3 files changed, 14 insertions, 5 deletions
diff --git a/actionpack/lib/action_controller/caching/actions.rb b/actionpack/lib/action_controller/caching/actions.rb
index bd3b0b5df3..ba96735e56 100644
--- a/actionpack/lib/action_controller/caching/actions.rb
+++ b/actionpack/lib/action_controller/caching/actions.rb
@@ -103,8 +103,10 @@ module ActionController #:nodoc:
       end
 
       def _save_fragment(name, options)
-        content = response_body
-        content = content.join if content.is_a?(Array)
+        content = ""
+        response_body.each do |parts|
+          content << parts
+        end
 
         if caching_allowed?
           write_fragment(name, content, options)
diff --git a/actionpack/lib/action_controller/metal/conditional_get.rb b/actionpack/lib/action_controller/metal/conditional_get.rb
index 1645400693..2a8e4c575e 100644
--- a/actionpack/lib/action_controller/metal/conditional_get.rb
+++ b/actionpack/lib/action_controller/metal/conditional_get.rb
@@ -110,16 +110,23 @@ 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.
+    #
+    # The method will also ensure a HTTP Date header for client compatibility.
     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}"}
+      response.date = Time.now unless response.date?
     end
 
     # Sets a HTTP 1.1 Cache-Control header of <tt>no-cache</tt> so no caching should occur by the browser or
diff --git a/actionpack/lib/action_controller/metal/responder.rb b/actionpack/lib/action_controller/metal/responder.rb
index 4ad64bff20..daa1ddd65f 100644
--- a/actionpack/lib/action_controller/metal/responder.rb
+++ b/actionpack/lib/action_controller/metal/responder.rb
@@ -267,7 +267,7 @@ module ActionController #:nodoc:
     end
 
     def resource_errors
-      respond_to?("#{format}_resource_errors") ? send("#{format}_resource_errors") : resource.errors
+      respond_to?("#{format}_resource_errors", true) ? send("#{format}_resource_errors") : resource.errors
     end
 
     def json_resource_errors