Using elm in Web Worker fails with Uncaught ReferenceError: document is not defined #756
Description
Describe the bug
If you attempt to start a Platform.worker app in a Web Worker script, you get
Worker.elm?import:23902 Uncaught ReferenceError: document is not defined
Reproducible repo
The gist is:
Worker.elm:
module Worker exposing (main)
main = Platform.worker
{ init = init
, update = update
, subscriptions = subscriptions
}
worker.ts:
import { Elm } from "./Worker.elm";
addEventListener("message", (event) => {
const app = Elm.Validator.Worker.init({
flags: event.data,
});
const subscriber = (val: T): void => {
app.ports.sendResult.unsubscribe(subscriber);
postMessage(val);
};
app.ports.sendResult.subscribe(subscriber);
}
});
index.ts:
const worker = new Worker(
new URL("./worker.ts", import.meta.url),
{ type: "module" },
);
worker.postMessage({});
Expected behavior
No errors.
Additional context
This seems to be a problem with the injected HMR code that assumes a standard browser context, but doesn't work in a Web Worker context (where globals like document are not defined).
Workaround
Plonking globalThis.document = {} at the top of the worker code makes it sort of usable, but HMR updates will still crash it.