class RuboCop::Cop::Rails::RedundantAllowNil


validates :x, length: { is: 5 }, allow_nil: true, allow_blank: false
# Here, ‘nil` is valid but `”` is not
# good
validates :x, length: { is: 5 }, allow_blank: false
# good
validates :x, length: { is: 5 }, allow_blank: true
# good
validates :x, length: { is: 5 }, allow_nil: false, allow_blank: false
# bad
validates :x, length: { is: 5 }, allow_nil: false, allow_blank: true
# bad
validates :x, length: { is: 5 }, allow_nil: true, allow_blank: true
# bad
@example
`allow_blank` is present.
Checks Rails model validations for a redundant `allow_nil` when

def autocorrect(node) 

def autocorrect(node)
  prv_sib = previous_sibling(node)
  nxt_sib = next_sibling(node)
  lambda do |corrector|
    if nxt_sib
      corrector.remove(range_between(node_beg(node), node_beg(nxt_sib)))
    elsif prv_sib
      corrector.remove(range_between(node_end(prv_sib), node_end(node)))
    else
      corrector.remove(node.loc.expression)
    end
  end
end

def find_allow_nil_and_allow_blank(node) 

def find_allow_nil_and_allow_blank(node)
  allow_nil = nil
  allow_blank = nil
  node.each_descendant do |descendant|
    next unless descendant.pair_type?
    key = descendant.children.first.value
    allow_nil = descendant if key == :allow_nil
    allow_blank = descendant if key == :allow_blank
    break if allow_nil && allow_blank
  end
  [allow_nil, allow_blank]
end

def next_sibling(node) 

def next_sibling(node)
  node.parent.children[node.sibling_index + 1]
end

def node_beg(node) 

def node_beg(node)
  node.loc.expression.begin_pos
end

def node_end(node) 

def node_end(node)
  node.loc.expression.end_pos
end

def on_send(node) 

def on_send(node)
  return unless node.method_name == :validates
  allow_nil, allow_blank = find_allow_nil_and_allow_blank(node)
  allow_nil_val = allow_nil.children.last
  allow_blank_val = allow_blank.children.last
  if allow_nil_val.type == allow_blank_val.type
    add_offense(allow_nil, message: MSG_SAME)
  elsif allow_nil_val.false_type? && allow_blank_val.true_type?
    add_offense(allow_nil, message: MSG_ALLOW_NIL_FALSE)
  end
end

def previous_sibling(node) 

def previous_sibling(node)
  node.parent.children[node.sibling_index - 1]
end