stop applying default headers in ActionDispatch::Response

I'm making this change so that I can construct response objects that
*don't* have the default headers applied.  For example, I would like to
construct a response object from the return value of a controller.

If you need to construct a response object with the default headers,
then please use the alternate constructor:
`ActionDispatch::Response.create`

5 files changed, 17 insertions, 13 deletions

diff --git a/actionpack/lib/action_controller/metal.rb b/actionpack/lib/action_controller/metal.rb
index 0384740fef..3d72755f1d 100644
--- a/actionpack/lib/action_controller/metal.rb
+++ b/actionpack/lib/action_controller/metal.rb
@@ -135,7 +135,7 @@ module ActionController
     end
 
     def self.make_response!(request)
-      ActionDispatch::Response.new.tap do |res|
+      ActionDispatch::Response.create.tap do |res|
         res.request = request
       end
     end
diff --git a/actionpack/lib/action_controller/metal/live.rb b/actionpack/lib/action_controller/metal/live.rb
index 667c7f87ca..c874165816 100644
--- a/actionpack/lib/action_controller/metal/live.rb
+++ b/actionpack/lib/action_controller/metal/live.rb
@@ -236,6 +236,10 @@ module ActionController
         end
       end
 
+      def initialize(status = 200, header = {}, body = [])
+        super(status, Header.new(self, header), body)
+      end
+
       private
 
       def before_committed
@@ -257,10 +261,6 @@ module ActionController
         buf
       end
 
-      def merge_default_headers(original, default)
-        Header.new self, super
-      end
-
       def handle_conditional_get!
         super unless committed?
       end
diff --git a/actionpack/lib/action_controller/test_case.rb b/actionpack/lib/action_controller/test_case.rb
index 47b6b5d4b3..cf78688126 100644
--- a/actionpack/lib/action_controller/test_case.rb
+++ b/actionpack/lib/action_controller/test_case.rb
@@ -585,7 +585,7 @@ module ActionController
       end
 
       def build_response(klass)
-        klass.new
+        klass.create
       end
 
       included do
diff --git a/actionpack/lib/action_dispatch/http/response.rb b/actionpack/lib/action_dispatch/http/response.rb
index b1b70f7d61..cbeea9e267 100644
--- a/actionpack/lib/action_dispatch/http/response.rb
+++ b/actionpack/lib/action_dispatch/http/response.rb
@@ -103,13 +103,21 @@ module ActionDispatch # :nodoc:
       end
     end
 
+    def self.create(status = 200, header = {}, body = [], default_headers: self.default_headers)
+      header = merge_default_headers(header, default_headers)
+      new status, header, body
+    end
+
+    def self.merge_default_headers(original, default)
+      default.respond_to?(:merge) ? default.merge(original) : original
+    end
+
     # The underlying body, as a streamable object.
     attr_reader :stream
 
-    def initialize(status = 200, header = {}, body = [], default_headers: self.class.default_headers)
+    def initialize(status = 200, header = {}, body = [])
       super()
 
-      header = merge_default_headers(header, default_headers)
       @header = header
 
       self.body, self.status = body, status
@@ -345,10 +353,6 @@ module ActionDispatch # :nodoc:
     def before_sending
     end
 
-    def merge_default_headers(original, default)
-      default.respond_to?(:merge) ? default.merge(original) : original
-    end
-
     def build_buffer(response, body)
       Buffer.new response, body
     end
diff --git a/actionpack/lib/action_dispatch/testing/test_response.rb b/actionpack/lib/action_dispatch/testing/test_response.rb
index 6a31d6243f..4b79a90242 100644
--- a/actionpack/lib/action_dispatch/testing/test_response.rb
+++ b/actionpack/lib/action_dispatch/testing/test_response.rb
@@ -7,7 +7,7 @@ module ActionDispatch
   # See Response for more information on controller response objects.
   class TestResponse < Response
     def self.from_response(response)
-      new response.status, response.headers, response.body, default_headers: nil
+      new response.status, response.headers, response.body
     end
 
     # Was the response successful?