fix(browser): forward uncaught worker errors with their stack

dev-packages/e2e-tests/test-applications/browser-webworker-vite/tests/errors.test.ts

@@ -7,6 +7,11 @@ function waitForPageloadSpan() {
   });
 }
 
+// The throw still bubbles to the page after the worker forwards it, but
+// the integration makes globalHandlers skip that frameless copy. So the
+// first error event to arrive must be the forwarded one.
+const WORKER_MECHANISM = 'auto.browser.web_worker.onerror';
+
 test('captures an error with debug ids and pageload trace context', async ({ page }) => {
   const errorEventPromise = waitForError('browser-webworker-vite', async event => {
     return !event.type && !!event.exception?.values?.[0];
@@ -24,9 +29,16 @@ test('captures an error with debug ids and pageload trace context', async ({ pag
   const pageloadSpan = await pageloadSpanPromise;
 
   expect(errorEvent.exception?.values).toHaveLength(1);
-  expect(errorEvent.exception?.values?.[0]?.value).toBe('Uncaught Error: Uncaught error in worker');
-  expect(errorEvent.exception?.values?.[0]?.stacktrace?.frames).toHaveLength(1);
-  expect(errorEvent.exception?.values?.[0]?.stacktrace?.frames?.[0]?.filename).toMatch(/worker-.+\.js$/);
+  expect(errorEvent.exception?.values?.[0]?.mechanism?.type).toBe(WORKER_MECHANISM);
+  expect(errorEvent.exception?.values?.[0]?.type).toBe('Error');
+  expect(errorEvent.exception?.values?.[0]?.value).toBe('Uncaught error in worker');
+  expect(errorEvent.exception?.values?.[0]?.stacktrace?.frames).toEqual(
+    expect.arrayContaining([expect.objectContaining({ filename: expect.stringMatching(/worker-.+\.js$/) })]),
+  );
+
+  expect(errorEvent.contexts?.worker).toEqual({
+    filename: expect.stringMatching(/worker-.+\.js$/),
+  });
 
   expect(errorEvent.transaction).toBe('/');
   expect(pageloadSpan.name).toBe('Pageload');
@@ -52,6 +64,38 @@ test('captures an error with debug ids and pageload trace context', async ({ pag
   });
 });
 
+test('emits exactly one event for an uncaught worker error', async ({ page }) => {
+  const mechanisms: Array<string | undefined> = [];
+  // Never resolves. It only records every error event that arrives, so
+  // the global handler's copy of a throw would show up here.
+  void waitForError('browser-webworker-vite', event => {
+    if (!event.type && event.exception?.values?.[0]) {
+      mechanisms.push(event.exception.values[0].mechanism?.type);
+    }
+    return false;
+  });
+
+  const firstErrorPromise = waitForError('browser-webworker-vite', event => {
+    return event.exception?.values?.[0]?.value === 'Uncaught error in worker';
+  });
+  const secondErrorPromise = waitForError('browser-webworker-vite', event => {
+    return event.exception?.values?.[0]?.value === 'Uncaught error in worker 2';
+  });
+
+  await page.goto('/');
+
+  await page.locator('#trigger-error').click();
+  await firstErrorPromise;
+
+  // The bubbled copy of the first throw is queued right behind the forwarded
+  // one, so the second worker's event arriving without it in between is the
+  // signal that it was suppressed.
+  await page.locator('#trigger-error-2').click();
+  await secondErrorPromise;
+
+  expect(mechanisms).toEqual([WORKER_MECHANISM, WORKER_MECHANISM]);
+});
+
 test("user worker message handlers don't trigger for sentry messages", async ({ page }) => {
   const workerReadyPromise = new Promise<number>(resolve => {
     let workerMessageCount = 0;
@@ -90,9 +134,11 @@ test('captures an error from the second eagerly added worker', async ({ page })
   const pageloadSpan = await pageloadSpanPromise;
 
   expect(errorEvent.exception?.values).toHaveLength(1);
-  expect(errorEvent.exception?.values?.[0]?.value).toBe('Uncaught Error: Uncaught error in worker 2');
-  expect(errorEvent.exception?.values?.[0]?.stacktrace?.frames).toHaveLength(1);
-  expect(errorEvent.exception?.values?.[0]?.stacktrace?.frames?.[0]?.filename).toMatch(/worker2-.+\.js$/);
+  expect(errorEvent.exception?.values?.[0]?.mechanism?.type).toBe(WORKER_MECHANISM);
+  expect(errorEvent.exception?.values?.[0]?.value).toBe('Uncaught error in worker 2');
+  expect(errorEvent.exception?.values?.[0]?.stacktrace?.frames).toEqual(
+    expect.arrayContaining([expect.objectContaining({ filename: expect.stringMatching(/worker2-.+\.js$/) })]),
+  );
 
   expect(errorEvent.transaction).toBe('/');
   expect(pageloadSpan.name).toBe('Pageload');
@@ -135,9 +181,11 @@ test('captures an error from the third lazily added worker', async ({ page }) =>
   const pageloadSpan = await pageloadSpanPromise;
 
   expect(errorEvent.exception?.values).toHaveLength(1);
-  expect(errorEvent.exception?.values?.[0]?.value).toBe('Uncaught Error: Uncaught error in worker 3');
-  expect(errorEvent.exception?.values?.[0]?.stacktrace?.frames).toHaveLength(1);
-  expect(errorEvent.exception?.values?.[0]?.stacktrace?.frames?.[0]?.filename).toMatch(/worker3-.+\.js$/);
+  expect(errorEvent.exception?.values?.[0]?.mechanism?.type).toBe(WORKER_MECHANISM);
+  expect(errorEvent.exception?.values?.[0]?.value).toBe('Uncaught error in worker 3');
+  expect(errorEvent.exception?.values?.[0]?.stacktrace?.frames).toEqual(
+    expect.arrayContaining([expect.objectContaining({ filename: expect.stringMatching(/worker3-.+\.js$/) })]),
+  );
 
   expect(errorEvent.transaction).toBe('/');
   expect(pageloadSpan.name).toBe('Pageload');
@@ -165,7 +213,7 @@ test('captures an error from the third lazily added worker', async ({ page }) =>
 
 test('worker errors are not tagged as third-party when module metadata is present', async ({ page }) => {
   const errorEventPromise = waitForError('browser-webworker-vite', async event => {
-    return !event.type && event.exception?.values?.[0]?.value === 'Uncaught Error: Uncaught error in worker';
+    return !event.type && event.exception?.values?.[0]?.value === 'Uncaught error in worker';
   });
 
   await page.goto('/');

packages/browser/src/integrations/globalhandlers.ts

@@ -156,7 +156,10 @@ export function _eventFromRejectionWithPrimitive(reason: Primitive): Event {
   };
 }
 
-function _enhanceEventWithInitialFrame(
+/**
+ * Adds a frame built from the error location when the event has none.
+ */
+export function _enhanceEventWithInitialFrame(
   event: Event,
   url: string | undefined,
   lineno: number | undefined,