Allow delivery method options to be set per mail instance

actionmailer/CHANGELOG.md

 ## Rails 4.0.0 (unreleased) ##
 
+* Allow delivery method options to be set per mail instance *Aditya Sanghi*
+
+  If your smtp delivery settings are dynamic,
+  you can now override settings per mail instance for e.g.
+
+      def my_mailer(user,company)
+        mail to: customer.email, subject: "Welcome!",
+             delivery_method_options: {user_name: company.smtp_user,
+                                       password: company.smtp_password}
+      end
+
+  This will ensure that your default SMTP settings will be overridden
+  by the company specific ones. You only have to override the settings
+  that are dynamic and leave the static setting in your environment
+  configuration file (e.g. config/environments/production.rb)
+
 * Allow to set default Action Mailer options via `config.action_mailer.default_options=` *Robert Pankowecki*
 
 * Raise an `ActionView::MissingTemplate` exception when no implicit template could be found. *Damien Mathieu*

actionmailer/lib/action_mailer/base.rb

@@ -683,7 +683,7 @@ def mail(headers={}, &block)
       m.charset = charset = headers[:charset]
 
       # Set configure delivery behavior
-      wrap_delivery_behavior!(headers.delete(:delivery_method))
+      wrap_delivery_behavior!(headers.delete(:delivery_method),headers.delete(:delivery_method_options))
 
       # Assign all headers except parts_order, content_type and body
       assignable = headers.except(:parts_order, :content_type, :body, :template_name, :template_path)

actionmailer/lib/action_mailer/delivery_methods.rb

@@ -57,7 +57,7 @@ def add_delivery_method(symbol, klass, default_options={})
         self.delivery_methods = delivery_methods.merge(symbol.to_sym => klass).freeze
       end
 
-      def wrap_delivery_behavior(mail, method=nil) #:nodoc:
+      def wrap_delivery_behavior(mail, method=nil, options=nil) #:nodoc:
         method ||= self.delivery_method
         mail.delivery_handler = self
 
@@ -66,7 +66,7 @@ def wrap_delivery_behavior(mail, method=nil) #:nodoc:
           raise "Delivery method cannot be nil"
         when Symbol
           if klass = delivery_methods[method]
-            mail.delivery_method(klass, send(:"#{method}_settings"))
+            mail.delivery_method(klass,(send(:"#{method}_settings") || {}).merge!(options || {}))
           else
             raise "Invalid delivery method #{method.inspect}"
           end

actionmailer/test/delivery_methods_test.rb

@@ -4,6 +4,13 @@
 class MyCustomDelivery
 end
 
+class MyOptionedDelivery
+  attr_reader :options
+  def initialize(options)
+    @options = options
+  end
+end
+
 class BogusDelivery
   def initialize(*)
   end
@@ -115,6 +122,38 @@ def teardown
     assert_instance_of Mail::TestMailer, email.delivery_method
   end
 
+  test "delivery method options default to class level options" do
+    default_options = {a: "b"}
+    ActionMailer::Base.add_delivery_method :optioned, MyOptionedDelivery, default_options
+    mail_instance = DeliveryMailer.welcome(:delivery_method => :optioned)
+    assert_equal default_options, mail_instance.delivery_method.options
+  end
+
+  test "delivery method options can be overridden per mail instance" do
+    default_options = {a: "b"}
+    ActionMailer::Base.add_delivery_method :optioned, MyOptionedDelivery, default_options
+    overridden_options = {a: "a"}
+    mail_instance = DeliveryMailer.welcome(:delivery_method => :optioned, :delivery_method_options => overridden_options)
+    assert_equal overridden_options, mail_instance.delivery_method.options
+  end
+
+  test "default delivery options can be overridden per mail instance" do
+    settings = { :address              => "localhost",
+                 :port                 => 25,
+                 :domain               => 'localhost.localdomain',
+                 :user_name            => nil,
+                 :password             => nil,
+                 :authentication       => nil,
+                 :enable_starttls_auto => true }
+    assert_equal settings, ActionMailer::Base.smtp_settings
+    overridden_options = {user_name: "overridden", :password => "somethingobtuse"}
+    mail_instance = DeliveryMailer.welcome(:delivery_method_options => overridden_options)
+    delivery_method_instance = mail_instance.delivery_method
+    assert_equal "overridden", delivery_method_instance.settings[:user_name]
+    assert_equal "somethingobtuse", delivery_method_instance.settings[:password]
+    assert_equal delivery_method_instance.settings.merge(overridden_options), delivery_method_instance.settings
+  end
+
   test "non registered delivery methods raises errors" do
     DeliveryMailer.delivery_method = :unknown
     assert_raise RuntimeError do