Can't run under Wrangler/Cloudflare Workers

[sntran]

Reporting as an issue, but I understand you may or may not want to tackle it.

Steps to Reproduce

• Creates a folder
• Create a _worker.js (content below)
• Add a "wrangler.json" (content below) to ensure wrangler uses Node.js polyfills.
• Run npx -y wrangler pages dev .

_worker.js

import { 
  XmlDocument, 
  XsltStylesheet as Stylesheet 
} from "libxslt-wasm";
import { registerModule } from "libxslt-wasm/exslt";

registerModule("common");

export default {
  async fetch(request) {
    const doc = await XmlDocument.fromFileOrUrl(
      "https://dailymed.nlm.nih.gov/dailymed/services/v2/spls/2b4255a7-f9f5-4235-8dbb-b0f03acbd624.xml",
    );
    const stylesheet = await Stylesheet.fromEmbeddedXmlDocument(doc);
    const result = await stylesheet.apply(doc, {});

    return new Response(result.toHtmlString({ format: true }), {
      headers: {
        "Content-Type": "text/html; charset=utf-8",
      },
    });
  },
}

wrangler.json

{
  "name": "test",
  "compatibility_flags": [
    "nodejs_compat"
  ],
  "compatibility_date": "2025-09-23"
}

Expected Result

See the transformed HTML on "http://localhost:8788/"

Actual Result

Wrangler throws an error in the shell:

[ERROR] service core:user:test: Uncaught TypeError: The argument 'path' The argument must be a file URL object, a file URL string, or an absolute path string.. Received 'undefined'

    at null.<anonymous> (node:module:12:15) in createRequire
    at null.<anonymous> (bundledWorker-0.5924026434449623.js:2421:42) in createRequire
    at null.<anonymous> (bundledWorker-0.5924026434449623.js:2756:22

Tracing Notes

The error is traced to line 59 of "dist/output/libxslt.js":

var require = createRequire(import.meta.url);

[jeremy-code]

I believe this is due to cloudflare/workers-sdk#7265 (esbuild by default doesn't have import.meta). When using the Cloudflare Vite plugin instead, that error doesn't appear — though it's not much better, since it fails to import node:worker_threads.

I believe I can fix this by changing the compiler settings, but first, I think I want to first update the code so there's no longer a dependency on Node.js. node:fs really shouldn't be necessary now that .fromBuffer/.from exist since you can just pass the files to them directly. That'll probably be more helpful instead

[jeremy-code]

I believe this is due to cloudflare/workers-sdk#7265 (esbuild by default doesn't have import.meta). When using the Cloudflare Vite plugin instead, that error doesn't appear — though it's not much better, since it fails to import node:worker_threads.

I believe I can fix this by changing the compiler settings, but first, I think I want to first update the code so there's no longer a dependency on Node.js. node:fs really shouldn't be necessary now that .fromBuffer/.from exist since you can just pass the files to them directly. That'll probably be more helpful instead

v0.0.12 should no longer have Node.js dependency, though when I tried to run it locally, I got the error "Aborted(Assertion failed: JSPI not supported by current environment. Perhaps it needs to be enabled via flags?)"

Cloudflare Workers uses V8 isolates so you would need a way to toggle JSPI. The thing is, I think the actual Cloudflare environment already has it enabled by default (https://github.com/cloudflare/workerd/blob/934a9046940699f2ac62530b9edac038e17a6089/src/workerd/jsg/jsg.h#L2679-L2680), so I suspect this could be an issue with miniflare? I haven't tried it in the Cloudflare Workers environment, but hopefully that's the case.

[sntran]

Thanks @jeremy-code!

I still encounter the error about createRequire with v0.0.12 when running under wrangler. Checking "dist/output/libxslt.js" still shows that it uses import.meta.url.

[jeremy-code]

Thanks @jeremy-code!

I still encounter the error about createRequire with v0.0.12 when running under wrangler. Checking "dist/output/libxslt.js" still shows that it uses import.meta.url.

Sorry let me clarify — wrangler uses esbuild so by default, wrangler wouldn't be able to use import.meta.url. Vite (which also uses esbuild but also has a default target with import.meta support). Hence, it won't work on Wrangler, but it will work on Vite with the Cloudflare plugin. I don't think there's any way around this since that's just on Emscripten/ESBuild's end.

EDIT:

However, I think that's a moot point, since miniflare actually uses workerd and not Node.js as I thought. I don't think JSPI is actually enabled by default

[sntran]

Thanks for the clarification, and for being patient with me trying to get it working!

though it's not much better, since it fails to import node:worker_threads. I believe I can fix this by changing the compiler settings

I manually patched import.meta.url but it indeed failed to import node:worker_threads. Can you adjust that with compiler settings?

(Side node: Cloudflare will have support for import.meta.url some time later this year).

I don't think JSPI is actually enabled by default

What about https://github.com/cloudflare/workerd/blob/934a9046940699f2ac62530b9edac038e17a6089/src/workerd/jsg/jsg.h#L2679-L2680? That is for workerd right?