This PR is a major change to Sass compilation in Discourse.
The new version of sass-ruby moves to dart-sass putting we back on the supported version of Sass. It does so while keeping compatibility with the existing method signatures, so minimal change is needed in Discourse for this change.
This moves us
From:
- sassc 2.0.1 (Feb 2019)
- libsass 3.5.2 (May 2018)
To:
- dart-sass 1.58
This update applies the following breaking changes:
>
> These breaking changes are coming soon or have recently been released:
>
> [Functions are stricter about which units they allow](https://sass-lang.com/documentation/breaking-changes/function-units) beginning in Dart Sass 1.32.0.
>
> [Selectors with invalid combinators are invalid](https://sass-lang.com/documentation/breaking-changes/bogus-combinators) beginning in Dart Sass 1.54.0.
>
> [/ is changing from a division operation to a list separator](https://sass-lang.com/documentation/breaking-changes/slash-div) beginning in Dart Sass 1.33.0.
>
> [Parsing the special syntax of @-moz-document will be invalid](https://sass-lang.com/documentation/breaking-changes/moz-document) beginning in Dart Sass 1.7.2.
>
> [Compound selectors could not be extended](https://sass-lang.com/documentation/breaking-changes/extend-compound) in Dart Sass 1.0.0 and Ruby Sass 4.0.0.
SCSS files have been migrated automatically using `sass-migrator division app/assets/stylesheets/**/*.scss`
We've had a couple of problems with the R2 gem where it generated a broken RTL CSS bundle that caused a badly broken layout when Discourse is used in an RTL language, see a3ce93b and 5926386. For this reason, we're replacing R2 with `rtlcss` that can handle modern CSS features better than R2 does.
`rltcss` is written in JS and available as an npm package. Calling the `rltcss` from rubyland is done via the `rtlcss_wrapper` gem which contains a distributable copy of the `rtlcss` package and loads/calls it with Mini Racer. See https://github.com/discourse/rtlcss_wrapper for more details.
Internal topic: t/76263.
Take 2 of https://github.com/discourse/discourse/pull/13466.
Fixes a few issues with the original PR:
- color definition stylesheet target now includes the theme id, to avoid themes set to use the default color scheme loading the same stylesheet
- changes the internal cache key for color definition stylesheet to reset the pre-existing cache
Themes can now declare custom colors that get compiled in core's color definitions stylesheet, thus allowing themes to better support dark/light color schemes.
For example, if you need your theme to use tertiary for an element in a light color scheme and quaternary in a dark scheme, you can add the following SCSS to your theme's `color_definitions.scss` file:
```
:root {
--mytheme-tertiary-or-quaternary: #{dark-light-choose($tertiary, $quaternary)};
}
```
And then use the `--mytheme-tertiary-or-quaternary` variable as the color property of that element. You can also use this file to add color variables that use SCSS color transformation functions (lighten, darken, saturate, etc.) without compromising your theme's compatibility with different color schemes.
A first step to adding automatic dark mode color scheme switching. Adds a new SCSS file at `color_definitions.scss` that serves to output all SCSS color variables as CSS custom properties. And replaces all SCSS color variables with the new CSS custom properties throughout the stylesheets.
This is an alpha feature at this point, can only be enabled via console using the `default_dark_mode_color_scheme_id` site setting.
Zeitwerk simplifies working with dependencies in dev and makes it easier reloading class chains.
We no longer need to use Rails "require_dependency" anywhere and instead can just use standard
Ruby patterns to require files.
This is a far reaching change and we expect some followups here.
This reduces chances of errors where consumers of strings mutate inputs
and reduces memory usage of the app.
Test suite passes now, but there may be some stuff left, so we will run
a few sites on a branch prior to merging
Theme developers can include any number of scss files within the /scss/ directory of a theme. These can then be imported from the main common/desktop/mobile scss.
If a theme setting contained invalid SCSS, it would cause an error 500 on the site, with no way to recover. This commit stops loading theme settings in the core stylesheets, and instead only loads the color scheme variables. This change also makes `common/foundation/variables.scss` available to themes without an explicit import.
This feature introduces the concept of themes. Themes are an evolution
of site customizations.
Themes introduce two very big conceptual changes:
- A theme may include other "child themes", children can include grand
children and so on.
- A theme may specify a color scheme
The change does away with the idea of "enabled" color schemes.
It also adds a bunch of big niceties like
- You can source a theme from a git repo
- History for themes is much improved
- You can only have a single enabled theme. Themes can be selected by
users, if you opt for it.
On a technical level this change comes with a whole bunch of goodies
- All CSS is now compiled using a custom pipeline that uses libsass
see /lib/stylesheet
- There is a single pipeline for css compilation (in the past we used
one for customizations and another one for the rest of the app
- The stylesheet pipeline is now divorced of sprockets, there is no
reliance on sprockets for CSS bundling
- CSS is generated with source maps everywhere (including themes) this
makes debugging much easier
- Our "live reloader" is smarter and avoid a flash of unstyled content
we run a file watcher in "puma" in dev so you no longer need to run
rake autospec to watch for CSS changes
