1 files changed, 20 insertions, 14 deletions
diff --git a/railties/lib/rails/mailers_controller.rb b/railties/lib/rails/mailers_controller.rb
index 32740d66da..38004fe99a 100644
--- a/railties/lib/rails/mailers_controller.rb
+++ b/railties/lib/rails/mailers_controller.rb
@@ -3,7 +3,7 @@ require 'rails/application_controller'
 class Rails::MailersController < Rails::ApplicationController # :nodoc:
   prepend_view_path ActionDispatch::DebugExceptions::RESCUES_TEMPLATE_PATH
 
-  before_action :require_local!
+  before_action :require_local!, unless: :show_previews?
   before_action :find_preview, only: :preview
 
   def index
@@ -16,31 +16,35 @@ class Rails::MailersController < Rails::ApplicationController # :nodoc:
       @page_title = "Mailer Previews for #{@preview.preview_name}"
       render action: 'mailer'
     else
-      email = File.basename(params[:path])
+      @email_action = File.basename(params[:path])
 
-      if @preview.email_exists?(email)
-        @email = @preview.call(email)
+      if @preview.email_exists?(@email_action)
+        @email = @preview.call(@email_action)
 
         if params[:part]
           part_type = Mime::Type.lookup(params[:part])
 
           if part = find_part(part_type)
             response.content_type = part_type
-            render text: part.respond_to?(:decoded) ? part.decoded : part
+            render plain: part.respond_to?(:decoded) ? part.decoded : part
           else
-            raise AbstractController::ActionNotFound, "Email part '#{part_type}' not found in #{@preview.name}##{email}"
+            raise AbstractController::ActionNotFound, "Email part '#{part_type}' not found in #{@preview.name}##{@email_action}"
           end
         else
-          @part = find_preferred_part(request.format, Mime::HTML, Mime::TEXT)
+          @part = find_preferred_part(request.format, Mime::Type[:HTML], Mime::Type[:TEXT])
           render action: 'email', layout: false, formats: %w[html]
         end
       else
-        raise AbstractController::ActionNotFound, "Email '#{email}' not found in #{@preview.name}"
+        raise AbstractController::ActionNotFound, "Email '#{@email_action}' not found in #{@preview.name}"
       end
     end
   end
 
   protected
+    def show_previews?
+      ActionMailer::Base.show_previews
+    end
+
     def find_preview
       candidates = []
       params[:path].to_s.scan(%r{/|$}){ candidates << $` }
@@ -54,18 +58,20 @@ class Rails::MailersController < Rails::ApplicationController # :nodoc:
     end
 
     def find_preferred_part(*formats)
-      if @email.multipart?
-        formats.each do |format|
-          return find_part(format) if @email.parts.any?{ |p| p.mime_type == format }
+      formats.each do |format|
+        if part = @email.find_first_mime_type(format)
+          return part
         end
-      else
+      end
+
+      if formats.any?{ |f| @email.mime_type == f }
         @email
       end
     end
 
     def find_part(format)
-      if @email.multipart?
-        @email.parts.find{ |p| p.mime_type == format }
+      if part = @email.find_first_mime_type(format)
+        part
       elsif @email.mime_type == format
         @email
       end