Merge branch 'master' into treewip

* master: (113 commits)
  remove useless method
  Updated file documentation [ci skip]
  changes caching guide to add note on weak etags
  Don't put config.action_mailer.perform_caching entry twice in development.rb
  Fix wording and wrong reference
  Add Ruby formatting to CHANGELOG entry
  Fix ActionView's cache section reference
  Do not define methods in the included block
  Add caching guide in ActionMailer basics
  Add ActionMailer configuration options
  Preparing for 5.0.0.beta3 release
  Update 5.0 release notes
  Enable tmp_restart plugin for puma
  Prep release for Rails 5 beta3
  [ci skip] Move collection caching changelog entry.
  Ensure `drop_table` even if tests failure or interrupted
  :bomb: run the test @rafaelfranca :angry:
  Remove changelog entry for reverted commit
  Add CHANGELOG for https://github.com/rails/rails/pull/23734 [ci skip]
  No need CHANGELOG entry for #23849.
  ...

3 files changed, 27 insertions, 11 deletions

diff --git a/actionmailer/lib/action_mailer/base.rb b/actionmailer/lib/action_mailer/base.rb
index 4259eb0bee..559cd06d91 100644
--- a/actionmailer/lib/action_mailer/base.rb
+++ b/actionmailer/lib/action_mailer/base.rb
@@ -430,6 +430,7 @@ module ActionMailer
     include AbstractController::Translation
     include AbstractController::AssetPaths
     include AbstractController::Callbacks
+    include AbstractController::Caching
 
     include ActionView::Layouts
 
@@ -947,6 +948,18 @@ module ActionMailer
       container.add_part(part)
     end
 
+    # This and #instrument_name is for caching instrument
+    def instrument_payload(key)
+      {
+        mailer: mailer_name,
+        key: key
+      }
+    end
+
+    def instrument_name
+      "action_mailer"
+    end
+
     ActiveSupport.run_load_hooks(:action_mailer, self)
   end
 end
diff --git a/actionmailer/lib/action_mailer/gem_version.rb b/actionmailer/lib/action_mailer/gem_version.rb
index a1ee5fb238..cbe5fc3e64 100644
--- a/actionmailer/lib/action_mailer/gem_version.rb
+++ b/actionmailer/lib/action_mailer/gem_version.rb
@@ -8,7 +8,7 @@ module ActionMailer
     MAJOR = 5
     MINOR = 0
     TINY  = 0
-    PRE   = "beta2"
+    PRE   = "beta3"
 
     STRING = [MAJOR, MINOR, TINY, PRE].compact.join(".")
   end
diff --git a/actionmailer/lib/action_mailer/railtie.rb b/actionmailer/lib/action_mailer/railtie.rb
index 22390c4953..215d0199af 100644
--- a/actionmailer/lib/action_mailer/railtie.rb
+++ b/actionmailer/lib/action_mailer/railtie.rb
@@ -25,6 +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.cache_store ||= Rails.cache
 
       if options.show_previews
         options.preview_path  ||= defined?(Rails.root) ? "#{Rails.root}/test/mailers/previews" : nil
@@ -45,13 +46,6 @@ module ActionMailer
 
         options.each { |k,v| send("#{k}=", v) }
 
-        if options.show_previews
-          app.routes.prepend do
-            get '/rails/mailers'         => "rails/mailers#index"
-            get '/rails/mailers/*path'   => "rails/mailers#preview"
-          end
-        end
-
         ActionDispatch::IntegrationTest.send :include, ActionMailer::TestCase::ClearTestDeliveries
       end
     end
@@ -62,9 +56,18 @@ module ActionMailer
       end
     end
 
-    config.after_initialize do
-      if ActionMailer::Base.preview_path
-        ActiveSupport::Dependencies.autoload_paths << ActionMailer::Base.preview_path
+    config.after_initialize do |app|
+      options = app.config.action_mailer
+
+      if options.show_previews
+        app.routes.prepend do
+          get '/rails/mailers'         => "rails/mailers#index", internal: true
+          get '/rails/mailers/*path'   => "rails/mailers#preview", internal: true
+        end
+
+        if options.preview_path
+          ActiveSupport::Dependencies.autoload_paths << options.preview_path
+        end
       end
     end
   end