fix(stylesheet): harden PDF preflight and surface worker failures (#3284)

Co-authored-by: Cursor Agent <cursoragent@cursor.com>

apps/web/src/features/resume/stylesheet/preflight.worker.test.ts

@@ -55,4 +55,42 @@ describe("stylesheet preflight worker", () => {
 			cause: { name: "ZodError", message: "Invalid resume data", issues },
 		});
 	});
+
+	it("includes a sanitized cause when PDF preflight throws an unexpected error", async () => {
+		let handler: ((event: MessageEvent<PreflightWorkerRequest>) => Promise<void>) | undefined;
+		const postMessage = vi.fn();
+		vi.stubGlobal("self", {
+			postMessage,
+			addEventListener: vi.fn((_type, listener) => {
+				handler = listener as typeof handler;
+			}),
+		});
+		mocks.renderPreflightPdf.mockRejectedValueOnce(new Error("Canvas is already closed"));
+		vi.resetModules();
+		await import("./preflight.worker");
+
+		await handler?.({
+			data: {
+				type: "preflight",
+				requestId: 8,
+				editGeneration: 4,
+				input: {} as never,
+				limits: {} as never,
+			},
+		} as unknown as MessageEvent<PreflightWorkerRequest>);
+
+		expect(postMessage).toHaveBeenCalledWith(
+			expect.objectContaining({
+				type: "preflight_result",
+				requestId: 8,
+				editGeneration: 4,
+				result: expect.objectContaining({
+					ok: false,
+					code: "STYLESHEET_PREFLIGHT_WORKER_FAILED",
+					message: expect.stringContaining("Canvas is already closed"),
+					diagnostics: [],
+				}),
+			}),
+		);
+	});
 });

apps/web/src/features/resume/stylesheet/preflight.worker.ts

@@ -20,6 +20,13 @@ const failure = (code: PdfPreflightFailure["code"], message: string): PdfPreflig
 	diagnostics: [],
 });
 
+const sanitizeWorkerCause = (cause: unknown): string => {
+	if (!(cause instanceof Error)) return "The PDF preflight worker failed.";
+	const detail = cause.message.replace(/\s+/g, " ").trim().slice(0, 200);
+	if (!detail) return "The PDF preflight worker failed.";
+	return `The PDF preflight worker failed. (${cause.name}: ${detail})`;
+};
+
 const serializeZodCause = (cause: unknown): SerializedPreflightCause | undefined => {
 	if (!(cause instanceof Error) || cause.name !== "ZodError" || !("issues" in cause) || !Array.isArray(cause.issues)) {
 		return;
@@ -49,7 +56,7 @@ self.addEventListener("message", async ({ data }: MessageEvent<PreflightWorkerRe
 			self.postMessage(response);
 			return;
 		}
-		const result = failure("STYLESHEET_PREFLIGHT_WORKER_FAILED", "The PDF preflight worker failed.");
+		const result = failure("STYLESHEET_PREFLIGHT_WORKER_FAILED", sanitizeWorkerCause(cause));
 		const response: PreflightWorkerResponse = {
 			type: "preflight_result",
 			requestId: data.requestId,

apps/web/src/features/resume/stylesheet/store.test.ts

@@ -759,6 +759,66 @@ describe("stylesheet store runtime", () => {
 		expect(runtime.store.getState().status).toBe("error");
 	});
 
+	it("surfaces browser preflight failures as diagnostics when the worker returns an empty list", async () => {
+		let resolveMutate!: (value: MutationResult & { diagnostics: never[] }) => void;
+		const mutate = vi.fn(
+			() =>
+				new Promise<MutationResult & { diagnostics: never[] }>((resolve) => {
+					resolveMutate = resolve;
+				}),
+		);
+		const runtime = createStylesheetStoreRuntime({
+			resumeId: "resume-1",
+			initial,
+			resumeData: defaultResumeData,
+			debounceMs: 0,
+			compile: async ({ editGeneration }) => ({
+				type: "compile_result",
+				requestId: editGeneration,
+				editGeneration,
+				program: { languageVersion: 1, rules: [] },
+				diagnostics: [],
+			}),
+			preflight: async ({ editGeneration }) => ({
+				type: "preflight_result",
+				requestId: editGeneration,
+				editGeneration,
+				result: {
+					ok: false,
+					code: "STYLESHEET_PREFLIGHT_WORKER_FAILED",
+					message: "The PDF preflight worker failed.",
+					diagnostics: [],
+				},
+			}),
+			mutate,
+		});
+
+		runtime.store.getState().setSourceText("@version 1;\nsection { color: teal; }");
+		await vi.runAllTimersAsync();
+
+		expect(runtime.store.getState().diagnostics).toEqual([
+			expect.objectContaining({
+				code: "STYLESHEET_PREFLIGHT_WORKER_FAILED",
+				severity: "error",
+				message: "The PDF preflight worker failed.",
+				range: {
+					start: { line: 1, column: 1, offset: 0 },
+					end: { line: 1, column: 1, offset: 0 },
+				},
+			}),
+		]);
+		expect(runtime.store.getState().diagnostics.some(({ severity }) => severity === "error")).toBe(true);
+		expect(mutate).toHaveBeenCalled();
+		resolveMutate({
+			stylesheet: stylesheet("@version 1;\n"),
+			revision: 4,
+			renderDataVersion: 7,
+			editGeneration: 1,
+			diagnostics: [],
+		});
+		await Promise.resolve();
+	});
+
 	it("finishes an edit when refreshIntelligence interleaves through the shared compile client", async () => {
 		const { createCompileWorkerClient } = await import("./worker-client");
 		const listeners = new Map<string, Set<EventListener>>();

apps/web/src/features/resume/stylesheet/store.ts

@@ -113,6 +113,18 @@ const emptySemanticTree = (): SemanticNode => ({
 const HISTORY_COALESCE_MS = 500;
 const MAX_HISTORY_ENTRIES = 50;
 
+const preflightFailureDiagnostic = (
+	result: Extract<PreflightWorkerResponse["result"], { ok: false }>,
+): SemanticCssDiagnostic => ({
+	code: result.code,
+	severity: "error",
+	message: result.message,
+	range: {
+		start: { line: 1, column: 1, offset: 0 },
+		end: { line: 1, column: 1, offset: 0 },
+	},
+});
+
 const inactiveState = (): Omit<
 	StylesheetStoreState,
 	"setSourceText" | "setFocused" | "activate" | "deactivate" | "undo" | "redo" | "refreshIntelligence"
@@ -389,7 +401,14 @@ export function createStylesheetStoreRuntime(options: CreateStylesheetStoreRunti
 			if (candidateValidationEpoch !== validationEpoch) return;
 			if (destroyed || preflight.editGeneration !== store.getState().editGeneration) return;
 			if (!preflight.result.ok) {
-				patch({ diagnostics: [...compiled.diagnostics, ...preflight.result.diagnostics], status: "error" });
+				patch({
+					diagnostics: [
+						...compiled.diagnostics,
+						...preflight.result.diagnostics,
+						preflightFailureDiagnostic(preflight.result),
+					],
+					status: "error",
+				});
 				if (candidate.transition !== "edit_source") return;
 			}
 		}

apps/web/src/features/resume/stylesheet/worker-client.test.ts

@@ -115,6 +115,20 @@ describe("stylesheet worker clients", () => {
 		vi.useRealTimers();
 	});
 
+	it("rejects pending preflight work when the worker emits an error event", async () => {
+		const fake = worker();
+		const client = createPreflightWorkerClient(() => fake, 5_000);
+		const pending = client.preflight({ editGeneration: 1 } as never);
+		const outcome = pending.catch((error: unknown) => error);
+
+		fake.emit({ type: "preflight_ready" });
+		await Promise.resolve();
+		fake.emitError({ message: "Worker crashed" } as ErrorEvent);
+
+		expect(await outcome).toMatchObject({ message: "Worker crashed" });
+		expect(fake.terminate).toHaveBeenCalled();
+	});
+
 	it("rejects structured resume-data failures without waiting for the timeout", async () => {
 		vi.useFakeTimers();
 		const fake = worker();

apps/web/src/features/resume/stylesheet/worker-client.ts

@@ -128,8 +128,18 @@ export function createPreflightWorkerClient(
 		pending.delete(response.requestId);
 		request.resolve(response);
 	};
-	const onError: WorkerErrorListener = () => {
+	const failPending = (error: Error) => {
+		for (const request of pending.values()) {
+			if (request.timer) clearTimeout(request.timer);
+			request.reject(error);
+		}
+		pending.clear();
+	};
+
+	const onError: WorkerErrorListener = (event) => {
+		const error = new Error(event.message || "Stylesheet preflight worker failed.");
 		terminate();
+		failPending(error);
 	};
 
 	const terminate = () => {