Is there a way to serve static assets?

[jpambrun]

I am trying to create a medical image viewer widget using cornerstone, but I am hitting several snag. Cornerstone make use of web workers that are not inlined and bundled in the main output. This pretty much prevents me from using esm.sh as cross origin loading of workers seems impossible. Essentially, I believe I now need a way to serve static assets. I am using marimo and they are serving anywidget assets via a special /@file/ endpoint. I feel like anywidget should mandate a way to serve various static assets (icons, worker src, wasm, etc) outside of the bundle, but can't find any documentation. Am I missing something?

I am also opened a ticket on the marimo repo.

[manzt]

Currently, the recommended approach for sharing static assets in anywidget is through the use of traitlets. This makes use of the underlying messaging channel (e.g., websockets), which is reliably available across various notebook environments.

Here's an example creating a Web Worker dynamically:

import traitlets
import anywidget

class Widget(anywidget.AnyWidget):
    _esm = """
    function render({ model, el }) {
        const blob = new Blob([model.get("_worker_asset")], { type: "application/javascript" });
        const worker = new Worker(URL.createObjectURL(blob));
        worker.postMessage({ name: model.get("_worker_name") });
        worker.onmessage = function(event) {
            console.log("Message from worker:", event.data);
        };
    }
    export default { render };
    """
    _worker_asset = traitlets.Unicode("""
    self.onmessage = function(event) {
        console.log("Worker received:", event.data);
        const response = "Hello, " + event.data.name + "!";
        self.postMessage(response);
    };
    """).tag(sync=True)
    _worker_name = traitlets.Unicode("anywidget").tag(sync=True)

I have considered creating a more declarative API for this, but it would essentially serve as sugar over this type of implementation. Something like JavaScript import maps could simplify handling JavaScript assets specifically, but this approach would require additional support from hosts (e.g., Marimo, Panel). I think it's worth discussing with the maintainers before adding such a requirement and explore the limitations of sending assets over the comms first.

[jpambrun]

The challenge here is the web worker usage is deep within a third party library that I don't want to fork. Even if I did, my next hurdle is that this web worker pulls in wasm modules and it would be very cumbersome to transfer these blobs to make them available from the worker.

I imagine many libraries will be unusable and many use case will be very challenging to implement without a standard way to use static assets.