class ActionDispatch::QueryParser

def self.each_pair(s, separator = nil)

the standard's interpretation can use `v.to_s`.
giving a nil value for keys that do not use '='. Callers that need
Note this departs from WHATWG's specified parsing algorithm by
-- 
def self.each_pair(s, separator = nil)
  return enum_for(:each_pair, s, separator) unless block_given?
  s ||= ""
  splitter =
    if separator
      COMMON_SEP[separator] || /[#{separator}] */n
    elsif strict_query_string_separator
      DEFAULT_SEP
    elsif SEMICOLON_COMPAT && s.include?(";")
      if strict_query_string_separator.nil?
        ActionDispatch.deprecator.warn("Using semicolon as a query string separator is deprecated and will not be supported in Rails 8.1 or Rack 3.0. Use `&` instead.")
      end
      COMPAT_SEP
    else
      DEFAULT_SEP
    end
  s.split(splitter).each do |part|
    next if part.empty?
    k, v = part.split("=", 2)
    k = URI.decode_www_form_component(k)
    v &&= URI.decode_www_form_component(v)
    yield k, v
  end
  nil
end