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

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]

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]

The following default gems are updated.

The following bundled gems are updated.

The following default gem is now bundled.

See GitHub releases like Logger or changelog for details of the default gems or bundled gems.

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.

Significant performance improvements over 3.2
- Splat and rest arguments support has been improved.
- Registers are allocated for stack operations of the virtual machine.
- More calls with optional arguments are compiled.
- Integer#!=, String#!=, Kernel#block_given?, Kernel#is_a?, Kernel#instance_of?, Module#=== are specially optimized.
- Instance variables no longer exit to the interpreter with megamorphic Object Shapes.
Metadata for compiled code uses a lot less memory.
Improved code generation 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
Exit tracing option now supports sampling
- --trace-exits-sample-rate=N
The default value for --yjit-exec-mem-size is changed from 64 to 128.
Multiple bug fixes

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.