module AbstractController::Collector

def self.generate_method_for_mime(mime)
  sym = mime.is_a?(Symbol) ? mime : mime.to_sym
  class_eval <<-RUBY, __FILE__, __LINE__ + 1
    def #{sym}(...)
      custom(Mime[:#{sym}], ...)
    end
  RUBY
end

def method_missing(symbol, ...)
  unless mime_constant = Mime[symbol]
    raise NoMethodError, "To respond to a custom format, register it as a MIME type first: " \
      "https://guides.rubyonrails.org/action_controller_overview.html#restful-downloads. " \
      "If you meant to respond to a variant like :tablet or :phone, not a custom format, " \
      "be sure to nest your variant response within a format response: " \
      "format.html { |html| html.tablet { ... } }"
  end
  if Mime::SET.include?(mime_constant)
    AbstractController::Collector.generate_method_for_mime(mime_constant)
    public_send(symbol, ...)
  else
    super
  end
end