From: "byroot (Jean Boussier) via ruby-core" Date: 2025-08-04T08:11:30+00:00 Subject: [ruby-core:122906] [Ruby Bug#21529] Deprecate the /o modifier and warn against using it Issue #21529 has been updated by byroot (Jean Boussier). > So should I just submit a PR with my suggestions for the docs Sure. I think updating the code snippets, and suggesting to use a constant could go a long way. ---------------------------------------- Bug #21529: Deprecate the /o modifier and warn against using it https://bugs.ruby-lang.org/issues/21529#change-114210 * Author: jpcamara (JP Camara) * Status: Open * Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN ---------------------------------------- I recently ran into a bug in some code because it was using the /o modifier as an optimization, not realizing it created a permanent, immutable value after the first time it gets evaluated. I dug into how the modifier works in CRuby and the history of it here: https://jpcamara.com/2025/08/02/the-o-in-ruby-regex.html. The feature seems like a total footgun with almost no upside. If I run a benchmark between a local regex, and a regex cached by /o, there is no real difference. ```rb require "benchmark" def letters "A-Za-z" end words = %w[the quick brown fox jumped over the lazy dog] Benchmark.bm do |bm| bm.report("without /o:") do regex = /\A[A-Za-z]+\z/ words.each do |word| word.match(regex) end end bm.report("with /o: ") do words.each do |word| word.match(/\A[#{letters}]+\z/o) end end end ``` Most of the time I found that "without /o" actually came out ahead. ``` user system total real without /o: 0.000019 0.000003 0.000022 ( 0.000014) with /o: 0.000020 0.000001 0.000021 ( 0.000020) ``` I'd like to deprecate the feature and update the docs to warn against using it. I'd be happy to submit a PR doing that. Thanks! -- https://bugs.ruby-lang.org/ ______________________________________________ ruby-core mailing list -- ruby-core@ml.ruby-lang.org To unsubscribe send an email to ruby-core-leave@ml.ruby-lang.org ruby-core info -- https://ml.ruby-lang.org/mailman3/lists/ruby-core.ml.ruby-lang.org/