Fix keyword arguments warnings in Action Mailer

actionmailer/lib/action_mailer/base.rb

@@ -619,6 +619,7 @@ def method_missing(method_name, *args)
           super
         end
       end
+      ruby2_keywords(:method_missing) if respond_to?(:ruby2_keywords, true)
 
       def respond_to_missing?(method, include_all = false)
         action_methods.include?(method.to_s) || super

actionmailer/lib/action_mailer/message_delivery.rb

@@ -23,6 +23,7 @@ def initialize(mailer_class, action, *args) #:nodoc:
       @processed_mailer = nil
       @mail_message = nil
     end
+    ruby2_keywords(:initialize) if respond_to?(:ruby2_keywords, true)
 
     # Method calls are delegated to the Mail::Message that's ready to deliver.
     def __getobj__ #:nodoc:
@@ -143,10 +144,16 @@ def enqueue_delivery(delivery_method, options = {})
 
       def arguments_for(delivery_job, delivery_method)
         if delivery_job <= MailDeliveryJob
-          [@mailer_class.name, @action.to_s, delivery_method.to_s, args: @args]
+          ruby2_keywords_arguments \
+            @mailer_class.name, @action.to_s, delivery_method.to_s, args: @args
         else
           [@mailer_class.name, @action.to_s, delivery_method.to_s, *@args]
         end
       end
+
+      def ruby2_keywords_arguments(*args)
+        args
+      end
+      ruby2_keywords(:ruby2_keywords_arguments) if respond_to?(:ruby2_keywords, true)
   end
 end

actionmailer/lib/action_mailer/parameterized.rb

@@ -132,6 +132,7 @@ def initialize(mailer_class, action, params, *args)
         super(mailer_class, action, *args)
         @params = params
       end
+      ruby2_keywords(:initialize) if respond_to?(:ruby2_keywords, true)
 
       private
         def processed_mailer
@@ -161,7 +162,8 @@ def delivery_job_class
 
         def arguments_for(delivery_job, delivery_method)
           if delivery_job <= MailDeliveryJob
-            [@mailer_class.name, @action.to_s, delivery_method.to_s, params: @params, args: @args]
+            ruby2_keywords_arguments \
+              @mailer_class.name, @action.to_s, delivery_method.to_s, params: @params, args: @args
           else
             [@mailer_class.name, @action.to_s, delivery_method.to_s, @params, *@args]
           end

actionmailer/test/mailers/delayed_mailer.rb

@@ -22,6 +22,10 @@ def test_message(*)
     mail(from: "test-sender@test.com", to: "test-receiver@test.com", subject: "Test Subject", body: "Test Body")
   end
 
+  def test_kwargs(argument:)
+    mail(from: "test-sender@test.com", to: "test-receiver@test.com", subject: "Test Subject", body: "Test Body")
+  end
+
   def test_raise(klass_name)
     raise klass_name.constantize, "boom"
   end

actionmailer/test/message_delivery_test.rb

@@ -164,4 +164,11 @@ def to_global_id(options = {})
     assert_equal DelayedMailer, DelayedMailer.last_rescue_from_instance
     assert_equal "Error while trying to deserialize arguments: boom, missing find", DelayedMailer.last_error.message
   end
+
+  test "allows for keyword arguments" do
+    assert_performed_with(job: ActionMailer::MailDeliveryJob, args: ["DelayedMailer", "test_kwargs", "deliver_now", args: [argument: 1]]) do
+      message = DelayedMailer.test_kwargs(argument: 1)
+      message.deliver_later
+    end
+  end
 end