Simplify renderer normalize keys

actionpack/lib/action_controller/renderer.rb

@@ -103,8 +103,13 @@ module ActionController
     private
       def normalize_keys(defaults, env)
         new_env = {}
-        defaults.each_pair { |k, v| new_env[rack_key_for(k)] = rack_value_for(k, v) }
         env.each_pair { |k, v| new_env[rack_key_for(k)] = rack_value_for(k, v) }
+
+        defaults.each_pair do |k, v|
+          key = rack_key_for(k)
+          new_env[key] = rack_value_for(k, v) unless new_env.key?(key)
+        end
+
         new_env["rack.url_scheme"] = new_env["HTTPS"] == "on" ? "https" : "http"
         new_env
       end
@@ -117,19 +122,19 @@ module ActionController
         input:       "rack.input"
       }
 
-      IDENTITY = ->(_) { _ }
-
-      RACK_VALUE_TRANSLATION = {
-        https: ->(v) { v ? "on" : "off" },
-        method: ->(v) { -v.upcase },
-      }
-
       def rack_key_for(key)
         RACK_KEY_TRANSLATION[key] || key.to_s
       end
 
       def rack_value_for(key, value)
-        RACK_VALUE_TRANSLATION.fetch(key, IDENTITY).call value
+        case key
+        when :https
+          value ? "on" : "off"
+        when :method
+          -value.upcase
+        else
+          value
+        end
       end
   end
 end