class RuboCop::Cop::Style::ParenthesesAroundCondition

condition of if/unless/while/until.
This cop checks for the presence of superfluous parentheses around the

def message(node) 

def message(node)
  kw = node.keyword
  article = kw == 'while' ? 'a' : 'an'
  "Don't use parentheses around the condition of #{article} `#{kw}`."
end

def modifier_op?(node) 

def modifier_op?(node)
  return false if node.if_type? && node.ternary?
  return true if node.rescue_type?
  MODIFIER_NODES.include?(node.type) &&
    node.modifier_form?
end

def on_if(node) 

def on_if(node)
  return if node.ternary?
  process_control_op(node)
end

def on_until(node) 

def on_until(node)
  process_control_op(node)
end

def on_while(node) 

def on_while(node)
  process_control_op(node)
end

def process_control_op(node) 

def process_control_op(node)
  cond = node.condition
  return unless cond.begin_type?
  return if cond.children.empty?
  return if modifier_op?(cond.children.first)
  return if parens_required?(node.children.first)
  return if safe_assignment?(cond) && safe_assignment_allowed?
  add_offense(cond, :expression, message(node))
end