Defer creating component provider list until we have to and optimistically create it on a separate thread

packages/react-native/ReactCommon/react/renderer/componentregistry/ComponentDescriptorProviderRegistry.cpp

@@ -71,10 +71,19 @@ ComponentDescriptorProviderRegistry::createComponentDescriptorRegistry(
   auto registry = std::make_shared<const ComponentDescriptorRegistry>(
       parameters, *this, parameters.contextContainer);
 
+ // for (const auto& pair : componentDescriptorProviders_) {
+ //   registry->add(pair.second);
+ // }
+
+  std::vector<ComponentDescriptorProvider> providers;
+  providers.reserve(componentDescriptorProviders_.size());
   for (const auto& pair : componentDescriptorProviders_) {
-    registry->add(pair.second);
+    providers.push_back(pair.second);
   }
 
+  // 2) enqueue async add
+  registry->addMultipleAsync(std::move(providers));
+
   componentDescriptorRegistries_.push_back(registry);
 
   return registry;

packages/react-native/ReactCommon/react/renderer/componentregistry/ComponentDescriptorRegistry.cpp

@@ -27,6 +27,34 @@ ComponentDescriptorRegistry::ComponentDescriptorRegistry(
       providerRegistry_(providerRegistry),
       contextContainer_(std::move(contextContainer)) {}
 
+void ComponentDescriptorRegistry::addMultipleAsync(
+    std::vector<ComponentDescriptorProvider> providers) const {
+  // Copy everything we need before the thread starts
+  auto parametersCopy = parameters_;
+  auto contextContainerCopy = contextContainer_;
+
+  // Start thread immediately
+  std::thread([this, providers = std::move(providers), parametersCopy, contextContainerCopy]() {
+    std::unique_lock lock(mutex_);
+
+    for (const auto& provider : providers) {
+      auto componentDescriptor = provider.constructor(
+          {parametersCopy.eventDispatcher,
+           contextContainerCopy,
+           provider.flavor});
+
+      react_native_assert(componentDescriptor->getComponentHandle() == provider.handle);
+      react_native_assert(componentDescriptor->getComponentName() == provider.name);
+
+      auto sharedComponentDescriptor =
+          std::shared_ptr<const ComponentDescriptor>(std::move(componentDescriptor));
+
+      _registryByHandle[provider.handle] = sharedComponentDescriptor;
+      _registryByName[provider.name] = sharedComponentDescriptor;
+    }
+  }).detach();
+}
+
 void ComponentDescriptorRegistry::add(
     ComponentDescriptorProvider componentDescriptorProvider) const {
   std::unique_lock lock(mutex_);

packages/react-native/ReactCommon/react/renderer/componentregistry/ComponentDescriptorRegistry.h

@@ -15,6 +15,7 @@
 #include <react/renderer/core/ComponentDescriptor.h>
 #include <react/renderer/core/InstanceHandle.h>
 #include <react/utils/ContextContainer.h>
+#include <thread>
 
 namespace facebook::react {
 
@@ -40,6 +41,8 @@ class ComponentDescriptorRegistry {
       const ComponentDescriptorProviderRegistry& providerRegistry,
       ContextContainer::Shared contextContainer);
 
+  void addMultipleAsync(std::vector<ComponentDescriptorProvider> providers) const;
+
   /*
    * This is broken. Please do not use.
    * If you requesting a ComponentDescriptor and unsure that it's there, you are