Fabric: Introducing `RCTComponentViewClassDescriptor`

Summary:
RCTComponentViewClassDescriptor is a pretty much the same as RCTComponentViewDescriptor but for *classes*. RCTComponentViewFactory uses a map of those data structures to create RCTComponentViewDescriptor instances (which reflects the same properties) efficiently.

Changelog: [Internal] Fabric-specific internal change.

Reviewed By: sammy-SC

Differential Revision: D18217103

fbshipit-source-id: ab7ab6b0712048d0085b61a3604b284b1fb5a68b

React/Fabric/Mounting/RCTComponentViewClassDescriptor.h

@@ -0,0 +1,25 @@
+/*
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#import <UIKit/UIKit.h>
+
+#import <React/RCTComponentViewProtocol.h>
+
+NS_ASSUME_NONNULL_BEGIN
+
+/*
+ * Holds a native view class and a set of attributes associated with it.
+ */
+class RCTComponentViewClassDescriptor final {
+ public:
+  /*
+   * Associated (and owned) native view class.
+   */
+  Class<RCTComponentViewProtocol> viewClass;
+};
+
+NS_ASSUME_NONNULL_END

React/Fabric/Mounting/RCTComponentViewFactory.mm

@@ -17,6 +17,7 @@
 
 #import "RCTARTSurfaceViewComponentView.h"
 #import "RCTActivityIndicatorViewComponentView.h"
+#import "RCTComponentViewClassDescriptor.h"
 #import "RCTImageComponentView.h"
 #import "RCTLegacyViewManagerInteropComponentView.h"
 #import "RCTModalHostViewComponentView.h"
@@ -33,7 +34,7 @@
 using namespace facebook::react;
 
 @implementation RCTComponentViewFactory {
-  better::map<ComponentHandle, Class<RCTComponentViewProtocol>> _componentViewClasses;
+  better::map<ComponentHandle, RCTComponentViewClassDescriptor> _componentViewClasses;
   ComponentDescriptorProviderRegistry _providerRegistry;
   better::shared_mutex _mutex;
 }
@@ -68,19 +69,26 @@ using namespace facebook::react;
 
       providerRegistry->add(ComponentDescriptorProvider{componentHandle, componentName, flavor, constructor});
 
-      componentViewFactory->_componentViewClasses[componentHandle] = [RCTLegacyViewManagerInteropComponentView class];
+      componentViewFactory->_componentViewClasses[componentHandle] = [componentViewFactory
+          _componentViewClassDescriptorFromClass:[RCTLegacyViewManagerInteropComponentView class]];
     }
   });
 
   return componentViewFactory;
 }
 
+- (RCTComponentViewClassDescriptor)_componentViewClassDescriptorFromClass:(Class<RCTComponentViewProtocol>)viewClass
+{
+  return RCTComponentViewClassDescriptor{.viewClass = viewClass};
+}
+
 - (void)registerComponentViewClass:(Class<RCTComponentViewProtocol>)componentViewClass
 {
   std::unique_lock<better::shared_mutex> lock(_mutex);
 
   auto componentDescriptorProvider = [componentViewClass componentDescriptorProvider];
-  _componentViewClasses[componentDescriptorProvider.handle] = componentViewClass;
+  _componentViewClasses[componentDescriptorProvider.handle] =
+      [self _componentViewClassDescriptorFromClass:componentViewClass];
   _providerRegistry.add(componentDescriptorProvider);
 
   auto supplementalComponentDescriptorProviders = [componentViewClass supplementalComponentDescriptorProviders];
@@ -109,9 +117,10 @@ using namespace facebook::react;
       @"ComponentView with componentHandle `%lli` (`%s`) not found.",
       componentHandle,
       (char *)componentHandle);
-  Class componentViewClass = iterator->second;
+  auto componentViewClassDescriptor = iterator->second;
+  Class viewClass = componentViewClassDescriptor.viewClass;
 
-  return RCTComponentViewDescriptor{.view = [[componentViewClass alloc] init]};
+  return RCTComponentViewDescriptor{.view = [[viewClass alloc] init]};
 }
 
 - (facebook::react::ComponentDescriptorRegistry::Shared)createComponentDescriptorRegistryWithParameters: