class RuboCop::Cop::Performance::FlatMap

This cop is used to identify usages of

@example

# bad
[1, 2, 3, 4].map { |e| [e, e] }.flatten(1)
[1, 2, 3, 4].collect { |e| [e, e] }.flatten(1)

# good
[1, 2, 3, 4].flat_map { |e| [e, e] }
[1, 2, 3, 4].map { |e| [e, e] }.flatten
[1, 2, 3, 4].collect { |e| [e, e] }.flatten

Constants

FLATTEN
FLATTEN_MULTIPLE_LEVELS
MSG

Public Instance Methods

autocorrect(node) click to toggle source
# File lib/rubocop/cop/performance/flat_map.rb, line 46
def autocorrect(node)
  receiver, _flatten, flatten_param = *node
  flatten_level, = *flatten_param
  return if flatten_level.nil?

  array, = *receiver

  lambda do |corrector|
    range = Parser::Source::Range.new(node.source_range.source_buffer,
                                      node.loc.dot.begin_pos,
                                      node.source_range.end_pos)

    corrector.remove(range)
    corrector.replace(array.loc.selector, 'flat_map')
  end
end
on_send(node) click to toggle source
# File lib/rubocop/cop/performance/flat_map.rb, line 24
def on_send(node)
  left, second_method, flatten_param = *node
  return unless FLATTEN.include?(second_method)
  flatten_level, = *flatten_param
  expression, = *left
  _array, first_method = *expression
  return unless first_method == :map || first_method == :collect

  message = MSG
  if cop_config['EnabledForFlattenWithoutParams'] && flatten_level.nil?
    message = MSG + FLATTEN_MULTIPLE_LEVELS
  elsif flatten_level != 1
    return
  end

  range = Parser::Source::Range.new(node.source_range.source_buffer,
                                    expression.loc.selector.begin_pos,
                                    node.loc.selector.end_pos)

  add_offense(node, range, format(message, first_method, second_method))
end