Native view configs in bridgeless mode: constantsToExport support (#39519)

Summary:
Pull Request resolved: #39519

If the `constantsToExport` method is overridden by RCTViewManager subclass, we'll out those constants in "Constants" property of the view config.
This diff also defines a property on UIManager for every view configs. This add support for `UIManager.RNTMyLegacyNativeView.Constants.PI` syntax in bridgeless mode.
Changelog: [Internal]

Differential Revision: https://internalfb.com/D49372561

fbshipit-source-id: 0ba1621e3ee4045d31a0b230a137f6b5fe0e8cb6

Author: dmytrorykun

packages/react-native/Libraries/ReactNative/BridgelessUIManager.js

@@ -29,7 +29,7 @@ function getCachedConstants(): Object {
   return cachedConstants;
 }
 
-module.exports = {
+const UIManagerJS: {[string]: $FlowFixMe} = {
   getViewManagerConfig: (viewManagerName: string): mixed => {
     if (ReactNativeFeatureFlags.enableNativeViewConfigsInBridgelessMode()) {
       return getCachedConstants()[viewManagerName];
@@ -178,3 +178,11 @@ module.exports = {
   dismissPopupMenu: (): void =>
     console.error(errorMessageForMethod('dismissPopupMenu')),
 };
+
+if (ReactNativeFeatureFlags.enableNativeViewConfigsInBridgelessMode()) {
+  Object.keys(getCachedConstants()).forEach(viewConfigName => {
+    UIManagerJS[viewConfigName] = getCachedConstants()[viewConfigName];
+  });
+}
+
+module.exports = UIManagerJS;

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

@@ -1490,8 +1490,7 @@ static void RCTMeasureLayout(RCTShadowView *view, RCTShadowView *ancestor, RCTRe
   // 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];
+  moduleConstants[@"Constants"] = viewConfig[@"Constants"];
 
   // Add direct events
   for (NSString *eventName in viewConfig[@"directEvents"]) {

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

@@ -414,6 +414,14 @@ - (void)setProps:(NSDictionary<NSString *, id> *)props forShadowView:(RCTShadowV
   return commands;
 }
 
++ (NSDictionary<NSString *, id> *)constantsForViewMangerClass:(Class)managerClass
+{
+  if ([managerClass instancesRespondToSelector:@selector(constantsToExport)]) {
+    return [[managerClass new] constantsToExport];
+  }
+  return @{};
+}
+
 + (NSDictionary<NSString *, id> *)viewConfigForViewMangerClass:(Class)managerClass
 {
   NSMutableArray<NSString *> *bubblingEvents = [NSMutableArray new];
@@ -498,6 +506,7 @@ - (void)setProps:(NSDictionary<NSString *, id> *)props forShadowView:(RCTShadowV
     @"capturingEvents" : capturingEvents,
     @"baseModuleName" : superClass == [NSObject class] ? (id)kCFNull : RCTViewManagerModuleNameForClass(superClass),
     @"Commands" : commands,
+    @"Constants" : [self constantsForViewMangerClass:managerClass],
   };
 }