5 files changed, 33 insertions, 3 deletions
diff --git a/actionpack/lib/action_controller/metal.rb b/actionpack/lib/action_controller/metal.rb
index f6a93a8940..1641d01c30 100644
--- a/actionpack/lib/action_controller/metal.rb
+++ b/actionpack/lib/action_controller/metal.rb
@@ -174,6 +174,7 @@ module ActionController
     def response_body=(body)
       body = [body] unless body.nil? || body.respond_to?(:each)
       response.reset_body!
+      return unless body
       body.each { |part|
         next if part.empty?
         response.write part
diff --git a/actionpack/lib/action_dispatch/http/headers.rb b/actionpack/lib/action_dispatch/http/headers.rb
index 12f81dc1a5..8e899174c6 100644
--- a/actionpack/lib/action_dispatch/http/headers.rb
+++ b/actionpack/lib/action_dispatch/http/headers.rb
@@ -2,9 +2,23 @@ module ActionDispatch
   module Http
     # Provides access to the request's HTTP headers from the environment.
     #
-    #   env     = { "CONTENT_TYPE" => "text/plain" }
+    #   env     = { "CONTENT_TYPE" => "text/plain", "HTTP_USER_AGENT" => "curl/7.43.0" }
     #   headers = ActionDispatch::Http::Headers.new(env)
     #   headers["Content-Type"] # => "text/plain"
+    #   headers["User-Agent"] # => "curl/7/43/0"
+    #
+    # Also note that when headers are mapped to CGI-like variables by the Rack
+    # server, both dashes and underscores are converted to underscores. This
+    # ambiguity cannot be resolved at this stage anymore. Both underscores and
+    # dashes have to be interpreted as if they were originally sent as dashes.
+    #
+    #   # GET / HTTP/1.1
+    #   # ...
+    #   # User-Agent: curl/7.43.0
+    #   # X_Custom_Header: token
+    #
+    #   headers["X_Custom_Header"] # => nil
+    #   headers["X-Custom-Header"] # => "token"
     class Headers
       CGI_VARIABLES = Set.new(%W[
         AUTH_TYPE
diff --git a/actionpack/lib/action_dispatch/testing/test_process.rb b/actionpack/lib/action_dispatch/testing/test_process.rb
index eca0439909..1ecd7d14a7 100644
--- a/actionpack/lib/action_dispatch/testing/test_process.rb
+++ b/actionpack/lib/action_dispatch/testing/test_process.rb
@@ -1,6 +1,5 @@
 require 'action_dispatch/middleware/cookies'
 require 'action_dispatch/middleware/flash'
-require 'active_support/core_ext/hash/indifferent_access'
 
 module ActionDispatch
   module TestProcess
diff --git a/actionpack/test/controller/new_base/bare_metal_test.rb b/actionpack/test/controller/new_base/bare_metal_test.rb
index c226fa57ee..ee3c498b1c 100644
--- a/actionpack/test/controller/new_base/bare_metal_test.rb
+++ b/actionpack/test/controller/new_base/bare_metal_test.rb
@@ -40,6 +40,22 @@ module BareMetalTest
     end
   end
 
+  class BareEmptyController < ActionController::Metal
+    def index
+      self.response_body = nil
+    end
+  end
+
+  class BareEmptyTest < ActiveSupport::TestCase
+    test "response body is nil" do
+      controller = BareEmptyController.new
+      controller.set_request!(ActionDispatch::Request.empty)
+      controller.set_response!(BareController.make_response!(controller.request))
+      controller.index
+      assert_equal nil, controller.response_body
+    end
+  end
+
   class HeadController < ActionController::Metal
     include ActionController::Head
 
diff --git a/actionpack/test/controller/render_test.rb b/actionpack/test/controller/render_test.rb
index 9430ab8db8..c814d4ea54 100644
--- a/actionpack/test/controller/render_test.rb
+++ b/actionpack/test/controller/render_test.rb
@@ -275,7 +275,7 @@ class ExpiresInRenderTest < ActionController::TestCase
     file.write "secrets!"
     file.flush
     assert_raises ActionView::MissingTemplate do
-      response = get :dynamic_render, params: { id: file.path }
+      get :dynamic_render, params: { id: file.path }
     end
   ensure
     file.close