1 files changed, 21 insertions, 8 deletions
diff --git a/actionmailer/lib/action_mailer/base.rb b/actionmailer/lib/action_mailer/base.rb
index ada86fbc4f..6f8ae05539 100644
--- a/actionmailer/lib/action_mailer/base.rb
+++ b/actionmailer/lib/action_mailer/base.rb
@@ -373,7 +373,11 @@ module ActionMailer
     include AbstractController::AssetPaths
     include AbstractController::Callbacks
 
-    self.protected_instance_variables = [:@_action_has_layout]
+    PROTECTED_IVARS = AbstractController::Rendering::DEFAULT_PROTECTED_INSTANCE_VARIABLES + [:@_action_has_layout]
+
+    def _protected_ivars # :nodoc:
+      PROTECTED_IVARS
+    end
 
     helper ActionMailer::MailHelper
 
@@ -511,11 +515,18 @@ module ActionMailer
       process(method_name, *args) if method_name
     end
 
-    def process(*args) #:nodoc:
-      lookup_context.skip_default_locale!
+    def process(method_name, *args) #:nodoc:
+      payload = {
+        mailer: self.class.name,
+        action: method_name
+      }
+
+      ActiveSupport::Notifications.instrument("process.action_mailer", payload) do
+        lookup_context.skip_default_locale!
 
-      super
-      @_message = NullMail.new unless @_mail_was_called
+        super
+        @_message = NullMail.new unless @_mail_was_called
+      end
     end
 
     class NullMail #:nodoc:
@@ -678,6 +689,8 @@ module ActionMailer
     #   end
     #
     def mail(headers = {}, &block)
+      return @_message if @_mail_was_called && headers.blank? && !block
+
       @_mail_was_called = true
       m = @_message
 
@@ -685,9 +698,9 @@ module ActionMailer
       content_type = headers[:content_type]
 
       # Call all the procs (if any)
-      class_default = self.class.default
-      default_values = class_default.merge(class_default) do |k,v|
-        v.is_a?(Proc) ? instance_eval(&v) : v
+      default_values = {}
+      self.class.default.each do |k,v|
+        default_values[k] = v.is_a?(Proc) ? instance_eval(&v) : v
       end
 
       # Handle defaults