5 files changed, 28 insertions, 18 deletions
diff --git a/actionmailer/lib/action_mailer.rb b/actionmailer/lib/action_mailer.rb
index ade3fe39a2..fabbdd1b25 100644
--- a/actionmailer/lib/action_mailer.rb
+++ b/actionmailer/lib/action_mailer.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 #--
-# Copyright (c) 2004-2017 David Heinemeier Hansson
+# Copyright (c) 2004-2018 David Heinemeier Hansson
 #
 # Permission is hereby granted, free of charge, to any person obtaining
 # a copy of this software and associated documentation files (the
diff --git a/actionmailer/lib/action_mailer/base.rb b/actionmailer/lib/action_mailer/base.rb
index eb8ae59533..3af95081ee 100644
--- a/actionmailer/lib/action_mailer/base.rb
+++ b/actionmailer/lib/action_mailer/base.rb
@@ -889,7 +889,7 @@ module ActionMailer
         default_values = self.class.default.map do |key, value|
           [
             key,
-            value.is_a?(Proc) ? instance_exec(&value) : value
+            compute_default(value)
           ]
         end.to_h
 
@@ -898,6 +898,16 @@ module ActionMailer
         headers_with_defaults
       end
 
+      def compute_default(value)
+        return value unless value.is_a?(Proc)
+
+        if value.arity == 1
+          instance_exec(self, &value)
+        else
+          instance_exec(&value)
+        end
+      end
+
       def assign_headers_to_message(message, headers)
         assignable = headers.except(:parts_order, :content_type, :body, :template_name,
                                     :template_path, :delivery_method, :delivery_method_options)
diff --git a/actionmailer/lib/action_mailer/gem_version.rb b/actionmailer/lib/action_mailer/gem_version.rb
index 6a7dd0a212..72eb5d61e8 100644
--- a/actionmailer/lib/action_mailer/gem_version.rb
+++ b/actionmailer/lib/action_mailer/gem_version.rb
@@ -7,10 +7,10 @@ module ActionMailer
   end
 
   module VERSION
-    MAJOR = 5
-    MINOR = 2
+    MAJOR = 6
+    MINOR = 0
     TINY  = 0
-    PRE   = "beta2"
+    PRE   = "alpha"
 
     STRING = [MAJOR, MINOR, TINY, PRE].compact.join(".")
   end
diff --git a/actionmailer/lib/action_mailer/inline_preview_interceptor.rb b/actionmailer/lib/action_mailer/inline_preview_interceptor.rb
index 4bef4a58d3..8a12f805cc 100644
--- a/actionmailer/lib/action_mailer/inline_preview_interceptor.rb
+++ b/actionmailer/lib/action_mailer/inline_preview_interceptor.rb
@@ -4,7 +4,7 @@ require "base64"
 
 module ActionMailer
   # Implements a mailer preview interceptor that converts image tag src attributes
-  # that use inline cid: style urls to data: style urls so that they are visible
+  # that use inline cid: style URLs to data: style URLs so that they are visible
   # when previewing an HTML email in a web browser.
   #
   # This interceptor is enabled by default. To disable it, delete it from the
diff --git a/actionmailer/lib/action_mailer/message_delivery.rb b/actionmailer/lib/action_mailer/message_delivery.rb
index a2ea45dc7b..2377aeb9a5 100644
--- a/actionmailer/lib/action_mailer/message_delivery.rb
+++ b/actionmailer/lib/action_mailer/message_delivery.rb
@@ -53,6 +53,12 @@ module ActionMailer
     #   Notifier.welcome(User.first).deliver_later!(wait: 1.hour)
     #   Notifier.welcome(User.first).deliver_later!(wait_until: 10.hours.from_now)
     #
+    # Options:
+    #
+    # * <tt>:wait</tt> - Enqueue the email to be delivered with a delay
+    # * <tt>:wait_until</tt> - Enqueue the email to be delivered at (after) a specific date / time
+    # * <tt>:queue</tt> - Enqueue the email on the specified queue
+    #
     # By default, the email will be enqueued using <tt>ActionMailer::DeliveryJob</tt>. Each
     # <tt>ActionMailer::Base</tt> class can specify the job to use by setting the class variable
     # +delivery_job+.
@@ -60,12 +66,6 @@ module ActionMailer
     #   class AccountRegistrationMailer < ApplicationMailer
     #     self.delivery_job = RegistrationDeliveryJob
     #   end
-    #
-    # Options:
-    #
-    # * <tt>:wait</tt> - Enqueue the email to be delivered with a delay
-    # * <tt>:wait_until</tt> - Enqueue the email to be delivered at (after) a specific date / time
-    # * <tt>:queue</tt> - Enqueue the email on the specified queue
     def deliver_later!(options = {})
       enqueue_delivery :deliver_now!, options
     end
@@ -77,6 +77,12 @@ module ActionMailer
     #   Notifier.welcome(User.first).deliver_later(wait: 1.hour)
     #   Notifier.welcome(User.first).deliver_later(wait_until: 10.hours.from_now)
     #
+    # Options:
+    #
+    # * <tt>:wait</tt> - Enqueue the email to be delivered with a delay.
+    # * <tt>:wait_until</tt> - Enqueue the email to be delivered at (after) a specific date / time.
+    # * <tt>:queue</tt> - Enqueue the email on the specified queue.
+    #
     # By default, the email will be enqueued using <tt>ActionMailer::DeliveryJob</tt>. Each
     # <tt>ActionMailer::Base</tt> class can specify the job to use by setting the class variable
     # +delivery_job+.
@@ -84,12 +90,6 @@ module ActionMailer
     #   class AccountRegistrationMailer < ApplicationMailer
     #     self.delivery_job = RegistrationDeliveryJob
     #   end
-    #
-    # Options:
-    #
-    # * <tt>:wait</tt> - Enqueue the email to be delivered with a delay.
-    # * <tt>:wait_until</tt> - Enqueue the email to be delivered at (after) a specific date / time.
-    # * <tt>:queue</tt> - Enqueue the email on the specified queue.
     def deliver_later(options = {})
       enqueue_delivery :deliver_now, options
     end