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' =~ /\Aab/
'abc'.match(/\Aab/)

@good
'abc' =~ /ab/
'abc' =~ /\A\w*/

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::ASGN_NODES, Util::BYTE_ORDER_MARK, Util::EQUALS_ASGN_NODES, Util::LITERAL_REGEX, Util::OPERATOR_METHODS, Util::SHORTHAND_ASGN_NODES, Util::STRING_ESCAPES, Util::STRING_ESCAPE_REGEX

Instance Attribute Summary

Attributes inherited from Cop

#config, #corrections, #offenses, #processed_source

Instance Method Summary collapse

Methods inherited from Cop

#add_offense, all, #config_to_allow_offenses, #config_to_allow_offenses=, #cop_config, cop_name, #cop_name, cop_type, #correct, #debug?, #details, #display_cop_names?, #display_style_guide?, #excluded_file?, #extra_details?, inherited, #initialize, #join_force?, lint?, match?, #message, non_rails, #parse, qualified_cop_name, #reference_url, #relevant_file?, #style_guide_url, #target_ruby_version

Methods included from Sexp

#s

Methods included from NodePattern::Macros

#def_node_matcher, #def_node_search, #node_search_body

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?, block_length, comment_line?, directions, double_quotes_acceptable?, double_quotes_required?, effective_column, ends_its_line?, first_part_of_call_chain, interpret_string_escapes, line_range, move_pos, numeric_range_size, on_node, operator?, parentheses?, parenthesized_call?, range_with_surrounding_comma, range_with_surrounding_space, source_range, strip_quotes, ternary_op?, to_string_literal, to_symbol_literal, within_node?

Methods included from PathUtil

absolute?, hidden?, issue_deprecation_warning, match_path?, relative_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 42

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 28

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 38

def on_send(node)
  add_offense(node, :expression, MSG) if redundant_regex?(node)
end