NEWS for Ruby 3.4.0 ↑

This document is a list of user-visible feature changes since the 3.3.0 release, except for bug fixes.

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

Language changes ↑

  • it is added to reference a block parameter. [Feature #18980]

  • String literals in files without a frozen_string_literal comment now emit a deprecation warning when they are mutated. These warnings can be enabled with -W:deprecated or by setting Warning[:deprecated] = true. To disable this change, you can run Ruby with the --disable-frozen-string-literal command line argument. [Feature #20205]

    • String#+@ now duplicates when mutating the string would emit a deprecation warning, offered as a replacement for the str.dup if str.frozen? pattern.

  • Keyword splatting nil when calling methods is now supported. **nil is treated similarly to **{}, passing no keywords, and not calling any conversion methods. [Bug #20064]

  • Block passing is no longer allowed in index assignment (e.g. a[0, &b] = 1). [Bug #19918]

  • Keyword arguments are no longer allowed in index assignment (e.g. a[0, kw: 1] = 2). [Bug #20218]

  • The toplevel name ::Ruby is reserved now, and the definition will be warned when Warning[:deprecated]. [Feature #20884]

Core classes updates ↑

Note: We’re only listing outstanding class updates.

Stdlib updates ↑

We only list stdlib changes that are notable feature changes.

Other changes are listed in the following sections. we also listed release history from the previous bundled version that is Ruby 3.3.0 if it has GitHub releases.

The following default gem is added.

  • win32-registry 0.1.0

The following default gems are updated.

The following bundled gem is added.

The following bundled gems are updated.

The following bundled gems are promoted from default gems.

Supported platforms ↑

Compatibility issues ↑

  • Error messages and backtrace displays have been changed.

    • Use a single quote instead of a backtick as an opening quote. [Feature #16495]

    • Display a class name before a method name (only when the class has a permanent name). [Feature #19117]

    • Extra rescue/ensure frames are no longer available on the backtrace. [Feature #20275]

    • Kernel#caller, Thread::Backtrace::Location’s methods, etc. are also changed accordingly.

      Old:

      test.rb:1:in `foo': undefined method `time' for an instance of Integer
        from test.rb:2:in `<main>'

      New:

      test.rb:1:in 'Object#foo': undefined method 'time' for an instance of Integer
        from test.rb:2:in '<main>'

  • Hash#inspect rendering have been changed. [Bug #20433]

    • Symbol keys are displayed using the modern symbol key syntax: "{user: 1}"

    • Other keys now have spaces around =>: '{"user" => 1}', while previously they didn’t: '{"user"=>1}'

  • Kernel#Float() now accepts a decimal string with decimal part omitted. [Feature #20705]

    Float("1.")    #=> 1.0 (previously, an ArgumentError was raised)
Float("1.E-1") #=> 0.1 (previously, an ArgumentError was raised)

  • String#to_f now accepts a decimal string with decimal part omitted. [Feature #20705] Note that the result changes when an exponent is specified.

    "1.".to_f    #=> 1.0
"1.E-1".to_f #=> 0.1 (previously, 1.0 was returned)

  • Refinement#refined_class has been removed. [Feature #19714]

Stdlib compatibility issues ↑

  • DidYouMean

    • DidYouMean::SPELL_CHECKERS[]= and DidYouMean::SPELL_CHECKERS.merge! are removed.

  • Net::HTTP

    • Removed the following deprecated constants:

      • Net::HTTP::ProxyMod

      • Net::NetPrivate::HTTPRequest

      • Net::HTTPInformationCode

      • Net::HTTPSuccessCode

      • Net::HTTPRedirectionCode

      • Net::HTTPRetriableCode

      • Net::HTTPClientErrorCode

      • Net::HTTPFatalErrorCode

      • Net::HTTPServerErrorCode

      • Net::HTTPResponseReceiver

      • Net::HTTPResponceReceiver

    These constants were deprecated from 2012.

  • Timeout

  • URI

    • Switched default parser to RFC 3986 compliant from RFC 2396 compliant. [Bug #19266]

C API updates ↑

  • rb_newobj and rb_newobj_of (and corresponding macros RB_NEWOBJ, RB_NEWOBJ_OF, NEWOBJ, NEWOBJ_OF) have been removed. [Feature #20265]

  • Removed deprecated function rb_gc_force_recycle. [Feature #18290]

Implementation improvements ↑

  • The default parser is now Prism. To use the conventional parser, use the command-line argument --parser=parse.y. [Feature #20564]

  • Happy Eyeballs version 2 (RFC8305), an algorithm that ensures faster and more reliable connections by attempting IPv6 and IPv4 concurrently, is used in Socket.tcp and TCPSocket.new. To disable it globally, set the environment variable RUBY_TCP_NO_FAST_FALLBACK=1 or call Socket.tcp_fast_fallback=false. Or to disable it on a per-method basis, use the keyword argument fast_fallback: false. [Feature #20108] [Feature #20782]

  • Alternative garbage collector (GC) implementations can be loaded dynamically through the modular garbage collector feature. To enable this feature, configure Ruby with --with-modular-gc at build time. GC libraries can be loaded at runtime using the environment variable RUBY_GC_LIBRARY. [Feature #20351]

  • Ruby's built-in garbage collector has been split into a separate file at gc/default/default.c and interacts with Ruby using an API defined in gc/gc_impl.h. The built-in garbage collector can now also be built as a library using make modular-gc MODULAR_GC=default and enabled using the environment variable RUBY_GC_LIBRARY=default. [Feature #20470]

  • An experimental GC library is provided based on MMTk. This GC library can be built using make modular-gc MODULAR_GC=mmtk and enabled using the environment variable RUBY_GC_LIBRARY=mmtk. This requires the Rust toolchain on the build machine. [Feature #20860]

YJIT ↑

New features ↑

  • Command-line options

    • --yjit-mem-size introduces a unified memory limit (default 128MiB) to track total YJIT memory usage, providing a more intuitive alternative to the old --yjit-exec-mem-size option.

    • --yjit-trace-exits=COUNTER allows tracing of counted exits and fallbacks.

    • --yjit-perf=codegen allows profiling of JIT code based on YJIT’s codegen functions.

    • --yjit-log enables a compilation log to track what gets compiled.

  • Ruby API

  • YJIT stats

New optimizations ↑

  • Compressed context reduces memory needed to store YJIT metadata

  • Allocate registers for local variables and Ruby method arguments

  • When YJIT is enabled, use more Core primitives written in Ruby:

  • Ability to inline small/trivial methods such as:

    • Empty methods

    • Methods returning a constant

    • Methods returning self

    • Methods directly returning an argument

  • Specialized codegen for many more runtime methods

  • Optimize String#getbyte, String#setbyte and other string methods

  • Optimize bitwise operations to speed up low-level bit/byte manipulation

  • Support shareable constants in multi-ractor mode

  • Various other incremental optimizations

Miscellaneous changes ↑

  • Passing a block to a method which doesn't use the passed block will show a warning on verbose mode (-w). In connection with this, a new strict_unused_block warning category was introduced. Turn them on with -W:strict_unused_block or Warning[:strict_unused_block] = true. [Feature #15554]

  • Redefining some core methods that are specially optimized by the interpreter and JIT like String#freeze or Integer#+ now emits a performance class warning (-W:performance or Warning[:performance] = true). [Feature #20429]