add app assets to load paths

Author: chipairon

README.md

@@ -36,6 +36,9 @@ Rails.application.config.dartsass.builds = {
 
 The hash key is the relative path to a Sass file in `app/assets/stylesheets/` and the hash value will be the name of the file output to `app/assets/builds/`.
 
+## Importing assets from gems
+`dartsass:build` includes application [assets paths](https://guides.rubyonrails.org/asset_pipeline.html#search-paths) as Sass [load paths](https://sass-lang.com/documentation/at-rules/use#load-paths). Assuming the gem has made assets visible to the Rails application, no additional configuration is required to use them.
+
 
 ## Version
 

lib/tasks/build.rake

@@ -3,13 +3,19 @@ CSS_LOAD_PATH  = Rails.root.join("app/assets/stylesheets")
 CSS_BUILD_PATH = Rails.root.join("app/assets/builds")
 
 def dartsass_build_mapping
-  Rails.application.config.dartsass.builds.map { |input, output| 
+  Rails.application.config.dartsass.builds.map { |input, output|
     "#{CSS_LOAD_PATH.join(input)}:#{CSS_BUILD_PATH.join(output)}"
   }.join(" ")
 end
 
 def dartsass_build_options
-  "--load-path #{CSS_LOAD_PATH} --style=compressed --no-source-map"
+  "#{load_paths} --style=compressed --no-source-map"
+end
+
+def load_paths
+  [CSS_LOAD_PATH].concat(Rails.application.config.assets.paths)
+                 .map { |path| "--load-path #{path}" }
+                 .join(" ")
 end
 
 def dartsass_compile_command