Change ActionMailer's default caching configuration and update generator's environment templates

actionmailer/lib/action_mailer/railtie.rb

@@ -25,7 +25,7 @@ module ActionMailer
       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?
-      options.perform_caching ||= true
+      options.cache_store ||= Rails.cache
 
       if options.show_previews
         options.preview_path  ||= defined?(Rails.root) ? "#{Rails.root}/test/mailers/previews" : nil

railties/lib/rails/generators/rails/app/templates/config/environments/development.rb.tt

@@ -15,12 +15,22 @@ Rails.application.configure do
   # Enable/disable caching. By default caching is disabled.
   if Rails.root.join('tmp/caching-dev.txt').exist?
     config.action_controller.perform_caching = true
+
+    <%- unless options.skip_action_mailer? -%>
+    config.action_mailer.perform_caching = false
+    <%- end -%>
+
     config.cache_store = :memory_store
     config.public_file_server.headers = {
       'Cache-Control' => 'public, max-age=172800'
     }
   else
     config.action_controller.perform_caching = false
+
+    <%- unless options.skip_action_mailer? -%>
+    config.action_mailer.perform_caching = false
+    <%- end -%>
+
     config.cache_store = :null_store
   end
   <%- unless options.skip_action_mailer? -%>

railties/lib/rails/generators/rails/app/templates/config/environments/production.rb.tt

@@ -71,6 +71,7 @@ Rails.application.configure do
   # config.active_job.queue_adapter     = :resque
   # config.active_job.queue_name_prefix = "<%= app_name %>_#{Rails.env}"
   <%- unless options.skip_action_mailer? -%>
+  config.action_mailer.perform_caching = false
 
   # Ignore bad email addresses and do not raise email delivery errors.
   # Set this to true and configure the email server for immediate delivery to raise delivery errors.

railties/lib/rails/generators/rails/app/templates/config/environments/test.rb.tt

@@ -28,6 +28,7 @@ Rails.application.configure do
   # Disable request forgery protection in test environment.
   config.action_controller.allow_forgery_protection = false
   <%- unless options.skip_action_mailer? -%>
+  config.action_mailer.perform_caching = false
 
   # Tell Action Mailer not to deliver emails to the real world.
   # The :test delivery method accumulates sent emails in the