpp` (entirely legacy code)
  - Remove `HERMES_V1_ENABLED` compile definition from `react-native-flags.cmake`
  - Remove `HERMES_V1_ENABLED` cache variable from Android `CMakeLists.txt`

  This is Phase 1 of removing legacy Hermes support. Since Hermes V1 is already the default on all platforms and the 0.86 branch has been cut, all legacy Hermes code
   is dead and can be safely removed.

## Changelog:
[General][Breaking] - Remove Legacy Hermes from C++ code

  ## Test plan
  - [x] Android: `./gradlew :packages:rn-tester:android:app:assembleDebug` — BUILD SUCCEEDED
  - [x] iOS: `xcodebuild` rn-tester on iPhone 16 Pro simulator — BUILD SUCCEEDED

Reviewed By: cortinico

Differential Revision: D104228879

Author: cipolleschi

packages/react-native/ReactAndroid/src/main/jni/CMakeLists.txt

@@ -22,8 +22,6 @@ file(TO_CMAKE_PATH "${REACT_ANDROID_DIR}" REACT_ANDROID_DIR)
 file(TO_CMAKE_PATH "${REACT_BUILD_DIR}" REACT_BUILD_DIR)
 file(TO_CMAKE_PATH "${REACT_COMMON_DIR}" REACT_COMMON_DIR)
 
-set(HERMES_V1_ENABLED OFF CACHE BOOL "Build with support for Hermes v1")
-
 # If you have ccache installed, we're going to honor it.
 find_program(CCACHE_FOUND ccache)
 if(CCACHE_FOUND)

packages/react-native/ReactCommon/cmake-utils/react-native-flags.cmake

@@ -32,7 +32,5 @@ function(target_compile_reactnative_options target_name scope)
   if(ANDROID)
     target_compile_definitions(${target_name} ${scope} RN_SERIALIZABLE_STATE)
   endif()
-  if(HERMES_V1_ENABLED)
-    target_compile_definitions(${target_name} ${scope} HERMES_V1_ENABLED=1)
-  endif()
+  target_compile_definitions(${target_name} ${scope} HERMES_V1_ENABLED=1)
 endfunction()

packages/react-native/ReactCommon/hermes/executor/HermesExecutorFactory.cpp

@@ -17,55 +17,13 @@
 
 #include <hermes/inspector-modern/chrome/HermesRuntimeTargetDelegate.h>
 
-#if defined(HERMES_ENABLE_DEBUGGER) && !defined(HERMES_V1_ENABLED)
-#include <hermes/inspector-modern/chrome/Registration.h>
-#include <hermes/inspector/RuntimeAdapter.h>
-#endif
-
 using namespace facebook::hermes;
 using namespace facebook::jsi;
 
 namespace facebook::react {
 
 namespace {
 
-#if defined(HERMES_ENABLE_DEBUGGER) && !defined(HERMES_V1_ENABLED)
-
-class HermesExecutorRuntimeAdapter
-    : public facebook::hermes::inspector_modern::RuntimeAdapter {
- public:
-  HermesExecutorRuntimeAdapter(
-      std::shared_ptr<HermesRuntime> runtime,
-      std::shared_ptr<MessageQueueThread> thread)
-      : runtime_(runtime), thread_(std::move(thread)) {}
-
-  virtual ~HermesExecutorRuntimeAdapter() = default;
-
-  HermesRuntime& getRuntime() override {
-    return *runtime_;
-  }
-
-  void tickleJs() override {
-    thread_->runOnQueue(
-        [weakRuntime = std::weak_ptr<HermesRuntime>(runtime_)]() {
-          auto runtime = weakRuntime.lock();
-          if (!runtime) {
-            return;
-          }
-          jsi::Function func =
-              runtime->global().getPropertyAsFunction(*runtime, "__tickleJs");
-          func.call(*runtime);
-        });
-  }
-
- private:
-  std::shared_ptr<HermesRuntime> runtime_;
-
-  std::shared_ptr<MessageQueueThread> thread_;
-};
-
-#endif // defined(HERMES_ENABLE_DEBUGGER) && !defined(HERMES_V1_ENABLED)
-
 struct ReentrancyCheck {
 // This is effectively a very subtle and complex assert, so only
 // include it in builds which would include asserts.
@@ -133,14 +91,11 @@ struct ReentrancyCheck {
 #endif
 };
 
-// This adds ReentrancyCheck and debugger enable/teardown to the given
-// Runtime.
+// This adds ReentrancyCheck to the given Runtime.
 class DecoratedRuntime : public jsi::WithRuntimeDecorator<ReentrancyCheck> {
  public:
   // The first argument may be another decorater which itself
   // decorates the real HermesRuntime, depending on the build config.
-  // The second argument is the real HermesRuntime as well to
-  // manage the debugger registration.
   DecoratedRuntime(
       std::unique_ptr<Runtime> runtime,
       HermesRuntime& hermesRuntime,
@@ -149,42 +104,17 @@ class DecoratedRuntime : public jsi::WithRuntimeDecorator<ReentrancyCheck> {
       const std::string& debuggerName)
       : jsi::WithRuntimeDecorator<ReentrancyCheck>(*runtime, reentrancyCheck_),
         runtime_(std::move(runtime)) {
-#if defined(HERMES_ENABLE_DEBUGGER) && !defined(HERMES_V1_ENABLED)
-    enableDebugger_ = enableDebugger;
-    if (enableDebugger_) {
-      std::shared_ptr<HermesRuntime> rt(runtime_, &hermesRuntime);
-      auto adapter =
-          std::make_unique<HermesExecutorRuntimeAdapter>(rt, jsQueue);
-      debugToken_ = facebook::hermes::inspector_modern::chrome::enableDebugging(
-          std::move(adapter), debuggerName);
-    }
-#else
+    (void)hermesRuntime;
     (void)jsQueue;
-#endif // HERMES_ENABLE_DEBUGGER
+    (void)enableDebugger;
+    (void)debuggerName;
   }
 
-  ~DecoratedRuntime() {
-#if defined(HERMES_ENABLE_DEBUGGER) && !defined(HERMES_V1_ENABLED)
-    if (enableDebugger_) {
-      facebook::hermes::inspector_modern::chrome::disableDebugging(debugToken_);
-    }
-#endif // HERMES_ENABLE_DEBUGGER
-  }
+  ~DecoratedRuntime() {}
 
  private:
-  // runtime_ is a potentially decorated Runtime.
-  // hermesRuntime is a reference to a HermesRuntime managed by runtime_.
-  //
-  // HermesExecutorRuntimeAdapter requirements are kept, because the
-  // dtor will disable debugging on the HermesRuntime before the
-  // member managing it is destroyed.
-
   std::shared_ptr<Runtime> runtime_;
   ReentrancyCheck reentrancyCheck_;
-#if defined(HERMES_ENABLE_DEBUGGER) && !defined(HERMES_V1_ENABLED)
-  bool enableDebugger_;
-  facebook::hermes::inspector_modern::chrome::DebugSessionToken debugToken_;
-#endif // HERMES_ENABLE_DEBUGGER
 };
 
 } // namespace
@@ -221,10 +151,7 @@ std::unique_ptr<JSExecutor> HermesExecutorFactory::createJSExecutor(
   //
   // DecoratedRuntime is held by JSIExecutor.  When it gets used, it
   // will check that it's on the right thread, do any necessary trace
-  // logging, then call the real HermesRuntime.  When it is destroyed,
-  // it will shut down the debugger before the HermesRuntime is.  In
-  // the normal case where debugging is not compiled in,
-  // all that's left is the thread checking.
+  // logging, then call the real HermesRuntime.
 
   // Add js engine information to Error.prototype so in error reporting we
   // can send this information.