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

Inherits:
Cop
  • Object
show all
Defined in:
lib/rubocop/cop/performance/start_with.rb

Overview

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

Examples:

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

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

Constant Summary collapse

MSG = 
'Use `String#start_with?` instead of a regex match anchored to ' \
'the beginning of the string.'.freeze
SINGLE_QUOTE = 
"'".freeze

Constants included from Util

Util::LITERAL_REGEX

Instance Attribute Summary

Attributes inherited from Cop

#config, #corrections, #offenses, #processed_source

Instance Method Summary collapse

Methods inherited from Cop

#add_offense, all, autocorrect_incompatible_with, badge, #config_to_allow_offenses, #config_to_allow_offenses=, #cop_config, cop_name, #cop_name, #correct, department, #duplicate_location?, #excluded_file?, #find_location, #highlights, inherited, #initialize, #join_force?, lint?, match?, #message, #messages, non_rails, #parse, qualified_cop_name, #relevant_file?, #target_rails_version, #target_ruby_version

Methods included from AST::Sexp

#s

Methods included from NodePattern::Macros

#def_node_matcher, #def_node_search, #node_search, #node_search_all, #node_search_body, #node_search_first

Methods included from AutocorrectLogic

#autocorrect?, #autocorrect_enabled?, #autocorrect_requested?, #support_autocorrect?

Methods included from IgnoredNode

#ignore_node, #ignored_node?, #part_of_ignored_node?

Methods included from Util

begins_its_line?, comment_line?, double_quotes_required?, escape_string, first_part_of_call_chain, interpret_string_escapes, line_range, needs_escaping?, on_node, parentheses?, same_line?, to_string_literal, to_supported_styles, tokens, trim_string_interporation_escape_character

Methods included from PathUtil

absolute?, chdir, hidden_dir?, hidden_file_in_not_hidden_dir?, match_path?, pwd, relative_path, reset_pwd, smart_path

Constructor Details

This class inherits a constructor from RuboCop::Cop::Cop

Instance Method Details

#autocorrect(node) ⇒ Object 



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# File 'lib/rubocop/cop/performance/start_with.rb', line 43

def autocorrect(node)
  redundant_regex?(node) do |receiver, regex_str|
    receiver, regex_str = regex_str, receiver if receiver.is_a?(String)
    regex_str = regex_str[2..-1] # drop \A anchor
    regex_str = interpret_string_escapes(regex_str)

    lambda do |corrector|
      new_source = receiver.source + '.start_with?(' +
                   to_string_literal(regex_str) + ')'
      corrector.replace(node.source_range, new_source)
    end
  end
end

#literal_at_start?(regex_str) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/rubocop/cop/performance/start_with.rb', line 27

def literal_at_start?(regex_str)
  # is this regexp 'literal' in the sense of only matching literal
  # chars, rather than using metachars like `.` and `*` and so on?
  # also, is it anchored at the start of the string?
  # (tricky: \s, \d, and so on are metacharacters, but other characters
  #  escaped with a slash are just literals. LITERAL_REGEX takes all
  #  that into account.)
  regex_str =~ /\A\\A(?:#{LITERAL_REGEX})+\z/
end

#on_send(node) ⇒ Object 



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# File 'lib/rubocop/cop/performance/start_with.rb', line 37

def on_send(node)
  return unless redundant_regex?(node)

  add_offense(node)
end