class RuboCop::Cop::Style::WhileUntilModifier

The maximum line length is configurable.
if written as a modifier while/until.
Checks for while and until statements that would fit on one line

def check(node) 

def check(node)
  return unless node.loc.end
  return unless fit_within_line_as_modifier_form?(node)
  add_offense(node, :keyword, message(node.loc.keyword.source))
end

def message(keyword) 

def message(keyword)
  "Favor modifier `#{keyword}` usage when having a single-line body."
end

def on_until(node) 

def on_until(node)
  check(node)
end

def on_while(node) 

def on_while(node)
  check(node)
end