build-sass: Create output directory if missing

[aduth]

🛠 Summary of changes

Enhances @18f/identity-build-sass to create the output directory if it does not already exist, to avoid imposing a requirement that the folder exists already. This avoids the need for workarounds like app/assets/builds/.keep.

Part of the goal of this is also to start establishing a pattern for testing CLI behaviors in the package.

📜 Testing Plan

yarn build:css should pass still, even after removing app/assets/builds/.keep.

[aduth]

Note:

• We deleted app/assets/builds/.keep (an empty file)
• We added an empty file for the fixture, in.css.scss

Git interpreted this as a "move".

[aduth]

We might need the .keep file after all, not because of build-sass, but because of the asset pipeline. 😕

     Failure/Error: //= link_tree ../builds
     
     ActionView::Template::Error:
       link_tree argument must be a directory

[zachmargolis]

We might need the .keep file after all, not because of build-sass, but because of the asset pipeline. 😕

     Failure/Error: //= link_tree ../builds
     
     ActionView::Template::Error:
       link_tree argument must be a directory

How does that play with the propshaft PR?

the .gitkeep isn't the end of the world

either way, LGTM

[aduth]

How does that play with the propshaft PR?

the .gitkeep isn't the end of the world

either way, LGTM

Not sure, actually! Good question though. I can test it.

[aduth]

Rebased after merge of #8387 and re-removed the .keep file in d844407, let's see how the build tolerates it.

[aduth]

Apparently still no dice 😢 Might need to keep it for now at least.

The error is a little different. Previously Sprockets complained about link_tree needing to reference a directory. Now it's just claiming that "'application.css' was not found in the load path". The file should exist at that point in app/assets/builds, which makes me wonder if it might be checking for the existence of the directory before the CSS finishes building.

[aduth]

Apparently it's "required" per the cssbundling-rails documentation:

A common issue is that your repository does not contain the output directory used by the build commands. You must have app/assets/builds available. Add the directory with a .gitkeep file, and you'll ensure it's available in production.

https://github.com/rails/cssbundling-rails#why-do-i-get-applicationcss-not-in-asset-pipeline-in-production

[aduth]

I might plan to publish this as a release prior to #8375, which includes a breaking change for the package.

(Just means bumping the version and updating the CHANGELOG accordingly)

[aduth]

Published to NPM as @18f/identity-build-sass@1.3.0.