class RuboCop::Cop::Performance::StartWith

This cop identifies unnecessary use of a regex where `String#start_with?` would suffice.

This cop has `SafeMultiline` configuration option that `true` by default because `^start` is unsafe as it will behave incompatible with `start_with?` for receiver is multiline string.

@example

# bad
'abc'.match?(/\Aab/)
/\Aab/.match?('abc')
'abc' =~ /\Aab/
/\Aab/ =~ 'abc'
'abc'.match(/\Aab/)
/\Aab/.match('abc')

# good
'abc'.start_with?('ab')

@example SafeMultiline: true (default)

# good
'abc'.match?(/^ab/)
/^ab/.match?('abc')
'abc' =~ /^ab/
/^ab/ =~ 'abc'
'abc'.match(/^ab/)
/^ab/.match('abc')

@example SafeMultiline: false

# bad
'abc'.match?(/^ab/)
/^ab/.match?('abc')
'abc' =~ /^ab/
/^ab/ =~ 'abc'
'abc'.match(/^ab/)
/^ab/.match('abc')

Constants

MSG
RESTRICT_ON_SEND

Public Instance Methods

on_match_with_lvasgn(node)
Alias for: on_send
on_send(node) click to toggle source
# File lib/rubocop/cop/performance/start_with.rb, line 58
def on_send(node)
  return unless (receiver, regex_str = redundant_regex?(node))

  add_offense(node) do |corrector|
    receiver, regex_str = regex_str, receiver if receiver.is_a?(String)
    regex_str = drop_start_metacharacter(regex_str)
    regex_str = interpret_string_escapes(regex_str)

    new_source = "#{receiver.source}.start_with?(#{to_string_literal(regex_str)})"

    corrector.replace(node.source_range, new_source)
  end
end
Also aliased as: on_match_with_lvasgn