[iOS] Bridgeless: Expose host delegate methods

packages/react-native/Libraries/AppDelegate/RCTAppDelegate.mm

@@ -11,6 +11,7 @@
 #import <React/RCTRootView.h>
 #import <React/RCTSurfacePresenterBridgeAdapter.h>
 #import <React/RCTUtils.h>
+#import <ReactCommon/RCTHost.h>
 #import <objc/runtime.h>
 #import <react/featureflags/ReactNativeFeatureFlags.h>
 #import <react/featureflags/ReactNativeFeatureFlagsDefaults.h>
@@ -34,7 +35,7 @@
 #import <react/nativemodule/featureflags/NativeReactNativeFeatureFlags.h>
 #import <react/nativemodule/microtasks/NativeMicrotasks.h>
 
-@interface RCTAppDelegate () <RCTComponentViewFactoryComponentProvider>
+@interface RCTAppDelegate () <RCTComponentViewFactoryComponentProvider, RCTHostDelegate>
 @end
 
 @implementation RCTAppDelegate
@@ -176,6 +177,20 @@ - (NSURL *)bundleURL
   return nullptr;
 }
 
+#pragma mark - RCTHostDelegate
+
+- (void)hostDidStart:(RCTHost *)host
+{
+}
+
+- (void)host:(RCTHost *)host
+    didReceiveJSErrorStack:(NSArray<NSDictionary<NSString *, id> *> *)stack
+                   message:(NSString *)message
+               exceptionId:(NSUInteger)exceptionId
+                   isFatal:(BOOL)isFatal
+{
+}
+
 #pragma mark - Bridge and Bridge Adapter properties
 
 - (RCTBridge *)bridge
@@ -273,6 +288,19 @@ - (RCTRootViewFactory *)createRCTRootViewFactory
     return [weakSelf sourceURLForBridge:bridge];
   };
 
+  configuration.hostDidStartBlock = ^(RCTHost *_Nonnull host) {
+    [weakSelf hostDidStart:host];
+  };
+
+  configuration.hostDidReceiveJSErrorStackBlock =
+      ^(RCTHost *_Nonnull host,
+        NSArray<NSDictionary<NSString *, id> *> *_Nonnull stack,
+        NSString *_Nonnull message,
+        NSUInteger exceptionId,
+        BOOL isFatal) {
+        [weakSelf host:host didReceiveJSErrorStack:stack message:message exceptionId:exceptionId isFatal:isFatal];
+      };
+
   if ([self respondsToSelector:@selector(extraModulesForBridge:)]) {
     configuration.extraModulesForBridge = ^NSArray<id<RCTBridgeModule>> *_Nonnull(RCTBridge *_Nonnull bridge)
     {

packages/react-native/Libraries/AppDelegate/RCTRootViewFactory.h

@@ -29,6 +29,13 @@ typedef NSURL *_Nullable (^RCTBundleURLBlock)(void);
 typedef NSArray<id<RCTBridgeModule>> *_Nonnull (^RCTExtraModulesForBridgeBlock)(RCTBridge *bridge);
 typedef NSDictionary<NSString *, Class> *_Nonnull (^RCTExtraLazyModuleClassesForBridge)(RCTBridge *bridge);
 typedef BOOL (^RCTBridgeDidNotFindModuleBlock)(RCTBridge *bridge, NSString *moduleName);
+typedef void (^RCTHostDidStartBlock)(RCTHost *host);
+typedef void (^RCTHostDidReceiveJSErrorStackBlock)(
+    RCTHost *host,
+    NSArray<NSDictionary<NSString *, id> *> *stack,
+    NSString *message,
+    NSUInteger exceptionId,
+    BOOL isFatal);
 
 #pragma mark - RCTRootViewFactory Configuration
 @interface RCTRootViewFactoryConfiguration : NSObject
@@ -132,6 +139,22 @@ typedef BOOL (^RCTBridgeDidNotFindModuleBlock)(RCTBridge *bridge, NSString *modu
  */
 @property (nonatomic, nullable) RCTBridgeDidNotFindModuleBlock bridgeDidNotFindModule;
 
+/**
+ * Called when `RCTHost` did started.
+ * @parameter: host - The started `RCTHost`.
+ */
+@property (nonatomic, nullable) RCTHostDidStartBlock hostDidStartBlock;
+
+/**
+ * Called when `RCTHost` received JS error.
+ * @parameter: host - `RCTHost` which received js error.
+ * @parameter: stack - JS error stack.
+ * @parameter: message - Error message.
+ * @parameter: exceptionId - Exception ID.
+ * @parameter: isFatal - YES if JS error is fatal.
+ */
+@property (nonatomic, nullable) RCTHostDidReceiveJSErrorStackBlock hostDidReceiveJSErrorStackBlock;
+
 @end
 
 #pragma mark - RCTRootViewFactory

packages/react-native/Libraries/AppDelegate/RCTRootViewFactory.mm

@@ -83,7 +83,7 @@ - (instancetype)initWithBundleURLBlock:(RCTBundleURLBlock)bundleURLBlock
 
 @end
 
-@interface RCTRootViewFactory () <RCTContextContainerHandling> {
+@interface RCTRootViewFactory () <RCTContextContainerHandling, RCTHostDelegate> {
   std::shared_ptr<const facebook::react::ReactNativeConfig> _reactNativeConfig;
   facebook::react::ContextContainer::Shared _contextContainer;
 }
@@ -180,6 +180,26 @@ - (UIView *)createRootViewWithBridge:(RCTBridge *)bridge
   return rootView;
 }
 
+#pragma mark - RCTHostDelegate
+
+- (void)hostDidStart:(RCTHost *)host
+{
+  if (self->_configuration.hostDidStartBlock) {
+    self->_configuration.hostDidStartBlock(host);
+  }
+}
+
+- (void)host:(RCTHost *)host
+    didReceiveJSErrorStack:(NSArray<NSDictionary<NSString *, id> *> *)stack
+                   message:(NSString *)message
+               exceptionId:(NSUInteger)exceptionId
+                   isFatal:(BOOL)isFatal
+{
+  if (self->_configuration.hostDidReceiveJSErrorStackBlock) {
+    self->_configuration.hostDidReceiveJSErrorStackBlock(host, stack, message, exceptionId, isFatal);
+  }
+}
+
 #pragma mark - RCTCxxBridgeDelegate
 - (std::unique_ptr<facebook::react::JSExecutorFactory>)jsExecutorFactoryForBridge:(RCTBridge *)bridge
 {
@@ -238,7 +258,7 @@ - (RCTHost *)createReactHost:(NSDictionary *)launchOptions
   __weak __typeof(self) weakSelf = self;
   RCTHost *reactHost =
       [[RCTHost alloc] initWithBundleURLProvider:self->_configuration.bundleURLBlock
-                                    hostDelegate:nil
+                                    hostDelegate:self
                       turboModuleManagerDelegate:_turboModuleManagerDelegate
                                 jsEngineProvider:^std::shared_ptr<facebook::react::JSRuntimeFactory>() {
                                   return [weakSelf createJSRuntimeFactory];