Ruby 1.9: ERB template encoding using a magic comment at the top of the file

actionpack/CHANGELOG

 *Edge*
 
+* Ruby 1.9: ERB template encoding using a magic comment at the top of the file.  [Jeremy Kemper]
+    <%# encoding: utf-8 %>
+
 * Change integration test helpers to accept Rack environment instead of just HTTP Headers [Pratik Naik]
 
   Before :  get '/path', {}, 'Accept' => 'text/javascript'

actionpack/lib/action_view/template/handlers/erb.rb

@@ -16,11 +16,7 @@ class ERB < TemplateHandler
       self.default_format = Mime::HTML
 
       def compile(template)
-        src = ::ERB.new("<% __in_erb_template=true %>#{template.source}", nil, erb_trim_mode, '@output_buffer').src
-
-        # Ruby 1.9 prepends an encoding to the source. However this is
-        # useless because you can only set an encoding on the first line
-        RUBY_VERSION >= '1.9' ? src.sub(/\A#coding:.*\n/, '') : src
+        ::ERB.new("<% __in_erb_template=true %>#{template.source}", nil, erb_trim_mode, '@output_buffer').src
       end
     end
   end

actionpack/lib/action_view/template/template.rb

@@ -52,16 +52,26 @@ def compile(locals, view)
       
       locals_code = locals.keys.map! { |key| "#{key} = local_assigns[:#{key}];" }.join
 
+      code = @handler.call(self)
+      encoding_comment = $1 if code.sub!(/\A(#.*coding.*)\n/, '')
+
       source = <<-end_src
         def #{method_name}(local_assigns)
-          old_output_buffer = output_buffer;#{locals_code};#{@handler.call(self)}
+          old_output_buffer = output_buffer;#{locals_code};#{code}
         ensure
           self.output_buffer = old_output_buffer
         end
       end_src
 
+      if encoding_comment
+        source = "#{encoding_comment}\n#{source}"
+        line = -1
+      else
+        line = 0
+      end
+
       begin
-        ActionView::Base::CompiledTemplates.module_eval(source, identifier, 0)
+        ActionView::Base::CompiledTemplates.module_eval(source, identifier, line)
         method_name
       rescue Exception => e # errors from template code
         if logger = (view && view.logger)
@@ -79,4 +89,4 @@ def build_method_name(locals)
       "_render_template_#{@identifier.hash}_#{__id__}_#{locals.keys.hash}".gsub('-', "_")
     end
   end
-end
\ No newline at end of file
+end

actionpack/test/fixtures/test/utf8.html.erb

+<%# encoding: utf-8 -%>
 Русский текст
-日本語のテキスト
\ No newline at end of file
+<%= "日".encoding %>
+<%= @output_buffer.encoding %>
+<%= __ENCODING__ %>

actionpack/test/template/render_test.rb

@@ -249,7 +249,7 @@ def test_render_with_nested_layout
   if '1.9'.respond_to?(:force_encoding)
     def test_render_utf8_template
       result = @view.render(:file => "test/utf8.html.erb", :layouts => "layouts/yield")
-      assert_equal "Русский текст\n日本語のテキスト", result
+      assert_equal "Русский текст\nUTF-8\nUTF-8\nUTF-8\n", result
       assert_equal Encoding::UTF_8, result.encoding
     end
   end