Fix #8650 for improved hidden files finder performance

[tleish]

Faster find of hidden files in TargetFinder class which improves rubocop initial startup speed.

Benchmarks now show a 57x improvement in one large project tested:

Comparison:
             select:       50.6 i/s
               glob:        0.9 i/s - 57.38x  (± 0.00) slower

---

Before submitting the PR make sure the following are checked:

• Wrote good commit messages.
• Commit message starts with [Fix #issue-number] (if the related issue exists).
• Feature branch is up-to-date with master (if not - rebase it).
• Squashed related commits together.
• Added tests.
• Added an entry to the Changelog if the new code introduces user-observable changes. See changelog entry format.
• The PR relates to only one subject with a clear title and description in grammatically correct, complete sentences.
• Run bundle exec rake default. It executes all tests and RuboCop for itself, and generates the documentation.

[marcandre]

57x is nice 😆
Could you not use grep with a regexp here?

[tleish]

Could you not use grep with a regexp here?

@marcandre - I previously tested this, but turns out that the proposed solution is faster.

      require "benchmark/ips"

      Benchmark.ips(7) do |x|
        x.report("glob") { hidden_files = Set.new(all_files - find_files(base_dir, 0)) }
        x.report("select") { hidden_files = all_files.select { |file| file.include?(HIDDEN_FILE_PATTERN) } }
        x.report("grep") { hidden_files = all_files.grep(%r{#{File::SEPARATOR}\.}) }
        x.compare!
      end

Comparison:
             select:       52.3 i/s
               grep:       23.5 i/s - 2.22x  (± 0.00) slower
               glob:        0.9 i/s - 59.16x  (± 0.00) slower

[marcandre]

Could you not use grep with a regexp here?

@marcandre - I previously tested this, but turns out that the proposed solution is faster.

Ah, right... Forgot about https://bugs.ruby-lang.org/issues/17030

[tleish]

Ah, right... Forgot about https://bugs.ruby-lang.org/issues/17030

FYI

Benchmark.ips(7) do |x|
    x.report("glob") { hidden_files = Set.new(all_files - find_files(base_dir, 0)) }
    x.report("include?") { hidden_files = all_files.select { |file| file.include?(HIDDEN_FILE_PATTERN) } }
    x.report("=~") { hidden_files = all_files.select { |file| file =~ hidden_file_regex } }
    x.report("match?") { hidden_files = all_files.select { |file| file.match?(hidden_file_regex) } }
    x.report("grep") { hidden_files = all_files.grep(hidden_file_regex) }
    x.compare!
end

Comparison:
            include?:       50.2 i/s
              match?:       42.9 i/s - 1.17x  (± 0.00) slower
                grep:       24.6 i/s - 2.04x  (± 0.00) slower
                  =~:       22.9 i/s - 2.19x  (± 0.00) slower
                glob:        0.9 i/s - 56.91x  (± 0.00) slower

[bbatsov]

I'm not sure that naming this "pattern" is a good idea, as it makes me think of regular expressions. :-)

[tleish]

updated to HIDDEN_PATH_SUBSTRING

[bbatsov]

I'd add a note we're doing this for performance reasons, as someone might want to optimize it for readability or whatever.

[tleish]

adde comment