allow mail rendering at delay time

The current solution to delayed mail delivery renders the mail template at delivery time:
    Notifier.delay.signup(@user)

When you try to explicitly delay delivery you will get an error:
    Notifier.signup(@user).delay.deliver
    > Use MyMailer.delay.mailer_action(args) to delay sending of emails.

The new approach will serialize the mail message at delay time using Mail::Message.encoded and deserialize using the constructor:
    Notifier.signup(@user).delay.deliver

lib/delayed/performable_mail.rb

@@ -0,0 +1,15 @@
+require 'mail'
+
+module Delayed
+ class PerformableMail < PerformableMethod
+ def initialize(raw_mail, method_name, args)
+ super(Mail.new(raw_mail), method_name, args)
+ end
+ end
+
+ module DelayMailMessage
+ def delay(options = {})
+ DelayProxy.new(PerformableMail, encoded, options)
+ end
+ end
+end

lib/delayed/performable_mailer.rb

@@ -13,9 +13,3 @@ def delay(options = {})
  end
  end
 end
-
-Mail::Message.class_eval do
- def delay(*_args)
- fail 'Use MyMailer.delay.mailer_action(args) to delay sending of emails.'
- end
-end

lib/delayed/railtie.rb

@@ -5,6 +5,11 @@ module Delayed
  class Railtie < Rails::Railtie
  initializer :after_initialize do
  ActiveSupport.on_load(:action_mailer) do
+ module Mail
+ class Message
+ include(Delayed::DelayMailMessage)
+ end
+ end
  ActionMailer::Base.extend(Delayed::DelayMail)
  end
  end

lib/delayed_job.rb

@@ -6,6 +6,7 @@
 
 if defined?(ActionMailer)
  require 'action_mailer/version'
+ require 'delayed/performable_mail'
  require 'delayed/performable_mailer'
 end
 

spec/helper.rb

@@ -14,6 +14,7 @@
 require 'logger'
 require 'rspec'
 
+require 'mail'
 require 'action_mailer'
 require 'active_support/dependencies'
 require 'active_record'
@@ -30,6 +31,11 @@
 ActiveSupport::Dependencies.autoload_paths << File.dirname(__FILE__)
 
 # Add this to simulate Railtie initializer being executed
+module Mail
+ class Message
+ include(Delayed::DelayMailMessage)
+ end
+end
 ActionMailer::Base.extend(Delayed::DelayMail)
 
 # Used to test interactions between DJ and an ORM

spec/performable_mailer_spec.rb

@@ -20,10 +20,12 @@ def signup(email)
  end
 
  describe 'delay on a mail object' do
- it 'raises an exception' do
+ it 'delays the mail object' do
  expect do
- MyMailer.signup('[email protected]').delay
- end.to raise_error(RuntimeError)
+ job = MyMailer.signup('[email protected]').delay.deliver
+ expect(job.payload_object.class).to eq(Delayed::PerformableMail)
+ expect(job.payload_object.method_name).to eq(:deliver)
+ end.to change { Delayed::Job.count }.by(1)
  end
  end