fix(android): Use componentStack as fallback for missing error stack traces (#5965)

* fix(android): Use componentStack as fallback for missing error stack traces

When React render errors occur on Android with Hermes, the error may
arrive at ErrorUtils.setGlobalHandler without a .stack property.
However, React attaches a .componentStack with component locations
and bundle offsets before the error reaches the handler.

Use componentStack as a fallback for error.stack so that
eventFromException can extract frames with source locations.

Fixes #5071

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* Update changelog

* fix: Also handle stack with no frames (message-only stack string)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix: Add null guard for error object in componentStack fallback

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix: Use optional chaining for error null check

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: antonis

CHANGELOG.md

@@ -10,6 +10,7 @@
 
 ### Fixes
 
+- Use React `componentStack` as fallback when error has no stack trace on Android ([#5965](https://github.com/getsentry/sentry-react-native/pull/5965)
 - Add `SENTRY_PROJECT_ROOT` env var to override project root in Xcode build phase scripts for monorepo setups ([#5961](https://github.com/getsentry/sentry-react-native/pull/5961))
 
 ### Features

packages/core/src/js/integrations/reactnativeerrorhandlers.ts

@@ -170,6 +170,16 @@ function setupErrorUtilsGlobalHandler(): void {
       return;
     }
 
+    // React render errors may arrive without useful frames in .stack but with a
+    // .componentStack (set by ReactFiberErrorDialog) that contains component
+    // locations with bundle offsets. Use componentStack as a fallback so
+    // eventFromException can extract frames with source locations.
+    // oxlint-disable-next-line typescript-eslint(no-unsafe-member-access)
+    if (error?.componentStack && (!error.stack || !hasStackFrames(error.stack))) {
+      // oxlint-disable-next-line typescript-eslint(no-unsafe-member-access)
+      error.stack = `${error.message || 'Error'}${error.componentStack}`;
+    }
+
     const hint: EventHint = {
       originalException: error,
       attachments: getCurrentScope().getScopeData().attachments,
@@ -211,3 +221,10 @@ function setupErrorUtilsGlobalHandler(): void {
     );
   });
 }
+
+/**
+ * Checks if a stack trace string contains at least one frame line.
+ */
+function hasStackFrames(stack: unknown): boolean {
+  return typeof stack === 'string' && stack.includes('\n');
+}

packages/core/test/integrations/reactnativeerrorhandlers.test.ts

@@ -140,6 +140,62 @@ describe('ReactNativeErrorHandlers', () => {
 
       expect(hint).toEqual(expect.objectContaining({ originalException: new Error('Test Error') }));
     });
+
+    test('Uses componentStack as fallback when error has no stack', async () => {
+      const integration = reactNativeErrorHandlersIntegration();
+      integration.setupOnce!();
+
+      const error: any = {
+        message: 'Value is undefined, expected an Object',
+        componentStack:
+          '\n    at UserMessage (http://localhost:8081/index.bundle:1:5274251)' +
+          '\n    at renderItem (http://localhost:8081/index.bundle:1:5280705)',
+      };
+
+      await errorHandlerCallback!(error, true);
+      await client.flush();
+
+      expect(error.stack).toBe(
+        'Value is undefined, expected an Object' +
+          '\n    at UserMessage (http://localhost:8081/index.bundle:1:5274251)' +
+          '\n    at renderItem (http://localhost:8081/index.bundle:1:5280705)',
+      );
+    });
+
+    test('Uses componentStack as fallback when stack has no frames', async () => {
+      const integration = reactNativeErrorHandlersIntegration();
+      integration.setupOnce!();
+
+      const error: any = {
+        message: 'Value is undefined, expected an Object',
+        stack: 'Error: Value is undefined, expected an Object',
+        componentStack:
+          '\n    at UserMessage (http://localhost:8081/index.bundle:1:5274251)' +
+          '\n    at renderItem (http://localhost:8081/index.bundle:1:5280705)',
+      };
+
+      await errorHandlerCallback!(error, true);
+      await client.flush();
+
+      expect(error.stack).toBe(
+        'Value is undefined, expected an Object' +
+          '\n    at UserMessage (http://localhost:8081/index.bundle:1:5274251)' +
+          '\n    at renderItem (http://localhost:8081/index.bundle:1:5280705)',
+      );
+    });
+
+    test('Does not override stack when error already has frames', async () => {
+      const integration = reactNativeErrorHandlersIntegration();
+      integration.setupOnce!();
+
+      const error = new Error('Test Error');
+      (error as any).componentStack = '\n    at SomeComponent (http://localhost:8081/index.bundle:1:100)';
+      const originalStack = error.stack;
+
+      await errorHandlerCallback!(error, false);
+
+      expect(error.stack).toBe(originalStack);
+    });
   });
 
   describe('onUnhandledRejection', () => {