rubocop: reduce a regex match for performance

[kenhys]

Which issue(s) this PR fixes:
Fixes #

What this PR does / why we need it:

This is cosmetic change, it does not change behavior at all. The following rubocop configuration detects it.

Performance/StringInclude:
  Enable: true

Benchmark result:

ruby 3.2.8 (2025-03-26 revision 13f495dc2c) +YJIT [x86_64-linux]
Warming up --------------------------------------
check method with ===
                       411.815k i/100ms
check method with include?
                         1.180M i/100ms
Calculating -------------------------------------
check method with ===
                          3.797M (± 5.3%) i/s  (263.38 ns/i) -     18.943M in   5.003267s
check method with include?
                         12.067M (± 3.5%) i/s   (82.87 ns/i) -     61.348M in   5.090688s

Comparison:
check method with include?: 12066561.6 i/s
check method with ===:  3796826.8 i/s - 3.18x  slower

ruby 3.2.8 (2025-03-26 revision 13f495dc2c) +YJIT [x86_64-linux]
Warming up --------------------------------------
check method with =~   353.806k i/100ms
check method with include?
                         1.170M i/100ms
Calculating -------------------------------------
check method with =~      3.371M (± 5.1%) i/s  (296.66 ns/i) -     16.983M in   5.051124s
check method with include?
                         12.155M (± 1.0%) i/s   (82.27 ns/i) -     60.849M in   5.006417s

Comparison:
check method with include?: 12155448.7 i/s
check method with =~:  3370848.9 i/s - 3.61x  slower

Appendix: benchmark script

require 'bundler/inline'
gemfile do
  source 'https://rubygems.org'
  gem 'benchmark-ips'
  gem 'benchmark-memory'
end

Benchmark.ips do |x|
  name = "x86_64-linux"
  x.report("check method with ===") {
    /linux/ === name
  }
  x.report("check method with include?") {
    name.include?("linux")
  }
  x.compare!
end

Benchmark.ips do |x|
  triplet = "powerpc64-apple-darwin"
  x.report("check method with =~") {
    /darwin/ =~ triplet
  }
  x.report("check method with include?") {
    triplet.include?("darwin")
  }
  x.compare!
end

Docs Changes:

N/A

Release Note:

N/A

[kenhys]

NOTE:

rubocop detects the following code, but it was a false positive.

Ofenses:

lib/fluent/command/plugin_config_formatter.rb:64:17: C: [Correctable] Performance/StringInclude: Use String#include? instead of a regex match with literal-only pattern.
        next if /::PluginHelper::/.match?(plugin_class.name)
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

ruby 3.2.8 (2025-03-26 revision 13f495dc2c) +YJIT [x86_64-linux]
Warming up --------------------------------------
check method with match?
                         1.291M i/100ms
check method with include?
                       744.908k i/100ms
Calculating -------------------------------------
check method with match?
                         13.453M (± 0.7%) i/s   (74.33 ns/i) -     68.399M in   5.084622s
check method with include?
                          7.220M (± 1.0%) i/s  (138.50 ns/i) -     36.500M in   5.055801s

Comparison:
check method with match?: 13452792.6 i/s
check method with include?:  7220336.0 i/s - 1.86x  slower