Web Workers throws a CSP error - could we disable them?

[ghiscoding]

Hello, I'm using fflate in a new project Excel-Export-Vanilla which sometime throws an error but only when the file is big enough and is starting to use Web Workers. Googling the error, I see that I might to adjust the CSP (Content Security Policy) rules, maybe something like worker-src 'self' blob: ;, however it would be nice if fflate had an option to not disable Web Workers (I know that they are used only when using zip and I could use zipAsync to disable them but that would require 2 implementations which I would prefer to avoid).

Basically, I'd like to know if there's a different approach to this error and/or if fflate could have a way to disable Web Worker. I'd like to keep using zip but provide a way to users of my lib to disable Web Worker if they want with just an option.

browser.js:12 Refused to create a worker from 'blob:http://localhost:8888/2667b3f9-5c8d-4510-9087-7b6cf1d24531' 
because it violates the following Content Security Policy directive: "script-src 'self' 'unsafe-inline'". 
Note that 'worker-src' was not explicitly set, so 'script-src' is used as a fallback.
...

browser.js:12 Uncaught (in promise) DOMException: Failed to construct 'Worker': Access to the script at 
'blob:http://localhost:8888/2667b3f9-5c8d-4510-9087-7b6cf1d24531' is denied by the document's Content Security Policy.

For confirmation, adding worker-src 'self' blob:; did fix the CSP error, but still an option to disable Web Worker when using zip would be nice.

[101arrowz]

To clarify, fflate offers two ZIP functions: zipSync and zip. zipSync runs synchronously and without any Web Workers. zip runs asynchronously and uses Web Workers. There is no reason to run zip in an environment that does not support blob-based Web Workers; the only reason you'd use it instead of zipSync is to take advantage of multicore compression using worker threads. The way to disable Web Workers is simply to use zipSync instead.

I'd like to keep using zip but provide a way to users of my lib to disable Web Worker if they want with just an option.

I recommend just conditionally using zip or zipSync based on the user options. Having two implementations is not as convoluted as it seems, and fflate is designed in such a way that it will only increase your bundle size by 200 bytes or so. For example:

import { zip, zipSync } from 'fflate';

const zipWorker = files => {
  return new Promise((resolve, reject) => {
    zip(files, (err, result) => err ? reject(err) : resolve(result));
  });
}
const zipNoWorker = async files => {
  return zipSync(files);
}

const zipFunc = canUseWorkers ? zipWorker : zipNoWorker;

async function main() {
  const result = await zipFunc({ 'yourfile.bin': new Uint8Array(10) });
  console.log(result); // your zip file
}

[ghiscoding]

The way to disable Web Workers is simply to use zipSync instead.

Thanks that is what I figured was the approach to use, also great to see a demo of that. I'll go with that, thanks again for the great lib, I now officially use it :)

[mkassm]

Hi @101arrowz,

Thanks for clarification, I have the same error with unzip method and there is no such as method for async version like unzipAsync. Is there any workaround for this?