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.
  ...

1 files changed, 62 insertions, 0 deletions

diff --git a/actionpack/lib/abstract_controller/caching.rb b/actionpack/lib/abstract_controller/caching.rb
new file mode 100644
index 0000000000..0dea50889a
--- /dev/null
+++ b/actionpack/lib/abstract_controller/caching.rb
@@ -0,0 +1,62 @@
+module AbstractController
+  module Caching
+    extend ActiveSupport::Concern
+    extend ActiveSupport::Autoload
+
+    eager_autoload do
+      autoload :Fragments
+    end
+
+    module ConfigMethods
+      def cache_store
+        config.cache_store
+      end
+
+      def cache_store=(store)
+        config.cache_store = ActiveSupport::Cache.lookup_store(store)
+      end
+
+      private
+        def cache_configured?
+          perform_caching && cache_store
+        end
+    end
+
+    include ConfigMethods
+    include AbstractController::Caching::Fragments
+
+    included do
+      extend ConfigMethods
+
+      config_accessor :default_static_extension
+      self.default_static_extension ||= '.html'
+
+      config_accessor :perform_caching
+      self.perform_caching = true if perform_caching.nil?
+
+      class_attribute :_view_cache_dependencies
+      self._view_cache_dependencies = []
+      helper_method :view_cache_dependencies if respond_to?(:helper_method)
+    end
+
+    module ClassMethods
+      def view_cache_dependency(&dependency)
+        self._view_cache_dependencies += [dependency]
+      end
+    end
+
+    def view_cache_dependencies
+      self.class._view_cache_dependencies.map { |dep| instance_exec(&dep) }.compact
+    end
+
+    protected
+      # Convenience accessor.
+      def cache(key, options = {}, &block)
+        if cache_configured?
+          cache_store.fetch(ActiveSupport::Cache.expand_cache_key(key, :controller), options, &block)
+        else
+          yield
+        end
+      end
+  end
+end