frontend/src/errorReporting.ts

@@ -13,12 +13,24 @@ export interface ClientErrorReport {
 
 // Fire and forget, and deliberately swallowing — the one place in this change
 // where swallowing is correct. This runs inside componentDidCatch, so a
-// reporter that rejected would throw from the very thing that exists to stop
-// throws, and there would be nothing left to catch it.
+// reporter that threw — or rejected — would throw from the very thing that
+// exists to stop throws, and there would be nothing left to catch it.
+//
+// The try/catch guards the synchronous part: JSON.stringify(report) and the
+// call to fetch() itself both run before any promise exists, so React does
+// not guarantee componentDidCatch is handed a real Error — code can throw
+// anything, and an object with a circular message or stack makes
+// JSON.stringify throw. The .catch on the returned promise guards the async
+// part, the rejection once fetch has actually started. Neither covers the
+// other; both are required.
 export function reportClientError(report: ClientErrorReport): void {
+  try {
     void fetch('/api/client-errors', {
       method: 'POST',
       headers: { 'Content-Type': 'application/json' },
       body: JSON.stringify(report)
     }).catch(() => undefined);
+  } catch {
+    // Nothing to do — see the comment above.
+  }
 }