Allow people to set their own etags, if they want more control over the process (closes #7580) []

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@6163 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

actionpack/lib/action_controller/base.rb

@@ -653,7 +653,7 @@ module ActionController #:nodoc:
       #
       # Rendering will automatically insert the etag header on 200 OK responses. The etag is calculated using MD5 of the
       # response body. If a request comes in that has a matching etag, the response will be changed to a 304 Not Modified
-      # and the response body will be set to an empty string.
+      # and the response body will be set to an empty string. No etag header will be inserted if it's already set.
       #
       # === Rendering a template
       #
@@ -879,7 +879,7 @@ module ActionController #:nodoc:
 
           if text.is_a?(String)
             if response.headers['Status'][0..2] == '200' && !response.body.empty?
-              response.headers['Etag'] = %("#{Digest::MD5.hexdigest(text)}")
+              response.headers['Etag'] ||= %("#{Digest::MD5.hexdigest(text)}")
 
               if request.headers['HTTP_IF_NONE_MATCH'] == response.headers['Etag']
                 response.headers['Status'] = "304 Not Modified"

actionpack/test/controller/render_test.rb

@@ -328,6 +328,13 @@ class RenderTest < Test::Unit::TestCase
     assert_nil @response.headers['Etag']
   end
 
+  def test_etag_should_not_be_changed_when_already_set
+    expected_etag = etag_for("hello somewhere else")
+    @response.headers["Etag"] = expected_etag
+    get :render_hello_world_from_variable
+    assert_equal expected_etag, @response.headers['Etag']
+  end
+
   protected
     def assert_deprecated_render(&block)
       assert_deprecated(/render/, &block)