Migrate to Dart Sass from LibSass

[matthillco]

What

Migrate Smart Answers to Dart Sass from LibSass Trello

Why

• LibSass is now deprecated
• Making changes ahead of Design System team dropping support for LibSass Dropping support for Ruby Sass and LibSass govuk-frontend#2632.

Visual Changes

None.

Anything else

Once the PR gets the green light, any temporary commits and references to local gems e.g. gem "govuk_publishing_components", path: "../govuk_publishing_components" will be removed.

See:

• Migrate to Dart Sass from LibSass govuk_publishing_components#3726
• Migrate to Dart Sass from LibSass email-alert-frontend#1655
• Migrate to Dart Sass from LibSass static#3190
• Migrate to Dart Sass from LibSass govuk-developer-docs#4216.

[jon-kirwan]

Thanks Matt, great work. All looks good and works fine. I've just added a couple of small comments and a general note around vendor CSS

[jon-kirwan]

I'm adding a note regarding vendor CSS which is currently uncompressed. It seems that joint.css is designed for internal use, meant to visualize Smart Answer journeys. To compress CSS files, it looks like the typical approach involves adding Sass configuration, like this:

config.sass.style = :compressed
config.sass.line_comments = false

However, this process seems closely linked to the sassc-rails gem, which has been removed. The only alternative I've come across for CSS compression is to add config.assets.css_compressor = :yui which requires the yui-compressor gem https://guides.rubyonrails.org/asset_pipeline.html#css-compression.

At present, the vendor CSS folder doesn't seem to be used in other UX applications that are being migrated to Dart Sass.

Otherwise, Sass files are compressed before being handled by the asset pipeline.

[matthillco]

@jon-kirwan I've made the requested changes, please could you have a final check? Thanks.

[jon-kirwan]

All working fine for me and the changes look great! Thanks Matt 👍