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

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

Author: antonis

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

@@ -170,11 +170,12 @@ function setupErrorUtilsGlobalHandler(): void {
       return;
     }
 
-    // React render errors may arrive without a .stack but with a .componentStack
-    // (set by ReactFiberErrorDialog). Use the componentStack as a fallback so
+    // 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.stack && error.componentStack) {
+    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}`;
     }
@@ -220,3 +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

@@ -162,7 +162,29 @@ describe('ReactNativeErrorHandlers', () => {
       );
     });
 
-    test('Does not override stack when error already has one', async () => {
+    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!();