Recover failed conversion workers and validate Nitro downloads correctly

src/lib/services/import/core/download.test.ts

@@ -1,5 +1,10 @@
 import { describe, expect, it } from "vitest";
-import { validatePngBytes, validateSwfBytes } from "./download";
+import { createNitroBundle } from "../../swf/nitro-builder";
+import {
+	validateNitroBytes,
+	validatePngBytes,
+	validateSwfBytes,
+} from "./download";
 
 describe("import/core/download validators", () => {
 	it("accepts FWS/CWS/ZWS swf magic", () => {
@@ -22,3 +27,14 @@ describe("import/core/download validators", () => {
 		expect(validatePngBytes(Buffer.from([1, 2, 3, 4, 5, 6, 7, 8]))).toBe(false);
 	});
 });
+
+it("validates nitro bundles separately from PNG files", () => {
+	const png = Buffer.from([137, 80, 78, 71, 13, 10, 26, 10]);
+	const bundle = createNitroBundle({ name: "chair" }, png, "chair");
+	expect(validateNitroBytes(bundle)).toBe(true);
+	expect(validatePngBytes(bundle)).toBe(false);
+	expect(validateNitroBytes(png)).toBe(false);
+	expect(validateNitroBytes(Buffer.from("<html>Access denied</html>"))).toBe(
+		false,
+	);
+});

src/lib/services/import/core/download.ts

@@ -1,4 +1,5 @@
 import { promises as fs } from "node:fs";
+import { parseNitroBundle } from "../../swf/nitro-builder";
 
 import { browserHeaders } from "./browser-headers";
 
@@ -18,6 +19,20 @@ export function validatePngBytes(buffer: Buffer): boolean {
 	);
 }
 
+export function validateNitroBytes(buffer: Buffer): boolean {
+	try {
+		const bundle = parseNitroBundle(buffer);
+		return (
+			!!bundle.json &&
+			typeof bundle.json === "object" &&
+			!Array.isArray(bundle.json) &&
+			validatePngBytes(bundle.png)
+		);
+	} catch {
+		return false;
+	}
+}
+
 export async function tryDownloadCandidates(
 	urls: string[],
 	destPath: string,
@@ -33,7 +48,7 @@ export async function tryDownloadCandidates(
 export async function downloadFile(
 	url: string,
 	destPath: string,
-	options?: { maxRetries?: number; validate?: "swf" | "png" },
+	options?: { maxRetries?: number; validate?: "swf" | "png" | "nitro" },
 ): Promise<{ ok: boolean; size: number }> {
 	const maxRetries = options?.maxRetries ?? 3;
 	const baseDelay = 1000;
@@ -79,6 +94,8 @@ export async function downloadFile(
 				}
 				continue;
 			}
+			if (options?.validate === "nitro" && !validateNitroBytes(buffer))
+				return { ok: false, size: 0 };
 			await fs.writeFile(/*turbopackIgnore: true*/ destPath, buffer);
 			return { ok: true, size: buffer.length };
 		} catch (err) {