class Grape::Validations::Validators::ExceptValuesValidator

def initialize(attrs, options, required, scope, opts)
  super
  except = option_value
  except_proc = except.is_a?(Proc)
  raise ArgumentError, 'except_values Proc must have arity of zero (use values: with a one-arity predicate for per-element checks)' if except_proc && !except.arity.zero?
  # Zero-arity procs (e.g. -> { User.pluck(:role) }) must be called per-request,
  # not at definition time, so they are wrapped in a lambda to defer execution.
  @excepts_call = except_proc ? except : -> { except }
end

def validate_param!(attr_name, params)
  return unless hash_like?(params) && params.key?(attr_name)
  excepts = @excepts_call.call
  return if excepts.nil?
  param_array = params[attr_name].nil? ? [nil] : Array.wrap(params[attr_name])
  return if param_array.none? { |param| excepts.include?(param) }
  validation_error!(attr_name)
end