Engine entry files cause issues with stylesheet_link_tag(:app)

[justinfrench]

I've been playing around with the new Engines integration, and have discovered an issue.

I've created an issue on propshaft with more detail, but I wanted to cross-post here for awareness.

TLDR:

• A fresh Rails app uses stylesheet_link_tag(:app), which adds in all CSS files in app/assets/, including files in app/assets/builds/, which includes the entry files generated (eg app/assets/builds/tailwind/<engine_name>.css).
• This means the entry files are served-up to the browser raw, rather than after being explicitly added to tailwind/application.css

I first noticed this when I saw an error in the browser console, because the file had a reference to the full local path on disk:

/* DO NOT MODIFY THIS FILE, it was auto-generated by tailwindcss-rails */

@import "/Users/whatever/my_gem/app/assets/tailwind/my_gem/engine.css";

[flavorjones]

cc @bopm

[bopm]

I tend to agree with @rafaelfranca on this one. We can try to move build artefacts out of the builds, but TailwindCSSes are full of magic and should not be processed by catch-all instruments like stylesheet_link_tag :app. Solution to create manual file and include all propshaft-related things in it, excluding Tailwind, seems more logical. But I am open to suggestions.

[justinfrench]

The simplest things I can think of are:

• Update the Rails generator to avoid using :all with --css=tailwind, and/or
• Move the :all functionality from propshaft into rails (with documentation) so it's more discoverable as a root cause

But those are clearly not things that tailwindcss-rails an solve for.

I don't understand enough about the internals, but could we avoid all of this by saving the entry to somewhere outside of the host app's asset path?

[bopm]

avoid all of this by saving the entry to somewhere outside of the host app's asset

My goal with this decision to use build dir was to avoid the installation process for this gem. I was looking for the location that already existed. It was clear that it was a bit controversial, but doing differently would make it more than a single PR here, and would push actual arrival of that feature to another half a year in the future at least.

At the same time, tailwind.css in assets should not be processed by propshaft, as it will generate invalid CSS because Propshaft doesn't know how to process TailwindCSS directives. That leads me to believe that :all should not be used with Tailwind configuration. I think it's worth updating docs here about that, and yep, probably PR to update generators. Want to do it @justinfrench, or prefer me or @flavorjones to take it away?

[justinfrench]

Yep, I’m happy to have a go at updating the docs, but if someone else gets to it first, that’s fine.