Support multiple preview paths for mailers

actionmailer/CHANGELOG.md

@@ -1,3 +1,9 @@
+*   Support multiple preview paths for mailers.
 
+    Option `config.action_mailer.preview_path` is deprecated in favor of
+    `config.action_mailer.preview_paths`. Appending paths to this configuration option
+    will cause those paths to be used in the search for mailer previews.
+
+    *fatkodima*
 
 Please check [7-0-stable](https://github.com/rails/rails/blob/7-0-stable/actionmailer/CHANGELOG.md) for previous changes.

actionmailer/lib/action_mailer/base.rb

@@ -368,7 +368,7 @@ module ActionMailer
   # = Previewing emails
   #
   # You can preview your email templates visually by adding a mailer preview file to the
-  # <tt>ActionMailer::Base.preview_path</tt>. Since most emails do something interesting
+  # <tt>ActionMailer::Base.preview_paths</tt>. Since most emails do something interesting
   # with database data, you'll need to write some scenarios to load messages with fake data:
   #
   #   class NotifierMailerPreview < ActionMailer::Preview
@@ -379,10 +379,10 @@ module ActionMailer
   #
   # Methods must return a <tt>Mail::Message</tt> object which can be generated by calling the mailer
   # method without the additional <tt>deliver_now</tt> / <tt>deliver_later</tt>. The location of the
-  # mailer previews directory can be configured using the <tt>preview_path</tt> option which has a default
+  # mailer preview directories can be configured using the <tt>preview_paths</tt> option which has a default
   # of <tt>test/mailers/previews</tt>:
   #
-  #   config.action_mailer.preview_path = "#{Rails.root}/lib/mailer_previews"
+  #   config.action_mailer.preview_paths << "#{Rails.root}/lib/mailer_previews"
   #
   # An overview of all previews is accessible at <tt>http://localhost:3000/rails/mailers</tt>
   # on a running development server instance.

actionmailer/lib/action_mailer/preview.rb

@@ -7,11 +7,11 @@ module ActionMailer
     extend ActiveSupport::Concern
 
     included do
-      # Set the location of mailer previews through app configuration:
+      # Add the location of mailer previews through app configuration:
       #
-      #     config.action_mailer.preview_path = "#{Rails.root}/lib/mailer_previews"
+      #     config.action_mailer.preview_paths << "#{Rails.root}/lib/mailer_previews"
       #
-      mattr_accessor :preview_path, instance_writer: false
+      mattr_accessor :preview_paths, instance_writer: false, default: []
 
       # Enable or disable mailer previews through app configuration:
       #
@@ -25,7 +25,31 @@ module ActionMailer
       mattr_accessor :preview_interceptors, instance_writer: false, default: [ActionMailer::InlinePreviewInterceptor]
     end
 
+    def preview_path
+      ActiveSupport::Deprecation.warn(<<-MSG.squish)
+        Using preview_path option is deprecated and will be removed in Rails 7.2.
+        Please use preview_paths instead.
+      MSG
+      self.class.preview_paths.first
+    end
+
     module ClassMethods
+      def preview_path=(value)
+        ActiveSupport::Deprecation.warn(<<-MSG.squish)
+          Using preview_path= option is deprecated and will be removed in Rails 7.2.
+          Please use preview_paths= instead.
+        MSG
+        self.preview_paths << value
+      end
+
+      def preview_path
+        ActiveSupport::Deprecation.warn(<<-MSG.squish)
+          Using preview_path option is deprecated and will be removed in Rails 7.2.
+          Please use preview_paths instead.
+        MSG
+        self.preview_paths.first
+      end
+
       # Register one or more Interceptors which will be called before mail is previewed.
       def register_preview_interceptors(*interceptors)
         interceptors.flatten.compact.each { |interceptor| register_preview_interceptor(interceptor) }
@@ -119,13 +143,13 @@ module ActionMailer
 
       private
         def load_previews
-          if preview_path
+          preview_paths.each do |preview_path|
             Dir["#{preview_path}/**/*_preview.rb"].sort.each { |file| require_dependency file }
           end
         end
 
-        def preview_path
-          Base.preview_path
+        def preview_paths
+          Base.preview_paths
         end
 
         def show_previews

actionmailer/lib/action_mailer/railtie.rb

@@ -8,6 +8,7 @@ require "abstract_controller/railties/routes_helpers"
 module ActionMailer
   class Railtie < Rails::Railtie # :nodoc:
     config.action_mailer = ActiveSupport::OrderedOptions.new
+    config.action_mailer.preview_paths = []
     config.eager_load_namespaces << ActionMailer
 
     initializer "action_mailer.logger" do
@@ -23,10 +24,7 @@ module ActionMailer
       options.stylesheets_dir ||= paths["public/stylesheets"].first
       options.show_previews = Rails.env.development? if options.show_previews.nil?
       options.cache_store ||= Rails.cache
-
-      if options.show_previews
-        options.preview_path ||= defined?(Rails.root) ? "#{Rails.root}/test/mailers/previews" : nil
-      end
+      options.preview_paths |= ["#{Rails.root}/test/mailers/previews"]
 
       # make sure readers methods get compiled
       options.asset_host          ||= app.config.asset_host
@@ -40,6 +38,7 @@ module ActionMailer
         register_interceptors(options.delete(:interceptors))
         register_preview_interceptors(options.delete(:preview_interceptors))
         register_observers(options.delete(:observers))
+        self.preview_paths |= options[:preview_paths]
 
         if delivery_job = options.delete(:delivery_job)
           self.delivery_job = delivery_job.constantize
@@ -65,12 +64,9 @@ module ActionMailer
       end
     end
 
-    initializer "action_mailer.set_autoload_paths" do |app|
+    initializer "action_mailer.set_autoload_paths", before: :set_autoload_paths do |app|
       options = app.config.action_mailer
-
-      if options.show_previews && options.preview_path
-        ActiveSupport::Dependencies.autoload_paths << options.preview_path
-      end
+      app.config.paths["test/mailers/previews"].concat(options.preview_paths)
     end
 
     initializer "action_mailer.compile_config_methods" do

guides/source/action_mailer_basics.md

@@ -556,12 +556,12 @@ visually see the new style instantly. A list of previews are also available
 in <http://localhost:3000/rails/mailers>.
 
 By default, these preview classes live in `test/mailers/previews`.
-This can be configured using the `preview_path` option. For example, if you
-want to change it to `lib/mailer_previews`, you can configure it in
+This can be configured using the `preview_paths` option. For example, if you
+want to add `lib/mailer_previews` to it, you can configure it in
 `config/application.rb`:
 
 ```ruby
-config.action_mailer.preview_path = "#{Rails.root}/lib/mailer_previews"
+config.action_mailer.preview_paths << "#{Rails.root}/lib/mailer_previews"
 ```
 
 ### Generating URLs in Action Mailer Views

guides/source/configuring.md

@@ -1859,12 +1859,12 @@ Registers interceptors which will be called before mail is previewed.
 config.action_mailer.preview_interceptors = ["MyPreviewMailInterceptor"]
 ```
 
-#### `config.action_mailer.preview_path`
+#### `config.action_mailer.preview_paths`
 
-Specifies the location of mailer previews.
+Specifies the locations of mailer previews. Appending paths to this configuration option will cause those paths to be used in the search for mailer previews.
 
 ```ruby
-config.action_mailer.preview_path = "#{Rails.root}/lib/mailer_previews"
+config.action_mailer.preview_paths << "#{Rails.root}/lib/mailer_previews"
 ```
 
 #### `config.action_mailer.show_previews`
@@ -2986,6 +2986,8 @@ Below is a comprehensive list of all the initializers found in Rails in the orde
 
 * `add_view_paths`: Adds the directory `app/views` from the application, railties, and engines to the lookup path for view files for the application.
 
+* `add_mailer_preview_paths`: Adds the directory `test/mailers/previews` from the application, railties, and engines to the lookup path for mailer preview files for the application.
+
 * `load_environment_config`: Loads the `config/environments` file for the current environment.
 
 * `prepend_helpers_path`: Adds the directory `app/helpers` from the application, railties, and engines to the lookup path for helpers for the application.

guides/source/upgrading_ruby_on_rails.md

@@ -287,6 +287,14 @@ If you don't want to use `SQLite3Adapter` in a strict mode, you can disable this
 config.active_record.sqlite3_adapter_strict_strings_by_default = false
 ```
 
+### Support multiple preview paths for `ActionMailer::Preview`
+
+Option `config.action_mailer.preview_path` is deprecated in favor of `config.action_mailer.preview_paths`. Appending paths to this configuration option will cause those paths to be used in the search for mailer previews.
+
+```ruby
+config.action_mailer.preview_paths << "#{Rails.root}/lib/mailer_previews"
+```
+
 Upgrading from Rails 6.1 to Rails 7.0
 -------------------------------------
 

railties/lib/rails/engine.rb

@@ -608,6 +608,13 @@ module Rails
       end
     end
 
+    initializer :add_mailer_preview_paths do
+      previews = paths["test/mailers/previews"].existent
+      unless previews.empty?
+        ActiveSupport.on_load(:action_mailer) { self.preview_paths |= previews }
+      end
+    end
+
     initializer :prepend_helpers_path do |app|
       if !isolated? || (app == self)
         app.config.helpers_paths.unshift(*paths["app/helpers"].existent)

railties/lib/rails/engine/configuration.rb

@@ -68,6 +68,8 @@ module Rails
           paths.add "vendor",              load_path: true
           paths.add "vendor/assets",       glob: "*"
 
+          paths.add "test/mailers/previews", eager_load: true
+
           paths
         end
       end

railties/test/application/mailer_previews_test.rb

@@ -55,7 +55,7 @@ module ApplicationTests
       assert_equal 200, last_response.status
     end
 
-    test "mailer previews are loaded from the default preview_path" do
+    test "mailer previews are loaded from the default preview_paths" do
       mailer "notifier", <<-RUBY
         class Notifier < ActionMailer::Base
           default from: "from@example.com"
@@ -85,37 +85,41 @@ module ApplicationTests
       assert_match '<li><a href="/rails/mailers/notifier/foo">foo</a></li>', last_response.body
     end
 
-    test "mailer previews are loaded from a custom preview_path" do
+    test "mailer previews are loaded from custom preview_paths" do
       app_dir "lib/mailer_previews"
-      add_to_config "config.action_mailer.preview_path = '#{app_path}/lib/mailer_previews'"
+      add_to_config "config.action_mailer.preview_paths = ['#{app_path}/lib/notifier_previews', '#{app_path}/lib/confirm_previews']"
 
-      mailer "notifier", <<-RUBY
-        class Notifier < ActionMailer::Base
-          default from: "from@example.com"
+      ["notifier", "confirm"].each do |keyword|
+        mailer keyword, <<-RUBY
+          class #{keyword.camelize} < ActionMailer::Base
+            default from: "from@example.com"
 
-          def foo
-            mail to: "to@example.org"
+            def foo
+              mail to: "to@example.org"
+            end
           end
-        end
-      RUBY
+        RUBY
 
-      text_template "notifier/foo", <<-RUBY
-        Hello, World!
-      RUBY
+        text_template "#{keyword}/foo", <<-RUBY
+          Hello, World!
+        RUBY
 
-      app_file "lib/mailer_previews/notifier_preview.rb", <<-RUBY
-        class NotifierPreview < ActionMailer::Preview
-          def foo
-            Notifier.foo
+        app_file "lib/#{keyword}_previews/notifier_preview.rb", <<-RUBY
+          class #{keyword.camelize}Preview < ActionMailer::Preview
+            def foo
+              #{keyword.camelize}.foo
+            end
           end
-        end
-      RUBY
+        RUBY
+      end
 
       app("development")
 
       get "/rails/mailers"
       assert_match '<h3><a href="/rails/mailers/notifier">Notifier</a></h3>', last_response.body
       assert_match '<li><a href="/rails/mailers/notifier/foo">foo</a></li>', last_response.body
+      assert_match '<h3><a href="/rails/mailers/confirm">Confirm</a></h3>', last_response.body
+      assert_match '<li><a href="/rails/mailers/confirm/foo">foo</a></li>', last_response.body
     end
 
     test "mailer previews are reloaded across requests" do
@@ -255,9 +259,29 @@ module ApplicationTests
       assert_no_match '<li><a href="/rails/mailers/notifier/bar">bar</a></li>', last_response.body
     end
 
-    test "mailer previews are reloaded from a custom preview_path" do
+    test "mailer preview_path option is deprecated" do
+      prev = ActionMailer::Base.preview_paths
+      ActionMailer::Base.preview_paths = ["#{app_path}/lib/mailer/previews"]
+      assert_deprecated do
+        assert "#{app_path}/lib/mailer/previews", ActionMailer::Base.preview_path
+      end
+    ensure
+      ActionMailer::Base.preview_paths = prev
+    end
+
+    test "mailer preview_path= option is deprecated" do
+      prev = ActionMailer::Base.preview_paths
+      assert_deprecated do
+        ActionMailer::Base.preview_path = "#{app_path}/lib/mailer/previews"
+      end
+      assert ["#{app_path}/lib/mailer/previews"], ActionMailer::Base.preview_paths
+    ensure
+      ActionMailer::Base.preview_paths = prev
+    end
+
+    test "mailer previews are reloaded from custom preview_paths" do
       app_dir "lib/mailer_previews"
-      add_to_config "config.action_mailer.preview_path = '#{app_path}/lib/mailer_previews'"
+      add_to_config "config.action_mailer.preview_paths = ['#{app_path}/lib/mailer_previews']"
 
       app("development")
 

railties/test/application/paths_test.rb

@@ -53,6 +53,7 @@ module ApplicationTests
       assert_path @paths["config/environments"], "config/environments/development.rb"
       assert_path @paths["config/routes.rb"],    "config/routes.rb"
       assert_path @paths["config/routes"],       "config/routes"
+      assert_path @paths["test/mailers/previews"], "test/mailers/previews"
 
       assert_equal root("app", "controllers"), @paths["app/controllers"].expanded.first
     end

railties/test/railties/engine_test.rb

@@ -302,6 +302,30 @@ module RailtiesTest
       assert_equal "Hi bukkits\n", response[2].body
     end
 
+    test "adds its mailer previews to mailer preview paths" do
+      @plugin.write "app/mailers/bukkit_mailer.rb", <<-RUBY
+        class BukkitMailer < ActionMailer::Base
+          def foo
+          end
+        end
+      RUBY
+
+      @plugin.write "test/mailers/previews/bukkit_mailer_preview.rb", <<-RUBY
+        class BukkitMailerPreview < ActionMailer::Preview
+          def foo
+          end
+        end
+      RUBY
+
+      @plugin.write "app/views/bukkit_mailer/foo.html.erb", "Bukkit"
+
+      boot_rails
+
+      get "/rails/mailers"
+      assert_match '<h3><a href="/rails/mailers/bukkit_mailer">Bukkit Mailer</a></h3>', last_response.body
+      assert_match '<li><a href="/rails/mailers/bukkit_mailer/foo">foo</a></li>', last_response.body
+    end
+
     test "adds helpers to controller views" do
       @plugin.write "app/controllers/bukkit_controller.rb", <<-RUBY
         class BukkitController < ActionController::Base