iOS: Add Commands and Constants properties to native view config (#38221)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/38221

View configs are supposed to have `Commands` and `Constants`. See [ReactNativeTypes.js](https://github.com/facebook/react-native/blob/main/packages/react-native/Libraries/Renderer/shims/ReactNativeTypes.js#L68-L69).
Android sets them in native: see [UIManagerModuleConstantsHelper.java](https://github.com/facebook/react-native/blob/main/packages/react-native/ReactAndroid/src/main/java/com/facebook/react/uimanager/UIManagerModuleConstantsHelper.java#L172-L179).
ut iOS doesn't: see [RCTUIManager.m](https://github.com/facebook/react-native/blob/main/packages/react-native/React/Modules/RCTUIManager.m#L1484-L1487)
Instead there is code for that in [PaperUIManager.js](https://github.com/facebook/react-native/blob/main/packages/react-native/Libraries/ReactNative/PaperUIManager.js#L117-L160).
It accesses viewManagers like this: `const viewManager = NativeModules[viewConfig.Manager]`. But `NativeModules` object is not available in the bridgeless mode. So we fail to provide complete native view configs in the New Architecture.

This diff implements `Commands` and `Constants` in native in iOS.
This change should have no effect in the old architecture because these properties are overwritten by `lazifyViewManagerConfig`.

Changelog: [Internal] - Add Commands and Constants properties to native view config.

Reviewed By: sammy-SC

Differential Revision: D47096624

fbshipit-source-id: e3b3183ba5e3d1d2fb3f3ff5d6ff89ad86095a6c

packages/react-native/React/Modules/RCTUIManager.m

@@ -1485,6 +1485,13 @@ NSMutableDictionary<NSString *, id> *RCTModuleConstantsForDestructuredComponent(
   moduleConstants[@"baseModuleName"] = viewConfig[@"baseModuleName"];
   moduleConstants[@"bubblingEventTypes"] = bubblingEventTypes;
   moduleConstants[@"directEventTypes"] = directEventTypes;
+  // In the Old Architecture the "Commands" and "Constants" properties of view manager config are populated by
+  // lazifyViewManagerConfig function in JS. This fuction uses NativeModules global object that is not available in the
+  // New Architecture. To make native view configs work in the New Architecture we will populate these properties in
+  // native.
+  moduleConstants[@"Commands"] = viewConfig[@"Commands"];
+  // In the Old Architecture "Constants" are empty.
+  moduleConstants[@"Constants"] = [NSDictionary new];
 
   // Add direct events
   for (NSString *eventName in viewConfig[@"directEvents"]) {

packages/react-native/React/Views/RCTComponentData.m

@@ -15,6 +15,7 @@
 #import "RCTConstants.h"
 #import "RCTConvert.h"
 #import "RCTEventDispatcherProtocol.h"
+#import "RCTModuleMethod.h"
 #import "RCTParserUtils.h"
 #import "RCTShadowView.h"
 #import "RCTUtils.h"
@@ -385,6 +386,34 @@ static RCTPropBlock createNSInvocationSetter(NSMethodSignature *typeSignature, S
   }];
 }
 
++ (NSDictionary<NSString *, NSNumber *> *)commandsForViewMangerClass:(Class)managerClass
+                                                             methods:(Method *)methods
+                                                         methodCount:(unsigned int)methodCount
+{
+  NSMutableDictionary<NSString *, NSNumber *> *commands = [NSMutableDictionary new];
+  static const char *prefix = "__rct_export__";
+  const unsigned int prefixLength = strlen(prefix);
+  int commandCount = 0;
+  for (int i = 0; i < methodCount; i++) {
+    SEL selector = method_getName(methods[i]);
+    const char *selectorName = sel_getName(selector);
+    if (strncmp(selectorName, prefix, prefixLength) != 0) {
+      continue;
+    }
+    RCTMethodInfo *methodInfo = ((RCTMethodInfo * (*)(id, SEL)) objc_msgSend)(managerClass, selector);
+    RCTModuleMethod *moduleMethod = [[RCTModuleMethod alloc] initWithExportedMethod:methodInfo
+                                                                        moduleClass:managerClass];
+    NSString *methodName = @(moduleMethod.JSMethodName);
+    commands[methodName] = @(commandCount);
+    commandCount += 1;
+  }
+  // View manager do not export getConstants with RCT_EXPORT_METHOD, so we inject it into "Commands" manually.
+  if (commandCount > 0) {
+    commands[@"getConstants"] = @(commandCount);
+  }
+  return commands;
+}
+
 + (NSDictionary<NSString *, id> *)viewConfigForViewMangerClass:(Class)managerClass
 {
   NSMutableArray<NSString *> *bubblingEvents = [NSMutableArray new];
@@ -442,6 +471,10 @@ static RCTPropBlock createNSInvocationSetter(NSMethodSignature *typeSignature, S
       propTypes[name] = type;
     }
   }
+
+  NSDictionary<NSString *, NSNumber *> *commands = [self commandsForViewMangerClass:managerClass
+                                                                            methods:methods
+                                                                        methodCount:count];
   free(methods);
 
 #if RCT_DEBUG
@@ -464,6 +497,7 @@ static RCTPropBlock createNSInvocationSetter(NSMethodSignature *typeSignature, S
     @"bubblingEvents" : bubblingEvents,
     @"capturingEvents" : capturingEvents,
     @"baseModuleName" : superClass == [NSObject class] ? (id)kCFNull : RCTViewManagerModuleNameForClass(superClass),
+    @"Commands" : commands,
   };
 }