January 2026 - ruby-core - ml.ruby-lang.org

[ruby-core:124496] [Ruby Bug#21824] performance regression in regexp matching after update to 4.0
by mackuba (Kuba Suder) 12 Jan '26

12 Jan '26

Issue #21824 has been updated by mackuba (Kuba Suder). I've tested latest master on my machine and it seems to be fixed, thank you! ---------------------------------------- Bug #21824: performance regression in regexp matching after update to 4.0 https://bugs.ruby-lang.org/issues/21824#change-116049 * Author: mackuba (Kuba Suder) * Status: Closed * ruby -v: ruby 4.0.0 (2025-12-25 revision 553f1675f3) +PRISM [arm64-darwin24] * Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN, 4.0: UNKNOWN ---------------------------------------- TLDR: a change in the regexp algorithm in regcomp.c merged around October was supposed to speed up the matching, but it seems it has slowed it down more in practice. === I'm running a service written in Ruby which serves some number of Bluesky feeds. As part of this service, I have a process that connects to a websocket API (w/ EventMachine), reads from it all new posts made on the network in real time (on the order of ~100 posts per second on average lately), and passes each post through a #post_matches? method in about 20 feed objects, each of which has a number of regexps configured (most have around 20-30, but one has a few hundred, probably something like 900 regexps in total). If a given post's text (up to 300 unicode characters) matches any of the regexps of the given feed (and/or matches some additional conditions), it's added to this feed in the database. I often use a slightly older version of this project with a fixed pre-downloaded chunk of the posts stream, with ~100k random but real posts in one large binary file, as a benchmark on different versions of Ruby. So I ran it again on 4.0 after it was released a week ago, and I got this: https://bsky.app/profile/mackuba.eu/post/3mb2quhdoqs23 The numbers are the calculated speed of processing, in events per second, after going through the whole sample of 100k events and a full set of feeds. So there was a 5-6% slowdown on Ruby 4.0 vs. Ruby 3.4 (with or without YJIT), putting it below any version of Ruby since 3.0. I started profiling which specific parts of the code got slower, and I narrowed it down to regexp matching (the full loop also does e.g. decoding of data from a binary format from the file). I made a demo project reproducing this here (note, linking to a slightly earlier commit): https://tangled.org/mackuba.eu/ruby4.0-regexp-test/tree/63e208de944debdc0a6…. There are 940 posts here in the sample and 17 regexps, and running 1000 loops takes 7 seconds on Ruby 3.4, but 13.5s on 4.0 (so almost 2x longer). Then, I started digging into the details to see if some specific posts or specific regexps cause the slowdown. It turned out that most of the 17 regexps, if tested alone, work about the same on 3.4 & 4.0, but two work around 4x slower: /\bslackware\b/i and /\bkde plasma\b/i. (This seems to be not only about the length of the regexp, but also specific characters, because e.g. /\blongstring\b/i does not trigger this effect.) It also seems that this only happens if the searched string contains non-ASCII characters. An updated, more minimal version of the demo is here: https://tangled.org/mackuba.eu/ruby4.0-regexp-test/tree/d9e145c1e9f39fca6dd…. One regexp and one string. With a million loops, it takes 0.75s on Ruby 3.4, but 2.7s on Ruby 4.0. (No change on latest master, ruby 4.1.0dev (2026-01-05T17:18:47Z master 7e81bf5c0c), i.e. it's still much slower than on 3.4.) If the few non-ASCII characters (apostrophe, ndash, ellipsis, TM) are removed from the string, the slowdown goes away. Finally, with some help from Codex I tried to track down which specific change between 3.4 and 4.0 caused this slowdown. It turned out to be this commit: https://github.com/ruby/ruby/commit/981ee02c7c664f19b983662d618d5e6bd87d1739, authored in November 2017 (!), but merged around 31st October this year. It says it "fixes performance problem with /k/i and /s/i". I'm not familiar with these string search algorithms so I'm not able to evaluate this in detail or say how this could be fixed, but from the description I'm assuming that it improves performance in some cases of text/regexp, but apparently degrades it in some others like mine. Since in my main test of a practical scenario which matches ~100k posts against ~900 regexps, as well as the earlier demo which matches 940 posts against 17 regexps, the updated version in 4.0 is slower (5% and 47% slower, respectively), my guess is that the net result will generally be negative, i.e. that this change committed in October makes more cases slower than it makes faster. But like I said, I don't know enough about regexp algorithms to analyze this deeper, I can only report my results. -- https://bugs.ruby-lang.org/

1 0

[ruby-core:124383] [Ruby Bug#21812] Kernel#sleep without arguments returns immediately when subprocess exits in another thread (regression in Ruby 4.0)
by jaimevelaz (Jaime Velaz) 12 Jan '26

12 Jan '26

Issue #21812 has been reported by jaimevelaz (Jaime Velaz). ---------------------------------------- Bug #21812: Kernel#sleep without arguments returns immediately when subprocess exits in another thread (regression in Ruby 4.0) https://bugs.ruby-lang.org/issues/21812 * Author: jaimevelaz (Jaime Velaz) * Status: Open * ruby -v: ruby 4.0.0 (2025-12-25 revision 553f1675f3) +PRISM [arm64-darwin25] * Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN, 4.0: UNKNOWN ---------------------------------------- **Description** In Ruby 4.0.0, Kernel#sleep without arguments returns 0 immediately when a subprocess (spawned via backticks in another thread) exits. This is a regression from Ruby 3.4.8 where sleep blocks indefinitely as expected. Note: sleep(N) with an argument is not affected. --- **Steps to reproduce** ``` # test_sleep.rb Thread.new do sleep 0.3 `echo hello` # Spawns subprocess puts "Subprocess exited" end puts "Main thread sleeping..." result = sleep # Should block forever puts "sleep returned: #{result.inspect}" ``` Run with: `$ ruby test_sleep.rb` --- Actual result (Ruby 4.0.0): Main thread sleeping... Subprocess exited sleep returned: 0 The program exits immediately after the subprocess completes. --- Expected result (Ruby 3.4.8 behavior): Main thread sleeping... Subprocess exited (process blocks indefinitely until interrupted by signal) The program should block forever until explicitly interrupted by SIGINT/SIGTERM. -- https://bugs.ruby-lang.org/

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[ruby-core:124394] [Ruby Bug#21815] Backport
by nobu (Nobuyoshi Nakada) 12 Jan '26

12 Jan '26

Issue #21815 has been reported by nobu (Nobuyoshi Nakada). ---------------------------------------- Bug #21815: Backport https://bugs.ruby-lang.org/issues/21815 * Author: nobu (Nobuyoshi Nakada) * Status: Open * Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN, 4.0: UNKNOWN ---------------------------------------- [GH-15737] [GH-15737]: https://github.com/ruby/ruby/pull/15737 -- https://bugs.ruby-lang.org/

2 1

[ruby-core:112045] [Ruby master Bug#19378] Windows: Use less syscalls for faster require of big gems
by aidog (Andi Idogawa) 12 Jan '26

12 Jan '26

Issue #19378 has been reported by aidog (Andi Idogawa). ---------------------------------------- Bug #19378: Windows: Use less syscalls for faster require of big gems https://bugs.ruby-lang.org/issues/19378 * Author: aidog (Andi Idogawa) * Status: Open * Priority: Normal * ruby -v: 3.2.0 * Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN ---------------------------------------- Hello 🙂 ## Problem require is slow on windows for big gems. (example: require 'gtk3'=> 3 seconds+). This is a problem for people who want to make cross platform GUI apps with ruby. ## Possible Reason As touched on in [#15797](https://bugs.ruby-lang.org/issues/15797) it seems like require uses realpath, which is emulated on windows. It checks every parent directory. The same syscalls run many times. ## Testfile C:\tmp\speedtest\testrequire.rb: ``` ruby require __dir__ + "/helloworld1.rb" require __dir__ + "/helloworld2.rb" ``` ``` shell ruby --disable-gems C:\tmp\speedtest\testrequire.rb ``` ### Syscalls per File/Directory: 1. CreateFile 2. QueryInformationVolume 3. QueryIdInformation 4. QueryAllInformationFile 5. QueryNameInformationFile 6. QueryNameInformationFile 7. QueryNormalizedNameInformationFile 8. CloseFile ### Files/Directories checked 1. C:\tmp 2. C:\tmp\speedtest 3. C:\tmp\speedtest\helloworld1.rb 4. C:\tmp 5. C:\tmp\speedtest 6. C:\tmp\speedtest\helloworld2.rb For two required files Ruby had to do 8*6 = **48** syscalls. The syscalls orginate from rb_w32_reparse_symlink_p / lstat Rubygems live in subfolders with 9+ parts: "C:\Ruby32-x64\lib\ruby\gems\3.2.0\gems\glib2-4.0.8\lib\glib2\variant.rb" Each file takes 8 * 9 = **72**+ calls. For variant.rb it is **80** calls. The result for the syscalls don't change in such a short time, so it should be possible to cache it. With require_relative it's twice as many calls. ## Other testcases Same result: ``` ruby File.realpath __dir__ + "/helloworld1.rb" File.realpath __dir__ + "/helloworld2.rb" ``` ``` ruby File.stat __dir__ + "/helloworld1.rb" File.stat __dir__ + "/helloworld2.rb" ``` It does not happen in $LOAD_PATH.resolve_feature_path(__dir__ + "/helloworld1.rb") ## Request Would it be possible to cache the stat calls when using require? I tried to implement a cache inside the ruby source code, but failed. If not, is there now a way to combine ruby files into one? I previously talked about require here: [YJIT: Windows support lacking.](https://bugs.ruby-lang.org/issues/19325#note-11) ## How to reproduce Ruby versions: At least 3.0+, most likely older ones too. Tested using Ruby Installer 3.1 and 3.2. [Procmon Software by Sysinternals](https://learn.microsoft.com/en-us/sysinternals/downloads/proc… -- https://bugs.ruby-lang.org/

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[ruby-core:124485] [Ruby Bug#21824] performance regression in regexp matching after update to 4.0
by mackuba (Kuba Suder) 12 Jan '26

12 Jan '26

Issue #21824 has been updated by mackuba (Kuba Suder). Hey - see the two links to the git repo on tangled.org in the bug description, it includes a test script. ---------------------------------------- Bug #21824: performance regression in regexp matching after update to 4.0 https://bugs.ruby-lang.org/issues/21824#change-116037 * Author: mackuba (Kuba Suder) * Status: Open * ruby -v: ruby 4.0.0 (2025-12-25 revision 553f1675f3) +PRISM [arm64-darwin24] * Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN, 4.0: UNKNOWN ---------------------------------------- TLDR: a change in the regexp algorithm in regcomp.c merged around October was supposed to speed up the matching, but it seems it has slowed it down more in practice. === I'm running a service written in Ruby which serves some number of Bluesky feeds. As part of this service, I have a process that connects to a websocket API (w/ EventMachine), reads from it all new posts made on the network in real time (on the order of ~100 posts per second on average lately), and passes each post through a #post_matches? method in about 20 feed objects, each of which has a number of regexps configured (most have around 20-30, but one has a few hundred, probably something like 900 regexps in total). If a given post's text (up to 300 unicode characters) matches any of the regexps of the given feed (and/or matches some additional conditions), it's added to this feed in the database. I often use a slightly older version of this project with a fixed pre-downloaded chunk of the posts stream, with ~100k random but real posts in one large binary file, as a benchmark on different versions of Ruby. So I ran it again on 4.0 after it was released a week ago, and I got this: https://bsky.app/profile/mackuba.eu/post/3mb2quhdoqs23 The numbers are the calculated speed of processing, in events per second, after going through the whole sample of 100k events and a full set of feeds. So there was a 5-6% slowdown on Ruby 4.0 vs. Ruby 3.4 (with or without YJIT), putting it below any version of Ruby since 3.0. I started profiling which specific parts of the code got slower, and I narrowed it down to regexp matching (the full loop also does e.g. decoding of data from a binary format from the file). I made a demo project reproducing this here (note, linking to a slightly earlier commit): https://tangled.org/mackuba.eu/ruby4.0-regexp-test/tree/63e208de944debdc0a6…. There are 940 posts here in the sample and 17 regexps, and running 1000 loops takes 7 seconds on Ruby 3.4, but 13.5s on 4.0 (so almost 2x longer). Then, I started digging into the details to see if some specific posts or specific regexps cause the slowdown. It turned out that most of the 17 regexps, if tested alone, work about the same on 3.4 & 4.0, but two work around 4x slower: /\bslackware\b/i and /\bkde plasma\b/i. (This seems to be not only about the length of the regexp, but also specific characters, because e.g. /\blongstring\b/i does not trigger this effect.) It also seems that this only happens if the searched string contains non-ASCII characters. An updated, more minimal version of the demo is here: https://tangled.org/mackuba.eu/ruby4.0-regexp-test/tree/d9e145c1e9f39fca6dd…. One regexp and one string. With a million loops, it takes 0.75s on Ruby 3.4, but 2.7s on Ruby 4.0. (No change on latest master, ruby 4.1.0dev (2026-01-05T17:18:47Z master 7e81bf5c0c), i.e. it's still much slower than on 3.4.) If the few non-ASCII characters (apostrophe, ndash, ellipsis, TM) are removed from the string, the slowdown goes away. Finally, with some help from Codex I tried to track down which specific change between 3.4 and 4.0 caused this slowdown. It turned out to be this commit: https://github.com/ruby/ruby/commit/981ee02c7c664f19b983662d618d5e6bd87d1739, authored in November 2017 (!), but merged around 31st October this year. It says it "fixes performance problem with /k/i and /s/i". I'm not familiar with these string search algorithms so I'm not able to evaluate this in detail or say how this could be fixed, but from the description I'm assuming that it improves performance in some cases of text/regexp, but apparently degrades it in some others like mine. Since in my main test of a practical scenario which matches ~100k posts against ~900 regexps, as well as the earlier demo which matches 940 posts against 17 regexps, the updated version in 4.0 is slower (5% and 47% slower, respectively), my guess is that the net result will generally be negative, i.e. that this change committed in October makes more cases slower than it makes faster. But like I said, I don't know enough about regexp algorithms to analyze this deeper, I can only report my results. -- https://bugs.ruby-lang.org/

1 0

[ruby-core:124482] [Ruby Bug#21824] performance regression in regexp matching after update to 4.0
by nobu (Nobuyoshi Nakada) 12 Jan '26

12 Jan '26

Issue #21824 has been updated by nobu (Nobuyoshi Nakada). Could you share how you measured the performance? ---------------------------------------- Bug #21824: performance regression in regexp matching after update to 4.0 https://bugs.ruby-lang.org/issues/21824#change-116032 * Author: mackuba (Kuba Suder) * Status: Open * ruby -v: ruby 4.0.0 (2025-12-25 revision 553f1675f3) +PRISM [arm64-darwin24] * Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN, 4.0: UNKNOWN ---------------------------------------- TLDR: a change in the regexp algorithm in regcomp.c merged around October was supposed to speed up the matching, but it seems it has slowed it down more in practice. === I'm running a service written in Ruby which serves some number of Bluesky feeds. As part of this service, I have a process that connects to a websocket API (w/ EventMachine), reads from it all new posts made on the network in real time (on the order of ~100 posts per second on average lately), and passes each post through a #post_matches? method in about 20 feed objects, each of which has a number of regexps configured (most have around 20-30, but one has a few hundred, probably something like 900 regexps in total). If a given post's text (up to 300 unicode characters) matches any of the regexps of the given feed (and/or matches some additional conditions), it's added to this feed in the database. I often use a slightly older version of this project with a fixed pre-downloaded chunk of the posts stream, with ~100k random but real posts in one large binary file, as a benchmark on different versions of Ruby. So I ran it again on 4.0 after it was released a week ago, and I got this: https://bsky.app/profile/mackuba.eu/post/3mb2quhdoqs23 The numbers are the calculated speed of processing, in events per second, after going through the whole sample of 100k events and a full set of feeds. So there was a 5-6% slowdown on Ruby 4.0 vs. Ruby 3.4 (with or without YJIT), putting it below any version of Ruby since 3.0. I started profiling which specific parts of the code got slower, and I narrowed it down to regexp matching (the full loop also does e.g. decoding of data from a binary format from the file). I made a demo project reproducing this here (note, linking to a slightly earlier commit): https://tangled.org/mackuba.eu/ruby4.0-regexp-test/tree/63e208de944debdc0a6…. There are 940 posts here in the sample and 17 regexps, and running 1000 loops takes 7 seconds on Ruby 3.4, but 13.5s on 4.0 (so almost 2x longer). Then, I started digging into the details to see if some specific posts or specific regexps cause the slowdown. It turned out that most of the 17 regexps, if tested alone, work about the same on 3.4 & 4.0, but two work around 4x slower: /\bslackware\b/i and /\bkde plasma\b/i. (This seems to be not only about the length of the regexp, but also specific characters, because e.g. /\blongstring\b/i does not trigger this effect.) It also seems that this only happens if the searched string contains non-ASCII characters. An updated, more minimal version of the demo is here: https://tangled.org/mackuba.eu/ruby4.0-regexp-test/tree/d9e145c1e9f39fca6dd…. One regexp and one string. With a million loops, it takes 0.75s on Ruby 3.4, but 2.7s on Ruby 4.0. (No change on latest master, ruby 4.1.0dev (2026-01-05T17:18:47Z master 7e81bf5c0c), i.e. it's still much slower than on 3.4.) If the few non-ASCII characters (apostrophe, ndash, ellipsis, TM) are removed from the string, the slowdown goes away. Finally, with some help from Codex I tried to track down which specific change between 3.4 and 4.0 caused this slowdown. It turned out to be this commit: https://github.com/ruby/ruby/commit/981ee02c7c664f19b983662d618d5e6bd87d1739, authored in November 2017 (!), but merged around 31st October this year. It says it "fixes performance problem with /k/i and /s/i". I'm not familiar with these string search algorithms so I'm not able to evaluate this in detail or say how this could be fixed, but from the description I'm assuming that it improves performance in some cases of text/regexp, but apparently degrades it in some others like mine. Since in my main test of a practical scenario which matches ~100k posts against ~900 regexps, as well as the earlier demo which matches 940 posts against 17 regexps, the updated version in 4.0 is slower (5% and 47% slower, respectively), my guess is that the net result will generally be negative, i.e. that this change committed in October makes more cases slower than it makes faster. But like I said, I don't know enough about regexp algorithms to analyze this deeper, I can only report my results. -- https://bugs.ruby-lang.org/

1 0

[ruby-core:124173] [Ruby Misc#21777] DevMeeting-2026-01-14
by mame (Yusuke Endoh) 10 Jan '26

10 Jan '26

Issue #21777 has been reported by mame (Yusuke Endoh). ---------------------------------------- Misc #21777: DevMeeting-2026-01-14 https://bugs.ruby-lang.org/issues/21777 * Author: mame (Yusuke Endoh) * Status: Open ---------------------------------------- # The next dev meeting **Date: 2026/01/14 13:00-17:00** (JST) Log: *TBD* - Dev meeting *IS NOT* a decision-making place. All decisions should be done at the bug tracker. - Dev meeting is a place we can ask Matz, nobu, nurse and other developers directly. - Matz is a very busy person. Take this opportunity to ask him. If you can not attend, other attendees can ask instead of you (if attendees can understand your issue). - We will write a record of the discussion in the file or to each ticket in English. - All activities are best-effort (keep in mind that most of us are volunteer developers). - The date, time and place of the meeting are scheduled according to when/where we can reserve Matz's time. - *DO NOT* discuss then on this ticket, please. # Call for agenda items If you have a ticket that you want matz and committers to discuss, please post it into this ticket in the following format: ``` * [Ticket ref] Ticket title (your name) * Comment (A summary of the ticket, why you put this ticket here, what point should be discussed, etc.) ``` Example: ``` * [Feature #14609] `Kernel#p` without args shows the receiver (ko1) * I feel this feature is very useful and some people say :+1: so let discuss this feature. ``` - It is recommended to add a comment by 2026/01/11. We hold a preparatory meeting to create an agenda a few days before the dev-meeting. - The format is strict. We'll use [this script to automatically create an markdown-style agenda](https://gist.github.com/mame/b0390509ce1491b43610b9ebb665eb86). We may ignore a comment that does not follow the format. - Your comment is mandatory. We cannot read all discussion of the ticket in a limited time. We appreciate it if you could write a short summary and update from a previous discussion. -- https://bugs.ruby-lang.org/

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[ruby-core:124469] [Ruby Feature#16848] Allow callables in $LOAD_PATH
by fxn (Xavier Noria) 09 Jan '26

09 Jan '26

Issue #16848 has been updated by fxn (Xavier Noria). BTW, the contract could be to return a file handle (which could be a StringIO) or `nil`. ---------------------------------------- Feature #16848: Allow callables in $LOAD_PATH https://bugs.ruby-lang.org/issues/16848#change-116020 * Author: byroot (Jean Boussier) * Status: Feedback ---------------------------------------- Make it easier to implement `$LOAD_PATH` caching, and speed up application boot time. I benchmarked it on Redmine's master using bootsnap with only the optimization enabled: ```ruby if ENV['CACHE_LOAD_PATH'] require 'bootsnap' Bootsnap.setup( cache_dir: 'tmp/cache', development_mode: false, load_path_cache: true, autoload_paths_cache: true, disable_trace: false, compile_cache_iseq: true, compile_cache_yaml: false, ) end ``` ``` $ RAILS_ENV=production time bin/rails runner 'p 1' 2.66 real 1.99 user 0.66 sys $ RAILS_ENV=production time bin/rails runner 'p 1' 2.71 real 1.97 user 0.66 sys $ CACHE_LOAD_PATH=1 RAILS_ENV=production time bin/rails runner 'p 1' 1.41 real 1.12 user 0.28 sys $ CACHE_LOAD_PATH=1 RAILS_ENV=production time bin/rails runner 'p 1' 1.41 real 1.12 user 0.28 sys ``` That's twice for a relatively small application. And the performance improvement is not linear; the larger the application, the larger the improvement. ### How it works `require` has `O($LOAD_PATH.size)` performance. The more gems you add to your `Gemfile`, the larger `$LOAD_PATH` becomes. `require "foo.rb"` will try to open the file in each of the `$LOAD_PATH` entries. And since more gems usually also means more `require` calls, loading Ruby code may take up to quadratic performance loss. To improve this, Bootsnap pre-computes a map of all the files in your `$LOAD_PATH`, and uses it to convert relative paths into absolute paths so that Ruby skips the `$LOAD_PATH` traversal. ```ruby $LOAD_PATH = $w(/gems/foo/lib /gems/bar/lib) BOOTSNAP_CACHE = { "bar.rb" => "/gems/bar/lib/bar.rb", } ``` This resolves file lookup by a single hash lookup, and reduces boot performance from roughly `O($LOAD_PATH.size * number_of_files_to_require)` to `O(number_of_files_to_require)`. This optimization is also used in [Gel](https://github.com/gel-rb/gel), a Rubygems/Bundler replacement. ### Trade offs Every time `$LOAD_PATH` is modified, the cache must become invalidated. While this is complex to do for Bootsnap, it would be fairly easy if it is implemented inside Ruby. More importantly, you have to invalidate the cache whenever you add or delete a file to/from one of the `$LOAD_PATH` members; otherwise, if you shadow or unshadow another file farther in the `$LOAD_PATH`, Bootsnap will load a wrong file. For instance, if `require "foo.rb"` initially resolves to `/some/gem/foo.rb`, and you create `lib/foo.rb`, you'll need to flush Bootsnap cache. That latter is trickier, and Bootsnap has decided that it is rare enough to cause actual problems, and so far that holds. But that is not a trade off Ruby can make. However that's probably a tradeoff Rubygems/Bundler can make. While it's common to edit your gems to debug something, it's really uncommon to add or remove files inside them. So in theory Rubygems/Bundler could compute a map of all files in a gem that can be required after it installs it. Then when you activate it, you merge it together with the other activated gems. ### Proposal This could be reasonably easy to implement if `$LOAD_PATH` accepted callables in addition to paths. Something like this: ```ruby $LOAD_PATH = [ 'my_app/lib', BundlerOrRubygems.method(:lookup), ] ``` The contract would be that `BundlerOrRubygems.lookup("some_relative/path.rb")` would return either an absolute path or `nil`. With such API, it would be easy to cache absolute paths only for gems and the stdlib, and preserve the current cache-less behavior for the application specific load paths, which are usually much less numerous. It would also allow frameworks such as Rails to implement the same caching for application paths when running in an environment where the source files are immutable (typically production). -- https://bugs.ruby-lang.org/

1 0

[ruby-core:124468] [Ruby Feature#16848] Allow callables in $LOAD_PATH
by fxn (Xavier Noria) 09 Jan '26

09 Jan '26

Issue #16848 has been updated by fxn (Xavier Noria). Hey, just saw this ticket. I wanted to share as a curiosity that Perl has this: You can store coderefs in `@INC`. That gives you plenty of flexibility. For example, the Perl Archive Toolkit provides a way to ship projects in one single .par file. Similar idea to .jar files in Java. PAR injects code in `@INC` to perform file lookups inside the .par files. ---------------------------------------- Feature #16848: Allow callables in $LOAD_PATH https://bugs.ruby-lang.org/issues/16848#change-116019 * Author: byroot (Jean Boussier) * Status: Feedback ---------------------------------------- Make it easier to implement `$LOAD_PATH` caching, and speed up application boot time. I benchmarked it on Redmine's master using bootsnap with only the optimization enabled: ```ruby if ENV['CACHE_LOAD_PATH'] require 'bootsnap' Bootsnap.setup( cache_dir: 'tmp/cache', development_mode: false, load_path_cache: true, autoload_paths_cache: true, disable_trace: false, compile_cache_iseq: true, compile_cache_yaml: false, ) end ``` ``` $ RAILS_ENV=production time bin/rails runner 'p 1' 2.66 real 1.99 user 0.66 sys $ RAILS_ENV=production time bin/rails runner 'p 1' 2.71 real 1.97 user 0.66 sys $ CACHE_LOAD_PATH=1 RAILS_ENV=production time bin/rails runner 'p 1' 1.41 real 1.12 user 0.28 sys $ CACHE_LOAD_PATH=1 RAILS_ENV=production time bin/rails runner 'p 1' 1.41 real 1.12 user 0.28 sys ``` That's twice for a relatively small application. And the performance improvement is not linear; the larger the application, the larger the improvement. ### How it works `require` has `O($LOAD_PATH.size)` performance. The more gems you add to your `Gemfile`, the larger `$LOAD_PATH` becomes. `require "foo.rb"` will try to open the file in each of the `$LOAD_PATH` entries. And since more gems usually also means more `require` calls, loading Ruby code may take up to quadratic performance loss. To improve this, Bootsnap pre-computes a map of all the files in your `$LOAD_PATH`, and uses it to convert relative paths into absolute paths so that Ruby skips the `$LOAD_PATH` traversal. ```ruby $LOAD_PATH = $w(/gems/foo/lib /gems/bar/lib) BOOTSNAP_CACHE = { "bar.rb" => "/gems/bar/lib/bar.rb", } ``` This resolves file lookup by a single hash lookup, and reduces boot performance from roughly `O($LOAD_PATH.size * number_of_files_to_require)` to `O(number_of_files_to_require)`. This optimization is also used in [Gel](https://github.com/gel-rb/gel), a Rubygems/Bundler replacement. ### Trade offs Every time `$LOAD_PATH` is modified, the cache must become invalidated. While this is complex to do for Bootsnap, it would be fairly easy if it is implemented inside Ruby. More importantly, you have to invalidate the cache whenever you add or delete a file to/from one of the `$LOAD_PATH` members; otherwise, if you shadow or unshadow another file farther in the `$LOAD_PATH`, Bootsnap will load a wrong file. For instance, if `require "foo.rb"` initially resolves to `/some/gem/foo.rb`, and you create `lib/foo.rb`, you'll need to flush Bootsnap cache. That latter is trickier, and Bootsnap has decided that it is rare enough to cause actual problems, and so far that holds. But that is not a trade off Ruby can make. However that's probably a tradeoff Rubygems/Bundler can make. While it's common to edit your gems to debug something, it's really uncommon to add or remove files inside them. So in theory Rubygems/Bundler could compute a map of all files in a gem that can be required after it installs it. Then when you activate it, you merge it together with the other activated gems. ### Proposal This could be reasonably easy to implement if `$LOAD_PATH` accepted callables in addition to paths. Something like this: ```ruby $LOAD_PATH = [ 'my_app/lib', BundlerOrRubygems.method(:lookup), ] ``` The contract would be that `BundlerOrRubygems.lookup("some_relative/path.rb")` would return either an absolute path or `nil`. With such API, it would be easy to cache absolute paths only for gems and the stdlib, and preserve the current cache-less behavior for the application specific load paths, which are usually much less numerous. It would also allow frameworks such as Rails to implement the same caching for application paths when running in an environment where the source files are immutable (typically production). -- https://bugs.ruby-lang.org/

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[ruby-core:124418] [Ruby Feature#21826] Deprecating RubyVM::AbstractSyntaxTree
by Eregon (Benoit Daloze) 09 Jan '26

09 Jan '26

Issue #21826 has been reported by Eregon (Benoit Daloze). ---------------------------------------- Feature #21826: Deprecating RubyVM::AbstractSyntaxTree https://bugs.ruby-lang.org/issues/21826 * Author: Eregon (Benoit Daloze) * Status: Open ---------------------------------------- I think it is time to deprecate `RubyVM::AbstractSyntaxTree`. [Matz has agreed that going forward the official parser API for Ruby will be the Prism API](https://railsatscale.com/2024-04-16-prism-in-2024/) so it's clear the official Ruby parsing API is the Prism API. `RubyVM::AbstractSyntaxTree` is CRuby-specific and does not work on any other Ruby implementation, the API is unstable, inconvenient, etc: > This module is experimental and its API is not stable, therefore it > might change without notice. As examples, the order of children nodes is > not guaranteed, the number of children nodes might change, there is no > way to access children nodes by name, etc. Because it's under `RubyVM`, it also has the following documented caveats: > This module is for very limited purposes, such as debugging, prototyping, and research. > Normal users must not use it. This module is not portable between Ruby implementations. Given these caveats I think it could possibly be fair enough to remove it without deprecation, however I see no urgency to remove it straight away so I think having it deprecated for one release is nicer for the few gems using it. The advantages of deprecating it are: * Make it clear that this API should not be used in new code * Encourage the few usages to migrate to the Prism API, which is stable, officially supported, designed with many people to be usable and convenient for every parsing/tooling usage, etc. * Improve portability of Ruby code between Ruby implementations So, let's deprecate `RubyVM::AbstractSyntaxTree` in 4.1, and remove it in 4.2? -- https://bugs.ruby-lang.org/

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