mailer can be anonymous

closes rails#5970

Author: lest

actionmailer/lib/action_mailer/base.rb

@@ -3,6 +3,7 @@
 require 'active_support/core_ext/object/blank'
 require 'active_support/core_ext/string/inflections'
 require 'active_support/core_ext/hash/except'
+require 'active_support/core_ext/module/anonymous'
 require 'action_mailer/log_subscriber'
 
 module ActionMailer #:nodoc:
@@ -401,7 +402,7 @@ def register_interceptor(interceptor)
       end
 
       def mailer_name
-        @mailer_name ||= name.underscore
+        @mailer_name ||= anonymous? ? "anonymous" : name.underscore
       end
       attr_writer :mailer_name
       alias :controller_path :mailer_name

actionmailer/test/base_test.rb

@@ -610,6 +610,19 @@ def notify
     assert_equal Set.new(["notify"]), FooMailer.action_methods
   end
 
+  test "mailer can be anonymous" do
+    mailer = Class.new(ActionMailer::Base) do
+      def welcome
+        mail
+      end
+    end
+
+    assert_equal "anonymous", mailer.mailer_name
+
+    assert_equal "Welcome", mailer.welcome.subject
+    assert_equal "Anonymous mailer body", mailer.welcome.body.encoded.strip
+  end
+
   protected
 
     # Execute the block setting the given values and restoring old values after

actionmailer/test/fixtures/anonymous/welcome.erb

@@ -0,0 +1 @@
+Anonymous mailer body