Use I18n on ActionMailer subjects by default.

actionmailer/lib/action_mailer/base.rb

@@ -463,9 +463,9 @@ def create!(method_name, *parameters) #:nodoc:
       # Create e-mail parts
       create_parts
 
-      # If this is a multipart e-mail add the mime_version if it is not
-      # already set.
-      @mime_version ||= "1.0" if !@parts.empty?
+      # Set the subject if not set yet
+      @subject ||= I18n.t(method_name, :scope => [:actionmailer, :subjects, mailer_name],
+                                       :default => method_name.humanize)
 
       # build the mail object itself
       @mail = create_mail
@@ -539,6 +539,10 @@ def create_parts
             @content_type = "multipart/alternative" if @content_type !~ /^multipart/
             @parts = sort_parts(@parts, @implicit_parts_order)
           end
+
+          # If this is a multipart e-mail add the mime_version if it is not
+          # already set.
+          @mime_version ||= "1.0" if !@parts.empty?
         end
       end
 

actionmailer/test/mail_service_test.rb

@@ -296,6 +296,12 @@ def body_ivar(recipient)
     body         :body => "foo", :bar => "baz"
   end
 
+  def subject_with_i18n(recipient)
+    recipients recipient
+    from       "system@loudthinking.com"
+    render :text => "testing"
+  end
+
   class << self
     attr_accessor :received_body
   end
@@ -392,6 +398,15 @@ def test_signed_up
     assert_equal expected.encoded, ActionMailer::Base.deliveries.first.encoded
   end
 
+  def test_subject_with_i18n
+    assert_nothing_raised { TestMailer.deliver_subject_with_i18n(@recipient) }
+    assert_equal "Subject with i18n", ActionMailer::Base.deliveries.first.subject
+
+    I18n.backend.store_translations('en', :actionmailer => {:subjects => {:test_mailer => {:subject_with_i18n => "New Subject!"}}})
+    assert_nothing_raised { TestMailer.deliver_subject_with_i18n(@recipient) }
+    assert_equal "New Subject!", ActionMailer::Base.deliveries.last.subject
+  end
+
   def test_custom_template
     expected = new_mail
     expected.to      = @recipient