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 find_allow_nil_and_allow_blank(node) 

def find_allow_nil_and_allow_blank(node)
  allow_nil, allow_blank = nil
  node.each_child_node do |child_node|
    if child_node.pair_type?
      key = child_node.children.first.source
      allow_nil = child_node if key == 'allow_nil'
      allow_blank = child_node if key == 'allow_blank'
    end
    return [allow_nil, allow_blank] if allow_nil && allow_blank
    found_in_children_nodes = find_allow_nil_and_allow_blank(child_node)
    return found_in_children_nodes if found_in_children_nodes
  end
  nil
end

def node_beg(node) 

def node_beg(node)
  node.source_range.begin_pos
end

def node_end(node) 

def node_end(node)
  node.source_range.end_pos
end

def on_send(node) 

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

def register_offense(allow_nil, message) 

def register_offense(allow_nil, message)
  add_offense(allow_nil, message: message) do |corrector|
    prv_sib = allow_nil.left_sibling
    nxt_sib = allow_nil.right_sibling
    if nxt_sib
      corrector.remove(range_between(node_beg(allow_nil), node_beg(nxt_sib)))
    elsif prv_sib
      corrector.remove(range_between(node_end(prv_sib), node_end(allow_nil)))
    else
      corrector.remove(allow_nil)
    end
  end
end