Ensure that cache-control headers are merged

There are several aspects to this commit, that don't well fit into broken down
commits, so they are detailed here:

 * When a user uses response.headers['Cache-Control'] = some_value, then the
   documented convention in ConditionalGet is not adhered to, in this case,
   response.cache_control is ignored due to `return if
   self[CACHE_CONTROL].present?`
 * When a middleware sets cache-control headers that would clobber, they're
   converted to symbols directly, without underscores. This would lead to bugs.
 * Items that would live in :extras if set through expires_in, are placed
   directly in the @cache_control hash, and not respected in many cases
   (somewhat adhering to the aforementioned documentation).
 * Although quite useless, any directive named 'extras' would be ignored.

The general convention applied is that expires_* take precedence, but no longer
overwrite everything and expires_* are ALWAYS applied, even if the header is
set.

I am still unhappy about the contents of this commit, and the code in general.
Ideally it should be refactored to no longer use :extras. I'd likely recommend
expanding @cache_control into a class, and giving it the power to handle the
merge in a more efficient fashion. Such a commit would be a larger change that
could have additional semantic changes for other libraries unless they utilize
expires_in in very standard ways.

1 files changed, 12 insertions, 0 deletions

diff --git a/actionpack/test/controller/render_test.rb b/actionpack/test/controller/render_test.rb
index 3d58c02338..e9cfda45a9 100644
--- a/actionpack/test/controller/render_test.rb
+++ b/actionpack/test/controller/render_test.rb
@@ -116,6 +116,12 @@ class TestController < ActionController::Base
     render :action => 'hello_world'
   end
 
+  def conditional_hello_with_cache_control_headers
+    response.headers['Cache-Control'] = 'no-transform'
+    expires_now
+    render :action => 'hello_world'
+  end
+
   def conditional_hello_with_bangs
     render :action => 'hello_world'
   end
@@ -1512,6 +1518,12 @@ class ExpiresInRenderTest < ActionController::TestCase
     assert_equal "no-cache", @response.headers["Cache-Control"]
   end
 
+  def test_expires_now
+    get :conditional_hello_with_cache_control_headers
+    assert_match /no-cache/, @response.headers["Cache-Control"]
+    assert_match /no-transform/, @response.headers["Cache-Control"]
+  end
+
   def test_date_header_when_expires_in
     time = Time.mktime(2011,10,30)
     Time.stubs(:now).returns(time)