Added ability to download `.eml` file for the email preview.

actionmailer/CHANGELOG.md

@@ -1,3 +1,7 @@
+*   Added ability to download `.eml` file for the email preview.
+
+    *Igor Kasyanchuk*
+
 *   Support multiple preview paths for mailers.
 
     Option `config.action_mailer.preview_path` is deprecated in favor of

actionmailer/lib/action_mailer/railtie.rb

@@ -80,7 +80,8 @@ module ActionMailer
 
       if options.show_previews
         app.routes.prepend do
-          get "/rails/mailers"       => "rails/mailers#index", internal: true
+          get "/rails/mailers" => "rails/mailers#index", internal: true
+          get "/rails/mailers/download/*path" => "rails/mailers#download", internal: true
           get "/rails/mailers/*path" => "rails/mailers#preview", internal: true
         end
       end

railties/lib/rails/mailers_controller.rb

@@ -5,8 +5,8 @@ require "rails/application_controller"
 class Rails::MailersController < Rails::ApplicationController # :nodoc:
   prepend_view_path ActionDispatch::DebugView::RESCUES_TEMPLATE_PATH
 
-  around_action :set_locale, only: :preview
-  before_action :find_preview, only: :preview
+  around_action :set_locale, only: [:preview, :download]
+  before_action :find_preview, only: [:preview, :download]
   before_action :require_local!, unless: :show_previews?
 
   helper_method :part_query, :locale_query
@@ -18,6 +18,16 @@ class Rails::MailersController < Rails::ApplicationController # :nodoc:
     @page_title = "Mailer Previews"
   end
 
+  def download
+    @email_action = File.basename(params[:path])
+    if @preview.email_exists?(@email_action)
+      @email = @preview.call(@email_action, params)
+      send_data @email.to_s, filename: "#{@email_action}.eml"
+    else
+      raise AbstractController::ActionNotFound, "Email '#{@email_action}' not found in #{@preview.name}"
+    end
+  end
+
   def preview
     if params[:path] == @preview.preview_name
       @page_title = "Mailer Previews for #{@preview.preview_name}"

railties/lib/rails/templates/rails/mailers/email.html.erb

@@ -125,6 +125,8 @@
         </select>
       </dd>
     <% end %>
+    <dt>EML File:</dt>
+    <dd><%= link_to "Download", action: :download %></dd>
   </dl>
 </header>
 

railties/test/application/mailer_previews_test.rb

@@ -355,6 +355,10 @@ module ApplicationTests
       get "/rails/mailers/notifier/bar"
       assert_predicate last_response, :not_found?
       assert_match "Email 'bar' not found in NotifierPreview", h(last_response.body)
+
+      get "/rails/mailers/download/notifier/bar"
+      assert_predicate last_response, :not_found?
+      assert_match "Email 'bar' not found in NotifierPreview", h(last_response.body)
     end
 
     test "mailer preview NullMail" do
@@ -444,6 +448,13 @@ module ApplicationTests
       assert_match "Ruby on Rails <core@rubyonrails.org>", last_response.body
       assert_match "Andrew White <andyw@pixeltrix.co.uk>", last_response.body
       assert_match "David Heinemeier Hansson <david@heinemeierhansson.com>", last_response.body
+
+      get "/rails/mailers/download/notifier/foo"
+      email = Mail.read_from_string(last_response.body)
+      assert_equal "attachment; filename=\"foo.eml\"; filename*=UTF-8''foo.eml", last_response.headers["Content-Disposition"]
+      assert_equal 200, last_response.status
+      assert_equal ["andyw@pixeltrix.co.uk"], email.to
+      assert_equal ["david@heinemeierhansson.com"], email.cc
     end
 
     test "part menu selects correct option" do
@@ -663,6 +674,13 @@ module ApplicationTests
       get "/rails/mailers/notifier/foo?part=text/plain"
       assert_equal 200, last_response.status
       assert_match %r[Hello, World!], last_response.body
+
+      get "/rails/mailers/download/notifier/foo"
+      assert_equal 200, last_response.status
+      email = Mail.read_from_string(last_response.body)
+      assert_equal 2, email.parts.size
+      assert_equal "text/plain; charset=UTF-8", email.parts[0].content_type
+      assert_equal "image/png; filename=pixel.png", email.parts[1].content_type
     end
 
     test "multipart mailer preview with attachment" do