fix(sentry): stop reporting Monaco cancellations when an editor closes

src/app/common/sentry.ts

@@ -27,13 +27,28 @@ export function reportError(error: unknown) {
     if (_queue && _queue.length < MAX_QUEUED_ERRORS) _queue.push(error);
 }
 
+/**
+ * True for the error Monaco uses to cancel pending work. Monaco does not
+ * handle some of these rejections, for example when an editor is disposed
+ * while a word highlight is pending. They are not failures.
+ * Same check as Monaco's `isCancellationError`.
+ */
+function isMonacoCancellation(error: unknown) {
+    return (
+        error instanceof Error &&
+        error.name === 'Canceled' &&
+        error.message === 'Canceled'
+    );
+}
+
 /**
  * Angular error handler. Logs errors to the console as the default handler
- * does, and sends them to Sentry.
+ * does, and sends them to Sentry. Ignores Monaco cancellations.
  */
 @Injectable()
 export class SentryReportingErrorHandler implements ErrorHandler {
     public handleError(error: unknown) {
+        if (isMonacoCancellation(error)) return;
         console.error(error);
         reportError(error);
     }

src/tests/common/sentry.spec.ts

@@ -63,6 +63,25 @@ describe('sentry', () => {
         expect(handle_error).toHaveBeenCalledWith('late');
     });
 
+    it('ignores Monaco cancellation errors', async () => {
+        const { initSentry, SentryReportingErrorHandler } = await loadSentry();
+        setAuthorityDsn(undefined);
+        await initSentry(injector, 'user-1');
+        const console_error = vi
+            .spyOn(console, 'error')
+            .mockImplementation(() => undefined);
+        const handler = new SentryReportingErrorHandler();
+        const canceled = new Error('Canceled');
+        canceled.name = 'Canceled';
+        handler.handleError(canceled);
+        expect(handle_error).not.toHaveBeenCalled();
+        expect(console_error).not.toHaveBeenCalled();
+        const error = new Error('Canceled');
+        handler.handleError(error);
+        expect(handle_error).toHaveBeenCalledWith(error);
+        console_error.mockRestore();
+    });
+
     it('does not load Sentry when the authority turns it off', async () => {
         const { initSentry, reportError } = await loadSentry();
         setAuthorityDsn('');