fix(node-native): Don't drop breadcrumbs from event loop block events

dev-packages/node-integration-tests/suites/thread-blocked-native/basic.mjs

@@ -14,6 +14,14 @@ Sentry.init({
   integrations: [eventLoopBlockIntegration()],
 });
 
+// Sentry.addBreadcrumb() writes to the isolation scope which is only captured via
+// AsyncLocalStorage, so we add to the current scope to test the poll state route
+Sentry.getCurrentScope().addBreadcrumb({
+  category: 'test',
+  message: 'blocking event loop soon',
+  level: 'info',
+});
+
 setTimeout(() => {
   longWork();
 }, 2000);

dev-packages/node-integration-tests/suites/thread-blocked-native/test.ts

@@ -105,7 +105,20 @@ describe('Thread Blocked Native', { timeout: 30_000 }, () => {
   test('ESM', async () => {
     await createRunner(__dirname, 'basic.mjs')
       .withMockSentryServer()
-      .expect({ event: ANR_EVENT_WITH_DEBUG_META('basic') })
+      .expect({
+        event: {
+          ...ANR_EVENT_WITH_DEBUG_META('basic'),
+          // Ensures breadcrumbs make it through the poll state rather than via AsyncLocalStorage
+          breadcrumbs: [
+            {
+              timestamp: expect.any(Number),
+              category: 'test',
+              message: 'blocking event loop soon',
+              level: 'info',
+            },
+          ],
+        },
+      })
       .start()
       .completed();
   });

packages/node-native/src/event-loop-block-watchdog.ts

@@ -225,6 +225,21 @@ function getExceptionAndThreads(
   };
 }
 
+/**
+ * Rehydrates a Scope from serialized ScopeData that has been passed over a JSON serialization boundary.
+ *
+ * `Scope.update()` only handles `ScopeContext` fields, so breadcrumbs have to be carried over separately.
+ * Attachments are deliberately not carried over since their binary data does not survive JSON serialization.
+ */
+function hydrateScope(data: Partial<ScopeData> | undefined): Scope {
+  const scope = new Scope();
+  if (data) {
+    scope.update(data);
+    data.breadcrumbs?.forEach(breadcrumb => scope.addBreadcrumb(breadcrumb));
+  }
+  return scope;
+}
+
 function applyScopeToEvent(event: Event, scope: ScopeData): void {
   applyScopeDataToEvent(event, scope);
 
@@ -274,9 +289,7 @@ async function sendBlockEvent(crashedThreadId: string): Promise<void> {
     ...getExceptionAndThreads(crashedThreadId, threads),
   };
 
-  const scope = crashedThread.pollState?.scope
-    ? new Scope().update(crashedThread.pollState.scope).getScopeData()
-    : new Scope().getScopeData();
+  const scope = hydrateScope(crashedThread.pollState?.scope).getScopeData();
 
   if (crashedThread?.asyncState?.isolationScope) {
     // We need to rehydrate the scope from the serialized object with properties beginning with _user, etc