Merge pull request #15970 from lengarvey/add_configuration_option_for_mail_preview

Add configuration to enable mail previews

actionmailer/CHANGELOG.md

+*   Add `config.action_mailer.preview_enabled` configuration option.
+
+    This config option can be used to enable the mail preview in environments
+    other than development (such as staging).
+
+    Defaults to `true` in development and false elsewhere.
+
+    *Leonard Garvey*
+
 *   Allow preview interceptors to be registered through
     `config.action_mailer.preview_interceptors`.
 

actionmailer/lib/action_mailer/preview.rb

@@ -11,6 +11,14 @@ module Previews #:nodoc:
       #
       mattr_accessor :preview_path, instance_writer: false
 
+      # Enable or disable mailer previews through app configuration:
+      #
+      #     config.action_mailer.preview_enabled = true
+      #
+      # Defaults to true for development environment
+      #
+      mattr_accessor :preview_enabled, instance_writer: false
+
       # :nodoc:
       mattr_accessor :preview_interceptors, instance_writer: false
       self.preview_interceptors = []
@@ -94,6 +102,10 @@ def preview_path #:nodoc:
           Base.preview_path
         end
 
+        def preview_enabled #:nodoc:
+          Base.preview_enabled
+        end
+
         def inform_preview_interceptors(message) #:nodoc:
           Base.preview_interceptors.each do |interceptor|
             interceptor.previewing_email(message)

actionmailer/lib/action_mailer/railtie.rb

@@ -18,8 +18,9 @@ class Railtie < Rails::Railtie # :nodoc:
       options.assets_dir      ||= paths["public"].first
       options.javascripts_dir ||= paths["public/javascripts"].first
       options.stylesheets_dir ||= paths["public/stylesheets"].first
+      options.preview_enabled = Rails.env.development? if options.preview_enabled.nil?
 
-      if Rails.env.development?
+      if options.preview_enabled
         options.preview_path  ||= defined?(Rails.root) ? "#{Rails.root}/test/mailers/previews" : nil
       end
 
@@ -37,6 +38,13 @@ class Railtie < Rails::Railtie # :nodoc:
         register_observers(options.delete(:observers))
 
         options.each { |k,v| send("#{k}=", v) }
+
+        if options.preview_enabled
+          app.routes.append do
+            get '/rails/mailers'         => "rails/mailers#index"
+            get '/rails/mailers/*path'   => "rails/mailers#preview"
+          end
+        end
       end
     end
 

guides/source/configuring.md

@@ -453,6 +453,18 @@ There are a number of settings available on `config.action_mailer`:
     config.action_mailer.interceptors = ["MailInterceptor"]
     ```
 
+* `config.action_mailer.preview_path` specifies the location of mailer previews.
+
+    ```ruby
+    config.action_mailer.preview_path = "#{Rails.root}/lib/mailer_previews"
+    ```
+
+* `config.action_mailer.preview_enabled` enable or disable mailer previews. By default this is `true` in development.
+
+    ```ruby
+    config.action_mailer.preview_enabled = false
+    ```
+
 ### Configuring Active Support
 
 There are a few configuration options available in Active Support:

railties/lib/rails/application/finisher.rb

@@ -22,8 +22,6 @@ module Finisher
       initializer :add_builtin_route do |app|
         if Rails.env.development?
           app.routes.append do
-            get '/rails/mailers'         => "rails/mailers#index"
-            get '/rails/mailers/*path'   => "rails/mailers#preview"
             get '/rails/info/properties' => "rails/info#properties"
             get '/rails/info/routes'     => "rails/info#routes"
             get '/rails/info'            => "rails/info#index"

railties/test/application/configuration_test.rb

@@ -965,5 +965,29 @@ def index
 
       assert db_config.is_a?(Hash)
     end
+
+    test 'config.mail_preview_enabled defaults to true in development' do
+      Rails.env = "development"
+      require "#{app_path}/config/environment"
+
+      assert Rails.application.config.action_mailer.preview_enabled
+    end
+
+    test 'config.mail_preview_enabled defaults to false in production' do
+      Rails.env = "production"
+      require "#{app_path}/config/environment"
+
+      assert_equal Rails.application.config.action_mailer.preview_enabled, false
+    end
+
+    test 'config.mail_preview_enabled can be set in the configuration file' do
+      Rails.env = "production"
+      add_to_config <<-RUBY
+        config.action_mailer.preview_enabled = true
+      RUBY
+      require "#{app_path}/config/environment"
+
+      assert_equal Rails.application.config.action_mailer.preview_enabled, true
+    end
   end
 end

railties/test/application/mailer_previews_test.rb

@@ -26,6 +26,20 @@ def teardown
       assert_equal 404, last_response.status
     end
 
+    test "/rails/mailers is accessible with correct configuraiton" do
+      add_to_config "config.action_mailer.preview_enabled = true"
+      app("production")
+      get "/rails/mailers"
+      assert_equal 200, last_response.status
+    end
+
+    test "/rails/mailers is not accessible with preview_enabled = false" do
+      add_to_config "config.action_mailer.preview_enabled = false"
+      app("development")
+      get "/rails/mailers"
+      assert_equal 404, last_response.status
+    end
+
     test "mailer previews are loaded from the default preview_path" do
       mailer 'notifier', <<-RUBY
         class Notifier < ActionMailer::Base