[iOS + Android] Add the ability to intercept errors from native side and forward them to JS console

CHANGELOG.md

@@ -10,6 +10,23 @@
 
 ### Features
 
+- Add `onNativeLog` callback to intercept and forward native SDK logs to JavaScript console ([#5622](https://github.com/getsentry/sentry-react-native/pull/5622))
+  - The callback receives native log events with `level`, `component`, and `message` properties
+  - Only works when `debug: true` is enabled in `Sentry.init`
+  - Use `logWithoutTracing` inside the callback to prevent feedback loops with Sentry's console integration
+    ```js
+    import * as Sentry from '@sentry/react-native';
+
+    Sentry.init({
+      debug: true,
+      onNativeLog: ({ level, component, message }) => {
+        // Use logWithoutTracing to avoid feedback loops
+        Sentry.logWithoutTracing(
+          `[Sentry Native] [${level.toUpperCase()}] [${component}] ${message}`
+        );
+      }
+    });
+    ```
 - Add expo constants on event context ([#5748](https://github.com/getsentry/sentry-react-native/pull/5748))
 - Capture dynamic route params as span attributes for Expo Router navigations ([#5750](https://github.com/getsentry/sentry-react-native/pull/5750))
 

packages/core/android/src/main/java/io/sentry/react/RNSentryLogger.java

@@ -0,0 +1,96 @@
+package io.sentry.react;
+
+import com.facebook.react.bridge.Arguments;
+import com.facebook.react.bridge.ReactApplicationContext;
+import com.facebook.react.bridge.WritableMap;
+import com.facebook.react.modules.core.DeviceEventManagerModule;
+import io.sentry.ILogger;
+import io.sentry.SentryLevel;
+import io.sentry.android.core.AndroidLogger;
+import java.lang.ref.WeakReference;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+/**
+ * Custom ILogger implementation that wraps AndroidLogger and forwards log messages to React Native.
+ * This allows native SDK logs to appear in the Metro console when debug mode is enabled.
+ */
+public class RNSentryLogger implements ILogger {
+  private static final String TAG = "RNSentry";
+  private static final String EVENT_NAME = "SentryNativeLog";
+
+  private final AndroidLogger androidLogger;
+  private WeakReference<ReactApplicationContext> reactContextRef;
+
+  public RNSentryLogger() {
+    this.androidLogger = new AndroidLogger(TAG);
+  }
+
+  public void setReactContext(@Nullable ReactApplicationContext context) {
+    this.reactContextRef = context != null ? new WeakReference<>(context) : null;
+  }
+
+  @Override
+  public void log(@NotNull SentryLevel level, @NotNull String message, @Nullable Object... args) {
+    // Always log to Logcat (default behavior)
+    androidLogger.log(level, message, args);
+
+    // Forward to JS
+    String formattedMessage =
+        (args == null || args.length == 0) ? message : String.format(message, args);
+    forwardToJS(level, formattedMessage);
+  }
+
+  @Override
+  public void log(
+      @NotNull SentryLevel level, @NotNull String message, @Nullable Throwable throwable) {
+    androidLogger.log(level, message, throwable);
+
+    String fullMessage = throwable != null ? message + ": " + throwable.getMessage() : message;
+    forwardToJS(level, fullMessage);
+  }
+
+  @Override
+  public void log(
+      @NotNull SentryLevel level,
+      @Nullable Throwable throwable,
+      @NotNull String message,
+      @Nullable Object... args) {
+    androidLogger.log(level, throwable, message, args);
+
+    String formattedMessage =
+        (args == null || args.length == 0) ? message : String.format(message, args);
+    if (throwable != null) {
+      formattedMessage += ": " + throwable.getMessage();
+    }
+    forwardToJS(level, formattedMessage);
+  }
+
+  @Override
+  public boolean isEnabled(@Nullable SentryLevel level) {
+    return androidLogger.isEnabled(level);
+  }
+
+  private void forwardToJS(@NotNull SentryLevel level, @NotNull String message) {
+    ReactApplicationContext context = reactContextRef != null ? reactContextRef.get() : null;
+    if (context == null || !context.hasActiveReactInstance()) {
+      return;
+    }
+
+    try {
+      WritableMap params = Arguments.createMap();
+      params.putString("level", level.name().toLowerCase());
+      params.putString("component", "Sentry");
+      params.putString("message", message);
+
+      context
+          .getJSModule(DeviceEventManagerModule.RCTDeviceEventEmitter.class)
+          .emit(EVENT_NAME, params);
+    } catch (Exception e) {
+      // Silently ignore - don't cause issues if JS bridge isn't ready
+      // We intentionally swallow this exception to avoid disrupting the app
+      // when the React Native bridge is not yet initialized or has been torn down
+      androidLogger.log(SentryLevel.DEBUG, "Failed to forward log to JS: " + e.getMessage());
+    }
+  }
+}

packages/core/android/src/main/java/io/sentry/react/RNSentryModuleImpl.java

@@ -40,7 +40,6 @@
 import io.sentry.SentryExecutorService;
 import io.sentry.SentryLevel;
 import io.sentry.SentryOptions;
-import io.sentry.android.core.AndroidLogger;
 import io.sentry.android.core.AndroidProfiler;
 import io.sentry.android.core.BuildInfoProvider;
 import io.sentry.android.core.InternalSentrySdk;
@@ -87,7 +86,8 @@ public class RNSentryModuleImpl {
 
   public static final String NAME = "RNSentry";
 
-  private static final ILogger logger = new AndroidLogger(NAME);
+  private static final RNSentryLogger rnLogger = new RNSentryLogger();
+  private static final ILogger logger = rnLogger;
   private static final BuildInfoProvider buildInfo = new BuildInfoProvider(logger);
   private static final String modulesPath = "modules.json";
   private static final Charset UTF_8 = Charset.forName("UTF-8"); // NOPMD - Allow using UTF-8
@@ -170,8 +170,17 @@ public void initNativeReactNavigationNewFrameTracking(Promise promise) {
   }
 
   public void initNativeSdk(final ReadableMap rnOptions, Promise promise) {
+    // Set the React context for the logger so it can forward logs to JS
+    rnLogger.setReactContext(this.reactApplicationContext);
+
     RNSentryStart.startWithOptions(
-        getApplicationContext(), rnOptions, getCurrentActivity(), logger);
+        getApplicationContext(),
+        rnOptions,
+        options -> {
+          // Use our custom logger that forwards to JS
+          options.setLogger(rnLogger);
+        },
+        logger);
 
     promise.resolve(true);
   }

packages/core/ios/RNSentry.mm

@@ -39,6 +39,7 @@
 
 #import "RNSentryDependencyContainer.h"
 #import "RNSentryEvents.h"
+#import "RNSentryNativeLogsForwarder.h"
 
 #if SENTRY_TARGET_REPLAY_SUPPORTED
 #    import "RNSentryReplay.h"
@@ -284,17 +285,19 @@ - (void)initFramesTracking
 - (void)startObserving
 {
     hasListeners = YES;
+    [[RNSentryNativeLogsForwarder shared] configureWithEventEmitter:self];
 }
 
 // Will be called when this module's last listener is removed, or on dealloc.
 - (void)stopObserving
 {
     hasListeners = NO;
+    [[RNSentryNativeLogsForwarder shared] stopForwarding];
 }
 
 - (NSArray<NSString *> *)supportedEvents
 {
-    return @[ RNSentryNewFrameEvent ];
+    return @[ RNSentryNewFrameEvent, RNSentryNativeLogEvent ];
 }
 
 RCT_EXPORT_METHOD(

packages/core/ios/RNSentryEvents.h

@@ -1,3 +1,4 @@
 #import <Foundation/Foundation.h>
 
 extern NSString *const RNSentryNewFrameEvent;
+extern NSString *const RNSentryNativeLogEvent;

packages/core/ios/RNSentryEvents.m

@@ -1,3 +1,4 @@
 #import "RNSentryEvents.h"
 
 NSString *const RNSentryNewFrameEvent = @"rn_sentry_new_frame";
+NSString *const RNSentryNativeLogEvent = @"SentryNativeLog";

packages/core/ios/RNSentryNativeLogsForwarder.h

@@ -0,0 +1,20 @@
+#import <Foundation/Foundation.h>
+#import <React/RCTEventEmitter.h>
+
+NS_ASSUME_NONNULL_BEGIN
+
+/**
+ * Singleton class that forwards native Sentry SDK logs to JavaScript via React Native events.
+ * This allows React Native developers to see native SDK logs in the Metro console.
+ */
+@interface RNSentryNativeLogsForwarder : NSObject
+
++ (instancetype)shared;
+
+- (void)configureWithEventEmitter:(RCTEventEmitter *)emitter;
+
+- (void)stopForwarding;
+
+@end
+
+NS_ASSUME_NONNULL_END

packages/core/ios/RNSentryNativeLogsForwarder.m

@@ -0,0 +1,145 @@
+#import "RNSentryNativeLogsForwarder.h"
+#import "RNSentryEvents.h"
+
+@import Sentry;
+
+@interface RNSentryNativeLogsForwarder ()
+
+@property (nonatomic, weak) RCTEventEmitter *eventEmitter;
+
+@end
+
+@implementation RNSentryNativeLogsForwarder
+
++ (instancetype)shared
+{
+    static RNSentryNativeLogsForwarder *instance = nil;
+    static dispatch_once_t onceToken;
+    dispatch_once(&onceToken, ^{ instance = [[RNSentryNativeLogsForwarder alloc] init]; });
+    return instance;
+}
+
+- (void)configureWithEventEmitter:(RCTEventEmitter *)emitter
+{
+    self.eventEmitter = emitter;
+
+    __weak RNSentryNativeLogsForwarder *weakSelf = self;
+
+    // Set up the Sentry SDK log output to forward logs to JS
+    [SentrySDKLog setOutput:^(NSString *_Nonnull message) {
+        // Always print to console (default behavior)
+        NSLog(@"%@", message);
+
+        // Forward to JS if we have an emitter
+        RNSentryNativeLogsForwarder *strongSelf = weakSelf;
+        if (strongSelf) {
+            [strongSelf forwardLogMessage:message];
+        }
+    }];
+
+    // Send a log to notify user the forwarding works
+    [self forwardLogMessage:
+            @"[Sentry] [info] [0] [RNSentryNativeLogsForwarder] Native log forwarding "
+            @"configured successfully"];
+}
+
+- (void)stopForwarding
+{
+    self.eventEmitter = nil;
+
+    // TODO: Ideally we should save the previous output block in configureWithEventEmitter:
+    // and restore it here instead of hardcoding NSLog.
+    // Reset to default print behavior
+    [SentrySDKLog setOutput:^(NSString *_Nonnull message) { NSLog(@"%@", message); }];
+}
+
+- (void)forwardLogMessage:(NSString *)message
+{
+    RCTEventEmitter *emitter = self.eventEmitter;
+    if (emitter == nil) {
+        return;
+    }
+
+    // Only forward messages that look like Sentry SDK logs
+    if (![message hasPrefix:@"[Sentry]"]) {
+        return;
+    }
+
+    // Parse the log message to extract level and component
+    // Format: "[Sentry] [level] [timestamp] [Component:line] message"
+    // or: "[Sentry] [level] [timestamp] message"
+    NSString *level = [self extractLevelFromMessage:message];
+    NSString *component = [self extractComponentFromMessage:message];
+    NSString *cleanMessage = [self extractCleanMessageFromMessage:message];
+
+    NSDictionary *body = @{
+        @"level" : level,
+        @"component" : component,
+        @"message" : cleanMessage,
+    };
+
+    // Dispatch async to avoid blocking the calling thread and potential deadlocks
+    dispatch_async(dispatch_get_main_queue(), ^{
+        RCTEventEmitter *currentEmitter = self.eventEmitter;
+        if (currentEmitter != nil) {
+            [currentEmitter sendEventWithName:RNSentryNativeLogEvent body:body];
+        }
+    });
+}
+
+- (NSString *)extractLevelFromMessage:(NSString *)message
+{
+    // Look for patterns like [debug], [info], [warning], [error], [fatal]
+    NSRegularExpression *regex =
+        [NSRegularExpression regularExpressionWithPattern:@"\\[(debug|info|warning|error|fatal)\\]"
+                                                  options:NSRegularExpressionCaseInsensitive
+                                                    error:nil];
+
+    NSTextCheckingResult *match = [regex firstMatchInString:message
+                                                    options:0
+                                                      range:NSMakeRange(0, message.length)];
+
+    if (match && match.numberOfRanges > 1) {
+        return [[message substringWithRange:[match rangeAtIndex:1]] lowercaseString];
+    }
+
+    return @"info";
+}
+
+- (NSString *)extractComponentFromMessage:(NSString *)message
+{
+    // Look for pattern like [ComponentName:123]
+    NSRegularExpression *regex =
+        [NSRegularExpression regularExpressionWithPattern:@"\\[([A-Za-z]+):\\d+\\]"
+                                                  options:0
+                                                    error:nil];
+
+    NSTextCheckingResult *match = [regex firstMatchInString:message
+                                                    options:0
+                                                      range:NSMakeRange(0, message.length)];
+
+    if (match && match.numberOfRanges > 1) {
+        return [message substringWithRange:[match rangeAtIndex:1]];
+    }
+
+    return @"Sentry";
+}
+
+- (NSString *)extractCleanMessageFromMessage:(NSString *)message
+{
+    // Remove the prefix parts: [Sentry] [level] [timestamp] [Component:line]
+    // and return just the actual message content
+    NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:
+            @"^\\[Sentry\\]\\s*\\[[^\\]]+\\]\\s*\\[[^\\]]+\\]\\s*(?:\\[[^\\]]+\\]\\s*)?"
+                                                                           options:0
+                                                                             error:nil];
+
+    NSString *cleanMessage = [regex stringByReplacingMatchesInString:message
+                                                             options:0
+                                                               range:NSMakeRange(0, message.length)
+                                                        withTemplate:@""];
+
+    return [cleanMessage stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]];
+}
+
+@end