module GraphQL::StaticValidation::SubscriptionRootExists

def on_operation_definition(node, _parent)
  if node.operation_type == "subscription" && context.warden.root_type_for_operation("subscription").nil?
    add_error(GraphQL::StaticValidation::SubscriptionRootExistsError.new(
      'Schema is not configured for subscriptions',
      nodes: node
    ))
  else
    super
  end
end