package extensions for mozilla/pdfjs-dist?

[jcamden]

Greetings!

I'm a big fan of Yarn 2. Thanks @arcanis et al! Lately, I've been wrestling with mozilla/pdfjs-dist. I've created a repo that repros the issues, and I submitted mozilla/pdf.js#12778. However, they immediately closed the issue because they don't do Yarn 2. Maybe you guys can help me sort this out:

From what I gather, when used in conjunction with webpack, pdfjs relies on worker-loader. In fact, they have a "zero-config" wepback entry point which automatically configures work-loader, accessed via import pdfjsLib from 'pdfjs-dist/webpack'; as per the "Worker loading" section of the readme for their webpack example. As expected, pdfjs cannot compile without the dependency:

This looks like a job for a package extension:

packageExtensions:
  pdfjs-dist@^2.6.347:
    dependencies:
      worker-loader: '^2.0.0'

(Note that, somewhere in their issues section, I read that pdfjs-dist relies on worker-loader ^2, whereas ^3 will break. Hard to tell without any deps listed in the package.json, but anyway) This is progress:

So worker-loader needs Webpack:

packageExtensions:
  pdfjs-dist@^2.6.347:
    dependencies:
      worker-loader: '^2.0.0'
  worker-loader@^2.0.0:
    dependencies:
      webpack: '^5.0.0'

When I extend worker-loader's deps with webpack, whether ^4 or ^5, both cases get me here:

From there, I'm not quite sure what's going on. It is indeed true that "esmodule" is not one of worker-loader's options. I'm not sure why that is getting passed as an option by pdfjs. I've also tried worker-loader ^3 with the same results. Has anyone had any success using pdfjs with webpack in a Yarn 2 repo? Or does anyone have any hints for what next steps I could take? I appreciate it :)

[merceyz]

Hello, tested your repro and as the error shows (sort of) they lack an optional(?) peer dependency on worker-loader@^3

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

It is indeed true that "esmodule" is not one of worker-loader's options.

It's one of the options for worker-loader@^3

[jcamden]

Wow, thanks! If you don't mind my asking, how did you discover that info? I had a hard time finding it. Anyway, in this case, there may be some additional issue(s) :/ I updated the package extensions as recommended in this repo, but I'm getting the same result (options['esModule'] is an invalid additional property). What am I doing wrong... 🤔

[jcamden]

Oh, doh, I got it: I still had worker-loader@^2 "manually" installed as a dep. Changed that to ^3 as well, and it works now. Thank you. You are a genius.

[merceyz]

If you don't mind my asking, how did you discover that info?

I ran PNP_DEBUG_LEVEL=1 yarn workspace @pdfjs-yarn2/client build and it told me explicitly that it's an undeclared dependency but based on your screenshot I could tell that its most likely an undeclared dependency and this comment mozilla/pdf.js#12778 (comment) made me assume it should be an optional peer dependency.

[jcamden]

I ran PNP_DEBUG_LEVEL=1 yarn workspace @pdfjs-yarn2/client build

Oh wow, I just checked it out. Very useful! Ah, and I see about optional = peerDep. Thanks very much! Sincerely appreciate it.