"invalid byte sequence in #{__ENCODING__}" because of directive_processor

lib/sprockets/directive_processor.rb

@@ -91,7 +91,11 @@ def prepare
     def evaluate(context, locals, &block)
       @context = context
 
-      @result = ""
+      @result = if context.environment.respond_to?(:default_external_encoding) #encoding aware ruby?
+                  "".encode(context.environment.default_external_encoding)
+                else
+                  ""
+                end
       @has_written_body = false
 
       process_directives

test/fixtures/context/utf8.js.erb

@@ -0,0 +1 @@
+console.log("Snowman: <%= "\xe2\x98\x83" %>")

test/test_directive_processor.rb

@@ -108,6 +108,19 @@ def directives(offset = 0)
   end
 end
 
+if "".respond_to?(:encoding)
+  class TestDirectiveProcessorEncoding < Sprockets::TestCase
+    def setup
+      @env = Sprockets::Environment.new
+      @env.append_path(fixture_path('context'))
+    end
+
+    test "encoding of evaluated string" do
+      assert_equal Encoding::UTF_8, @env['utf8.js'].source.encoding
+    end
+  end
+end
+
 class TestCustomDirectiveProcessor < Sprockets::TestCase
   def setup
     @env = Sprockets::Environment.new