Switch to DartSass

Gemfile.lock

@@ -3,28 +3,59 @@ PATH
   specs:
     easol-canvas (2.2.0)
       cli-ui (~> 1.5)
+      dartsass-rails (~> 0.4.0)
       json-schema (~> 3)
       liquid (~> 5.3)
       nokogiri (~> 1.13)
-      sassc (~> 2.4)
       thor (~> 1.2)
 
 GEM
   remote: https://rubygems.org/
   specs:
+    actionpack (7.0.3.1)
+      actionview (= 7.0.3.1)
+      activesupport (= 7.0.3.1)
+      rack (~> 2.0, >= 2.2.0)
+      rack-test (>= 0.6.3)
+      rails-dom-testing (~> 2.0)
+      rails-html-sanitizer (~> 1.0, >= 1.2.0)
+    actionview (7.0.3.1)
+      activesupport (= 7.0.3.1)
+      builder (~> 3.1)
+      erubi (~> 1.4)
+      rails-dom-testing (~> 2.0)
+      rails-html-sanitizer (~> 1.1, >= 1.2.0)
+    activesupport (7.0.3.1)
+      concurrent-ruby (~> 1.0, >= 1.0.2)
+      i18n (>= 1.6, < 2)
+      minitest (>= 5.1)
+      tzinfo (~> 2.0)
     addressable (2.8.0)
       public_suffix (>= 2.0.2, < 5.0)
     ast (2.4.2)
+    builder (3.2.4)
     cli-ui (1.5.1)
     coderay (1.1.3)
+    concurrent-ruby (1.1.10)
+    crass (1.0.6)
+    dartsass-rails (0.4.0)
+      railties (>= 6.0.0)
     diff-lcs (1.5.0)
-    ffi (1.15.5)
+    erubi (1.11.0)
+    i18n (1.12.0)
+      concurrent-ruby (~> 1.0)
     json-schema (3.0.0)
       addressable (>= 2.8)
     liquid (5.4.0)
+    loofah (2.18.0)
+      crass (~> 1.0.2)
+      nokogiri (>= 1.5.9)
     method_source (1.0.0)
+    minitest (5.16.3)
     nokogiri (1.13.8-arm64-darwin)
       racc (~> 1.4)
+    nokogiri (1.13.8-x86_64-linux)
+      racc (~> 1.4)
     parallel (1.21.0)
     parser (3.0.3.2)
       ast (~> 2.4.1)
@@ -33,7 +64,23 @@ GEM
       method_source (~> 1.0)
     public_suffix (4.0.7)
     racc (1.6.0)
+    rack (2.2.4)
+    rack-test (2.0.2)
+      rack (>= 1.3)
+    rails-dom-testing (2.0.3)
+      activesupport (>= 4.2.0)
+      nokogiri (>= 1.6)
+    rails-html-sanitizer (1.4.3)
+      loofah (~> 2.3)
+    railties (7.0.3.1)
+      actionpack (= 7.0.3.1)
+      activesupport (= 7.0.3.1)
+      method_source
+      rake (>= 12.2)
+      thor (~> 1.0)
+      zeitwerk (~> 2.5)
     rainbow (3.0.0)
+    rake (13.0.6)
     regexp_parser (2.2.0)
     rexml (3.2.5)
     rspec (3.10.0)
@@ -64,17 +111,19 @@ GEM
       rubocop (>= 1.7.0, < 2.0)
       rubocop-ast (>= 0.4.0)
     ruby-progressbar (1.11.0)
-    sassc (2.4.0)
-      ffi (~> 1.9)
     standard (1.5.0)
       rubocop (= 1.23.0)
       rubocop-performance (= 1.12.0)
     thor (1.2.1)
+    tzinfo (2.0.5)
+      concurrent-ruby (~> 1.0)
     unicode-display_width (2.1.0)
+    zeitwerk (2.6.0)
 
 PLATFORMS
   arm64-darwin-20
   arm64-darwin-21
+  x86_64-linux
 
 DEPENDENCIES
   easol-canvas!

canvas.gemspec

@@ -22,6 +22,6 @@ Gem::Specification.new do |s|
   s.add_dependency "nokogiri", "~> 1.13"
   s.add_dependency "cli-ui", "~> 1.5"
   s.add_dependency "liquid", "~> 5.3"
-  s.add_dependency "sassc", "~> 2.4"
+  s.add_dependency "dartsass-rails", "~> 0.4.0"
   s.add_dependency "json-schema", "~> 3"
 end

lib/canvas/dartsass.rb

@@ -0,0 +1,47 @@
+# frozen_string_literal: true
+
+require "open3"
+
+module Canvas
+  # This is a thin wrapper around the dartsass binary as provided by
+  # dartsass-rails.
+  #
+  # It is compatible with SassC::Engine as much as we were using it, but 100%
+  # compatability is not a goal.
+  class DartSass
+    Error = Class.new(StandardError)
+
+    def initialize(css, config)
+      @css = css
+      @config = config
+    end
+
+    def render
+      stdout, stderr, status = Open3.capture3(*command, stdin_data: @css)
+
+      if status == 0
+        stdout
+      else
+        raise Error.new(stderr)
+      end
+    end
+
+    private
+
+    def command
+      [dartsass, "--stdin", style, *load_paths].compact
+    end
+
+    def dartsass
+      Gem.bin_path("dartsass-rails", "dartsass").shellescape
+    end
+
+    def style
+      (s = @config[:style]) && "--style=#{s.to_s.shellescape}"
+    end
+
+    def load_paths
+      Array(@config[:load_paths]).map { "--load-path=#{_1.shellescape}" }
+    end
+  end
+end

lib/canvas/validators/sass.rb

@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require "sassc"
+require "canvas/dartsass"
 
 module Canvas
   module Validator
@@ -15,9 +15,9 @@ def initialize(file)
       end
 
       def validate
-        SassC::Engine.new(@file, style: :compressed).render
+        DartSass.new(@file, style: :compressed).render
         true
-      rescue SassC::SyntaxError => e
+      rescue DartSass::Error => e
         @errors = [e.message]
         false
       end

spec/lib/canvas/checks/valid_sass_check_spec.rb

@@ -15,16 +15,15 @@
     it "adds an offense when a file contains invalid Sass" do
       copy_example_directory("alchemist")
       subject.run
-      message = <<~MESSAGE.chop
-        Invalid Sass: assets/index.css - \n
-        Error: Undefined variable: "$gray-100".
-                on line 1:13 of stdin
-        >> h1 { color: $gray-100 }
-      MESSAGE
 
       expect(subject.offenses).to match_array(
         [
-          have_attributes(message: include(message.squeeze("\n")))
+          have_attributes(
+            message: include("Invalid Sass: assets/index.css") &
+              include("Error: Undefined variable") &
+              include("1:13") &
+              include("h1 { color: $gray-100 }")
+          )
         ]
       )
     end