class RuboCop::Cop::Style::RedundantArgument

Checks for a redundant argument passed to certain methods.

NOTE: This cop is limited to methods with single parameter.

Method names and their redundant arguments can be configured like this:

source,yaml

Methods:

join: ''
sum: 0
split: ' '
chomp: "\n"
chomp!: "\n"
foo: 2

@safety

This cop is unsafe because of the following limitations:

1. This cop matches by method names only and hence cannot tell apart
   methods with same name in different classes.
2. This cop may be unsafe if certain special global variables (e.g. `$;`, `$/`) are set.
   That depends on the nature of the target methods, of course. For example, the default
   argument to join is `$OUTPUT_FIELD_SEPARATOR` (or `$,`) rather than `''`, and if that
   global is changed, `''` is no longer a redundant argument.

@example

# bad
array.join('')
[1, 2, 3].join("")
array.sum(0)
exit(true)
exit!(false)
string.split(" ")
"first\nsecond".split(" ")
string.chomp("\n")
string.chomp!("\n")
A.foo(2)

# good
array.join
[1, 2, 3].join
array.sum
exit
exit!
string.split
"first second".split
string.chomp
string.chomp!
A.foo

Constants

MSG
NO_RECEIVER_METHODS

Public Instance Methods

on_send(node) click to toggle source

# File lib/rubocop/cop/style/redundant_argument.rb, line 64
def on_send(node)
  return if !NO_RECEIVER_METHODS.include?(node.method_name) && node.receiver.nil?
  return if node.arguments.count != 1
  return unless redundant_argument?(node)

  offense_range = argument_range(node)
  message = format(MSG, arg: node.arguments.first.source)

  add_offense(offense_range, message: message) do |corrector|
    corrector.remove(offense_range)
  end
end

Private Instance Methods

argument_range(node) click to toggle source

# File lib/rubocop/cop/style/redundant_argument.rb, line 93
def argument_range(node)
  if node.parenthesized?
    range_between(node.loc.begin.begin_pos, node.loc.end.end_pos)
  else
    range_with_surrounding_space(node.first_argument.source_range, newlines: false)
  end
end

redundant_arg_for_method(method_name) click to toggle source

# File lib/rubocop/cop/style/redundant_argument.rb, line 86
def redundant_arg_for_method(method_name)
  arg = cop_config['Methods'].fetch(method_name) { return }

  @mem ||= {}
  @mem[method_name] ||= parse(arg.inspect).ast
end

redundant_argument?(node) click to toggle source

# File lib/rubocop/cop/style/redundant_argument.rb, line 79
def redundant_argument?(node)
  redundant_argument = redundant_arg_for_method(node.method_name.to_s)
  return false if redundant_argument.nil?

  node.arguments.first == redundant_argument
end