Webpack entry point cannot find worker-loader in Yarn 2 repo

Attach (recommended) or Link to PDF file here: https://www.w3.org/WAI/ER/tests/xhtml/testfiles/resources/pdf/dummy.pdf

Configuration:

• Web browser and its version: Firefox 84.0
• Operating system and its version: Ubuntu 20.10
• PDF.js version: 2.6.347
• Also note: Webpack 5.11.0 and Yarn 2.3.3 workspaces

Steps to reproduce the problem: To see the manual worker setup resort to fake worker:

1. clone and setup with Yarn 2: https://github.com/jcamden/pdfjs-yarn-2
2. run the webpack dev server with yarn start
3. check browser console log for ‘Warning: Setting up fake worker.’

To see the webpack entry point fail:

1. uncomment line 8 of packages/client/App.tsx “// pdfWebpackEntry(‘./dummy.pdf’);”
2. run the webpack dev server with ‘yarn start’
3. check terminal for ‘Module not found: Error: Can’t resolve ‘worker-loader’…’

What is the expected behavior? (add screenshot)

1. Using the Webpack entry point succeeds, or
2. Manually configuring the worker succeeds, or
3. I make a million dollars.

What went wrong? (add screenshot)

1. Manually setting up worker fails:
2. Webpack entry point fails:
3. Still no million dollars.

[merceyz]

Did you install the worker-loader package, since that needs to be done manually?

@Snuffleupagus The issue is that pdfjs-dist lacks an optional(?) peer dependency on worker-loader so Yarn PnP (not Yarn 2) is denying it access

You guys wouldn’t happen to have any leads for me as to why pdfjs-dist seems to be passing “esModule” as worker-loader option, would you? It is indeed true that “esModule” is not one of the options that worker-loader takes. I’ve tried requiring instead of importing, but seeing the same error. Any guidance, appreciated 😃

You’re installing worker-loader@^2 but esModule is a worker-loader@^3 option, granted if pdfjs-dist properly declared its dependencies that would have been avoided

[jcamden]

Just want to clarify a couple of things for posterity:

1. To use pdfjs with Yarn PnP, one must add a package extension for pdfjs-dist to yarnrc.yml since pdfjs-dist does not declare its dependencies. In this case, you want worker-loader as a peer-dep (as @merceyz explained above):

packageExtensions:
  'pdfjs-dist@*':
    peerDependencies:
      worker-loader: '^3'

1. To use pdfjs in any case, note that the global approach (i.e. import pdfjsLib from 'pdfjs-dist/webpack';) evinced in the docs and examples (e.g. here) is now deprecated. It took me some time to sort out why pdfjs was not defined—since my mind was already operating in the realm of worker issues; so I hope to save someone else some time.

I’ve updated the repro repo with the fixes to serve as an example for anyone trying to integrate pdfjs into a Yarn PnP monorepo with webpack 5. That’s the least I can do to pay it forward. Thank you for your awesome contributions.