Lazy-init HermesRuntimeTargetDelegate

Summary:
Changelog: [Internal]

We are currently eagerly constructing a `HermesRuntimeTargetDelegate` regardless of whether the Fusebox feature flags are enabled. This can interfere with the legacy CDP backend. Instead, let's lazily construct the target delegate in a code path that only runs when the modern backend is in use.

bypass-github-export-checks

Reviewed By: rozele

Differential Revision: D54907887

fbshipit-source-id: 7dc13506739866ea6690ed21d03d91ad24ef68c5

Author: motiz88

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

@@ -253,12 +253,14 @@ HermesExecutor::HermesExecutor(
     HermesRuntime& hermesRuntime)
     : JSIExecutor(runtime, delegate, timeoutInvoker, runtimeInstaller),
       runtime_(runtime),
-      targetDelegate_{
-          std::shared_ptr<HermesRuntime>(runtime_, &hermesRuntime)} {}
+      hermesRuntime_(runtime_, &hermesRuntime) {}
 
 jsinspector_modern::RuntimeTargetDelegate&
 HermesExecutor::getRuntimeTargetDelegate() {
-  return targetDelegate_;
+  if (!targetDelegate_) {
+    targetDelegate_.emplace(hermesRuntime_);
+  }
+  return *targetDelegate_;
 }
 
 } // namespace facebook::react

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

@@ -61,7 +61,9 @@ class HermesExecutor : public JSIExecutor {
  private:
   JSIScopedTimeoutInvoker timeoutInvoker_;
   std::shared_ptr<jsi::Runtime> runtime_;
-  jsinspector_modern::HermesRuntimeTargetDelegate targetDelegate_;
+  std::shared_ptr<hermes::HermesRuntime> hermesRuntime_;
+  std::optional<jsinspector_modern::HermesRuntimeTargetDelegate>
+      targetDelegate_;
 };
 
 } // namespace facebook::react

packages/react-native/ReactCommon/react/runtime/hermes/HermesInstance.cpp

@@ -95,20 +95,24 @@ class DecoratedRuntime : public jsi::RuntimeDecorator<jsi::Runtime> {
 class HermesJSRuntime : public JSRuntime {
  public:
   HermesJSRuntime(std::unique_ptr<HermesRuntime> runtime)
-      : runtime_(std::move(runtime)), targetDelegate_{runtime_} {}
+      : runtime_(std::move(runtime)) {}
 
   jsi::Runtime& getRuntime() noexcept override {
     return *runtime_;
   }
 
   jsinspector_modern::RuntimeTargetDelegate& getRuntimeTargetDelegate()
       override {
-    return targetDelegate_;
+    if (!targetDelegate_) {
+      targetDelegate_.emplace(runtime_);
+    }
+    return *targetDelegate_;
   }
 
  private:
   std::shared_ptr<HermesRuntime> runtime_;
-  jsinspector_modern::HermesRuntimeTargetDelegate targetDelegate_;
+  std::optional<jsinspector_modern::HermesRuntimeTargetDelegate>
+      targetDelegate_;
 };
 
 std::unique_ptr<JSRuntime> HermesInstance::createJSRuntime(