Replace Sprockets with Propshaft

[aduth]

🛠 Summary of changes

This pull request proposes to replace Sprockets with Propshaft for managing the asset pipeline.

Propshaft is an officially-maintained successor to Sprockets whose goals are closer in alignment to our current asset build tooling than Sprockets, since we perform most of the asset transformations separate from Rails (source). The remaining features we rely on from Sprockets (URL remapping, filename digests) are also available in Propshaft.

Generally, the hope would be that moving to Propshaft would...

• Improve performance (primarily in local development, specs, and asset compilation, not as much at production runtime)
• Bring us into closer alignment to Rails future defaults
• Avoid ongoing issues related to undesirable Sprockets default behaviors (e.g. sassc errors)

[aduth]

From a developer experience perspective, I actually preferred having node_modules as a load path and requiring fully-qualified paths to specific dependencies. It still works in Propshaft; however, Propshaft will copy all files from load paths into public/assets, which essentially would mean copying over the entirety of node_modules.

[aduth]

I was hoping to see a noticeable drop in GitLab build time, but it looks roughly the same as previous times. It looks like it could save around 30 seconds overall time (3-4%), though that's based on a few data points and a high margin for error.

[aduth]

This looks to work pretty well at a glance in my sandbox after the changes in 4149043.

At this point, the only concern I might have is the blurb about "beta software" in the Propshaft documentation (docs). I hadn't noticed this 'til putting together the pull request, so wondering how much appetite we'd have for running it in production.

[zachmargolis]

At this point, the only concern I might have is the blurb about "beta software" in the Propshaft documentation (docs). I hadn't noticed this 'til putting together the pull request, so wondering how much appetite we'd have for running it in production.

The changes seem relatively minimal, we could always revert if we want to switch course? This doesn't feel like a super big commitment to me to try it out

[mitchellhenke]

At this point, the only concern I might have is the blurb about "beta software" in the Propshaft documentation (docs). I hadn't noticed this 'til putting together the pull request, so wondering how much appetite we'd have for running it in production.

The changes seem relatively minimal, we could always revert if we want to switch course? This doesn't feel like a super big commitment to me to try it out

Agreed 👍🏼

[aduth]

👍 Let's give it a shot!