Set compressors after the configure blocks

Sprockets only allow to set compressors to registeres compressors. If
any new compressor is registered in the configure block it will will
blow because we were setting the compressor before it being registered.

Author: rafaelfranca

lib/sprockets/railtie.rb

@@ -79,11 +79,6 @@ def configure(&block)
       config.assets.paths.each { |path| env.append_path(path) }
     end
 
-    config.assets.configure do |env|
-      env.js_compressor  = config.assets.js_compressor
-      env.css_compressor = config.assets.css_compressor
-    end
-
     config.assets.configure do |env|
       env.context_class.send :include, ::Sprockets::Rails::Context
       env.context_class.assets_prefix = config.assets.prefix
@@ -123,16 +118,23 @@ def build_environment(app, initialized = nil)
 
       env = Sprockets::Environment.new(app.root.to_s)
 
+      config = app.config
+
       # Run app.assets.configure blocks
-      app.config.assets._blocks.each do |block|
+      config.assets._blocks.each do |block|
         block.call(env)
       end
 
+      # Set compressors after the configure blocks since they can
+      # define new compressors and we only accept existent compressors.
+      env.js_compressor  = config.assets.js_compressor
+      env.css_compressor = config.assets.css_compressor
+
       # No more configuration changes at this point.
       # With cache classes on, Sprockets won't check the FS when files
       # change. Preferable in production when the FS only changes on
       # deploys when the app restarts.
-      if app.config.cache_classes
+      if config.cache_classes
         env = env.cached
       end
 

test/test_railtie.rb

@@ -138,6 +138,23 @@ def test_compressors
     assert_equal Sprockets::SassCompressor.name, env.css_compressor.name
   end
 
+  def test_custom_compressors
+    compressor = Class.new
+    app.configure do
+      config.assets.configure do |env|
+        env.register_compressor "application/javascript", :test_js, compressor
+        env.register_compressor "text/css", :test_css, compressor
+      end
+      config.assets.js_compressor  = :test_js
+      config.assets.css_compressor = :test_css
+    end
+    app.initialize!
+
+    assert env = app.assets
+    assert_equal compressor, env.js_compressor
+    assert_equal compressor, env.css_compressor
+  end
+
   def test_version
     app.configure do
       config.assets.version = 'v2'