class RuboCop::Cop::Lint::UnusedBlockArgument

Checks for unused block arguments.

@example

# bad
do_something do |used, unused|
  puts used
end

do_something do |bar|
  puts :foo
end

define_method(:foo) do |bar|
  puts :baz
end

# good
do_something do |used, _unused|
  puts used
end

do_something do
  puts :foo
end

define_method(:foo) do |_bar|
  puts :baz
end

@example IgnoreEmptyBlocks: true (default)

# good
do_something { |unused| }

@example IgnoreEmptyBlocks: false

# bad
do_something { |unused| }

@example AllowUnusedKeywordArguments: false (default)

# bad
do_something do |unused: 42|
  foo
end

@example AllowUnusedKeywordArguments: true

# good
do_something do |unused: 42|
  foo
end

Public Class Methods

joining_forces() click to toggle source
# File lib/rubocop/cop/lint/unused_block_argument.rb, line 59
def self.joining_forces
  VariableForce
end

Private Instance Methods

allow_unused_keyword_arguments?() click to toggle source
# File lib/rubocop/cop/lint/unused_block_argument.rb, line 162
def allow_unused_keyword_arguments?
  cop_config['AllowUnusedKeywordArguments']
end
allowed_block?(variable) click to toggle source
# File lib/rubocop/cop/lint/unused_block_argument.rb, line 81
def allowed_block?(variable)
  !variable.block_argument? || (ignore_empty_blocks? && empty_block?(variable))
end
allowed_keyword_argument?(variable) click to toggle source
# File lib/rubocop/cop/lint/unused_block_argument.rb, line 85
def allowed_keyword_argument?(variable)
  variable.keyword_argument? && allow_unused_keyword_arguments?
end
augment_message(message, variable) click to toggle source
# File lib/rubocop/cop/lint/unused_block_argument.rb, line 99
def augment_message(message, variable)
  scope = variable.scope
  all_arguments = scope.variables.each_value.select(&:block_argument?)

  augmentation = if scope.node.lambda?
                   message_for_lambda(variable, all_arguments)
                 else
                   message_for_normal_block(variable, all_arguments)
                 end

  [message, augmentation].join(' ')
end
autocorrect(corrector, node) click to toggle source
# File lib/rubocop/cop/lint/unused_block_argument.rb, line 65
def autocorrect(corrector, node)
  UnusedArgCorrector.correct(corrector, processed_source, node)
end
check_argument(variable) click to toggle source
# File lib/rubocop/cop/lint/unused_block_argument.rb, line 69
def check_argument(variable)
  return if allowed_block?(variable) ||
            allowed_keyword_argument?(variable) ||
            used_block_local?(variable)

  super
end
define_method_call?(variable) click to toggle source
# File lib/rubocop/cop/lint/unused_block_argument.rb, line 149
def define_method_call?(variable)
  call, = *variable.scope.node
  _, method, = *call

  method == :define_method
end
empty_block?(variable) click to toggle source
# File lib/rubocop/cop/lint/unused_block_argument.rb, line 156
def empty_block?(variable)
  _send, _args, body = *variable.scope.node

  body.nil?
end
ignore_empty_blocks?() click to toggle source
# File lib/rubocop/cop/lint/unused_block_argument.rb, line 166
def ignore_empty_blocks?
  cop_config['IgnoreEmptyBlocks']
end
message(variable) click to toggle source
# File lib/rubocop/cop/lint/unused_block_argument.rb, line 89
def message(variable)
  message = "Unused #{variable_type(variable)} - `#{variable.name}`."

  if variable.explicit_block_local_variable?
    message
  else
    augment_message(message, variable)
  end
end
message_for_lambda(variable, all_arguments) click to toggle source
# File lib/rubocop/cop/lint/unused_block_argument.rb, line 132
def message_for_lambda(variable, all_arguments)
  message = message_for_underscore_prefix(variable)

  if all_arguments.none?(&:referenced?)
    proc_message = 'Also consider using a proc without arguments ' \
                   'instead of a lambda if you want it ' \
                   "to accept any arguments but don't care about them."
  end

  [message, proc_message].compact.join(' ')
end
message_for_normal_block(variable, all_arguments) click to toggle source
# File lib/rubocop/cop/lint/unused_block_argument.rb, line 120
def message_for_normal_block(variable, all_arguments)
  if all_arguments.none?(&:referenced?) && !define_method_call?(variable)
    if all_arguments.count > 1
      "You can omit all the arguments if you don't care about them."
    else
      "You can omit the argument if you don't care about it."
    end
  else
    message_for_underscore_prefix(variable)
  end
end
message_for_underscore_prefix(variable) click to toggle source
# File lib/rubocop/cop/lint/unused_block_argument.rb, line 144
def message_for_underscore_prefix(variable)
  "If it's necessary, use `_` or `_#{variable.name}` " \
    "as an argument name to indicate that it won't be used."
end
used_block_local?(variable) click to toggle source
# File lib/rubocop/cop/lint/unused_block_argument.rb, line 77
def used_block_local?(variable)
  variable.explicit_block_local_variable? && !variable.assignments.empty?
end
variable_type(variable) click to toggle source
# File lib/rubocop/cop/lint/unused_block_argument.rb, line 112
def variable_type(variable)
  if variable.explicit_block_local_variable?
    'block local variable'
  else
    'block argument'
  end
end