Class: RuboCop::Cop::Performance::StartWith

Inherits:
Base
  • Object
show all
Extended by:
AutoCorrector
Includes:
RegexpMetacharacter
Defined in:
lib/rubocop/cop/performance/start_with.rb

Overview

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.

Examples:

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

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

SafeMultiline: true (default)


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

SafeMultiline: false


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

Constant Summary collapse

MSG = 
'Use `String#start_with?` instead of a regex match anchored to the beginning of the string.'
RESTRICT_ON_SEND = 
%i[match =~ match?].freeze

Instance Method Summary collapse

Instance Method Details

#on_send(node) ⇒ Object Also known as: on_csend, on_match_with_lvasgn 



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# File 'lib/rubocop/cop/performance/start_with.rb', line 63

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)
    dot = node.loc.dot ? node.loc.dot.source : '.'

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

    corrector.replace(node, new_source)
  end
end