class RuboCop::Cop::Style::MethodDefParentheses

Checks for parentheses around the arguments in method definitions. Both instance and class/singleton methods are checked.

Regardless of style, parentheses are necessary for:

  1. Endless methods

  2. Argument lists containing a ‘forward-arg` (`…`)

  3. Argument lists containing an anonymous rest arguments forwarding (‘*`)

  4. Argument lists containing an anonymous keyword rest arguments forwarding (‘**`)

  5. Argument lists containing an anonymous block forwarding (‘&`)

Removing the parens would be a syntax error here.

@example EnforcedStyle: require_parentheses (default)

# The `require_parentheses` style requires method definitions
# to always use parentheses

# bad
def bar num1, num2
  num1 + num2
end

def foo descriptive_var_name,
        another_descriptive_var_name,
        last_descriptive_var_name
  do_something
end

# good
def bar(num1, num2)
  num1 + num2
end

def foo(descriptive_var_name,
        another_descriptive_var_name,
        last_descriptive_var_name)
  do_something
end

@example EnforcedStyle: require_no_parentheses

# The `require_no_parentheses` style requires method definitions
# to never use parentheses

# bad
def bar(num1, num2)
  num1 + num2
end

def foo(descriptive_var_name,
        another_descriptive_var_name,
        last_descriptive_var_name)
  do_something
end

# good
def bar num1, num2
  num1 + num2
end

def foo descriptive_var_name,
        another_descriptive_var_name,
        last_descriptive_var_name
  do_something
end

@example EnforcedStyle: require_no_parentheses_except_multiline

# The `require_no_parentheses_except_multiline` style prefers no
# parentheses when method definition arguments fit on single line,
# but prefers parentheses when arguments span multiple lines.

# bad
def bar(num1, num2)
  num1 + num2
end

def foo descriptive_var_name,
        another_descriptive_var_name,
        last_descriptive_var_name
  do_something
end

# good
def bar num1, num2
  num1 + num2
end

def foo(descriptive_var_name,
        another_descriptive_var_name,
        last_descriptive_var_name)
  do_something
end

Constants

MSG_MISSING
MSG_PRESENT

Public Instance Methods

on_def(node) click to toggle source
# File lib/rubocop/cop/style/method_def_parentheses.rb, line 105
def on_def(node)
  return if forced_parentheses?(node)

  args = node.arguments

  if require_parentheses?(args)
    if arguments_without_parentheses?(node)
      missing_parentheses(node)
    else
      correct_style_detected
    end
  elsif parentheses?(args)
    unwanted_parentheses(args)
  else
    correct_style_detected
  end
end
Also aliased as: on_defs
on_defs(node)
Alias for: on_def

Private Instance Methods

anonymous_arguments?(node) click to toggle source
# File lib/rubocop/cop/style/method_def_parentheses.rb, line 169
def anonymous_arguments?(node)
  return true if node.arguments.any? do |arg|
    arg.forward_arg_type? || arg.restarg_type? || arg.kwrestarg_type?
  end
  return false unless (last_argument = node.last_argument)

  last_argument.blockarg_type? && last_argument.name.nil?
end
arguments_without_parentheses?(node) click to toggle source
# File lib/rubocop/cop/style/method_def_parentheses.rb, line 147
def arguments_without_parentheses?(node)
  node.arguments? && !parentheses?(node.arguments)
end
correct_arguments(arg_node, corrector) click to toggle source
# File lib/rubocop/cop/style/method_def_parentheses.rb, line 126
def correct_arguments(arg_node, corrector)
  corrector.replace(arg_node.loc.begin, ' ')
  corrector.remove(arg_node.loc.end)
end
forced_parentheses?(node) click to toggle source
# File lib/rubocop/cop/style/method_def_parentheses.rb, line 131
def forced_parentheses?(node)
  # Regardless of style, parentheses are necessary for:
  # 1. Endless methods
  # 2. Argument lists containing a `forward-arg` (`...`)
  # 3. Argument lists containing an anonymous rest arguments forwarding (`*`)
  # 4. Argument lists containing an anonymous keyword rest arguments forwarding (`**`)
  # 5. Argument lists containing an anonymous block forwarding (`&`)
  # Removing the parens would be a syntax error here.
  node.endless? || anonymous_arguments?(node)
end
missing_parentheses(node) click to toggle source
# File lib/rubocop/cop/style/method_def_parentheses.rb, line 151
def missing_parentheses(node)
  location = node.arguments.source_range

  add_offense(location, message: MSG_MISSING) do |corrector|
    add_parentheses(node.arguments, corrector)

    unexpected_style_detected 'require_no_parentheses'
  end
end
require_parentheses?(args) click to toggle source
# File lib/rubocop/cop/style/method_def_parentheses.rb, line 142
def require_parentheses?(args)
  style == :require_parentheses ||
    (style == :require_no_parentheses_except_multiline && args.multiline?)
end
unwanted_parentheses(args) click to toggle source
# File lib/rubocop/cop/style/method_def_parentheses.rb, line 161
def unwanted_parentheses(args)
  add_offense(args, message: MSG_PRESENT) do |corrector|
    # offense is registered on args node when parentheses are unwanted
    correct_arguments(args, corrector)
    unexpected_style_detected 'require_parentheses'
  end
end