pack dependency

[firien]

Consider this mozilla pdf.js pack file in packs/pdf.js.erb:

require('pdfjs-dist');
PDFJS.workerSrc = "<%= ActionController::Base.helpers.asset_pack_path('wpdf.js') %>"

webpacker:compile fails because wpdf is not yet compiled:

• webpacker v2.x - Is webpack still compiling? (Webpacker::FileLoader::NotFoundError)
• webpacker v3.x - runs indefinitely (Webpack dev server with rails-erb-loader and spring hangs usabilityhub/rails-erb-loader#47)

In sprockets world I would include depend_on at the top file, and reference asset with <%= asset_path('required-asset.js') %>

Is there a way for a pack to reference and depend on another pack?

[gauravtiwari]

Where is this file located - wpdf.js? You could import it at the top no?

import "path-to/wpdf.js"

[firien]

its another pack file. Doesn't import pull in the js code? I don't need the code, just the path to the file - then the pdf library automatically sets up the web worker.

[rossta]

This feels like a question better suited for the pdf.js repo and I don't know much about the project myself, but I'll take a stab:

The pdf.js webpack example assumes the src is known ahead of time. I don't believe you can reference ActionController::Base.helpers.asset_pack_path until after the js is compiled as you have observed. If the src is in node_modules, you can try require.resolve('path/to/wpdf');. Otherwise, if this wpdf file is one of your custom "packs", here are a few ideas:

1. Wrap your pdf set up in some kind of a initializer function exposed to the Rails view from which you can pass the src, i.e. ActionController::Base.helpers.asset_pack_path('wpdf.js')
2. Proxy a hard-coded source path to asset_pack_path in a Rails middleware
3. Write a webpack plugin (I couldn't find any for this purpose) that modifies the Webpack source at build time to insert the proper path

[firien]

I was able to get it working by removing my wpdf.js pack file, and using worker-loader* to create one on the fly. The wpdf.js is no longer in the webpacker manifest, but that is fine because I shouldn't need to reference it anywhere else.

// no longer a js.erb file - just javascript
require('pdfjs-dist')

var worker = require("worker-loader?name=wpdf.[hash].js!pdfjs-dist/build/pdf.worker")
// ugly, but I just need the path to the file
var workerPath = (/wpdf\.\w+\.js/i).exec(worker.toString())
PDFJS.workerSrc = "/packs/" + workerPath[0]

Thanks for your suggestions

* using the master branch, not published npm

[firien]

Somewhat different, but related issue; again this is about js files depending on one another.

---

Now that Webpacker is the default JavaScript bundler for Rails, I am struggling to hoist my old WebWorker workflow into it.

Old workflow with Sprockets

Consider a javascript file for the main thread (let's call it index.js.coffee.erb) that loads a web worker.

#= depend_on awesome-worker
worker = new Worker "<%= asset_path('awesome-worker') %>"
…

then in awesome-worker.js.coffee.erb, we import some other scripts.

#= depend_on mini-js-lib
importScripts "<%= asset_path('mini-js-lib') %>"
…

Any edits to mini-js-lib.js.coffee would trigger new versions of both:

• index.js
• awesome-worker.js

---

Webpack workflow

The closest out-of-the-box solution i can find would be to use worker-loader, abandon importScripts and instead just import code directly in the worker.

index.coffee

import awesomeWorker from "worker-loader!./awesome-worker"
worker = new awesomeWorker()
…

awesome-worker.coffee:

import miniJsLib from 'mini-js-lib'
…

OR…

Write a new Plugin

---

Something more elegant would be to fork Google's worker-plugin to handle importScripts too. So you can have some sane looking javascript.

worker = new Worker("./awesome-worker")
…

awesome-worker.js

importScripts("./mini-js-lib")
…

I am not opposed to writing a new webpack plugin, but I can't imagine that I am the only one with this issue. Am I missing something? - Is there a simpler solution to this problem?