Snowpack dev fails due to worker_threads module

[paradoxrevolver]

I apologize if my understanding of this is flawed, I'm still trying to learn the difference between types of modules and how Snowpack works under the hood.

I have an existing project with a number of npm modules and I'd like to be able to run snowpack dev and snowpack build. I installed Snowpack and ran snowpack dev but got a number of errors from esinstall telling me that modules like os, fs, path, and worker_threads were Node.js built-in modules and had to be "polyfilled." After some reading, I put together snowpack.config.mjs and added

// ...
    packageOptions: {
        polyfillNode: true
    },
// ...

This fixed everything except for worker_threads, which still says

[20:19:42] [esinstall:jest-worker] /home/[hidden for privacy]/node_modules/jest-worker/build/workers/NodeThreadsWorker.js
   Module "worker_threads" (Node.js built-in) is not available in the browser. Run Snowpack with --polyfill-node to fix.

So, I looked around at Snowpack plugins and Rollup plugins and attempted

import { workerThreadsSuffix } from 'rollup-plugin-worker-threads';
// ...
    packageOptions: {
        polyfillNode: true,
        rollup: {
            plugins: [
                workerThreadsSuffix()
            ]
        }
    },
// ...

but this doesn't change anything, and I haven't convinced myself that any of the alternative worker thread plugins will do anything different. I believe this is a relatively common issue to get, where an npm module can't be processed by Snowpack and a plugin needs to be added or configured to help. I have noted that worker_threads is not actually a module available on npm.

I think I may be misunderstanding how these plugins work, how to get Snowpack to recognize unusual npm packages, and what worker_threads really is. What should I be doing instead?

[tobias-edwards]

I'm experiencing this issue in Snowpack version 3.8.8 (I also tried reverting to earlier versions of Snowpack 3). The docs say to set polyfillNode: false, but I tried this and still get the same error.

[georgefeast-onit]

I also had this issue and resolved it by adding the rollup plugins to the external option in packageOptions in snowpack.config (as rollup and snowpack never run together in my setup)