Remove default argument, and extract internal convenience method

actionpack/lib/action_dispatch/http/response.rb

@@ -226,7 +226,7 @@ def status=(status)
     def content_type=(content_type)
       return unless content_type
       new_header_info = parse_content_type(content_type.to_s)
-      prev_header_info = parse_content_type(get_header(CONTENT_TYPE))
+      prev_header_info = parsed_content_type_header
       set_content_type new_header_info.mime_type, new_header_info.charset || prev_header_info.charset || self.class.default_charset
     end
 
@@ -240,7 +240,7 @@ def content_type=(content_type)
     # information.
 
     def content_type
-      parse_content_type.mime_type
+      parsed_content_type_header.mime_type
     end
 
     def sending_file=(v)
@@ -255,7 +255,7 @@ def sending_file=(v)
     #   response.charset = 'utf-16' # => 'utf-16'
     #   response.charset = nil      # => 'utf-8'
     def charset=(charset)
-      header_info = parse_content_type
+      header_info = parsed_content_type_header
       if false == charset
         set_header CONTENT_TYPE, header_info.mime_type
       else
@@ -267,7 +267,7 @@ def charset=(charset)
     # The charset of the response. HTML wants to know the encoding of the
     # content you're giving them, so we need to send that along.
     def charset
-      header_info = parse_content_type
+      header_info = parsed_content_type_header
       header_info.charset || self.class.default_charset
     end
 
@@ -405,7 +405,7 @@ def cookies
     ContentTypeHeader = Struct.new :mime_type, :charset
     NullContentTypeHeader = ContentTypeHeader.new nil, nil
 
-    def parse_content_type(content_type = get_header(CONTENT_TYPE))
+    def parse_content_type(content_type)
       if content_type
         type, charset = content_type.split(/;\s*charset=/)
         type = nil if type.empty?
@@ -415,6 +415,12 @@ def parse_content_type(content_type = get_header(CONTENT_TYPE))
       end
     end
 
+    # Small internal convenience method to get the parsed version of the current
+    # content type header.
+    def parsed_content_type_header
+      parse_content_type(get_header(CONTENT_TYPE))
+    end
+
     def set_content_type(content_type, charset)
       type = (content_type || "").dup
       type << "; charset=#{charset}" if charset
@@ -451,7 +457,7 @@ def munge_body_object(body)
     def assign_default_content_type_and_charset!
       return if content_type
 
-      ct = parse_content_type
+      ct = parsed_content_type_header
       set_content_type(ct.mime_type || Mime[:html].to_s,
                        ct.charset || self.class.default_charset)
     end