class RuboCop::Cop::Rails::DelegateAllowBlank

delegate :foo, to: :bar, allow_nil: true
# good
delegate :foo, to: :bar, allow_blank: true
# bad
@example
to ActiveSupport#delegate.
instead of :allow_nil. :allow_blank is not a valid option to pass
Looks for delegations that pass :allow_blank as an option

def on_send(node) 

def on_send(node)
  return unless (offending_node = allow_blank_option(node))
  add_offense(offending_node) do |corrector|
    corrector.replace(offending_node.key, 'allow_nil')
  end
end