3 files changed, 13 insertions, 4 deletions
diff --git a/actionpack/lib/action_dispatch/http/mime_type.rb b/actionpack/lib/action_dispatch/http/mime_type.rb
index 6b718e3682..1583a8f87f 100644
--- a/actionpack/lib/action_dispatch/http/mime_type.rb
+++ b/actionpack/lib/action_dispatch/http/mime_type.rb
@@ -1,7 +1,6 @@
 # -*- frozen-string-literal: true -*-
 
 require "singleton"
-require "active_support/core_ext/module/attribute_accessors"
 require "active_support/core_ext/string/starts_ends_with"
 
 module Mime
@@ -298,7 +297,7 @@ module Mime
       end
 
       def respond_to_missing?(method, include_private = false)
-        method.to_s.ends_with? "?"
+        (method.to_s.ends_with? "?") || super
       end
   end
 
diff --git a/actionpack/lib/action_dispatch/http/parameters.rb b/actionpack/lib/action_dispatch/http/parameters.rb
index ad4aadacf5..8f21eca440 100644
--- a/actionpack/lib/action_dispatch/http/parameters.rb
+++ b/actionpack/lib/action_dispatch/http/parameters.rb
@@ -22,6 +22,7 @@ module ActionDispatch
 
       included do
         class << self
+          # Returns the parameter parsers.
           attr_reader :parameter_parsers
         end
 
@@ -29,7 +30,16 @@ module ActionDispatch
       end
 
       module ClassMethods
-        def parameter_parsers=(parsers) # :nodoc:
+        # Configure the parameter parser for a given mime type.
+        #
+        # It accepts a hash where the key is the symbol of the mime type
+        # and the value is a proc.
+        #
+        #     original_parsers = ActionDispatch::Request.parameter_parsers
+        #     xml_parser = -> (raw_post) { Hash.from_xml(raw_post) || {} }
+        #     new_parsers = original_parsers.merge(xml: xml_parser)
+        #     ActionDispatch::Request.parameter_parsers = new_parsers
+        def parameter_parsers=(parsers)
           @parameter_parsers = parsers.transform_keys { |key| key.respond_to?(:symbol) ? key.symbol : key }
         end
       end
diff --git a/actionpack/lib/action_dispatch/http/response.rb b/actionpack/lib/action_dispatch/http/response.rb
index 516a2af69a..dc159596c4 100644
--- a/actionpack/lib/action_dispatch/http/response.rb
+++ b/actionpack/lib/action_dispatch/http/response.rb
@@ -425,7 +425,7 @@ module ActionDispatch # :nodoc:
 
     def set_content_type(content_type, charset)
       type = (content_type || "").dup
-      type << "; charset=#{charset}" if charset
+      type << "; charset=#{charset.to_s.downcase}" if charset
       set_header CONTENT_TYPE, type
     end