class RuboCop::Cop::Style::SelectByRegexp

Looks for places where an subset of an Enumerable (array, range, set, etc.; see note below) is calculated based on a `Regexp` match, and suggests `grep` or `grep_v` instead.

NOTE: Hashes do not behave as you may expect with `grep`, which means that `hash.grep` is not equivalent to `hash.select`. Although RuboCop is limited by static analysis, this cop attempts to avoid registering an offense when the receiver is a hash (hash literal, `Hash.new`, `Hash#[]`, or `to_h`/`to_hash`).

NOTE: `grep` and `grep_v` were optimized when used without a block in Ruby 3.0, but may be slower in previous versions. See bugs.ruby-lang.org/issues/17030

@safety

Autocorrection is marked as unsafe because `MatchData` will
not be created by `grep`, but may have previously been relied
upon after the `match?` or `=~` call.

Additionally, the cop cannot guarantee that the receiver of
`select` or `reject` is actually an array by static analysis,
so the correction may not be actually equivalent.

@example

# bad (select or find_all)
array.select { |x| x.match? /regexp/ }
array.select { |x| /regexp/.match?(x) }
array.select { |x| x =~ /regexp/ }
array.select { |x| /regexp/ =~ x }

# bad (reject)
array.reject { |x| x.match? /regexp/ }
array.reject { |x| /regexp/.match?(x) }
array.reject { |x| x =~ /regexp/ }
array.reject { |x| /regexp/ =~ x }

# good
array.grep(regexp)
array.grep_v(regexp)

Constants

MSG
REGEXP_METHODS
REPLACEMENTS
RESTRICT_ON_SEND

Public Instance Methods

on_send(node) click to toggle source
# File lib/rubocop/cop/style/select_by_regexp.rb, line 86
def on_send(node)
  return unless (block_node = node.block_node)
  return if block_node.body.begin_type?
  return if receiver_allowed?(block_node.receiver)
  return unless (regexp_method_send_node = extract_send_node(block_node))
  return if match_predicate_without_receiver?(regexp_method_send_node)

  regexp = find_regexp(regexp_method_send_node, block_node)
  register_offense(node, block_node, regexp)
end

Private Instance Methods

extract_send_node(block_node) click to toggle source
# File lib/rubocop/cop/style/select_by_regexp.rb, line 118
def extract_send_node(block_node)
  return unless (block_arg_name, regexp_method_send_node = regexp_match?(block_node))

  block_arg_name = :"_#{block_arg_name}" if block_node.numblock_type?
  return unless calls_lvar?(regexp_method_send_node, block_arg_name)

  regexp_method_send_node
end
find_regexp(node, block) click to toggle source
# File lib/rubocop/cop/style/select_by_regexp.rb, line 127
def find_regexp(node, block)
  return node.child_nodes.first if node.match_with_lvasgn_type?

  if node.receiver.lvar_type? &&
     (block.numblock_type? || node.receiver.source == block.arguments.first.source)
    node.first_argument
  elsif node.first_argument.lvar_type?
    node.receiver
  end
end
match_predicate_without_receiver?(node) click to toggle source
# File lib/rubocop/cop/style/select_by_regexp.rb, line 138
def match_predicate_without_receiver?(node)
  node.send_type? && node.method?(:match?) && node.receiver.nil?
end
receiver_allowed?(node) click to toggle source
# File lib/rubocop/cop/style/select_by_regexp.rb, line 99
def receiver_allowed?(node)
  return false unless node

  node.hash_type? || creates_hash?(node) || env_const?(node)
end
register_offense(node, block_node, regexp) click to toggle source
# File lib/rubocop/cop/style/select_by_regexp.rb, line 105
def register_offense(node, block_node, regexp)
  replacement = REPLACEMENTS[node.method_name.to_sym]
  message = format(MSG, replacement: replacement, original_method: node.method_name)

  add_offense(block_node, message: message) do |corrector|
    # Only correct if it can be determined what the regexp is
    if regexp
      range = range_between(node.loc.selector.begin_pos, block_node.loc.end.end_pos)
      corrector.replace(range, "#{replacement}(#{regexp.source})")
    end
  end
end