Revert "Add QueryParser#missing_value for handling missing values +…

… tests. (rack#2052)"

This reverts commit 59d9ba9.

lib/rack.rb

@@ -41,7 +41,6 @@ module Rack
   autoload :MethodOverride, "rack/method_override"
   autoload :Mime, "rack/mime"
   autoload :NullLogger, "rack/null_logger"
-  autoload :QueryParser, "rack/query_parser"
   autoload :Recursive, "rack/recursive"
   autoload :Reloader, "rack/reloader"
   autoload :RewindableInput, "rack/rewindable_input"

lib/rack/query_parser.rb

@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require_relative 'bad_request'
-require 'uri'
 
 module Rack
   class QueryParser
@@ -112,14 +111,6 @@ def normalize_params(params, name, v, _depth=nil)
       _normalize_params(params, name, v, 0)
     end
 
-    # This value is used by default when a parameter is missing (nil). This
-    # usually happens when a parameter is specified without an `=value` part.
-    # The default value is an empty string, but this can be overridden by
-    # subclasses.
-    def missing_value
-      String.new
-    end
-
     private def _normalize_params(params, name, v, depth)
       raise ParamsTooDeepError if depth >= param_depth_limit
 
@@ -154,7 +145,7 @@ def missing_value
 
       return if k.empty?
 
-      v ||= missing_value
+      v ||= String.new
 
       if after == ''
         if k == '[]' && depth != 0
@@ -216,8 +207,8 @@ def params_hash_has_key?(hash, key)
       true
     end
 
-    def unescape(string, encoding = Encoding::UTF_8)
-      URI.decode_www_form_component(string, encoding)
+    def unescape(s)
+      Utils.unescape(s)
     end
 
     class Params < Hash