let expires_in accept a must_revalidate flag

actionpack/CHANGELOG.md

@@ -1,5 +1,8 @@
 ## Rails 4.0.0 (unreleased) ##
 
+*   `expires_in` accepts a `must_revalidate` flag. If true, "must-revalidate"
+    is added to the Cache-Control header. *fxn*
+
 *   Add `date_field` and `date_field_tag` helpers which render an `input[type="date"]` tag *Olek Janiszewski*
 
 *   Adds `image_url`, `javascript_url`, `stylesheet_url`, `audio_url`, `video_url`, and `font_url`

actionpack/lib/action_controller/metal/conditional_get.rb

@@ -110,13 +110,17 @@ module ActionController
     #
     # Examples:
     #   expires_in 20.minutes
-    #   expires_in 3.hours, :public => true
+    #   expires_in 3.hours, :public => true, :must_revalidate => true
     #   expires_in 3.hours, 'max-stale' => 5.hours, :public => true
     #
     # This method will overwrite an existing Cache-Control header.
     # See http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html for more possibilities.
     def expires_in(seconds, options = {}) #:doc:
-      response.cache_control.merge!(:max_age => seconds, :public => options.delete(:public))
+      response.cache_control.merge!(
+        :max_age         => seconds,
+        :public          => options.delete(:public),
+        :must_revalidate => options.delete(:must_revalidate)
+      )
       options.delete(:private)
 
       response.cache_control[:extras] = options.map {|k,v| "#{k}=#{v}"}

actionpack/test/controller/render_test.rb

@@ -91,6 +91,16 @@ class TestController < ActionController::Base
     render :action => 'hello_world'
   end
 
+  def conditional_hello_with_expires_in_with_must_revalidate
+    expires_in 1.minute, :must_revalidate => true
+    render :action => 'hello_world'
+  end
+
+  def conditional_hello_with_expires_in_with_public_and_must_revalidate
+    expires_in 1.minute, :public => true, :must_revalidate => true
+    render :action => 'hello_world'
+  end
+
   def conditional_hello_with_expires_in_with_public_with_more_keys
     expires_in 1.minute, :public => true, 'max-stale' => 5.hours
     render :action => 'hello_world'
@@ -1399,6 +1409,16 @@ class ExpiresInRenderTest < ActionController::TestCase
     assert_equal "max-age=60, public", @response.headers["Cache-Control"]
   end
 
+  def test_expires_in_header_with_must_revalidate
+    get :conditional_hello_with_expires_in_with_must_revalidate
+    assert_equal "max-age=60, private, must-revalidate", @response.headers["Cache-Control"]
+  end
+
+  def test_expires_in_header_with_public_and_must_revalidate
+    get :conditional_hello_with_expires_in_with_public_and_must_revalidate
+    assert_equal "max-age=60, public, must-revalidate", @response.headers["Cache-Control"]
+  end
+
   def test_expires_in_header_with_additional_headers
     get :conditional_hello_with_expires_in_with_public_with_more_keys
     assert_equal "max-age=60, public, max-stale=18000", @response.headers["Cache-Control"]