4 files changed, 51 insertions, 14 deletions

diff --git a/actionmailer/lib/action_mailer/base.rb b/actionmailer/lib/action_mailer/base.rb
index 135cf35ac0..d9b88ec608 100644
--- a/actionmailer/lib/action_mailer/base.rb
+++ b/actionmailer/lib/action_mailer/base.rb
@@ -394,7 +394,7 @@ module ActionMailer
   #   implement for a custom delivery agent.
   #
   # * <tt>perform_deliveries</tt> - Determines whether emails are actually sent from Action Mailer when you
-  #   call <tt>.deliver</tt> on an mail message or on an Action Mailer method. This is on by default but can
+  #   call <tt>.deliver</tt> on an email message or on an Action Mailer method. This is on by default but can
   #   be turned off to aid in functional testing.
   #
   # * <tt>deliveries</tt> - Keeps an array of all the emails sent out through the Action Mailer with
@@ -649,7 +649,22 @@ module ActionMailer
     #  mail.attachments[0]                # => Mail::Part (first attachment)
     #
     def attachments
-      @_message.attachments
+      if @_mail_was_called
+        LateAttachmentsProxy.new(@_message.attachments)
+      else
+        @_message.attachments
+      end
+    end
+
+    class LateAttachmentsProxy < SimpleDelegator
+      def inline; _raise_error end
+      def []=(_name, _content); _raise_error end
+
+      private
+        def _raise_error
+          raise RuntimeError, "Can't add attachments after `mail` was called.\n" \
+                              "Make sure to use `attachments[]=` before calling `mail`."
+        end
     end
 
     # The main method that creates the message and renders the email templates. There are
diff --git a/actionmailer/lib/action_mailer/log_subscriber.rb b/actionmailer/lib/action_mailer/log_subscriber.rb
index e4aaab34b1..5b57c75ec3 100644
--- a/actionmailer/lib/action_mailer/log_subscriber.rb
+++ b/actionmailer/lib/action_mailer/log_subscriber.rb
@@ -6,25 +6,27 @@ module ActionMailer
   class LogSubscriber < ActiveSupport::LogSubscriber
     # An email was delivered.
     def deliver(event)
-      return unless logger.info?
-      recipients = Array(event.payload[:to]).join(', ')
-      info("\nSent mail to #{recipients} (#{event.duration.round(1)}ms)")
-      debug(event.payload[:mail])
+      info do
+        recipients = Array(event.payload[:to]).join(', ')
+        "\nSent mail to #{recipients} (#{event.duration.round(1)}ms)"
+      end
+
+      debug { event.payload[:mail] }
     end
 
     # An email was received.
     def receive(event)
-      return unless logger.info?
-      info("\nReceived mail (#{event.duration.round(1)}ms)")
-      debug(event.payload[:mail])
+      info { "\nReceived mail (#{event.duration.round(1)}ms)" }
+      debug { event.payload[:mail] }
     end
 
     # An email was generated.
     def process(event)
-      return unless logger.debug?
-      mailer = event.payload[:mailer]
-      action = event.payload[:action]
-      debug("\n#{mailer}##{action}: processed outbound mail in #{event.duration.round(1)}ms")
+      debug do
+        mailer = event.payload[:mailer]
+        action = event.payload[:action]
+        "\n#{mailer}##{action}: processed outbound mail in #{event.duration.round(1)}ms"
+      end
     end
 
     # Use the logger configured for ActionMailer::Base
diff --git a/actionmailer/lib/action_mailer/preview.rb b/actionmailer/lib/action_mailer/preview.rb
index 33a9faa7e7..33de1dc049 100644
--- a/actionmailer/lib/action_mailer/preview.rb
+++ b/actionmailer/lib/action_mailer/preview.rb
@@ -11,6 +11,14 @@ module ActionMailer
       #
       mattr_accessor :preview_path, instance_writer: false
 
+      # Enable or disable mailer previews through app configuration:
+      #
+      #     config.action_mailer.show_previews = true
+      #
+      # Defaults to true for development environment
+      #
+      mattr_accessor :show_previews, instance_writer: false
+
       # :nodoc:
       mattr_accessor :preview_interceptors, instance_writer: false
       self.preview_interceptors = []
@@ -94,6 +102,10 @@ module ActionMailer
           Base.preview_path
         end
 
+        def show_previews #:nodoc:
+          Base.show_previews
+        end
+
         def inform_preview_interceptors(message) #:nodoc:
           Base.preview_interceptors.each do |interceptor|
             interceptor.previewing_email(message)
diff --git a/actionmailer/lib/action_mailer/railtie.rb b/actionmailer/lib/action_mailer/railtie.rb
index 671551fa53..6f760732e2 100644
--- a/actionmailer/lib/action_mailer/railtie.rb
+++ b/actionmailer/lib/action_mailer/railtie.rb
@@ -18,8 +18,9 @@ module ActionMailer
       options.assets_dir      ||= paths["public"].first
       options.javascripts_dir ||= paths["public/javascripts"].first
       options.stylesheets_dir ||= paths["public/stylesheets"].first
+      options.show_previews = Rails.env.development? if options.show_previews.nil?
 
-      if Rails.env.development?
+      if options.show_previews
         options.preview_path  ||= defined?(Rails.root) ? "#{Rails.root}/test/mailers/previews" : nil
       end
 
@@ -37,6 +38,13 @@ module ActionMailer
         register_observers(options.delete(:observers))
 
         options.each { |k,v| send("#{k}=", v) }
+
+        if options.show_previews
+          app.routes.append do
+            get '/rails/mailers'         => "rails/mailers#index"
+            get '/rails/mailers/*path'   => "rails/mailers#preview"
+          end
+        end
       end
     end