class RuboCop::Cop::Performance::FlatMap

This cop is used to identify usages of `map { … }.flatten` and change them to use `flat_map { … }` instead.

@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_MULTIPLE_LEVELS
MSG
RESTRICT_ON_SEND

Public Instance Methods

on_send(node) click to toggle source
# File lib/rubocop/cop/performance/flat_map.rb, line 39
def on_send(node)
  flat_map_candidate?(node) do |map_node, first_method, flatten, params|
    flatten_level, = *params.first
    if cop_config['EnabledForFlattenWithoutParams'] && !flatten_level
      offense_for_levels(node, map_node, first_method, flatten)
    elsif flatten_level == 1
      offense_for_method(node, map_node, first_method, flatten)
    end
  end
end

Private Instance Methods

autocorrect(corrector, node) click to toggle source
# File lib/rubocop/cop/performance/flat_map.rb, line 71
def autocorrect(corrector, node)
  map_node, _first_method, _flatten, params = flat_map_candidate?(node)
  flatten_level, = *params.first

  return unless flatten_level

  range = range_between(node.loc.dot.begin_pos, node.source_range.end_pos)

  corrector.remove(range)
  corrector.replace(map_node.loc.selector, 'flat_map')
end
offense_for_levels(node, map_node, first_method, flatten) click to toggle source
# File lib/rubocop/cop/performance/flat_map.rb, line 52
def offense_for_levels(node, map_node, first_method, flatten)
  message = MSG + FLATTEN_MULTIPLE_LEVELS

  register_offense(node, map_node, first_method, flatten, message)
end
offense_for_method(node, map_node, first_method, flatten) click to toggle source
# File lib/rubocop/cop/performance/flat_map.rb, line 58
def offense_for_method(node, map_node, first_method, flatten)
  register_offense(node, map_node, first_method, flatten, MSG)
end
register_offense(node, map_node, first_method, flatten, message) click to toggle source
# File lib/rubocop/cop/performance/flat_map.rb, line 62
def register_offense(node, map_node, first_method, flatten, message)
  range = range_between(map_node.loc.selector.begin_pos, node.loc.expression.end_pos)
  message = format(message, method: first_method, flatten: flatten)

  add_offense(range, message: message) do |corrector|
    autocorrect(corrector, node)
  end
end