Using WickedPDF with Webpacker & Bulma CSS - ruby-on-rails

Question

I'm trying to use WickedPDF in a Rails 6 project that uses the Bulma CSS framework. However, I cannot get it to work properly and I'm wondering what I am doing wrong.
I have a pdf.html.slim layout file with the following:
doctype html
html
head
meta charset="utf-8"
meta name="viewport" content="width=device-width, initial-scale=1"
title= content_for?(:title) ? content_for(:title) : t('website.title')
= wicked_pdf_stylesheet_pack_tag 'pdf'
= wicked_pdf_javascript_pack_tag 'pdf'
body
.containers
.container
= yield
My app/javascript/packs/pdf.js file looks like this:
import 'stylesheets/pdf';
which in turn calls app/javascript/stylesheets/pdf.scss
#import 'colors';
// ~ to tell webpack that this is not a relative
// import (but in node_modules dir):
#import '~bulma';
When I open a PDF, however, none of the Bulma styling is applied.
I'm using a vanilla config/webpacker.yml file:
# Note: You must restart bin/webpack-dev-server for changes to take effect
default: &default
source_path: app/javascript
source_entry_path: packs
public_root_path: public
public_output_path: packs
cache_path: tmp/cache/webpacker
check_yarn_integrity: false
webpack_compile_output: true
# Additional paths webpack should lookup modules
# ['app/assets', 'engine/foo/app/assets']
resolved_paths: []
# Reload manifest.json on all requests so we reload latest compiled packs
cache_manifest: false
# Extract and emit a css file
extract_css: false
static_assets_extensions:
- .jpg
- .jpeg
- .png
- .gif
- .tiff
- .ico
- .svg
- .eot
- .otf
- .ttf
- .woff
- .woff2
extensions:
- .vue
- .mjs
- .js
- .sass
- .scss
- .css
- .module.sass
- .module.scss
- .module.css
- .png
- .svg
- .gif
- .jpeg
- .jpg
development:
<<: *default
compile: true
# Verifies that correct packages and versions are installed by inspecting package.json, yarn.lock, and node_modules
check_yarn_integrity: true
# Reference: https://webpack.js.org/configuration/dev-server/
dev_server:
https: false
host: localhost
port: 3035
public: localhost:3035
hmr: false
# Inline should be set to true if using HMR
inline: true
overlay: true
compress: true
disable_host_check: true
use_local_ip: false
quiet: false
pretty: false
headers:
'Access-Control-Allow-Origin': '*'
watch_options:
ignored: '**/node_modules/**'
test:
<<: *default
compile: true
# Compile test packs to a separate directory
public_output_path: packs-test
production:
<<: *default
# Production depends on precompilation of packs prior to booting for performance.
compile: false
# Extract and emit a css file
extract_css: true
# Cache manifest.json for performance
cache_manifest: true
The styling currently works as expected on the website but not on PDFs.
I can also confirm that if I use a link to the assets via a CDN, the PDF renders correctly.
I'd expect that using Bulma CSS via webpacker displays styles properly in wicked_pdf generated files.
System specifications
OS: MacOS 10.15.5
Rails version: 6.0.3.2
wicked_pdf gem version: 2.1.0
wkhtmltopdf version: 0.12.6