Fabric: Introduced ComponentDescriptorRegistry::at() method family

Summary: This is more usable (because it allows to use `->` operator) and safe (const-style) methods replacing old `operator[]` methods.

Reviewed By: mdvacca

Differential Revision: D12876744

fbshipit-source-id: 8ea7398c9777f8be3e88db873ec00915d0761615

ReactCommon/fabric/uimanager/ComponentDescriptorRegistry.cpp

@@ -81,6 +81,24 @@ static const std::string componentNameByReactViewName(std::string viewName) {
   return viewName;
 }
 
+const ComponentDescriptor &ComponentDescriptorRegistry::at(
+    ComponentName componentName) const {
+  auto unifiedComponentName = componentNameByReactViewName(componentName);
+
+  auto it = _registryByName.find(unifiedComponentName);
+  if (it == _registryByName.end()) {
+    throw std::invalid_argument(
+        ("Unable to find componentDescriptor for " + unifiedComponentName)
+            .c_str());
+  }
+  return *it->second;
+}
+
+const ComponentDescriptor &ComponentDescriptorRegistry::at(
+    ComponentHandle componentHandle) const {
+  return *_registryByHandle.at(componentHandle);
+}
+
 SharedShadowNode ComponentDescriptorRegistry::createNode(
     Tag tag,
     const std::string &viewName,

ReactCommon/fabric/uimanager/ComponentDescriptorRegistry.h

@@ -25,6 +25,9 @@ class ComponentDescriptorRegistry {
   void registerComponentDescriptor(
       SharedComponentDescriptor componentDescriptor);
 
+  const ComponentDescriptor &at(ComponentName componentName) const;
+  const ComponentDescriptor &at(ComponentHandle componentHandle) const;
+
   const SharedComponentDescriptor operator[](
       const SharedShadowNode &shadowNode) const;
   const SharedComponentDescriptor operator[](