module GraphQL::StaticValidation::ArgumentNamesAreUnique

def on_directive(node, parent)
  validate_arguments(node)
  super
end

def on_field(node, parent)
  validate_arguments(node)
  super
end

def validate_arguments(node)
  argument_defns = node.arguments
  if argument_defns.any?
    args_by_name = Hash.new { |h, k| h[k] = [] }
    argument_defns.each { |a| args_by_name[a.name] << a }
    args_by_name.each do |name, defns|
      if defns.size > 1
        add_error(GraphQL::StaticValidation::ArgumentNamesAreUniqueError.new("There can be only one argument named \"#{name}\"", nodes: defns, name: name))
      end
    end
  end
end