Support sass-embedded as alternative implementation

Gemfile

@@ -5,3 +5,5 @@ gemspec
 
 gem "jekyll", ENV["JEKYLL_VERSION"] ? "~> #{ENV["JEKYLL_VERSION"]}" : ">= 4.0"
 gem "minima"
+
+gem "sass-embedded", "~> 0.9.1" if RUBY_VERSION >= "2.6.0"

README.md

@@ -29,6 +29,32 @@ Jekyll Sass Converter comes bundled with Jekyll 2.0.0 and greater. For more
 information about usage, visit the [Jekyll Assets Documentation
 page](https://jekyllrb.com/docs/assets/).
 
+### Sass Implementations
+
+#### SassC
+
+By default, Jekyll Sass Converter uses [sassc](https://rubygems.org/gems/sassc)
+for Sass implmentation. `sassc` is based on LibSass, and
+[LibSass is deprecated](https://sass-lang.com/blog/libsass-is-deprecated).
+
+#### Sass Embedded
+
+[sass-embedded](https://rubygems.org/gems/sass-embedded) is a host for the
+[Sass embedded protocol](https://github.com/sass/embedded-protocol). The host
+runs [Dart Sass compiler](https://github.com/sass/dart-sass-embedded) as a subprocess
+and communicates with the dart-sass compiler via message-passing.
+
+`sass-embedded` is currently experimental and unstable. It requires Ruby 2.6 or higher.
+
+To use the `sass-embedded` implementation, you need to add a dependency on the
+`sass-embedded` gem. For example, if you're using a Gemfile, run `bundle add sass-embedded`. Then, you'll be able to
+specify `sass-embedded` in your `_config.yml`:
+
+  ```yml
+  sass:
+    implementation: sass-embedded
+  ```
+
 ### Source Maps
 
 Starting with `v2.0`, the Converter will by default generate a _source map_ file along with
@@ -53,14 +79,22 @@ Configuration options are specified in the `_config.yml` file in the following w
 
 Available options are:
 
+  * **`implementation`**
+
+    Sets the Sass implementation to use.
+    Can be `sassc` or `sass-embedded`.
+
+    Defaults to `sassc`.
+
   * **`style`**
 
     Sets the style of the CSS-output.
     Can be `nested`, `compact`, `compressed`, or `expanded`.
     See the [SASS_REFERENCE](https://sass-lang.com/documentation/cli/dart-sass#style)
     for details.
 
-    Defaults to `compact`.
+    Defaults to `compact` for `sassc`.
+    Defaults to `expanded` for `sass-embedded`.
 
   * **`sass_dir`**
 

lib/jekyll/converters/scss.rb

@@ -35,6 +35,7 @@ class Scss < Converter
         end
       end
 
+      ALLOWED_IMPLEMENTATIONS = %w(sassc sass-embedded).freeze
       ALLOWED_STYLES = %w(nested expanded compact compressed).freeze
 
       # Associate this Converter with the "page" object that manages input and output files for
@@ -113,9 +114,15 @@ def sass_dir
         jekyll_sass_configuration["sass_dir"]
       end
 
+      def sass_implementation
+        implementation = jekyll_sass_configuration["implementation"]
+        ALLOWED_IMPLEMENTATIONS.include?(implementation) ? implementation : "sassc"
+      end
+
       def sass_style
-        style = jekyll_sass_configuration.fetch("style", :compact)
-        ALLOWED_STYLES.include?(style.to_s) ? style.to_sym : :compact
+        default = sass_implementation == "sassc" ? :compact : :expanded
+        style = jekyll_sass_configuration.fetch("style", default)
+        ALLOWED_STYLES.include?(style.to_s) ? style.to_sym : default
       end
 
       def user_sass_load_paths
@@ -179,18 +186,53 @@ def sass_configs
         )
       end
 
+      def sass_embedded_config(data)
+        {
+          :data                => data,
+          :file                => file_path,
+          :indented_syntax     => syntax == :sass,
+          :include_paths       => sass_load_paths,
+          :output_style        => sass_style,
+          :source_map          => sourcemap_required?,
+          :out_file            => output_path,
+          :omit_source_map_url => !sourcemap_required?,
+          :source_map_contents => true,
+        }
+      end
+
       def convert(content)
+        case sass_implementation
+        when "sass-embedded"
+          Jekyll::External.require_with_graceful_fail("sass-embedded")
+          sass_embedded_convert(content)
+        when "sassc"
+          sass_convert(content)
+        end
+      end
+
+      private
+
+      def sass_convert(content)
         config = sass_configs
         engine = SassC::Engine.new(content.dup, config)
         output = engine.render
-        generate_source_map(engine) if sourcemap_required?
+        sass_generate_source_map(engine) if sourcemap_required?
         replacement = add_charset? ? '@charset "UTF-8";' : ""
         output.sub(BYTE_ORDER_MARK, replacement)
       rescue SassC::SyntaxError => e
         raise SyntaxError, e.to_s
       end
 
-      private
+      def sass_embedded_convert(content)
+        output = ::Sass.render(**sass_embedded_config(content))
+        sass_embedded_generate_source_map(output.map) if sourcemap_required?
+        replacement = add_charset? ? '@charset "UTF-8";' : ""
+        eof = sourcemap_required? ? "" : "\n"
+        output.css.sub(BYTE_ORDER_MARK, replacement) + eof
+      rescue ::Sass::Embedded::RenderError => e
+        Jekyll.logger.error e.formatted
+        raise SyntaxError, e.to_s
+      end
 
       # The Page instance for which this object acts as a converter.
       attr_reader :sass_page
@@ -209,6 +251,16 @@ def filename
         File.join(site_source_relative_from_pwd, sass_page.name)
       end
 
+      # The path of the input scss (or sass) file. This information will be used for error
+      # reporting and will written into the source map file as main source.
+      #
+      # Returns the path of the input file or nil if #associate_page failed
+      def file_path
+        return nil if associate_page_failed?
+
+        File.join(site_source_relative_from_pwd, sass_page.path)
+      end
+
       # The value of the `line_comments` option.
       # When set to `true` causes the line number and filename of the source be emitted into the
       # compiled CSS-file. Useful for debugging when the source-map is not available.
@@ -266,7 +318,7 @@ def source_map_page
       # Reads the source-map from the engine and adds it to the source-map-page.
       #
       # @param [::SassC::Engine] engine The sass Compiler engine.
-      def generate_source_map(engine)
+      def sass_generate_source_map(engine)
         return if associate_page_failed?
 
         source_map_page.source_map(engine.source_map)
@@ -275,6 +327,13 @@ def generate_source_map(engine)
         Jekyll.logger.warn "Could not generate source map #{e.message} => #{e.cause}"
       end
 
+      def sass_embedded_generate_source_map(source_map)
+        return if associate_page_failed?
+
+        source_map_page.source_map(source_map)
+        site.pages << source_map_page
+      end
+
       def site
         if associate_page_failed?
           Jekyll.sites.last

script/test

@@ -1,2 +1,11 @@
 #!/bin/bash
-bundle exec rspec $@
+
+set -e
+
+echo "Running rspec with sassc"
+SASS_IMPLEMENTATION=sassc bundle exec rspec $@
+
+if bundle info sass-embedded; then
+  echo "Running rspec with sass-embedded"
+  SASS_IMPLEMENTATION=sass-embedded bundle exec rspec $@
+fi

spec/sass_converter_spec.rb

@@ -21,7 +21,16 @@
     SASS
   end
 
-  let(:css_output) do
+  let(:expanded_css_output) do
+    <<~CSS
+      body {
+        font-family: Helvetica, sans-serif;
+        font-color: fuschia;
+      }
+    CSS
+  end
+
+  let(:compact_css_output) do
     <<~CSS
       body { font-family: Helvetica, sans-serif; font-color: fuschia; }
     CSS
@@ -51,15 +60,21 @@ def converter(overrides = {})
 
   context "converting sass" do
     it "produces CSS" do
-      expect(converter.convert(content)).to eql(css_output)
+      expected = sass_embedded? ? expanded_css_output : compact_css_output
+      expect(converter.convert(content)).to eql(expected)
     end
 
     it "includes the syntax error line in the syntax error message" do
-      error_message = 'Error: Invalid CSS after "f": expected 1 selector or at-rule.'
-      error_message = %r!\A#{error_message} was "font-family: \$font-"\s+on line 1:1 of stdin!
+      expected = if sass_embedded?
+                   %r!Expected newline!i
+                 else
+                   error_message = 'Error: Invalid CSS after "f": expected 1 selector or at-rule.'
+                   %r!\A#{error_message} was "font-family: \$font-"\s+on line 1:1 of stdin!
+                 end
+
       expect do
         converter.convert(invalid_content)
-      end.to raise_error(Jekyll::Converters::Scss::SyntaxError, error_message)
+      end.to raise_error(Jekyll::Converters::Scss::SyntaxError, expected)
     end
 
     it "removes byte order mark from compressed Sass" do
@@ -81,7 +96,7 @@ def converter(overrides = {})
       make_site(
         "source"      => File.expand_path("pages-collection", __dir__),
         "sass"        => {
-          "style" => :compact,
+          "style" => :expanded,
         },
         "collections" => {
           "pages" => {
@@ -93,7 +108,7 @@ def converter(overrides = {})
 
     it "produces CSS without raising errors" do
       expect { site.process }.not_to raise_error
-      expect(sass_converter.convert(content)).to eql(css_output)
+      expect(sass_converter.convert(content)).to eql(expanded_css_output)
     end
   end
 
@@ -102,14 +117,14 @@ def converter(overrides = {})
       make_site(
         "source" => File.expand_path("[alpha]beta", __dir__),
         "sass"   => {
-          "style" => :compact,
+          "style" => :expanded,
         }
       )
     end
 
     it "produces CSS without raising errors" do
       expect { site.process }.not_to raise_error
-      expect(sass_converter.convert(content)).to eql(css_output)
+      expect(sass_converter.convert(content)).to eql(expanded_css_output)
     end
   end
 end

spec/scss_converter_spec.rb

@@ -22,7 +22,16 @@
     SCSS
   end
 
-  let(:css_output) do
+  let(:expanded_css_output) do
+    <<~CSS
+      body {
+        font-family: Helvetica, sans-serif;
+        font-color: fuschia;
+      }
+    CSS
+  end
+
+  let(:compact_css_output) do
     <<~CSS
       body { font-family: Helvetica, sans-serif; font-color: fuschia; }
     CSS
@@ -112,8 +121,9 @@ def converter(overrides = {})
         expect(verter.sass_configs[:style]).to eql(:compressed)
       end
 
-      it "defaults style to :compact" do
-        expect(verter.sass_configs[:style]).to eql(:compact)
+      it "defaults style to :expanded for sass-embedded or :compact for sassc" do
+        expected = sass_embedded? ? :expanded : :compact
+        expect(verter.sass_configs[:style]).to eql(expected)
       end
 
       it "at least contains :syntax and :load_paths keys" do
@@ -124,14 +134,19 @@ def converter(overrides = {})
 
   context "converting SCSS" do
     it "produces CSS" do
-      expect(converter.convert(content)).to eql(css_output)
+      expected = sass_embedded? ? expanded_css_output : compact_css_output
+      expect(converter.convert(content)).to eql(expected)
     end
 
     it "includes the syntax error line in the syntax error message" do
-      error_message = 'Error: Invalid CSS after "body": expected 1 selector or at-rule, was "{"'
-      error_message = %r!\A#{error_message}\s+on line 2!
+      expected = if sass_embedded?
+                   %r!expected ";"!i
+                 else
+                   error_message = 'Error: Invalid CSS after "body": expected 1 selector or at-rule'
+                   %r!\A#{error_message}, was "{"\s+on line 2!
+                 end
       expect { scss_converter.convert(invalid_content) }.to(
-        raise_error(Jekyll::Converters::Scss::SyntaxError, error_message)
+        raise_error(Jekyll::Converters::Scss::SyntaxError, expected)
       )
     end
 
@@ -197,9 +212,13 @@ def converter(overrides = {})
 
       it "brings in the grid partial" do
         site.process
-        expect(File.read(test_css_file)).to eql(
-          "a { color: #999999; }\n\n/*# sourceMappingURL=main.css.map */"
-        )
+
+        expected = if sass_embedded?
+                     "a {\n  color: #999999;\n}\n\n/*# sourceMappingURL=main.css.map */"
+                   else
+                     "a { color: #999999; }\n\n/*# sourceMappingURL=main.css.map */"
+                   end
+        expect(File.read(test_css_file)).to eql(expected)
       end
 
       context "with the sass_dir specified twice" do
@@ -326,7 +345,7 @@ def converter(overrides = {})
       make_site(
         "source"      => File.expand_path("pages-collection", __dir__),
         "sass"        => {
-          "style" => :compact,
+          "style" => :expanded,
         },
         "collections" => {
           "pages" => {
@@ -338,7 +357,7 @@ def converter(overrides = {})
 
     it "produces CSS without raising errors" do
       expect { site.process }.not_to raise_error
-      expect(scss_converter.convert(content)).to eql(css_output)
+      expect(scss_converter.convert(content)).to eql(expanded_css_output)
     end
   end
 
@@ -347,14 +366,14 @@ def converter(overrides = {})
       make_site(
         "source" => File.expand_path("[alpha]beta", __dir__),
         "sass"   => {
-          "style" => :compact,
+          "style" => :expanded,
         }
       )
     end
 
     it "produces CSS without raising errors" do
       expect { site.process }.not_to raise_error
-      expect(scss_converter.convert(content)).to eql(css_output)
+      expect(scss_converter.convert(content)).to eql(expanded_css_output)
     end
   end
 
@@ -388,7 +407,10 @@ def converter(overrides = {})
 
       it "contains relevant sass sources" do
         sources = sourcemap_data["sources"]
-        expect(sources).to include("main.scss")
+        # sass-embedded (dart-sass) does not inlcude main.scss in sources
+        # because main.scss only contains @import statements
+        # thus there is no actual scss code to be mapped
+        expect(sources).to include("main.scss") unless sass_embedded?
         expect(sources).to include("_sass/_grid.scss")
         expect(sources).to_not include("_sass/_color.scss") # not imported into "main.scss"
       end