class RuboCop::Cop::Style::GuardClause

end
work if something
def test
# also good
end
work
return unless something
def test
# good
end
end
work
if something
def test
# bad
@example
expression
Use a guard clause instead of wrapping the code inside a conditional

def check_if_node(node) 

def check_if_node(node)
  _cond, body, else_body = *node
  return if body && else_body
  # discard modifier ifs and ternary_ops
  return if modifier_if?(node) || ternary_op?(node)
  # discard short ifs
  return unless min_body_length?(node)
  add_offense(node, :keyword, MSG)
end

def if?(body) 

def if?(body)
  body && body.type == :if
end

def min_body_length 

def min_body_length
  length = cop_config['MinBodyLength'] || 1
  return length if length.is_a?(Integer) && length > 0
  fail 'MinBodyLength needs to be a positive integer!'
end

def min_body_length?(node) 

def min_body_length?(node)
  (node.loc.end.line - node.loc.keyword.line) > min_body_length
end

def on_def(node) 

def on_def(node)
  _, _, body = *node
  return unless body
  if if?(body)
    check_if_node(body)
  elsif body.type == :begin
    expressions = *body
    last_expr = expressions.last
    check_if_node(last_expr) if if?(last_expr)
  end
end