ruby/NEWS.md

# NEWS for Ruby 3.3.0

This document is a list of user-visible feature changes
since the **3.2.0** release, except for bug fixes.

Note that each entry is kept to a minimum, see links for details.

## Language changes

## Command line options

* A new `performance` warning category was introduced.
  They are not displayed by default even in verbose mode.
  Turn them on with `-W:performance` or `Warning[:performance] = true`. [[Feature #19538]]
* The `RUBY_GC_HEAP_INIT_SLOTS` environment variable has been deprecated and
  removed. Environment variables `RUBY_GC_HEAP_%d_INIT_SLOTS` should be
  used instead.  [[Feature #19785]]

## Core classes updates

Note: We're only listing outstanding class updates.

* Array

    * Array#pack now raises ArgumentError for unknown directives. [[Bug #19150]]

* Dir

    * Dir.for_fd added for returning a Dir object for the directory specified
      by the provided directory file descriptor. [[Feature #19347]]
    * Dir.fchdir added for changing the directory to the directory specified
      by the provided directory file descriptor. [[Feature #19347]]
    * Dir#chdir added for changing the directory to the directory specified by
      the provided `Dir` object. [[Feature #19347]]

* MatchData

    * MatchData#named_captures now accepts optional `symbolize_names`
      keyword. [[Feature #19591]]

* String

    * String#unpack now raises ArgumentError for unknown directives. [[Bug #19150]]
    * String#bytesplice now accepts new arguments index/length or range of the
      source string to be copied.  [[Feature #19314]]

* ObjectSpace::WeakKeyMap

    * New core class to build collections with weak references.
      The class use equality semantic to lookup keys like a regular hash,
      but it doesn't hold strong references on the keys. [[Feature #18498]]

* Module

    * Module#set_temporary_name added for setting a temporary name for a
      module. [[Feature #19521]]

* Process.warmup

    * Notify the Ruby virtual machine that the boot sequence is finished,
      and that now is a good time to optimize the application. This is useful
      for long running applications. The actual optimizations performed are entirely
      implementation specific and may change in the future without notice. [[Feature #18885]]

* Refinement

    * Add Refinement#target as an alternative of Refinement#refined_class.
      Refinement#refined_class is deprecated and will be removed in Ruby
      3.4.  [[Feature #19714]]

## Stdlib updates

* RubyGems and Bundler warn if users require gem that is scheduled to become the bundled gems
  in the future version of Ruby. [[Feature #19351]] [[Feature #19776]] [[Feature #19843]]

* Random::Formatter#alphanumeric is extended to accept optional `chars`
  keyword argument. [[Feature #18183]]

The following default gems are updated.

* RubyGems 3.5.0.dev
* bigdecimal 3.1.4
* bundler 2.5.0.dev
* csv 3.2.8
* erb 4.0.3
* fiddle 1.1.2
* fileutils 1.7.1
* irb 1.8.1
* nkf 0.1.3
* optparse 0.4.0.pre.1
* psych 5.1.0
* reline 0.3.8
* stringio 3.0.9
* strscan 3.0.7
* syntax_suggest 1.1.0
* time 0.2.2
* timeout 0.4.0
* uri 0.12.2
* yarp 0.11.0

The following bundled gems are updated.

* minitest 5.20.0
* test-unit 3.6.1
* rexml 3.2.6
* rss 0.3.0
* net-imap 0.3.7
* rbs 3.2.1
* typeprof 0.21.8
* debug 1.8.0

The following default gem is now bundled.

* racc 1.7.1

See GitHub releases like [Logger](https://github.com/ruby/logger/releases) or
changelog for details of the default gems or bundled gems.

## Supported platforms

## Compatibility issues

## Stdlib compatibility issues

* `racc` is promoted bundled gems.
  * You need to add `racc` to your `Gemfile` if you use `racc` under bundler environment.
* `ext/readline` is retired
  * We have `reline` that is pure Ruby implementation compatible with `ext/readline` API. We rely on `reline` in the future. If you need to use `ext/readline`, you can install `ext/readline` via rubygems.org with `gem install readline-ext`.
  * We no longer need to install libraries like `libreadline` or `libedit`.

## C API updates

## Implementation improvements

* `defined?(@ivar)` is optimized with Object Shapes.

### YJIT

* Major performance improvements over 3.2
  * Support for splat and rest arguments has been improved.
  * Registers are allocated for stack operations of the virtual machine.
  * More calls with optional arguments are compiled.
  * Exception handlers are also compiled.
  * Instance variables no longer exit to the interpreter
    with megamorphic Object Shapes.
  * Unsupported call types no longer exit to the interpreter.
  * Integer#!=, String#!=, Kernel#block_given?, Kernel#is_a?,
    Kernel#instance_of?, Module#=== are specially optimized.
  * Now more than 3x faster than the interpreter on optcarrot!
* Metadata for compiled code uses a lot less memory.
* Generate more compact code on ARM64
* Option to start YJIT in paused mode and then later enable it manually
  * `--yjit-pause` and RubyVM::YJIT.resume
  * This can be used to enable YJIT only once your application is done booting
* `ratio_in_yjit` stat produced by `--yjit-stats` is now avaiable in release builds,
  a special stats or dev build is no longer required.
* Exit tracing option now supports sampling
  * `--trace-exits-sample-rate=N`
* `--yjit-stats=quiet` is added to avoid printing stats on exit.
* The default value for `--yjit-exec-mem-size` is changed from 64 to 128.
* More thorough testing and multiple bug fixes

### RJIT

* Introduced a pure-Ruby JIT compiler RJIT and replaced MJIT.
  * RJIT supports only x86\_64 architecture on Unix platforms.
  * Unlike MJIT, it doesn't require a C compiler at runtime.
* RJIT exists only for experimental purposes.
  * You should keep using YJIT in production.

[Feature #18183]: https://bugs.ruby-lang.org/issues/18183
[Feature #18498]: https://bugs.ruby-lang.org/issues/18498
[Feature #18885]: https://bugs.ruby-lang.org/issues/18885
[Bug #19150]:     https://bugs.ruby-lang.org/issues/19150
[Feature #19314]: https://bugs.ruby-lang.org/issues/19314
[Feature #19347]: https://bugs.ruby-lang.org/issues/19347
[Feature #19351]: https://bugs.ruby-lang.org/issues/19351
[Feature #19521]: https://bugs.ruby-lang.org/issues/19521
[Feature #19538]: https://bugs.ruby-lang.org/issues/19538
[Feature #19591]: https://bugs.ruby-lang.org/issues/19591
[Feature #19714]: https://bugs.ruby-lang.org/issues/19714
[Feature #19776]: https://bugs.ruby-lang.org/issues/19776
[Feature #19785]: https://bugs.ruby-lang.org/issues/19785
[Feature #19843]: https://bugs.ruby-lang.org/issues/19843