`Cannot find module` error when trying to use localForage from worker

[eth0fox]

🐛 bug report

🤔 Expected Behavior

Module imports successfully - and if there is an actual issue a more relevant runtime exception is thrown.

😯 Current Behavior

Uncaught Error: Cannot find module 'j5VoO'
    at newRequire (worker.7a4fd70f.js?9b7af6674c1003ee52f29e28690d5705109330f0:74:19)
    at newRequire (worker.7a4fd70f.js?9b7af6674c1003ee52f29e28690d5705109330f0:58:18)
    at localRequire (worker.7a4fd70f.js?9b7af6674c1003ee52f29e28690d5705109330f0:144:14)
    at 3ZSAf.localforage (worker.7a4fd70f.js?9b7af6674c1003ee52f29e28690d5705109330f0:717:20)
    at newRequire (worker.7a4fd70f.js?9b7af6674c1003ee52f29e28690d5705109330f0:84:24)
    at worker.7a4fd70f.js?9b7af6674c1003ee52f29e28690d5705109330f0:191:5
    at worker.7a4fd70f.js?9b7af6674c1003ee52f29e28690d5705109330f0:210:3

💁 Possible Solution

🔦 Context

I'm working on a project that uses a SharedWorker - but trying to import localForage throws an exception.

💻 Code Sample

https://gist.github.com/eth0fox/a22103e3bdbb0c859d4647a02c832e10

🌍 Your Environment

Software	Version(s)
Parcel	2.16.4
Node	v25.3.0
npm/Yarn	11.7.0
Operating System	macOS 15.7.5 arm64

[eth0fox]

Hm. even trying to copy the built localforage.min.js file to the project directory causes the error, just taking the src folder from the localforage git repo does to, and manually combining it all into one file to avoid any imports also causes the issue. There is something Parcel does not like about the library and I cannot figure out what.

[eth0fox]

Ok, so I think the problem is less localforage, and more adding a large enough library triggers Parcel's codesplitting, but Parcel is including information about to find the split bundle in the main JS bundle (in index.html) actually, rather than in the js bundle for the worker.

[eth0fox]

Okay. It appears that because the way I was passing the URL to the worker constructor:

   let workerUrl = new URL("./worker.ts", import.meta.url);

    if (process.env.NODE_ENV !== "production") {
        // @ts-ignore 
        let workerContent = await import("bundle-text:./worker.ts");
        let hash = await crypto.subtle.digest("SHA-1", (new TextEncoder()).encode(workerContent));
        let hex = [...new Uint8Array(hash)].map(a => a.toString(16).padStart(2,'0')).join('')
        workerUrl.search = "?" + hex;
    }
    let worker = new SharedWorker(workerUrl, {
        type: "module",
        name: "TestWorker (" + workerUrl + ")"
    });

Because I had to hack around #9931 being closed despite never actually being solved (sadly, I do not live in the fantasy land where a stalebot resolves all the bugs in my code), it appears that not directly passing the constructed URL object to the Worker constructor causes Parcel's flawed heuristics to fail to detect that this code will be executed in a different context.