TypeError: file name contained an unexpected NUL byte: lstat occurs when trying to cache a specific URL.
This was quite an interesting error.
The cause of this error was that SHA-256 generated output containing a null byte.
detail
The following error occurred only when trying to cache a specific URL: e.g. https://esm.sh/stable/react@18
Uncaught (in promise) TypeError: file name contained an unexpected NUL byte: lstat '<cache dir>/�g��E=m�Y:M���t ���-�Ƀ�c���j'
Here’s the minimal code to reproduce the issue:
import { cache } from "jsr:@denosaurs/[email protected]";
const ns = "";
const url = "https://esm.sh/stable/react@18";
const fs = await cache(url, undefined, ns);
console.log("cached: %o %o", fs.path, fs.meta);The error occurred only when providing react@18 to esm.sh, so I assume this was an error I encountered probabilistically. Since I found it intriguing, I decided to investigate further.
It seems that, depending on the combination of SHA256 and input used in the process of computing the file name for cache storage, a NUL byte is unintentionally included.
Here's a version of the code with fewer dependencies:
// pick from https://github.com/denosaurs/cache/blob/83e4287694b0affe39bcad72f4cb7f99d3679057/file.ts#L125
async function hash(url: URL): Promise<string> {
const formatted = `${url.pathname}${url.search ? "?" + url.search : ""}`;
const encoder = new TextEncoder();
const data = encoder.encode(formatted);
const hash = await crypto.subtle.digest("SHA-256", data);
return new TextDecoder().decode(hash);
}
// await Deno.lstat("hello\0world"); // same error is occurred
const url = "https://esm.sh/stable/react@18";
const calculatedPath = await hash(new URL(url));
console.log("calculated path", calculatedPath);
console.log("has null byte?", calculatedPath.includes("\0")); // true
console.log(await Deno.lstat(calculatedPath)); // same error is occurred
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