Sprockets 4 Compatibility

I'm able to get a really simple test app working with this gem with these changes, but so far haven't gotten the tests to pass.

.travis.yml

@@ -7,6 +7,7 @@ script: "bundle exec rake test"
 gemfile:
   - gemfiles/sprockets_2_12.gemfile
   - gemfiles/sprockets_3_0.gemfile
+  - gemfiles/sprockets_4_0.gemfile
   - gemfiles/sprockets-rails_3_0.gemfile
   - gemfiles/rails_4_2.gemfile
   - gemfiles/rails_4_1.gemfile

gemfiles/sprockets_4_0.gemfile

@@ -0,0 +1,6 @@
+source 'https://rubygems.org'
+
+gem "sprockets", "~> 4.0.x"
+
+# Specify your gem's dependencies in sassc-rails.gemspec
+gemspec path: "../"

lib/sassc/rails/railtie.rb

@@ -50,8 +50,13 @@ class Railtie < ::Rails::Railtie
           self.sass_config = app.config.sass
         end
 
-        env.register_engine '.sass', SassC::Rails::SassTemplate
-        env.register_engine '.scss', SassC::Rails::ScssTemplate
+        if env.respond_to?(:register_transformer)
+          env.register_transformer 'text/sass', 'text/css', SassC::Rails::SassTemplate.new #->() { puts "yoyoyoy" }
+          env.register_transformer 'text/scss', 'text/css', SassC::Rails::ScssTemplate.new #->() { puts "yoyoyoy" }
+        else
+          env.register_engine '.sass', SassC::Rails::SassTemplate
+          env.register_engine '.scss', SassC::Rails::ScssTemplate
+        end
       end
     end
 

lib/sassc/rails/template.rb

@@ -1,9 +1,16 @@
 require "sprockets/version"
-require "sprockets/sass_template"
+
+begin
+  require 'sprockets/sass_processor'
+rescue LoadError
+  require "sprockets/sass_template"
+end
+
 require "sprockets/utils"
 
 module SassC::Rails
-  class SassTemplate < Sprockets::SassTemplate
+
+  class SassTemplate < defined?(Sprockets::SassProcessor) ? Sprockets::SassProcessor : Sprockets::SassTemplate
     module Sprockets3
       def call(input)
         context = input[:environment].context_class.new(input)