module GraphQL::StaticValidation::InputObjectNamesAreUnique

def on_input_object(node, parent)
  validate_input_fields(node)
  super
end

def validate_input_fields(node)
  input_field_defns = node.arguments
  input_fields_by_name = Hash.new { |h, k| h[k] = [] }
  input_field_defns.each { |a| input_fields_by_name[a.name] << a }
  input_fields_by_name.each do |name, defns|
    if defns.size > 1
      error = GraphQL::StaticValidation::InputObjectNamesAreUniqueError.new(
        "There can be only one input field named \"#{name}\"",
        nodes: defns,
        name: name
      )
      add_error(error)
    end
  end
end