NEWS.md

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

• 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]

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

• 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]

Core classes updates

Note: We're only listing outstanding class updates.

• Exception

  • Exception#set_backtrace now accepts arrays of Thread::Backtrace::Location. Kernel#raise, Thread#raise and Fiber#raise also accept this new format. [Feature #13557]

• GC

  • GC.config added to allow setting configuration variables on the Garbage Collector. [Feature #20443]

  • GC configuration parameter rgengc_allow_full_mark introduced. When false GC will only mark young objects. Default is true. [Feature #20443]

• Hash

  • Hash.new now accepts an optional capacity: argument, to preallocate the hash with a given capacity. This can improve performance when building large hashes incrementally by saving on reallocation and rehashing of keys. [Feature #19236]

• Fiber::Scheduler

  • An optional Fiber::Scheduler#blocking_operation_wait hook allows blocking operations to be moved out of the event loop in order to reduce latency and improve multi-core processor utilization. [Feature #20876]

• IO::Buffer

  • IO::Buffer#copy can release the GVL, allowing other threads to run while copying data. [Feature #20902]

• Integer

  • Integer#** used to return Float::INFINITY when the return value is large, but now returns an Integer. If the return value is extremely large, it raises an exception. [Feature #20811]

• MatchData

  • MatchData#bytebegin and MatchData#byteend have been added. [Feature #20576]

• Ractor

  • require in Ractor is allowed. The requiring process will be run on the main Ractor. Ractor._require(feature) is added to run requiring process on the main Ractor. [Feature #20627]

  • Ractor.main? is added. [Feature #20627]

  • Ractor.[] and Ractor.[]= are added to access the ractor local storage of the current Ractor. [Feature #20715]

• Range

  • Range#size now raises TypeError if the range is not iterable. [Misc #18984]

  • Range#step now consistently has a semantics of iterating by using + operator for all types, not only numerics. [Feature #18368]

    (Time.utc(2022, 2, 24)..).step(24*60*60).take(3)
    #=> [2022-02-24 00:00:00 UTC, 2022-02-25 00:00:00 UTC, 2022-02-26 00:00:00 UTC]

• Rational

  • Rational#** used to return Float::INFINITY or Float::NAN when the numerator of the return value is large, but now returns an Integer. If it is extremely large, it raises an exception. [Feature #20811]

• Refinement

  • Removed deprecated method Refinement#refined_class. [Feature #19714]

• RubyVM::AbstractSyntaxTree

  • Add RubyVM::AbstractSyntaxTree::Node#locations method which returns location objects associated with the AST node. [Feature #20624]
  • Add RubyVM::AbstractSyntaxTree::Location class which holds location information. [Feature #20624]

• Time

  • On Windows, now Time#zone encodes the system timezone name in UTF-8 instead of the active code page, if it contains non-ASCII characters. [Bug #20929]

• Warning

  • Add Warning.categories method which returns a list of possible warning categories. [Feature #20293]

Stdlib updates

• 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.

• Tempfile

  • The keyword argument anonymous: true is implemented for Tempfile.create. Tempfile.create(anonymous: true) removes the created temporary file immediately. So applications don't need to remove the file. [Feature #20497]

• Timeout

  • Reject negative values for Timeout.timeout. [Bug #20795]

• URI

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

• win32/sspi.rb

  • This library is now extracted from the Ruby repository to ruby/net-http-sspi. [Feature #20775]

The following default gem is added.

• win32-registry 0.1.0

The following default gems are updated.

• RubyGems 3.6.0.dev
• benchmark 0.4.0
• bundler 2.6.0.dev
• date 3.4.1
• delegate 0.4.0
• did_you_mean 2.0.0
• erb 4.0.4
• error_highlight 0.7.0
• etc 1.4.4
• fcntl 1.2.0
• fiddle 1.1.6.dev
• fileutils 1.7.3
• io-console 0.8.0
• io-nonblock 0.3.1
• ipaddr 1.2.7
• irb 1.14.1
• json 2.9.0
• logger 1.6.2
• net-http 0.6.0
• open-uri 0.5.0
• optparse 0.6.0
• ostruct 0.6.1
• pathname 0.4.0
• pp 0.6.2
• prism 1.0.0
• pstore 0.1.4
• psych 5.2.0
• rdoc 6.8.1
• reline 0.5.12
• resolv 0.5.0
• securerandom 0.4.0
• set 1.1.1
• shellwords 0.2.1
• singleton 0.3.0
• stringio 3.1.2.dev
• strscan 3.1.1.dev
• syntax_suggest 2.0.2
• tempfile 0.3.1
• time 0.4.1
• timeout 0.4.2
• tmpdir 0.3.0
• uri 1.0.2
• win32ole 1.9.0
• yaml 0.4.0
• zlib 3.2.0

The following bundled gem is added.

• repl_type_completor 0.1.7

The following bundled gems are updated.

• minitest 5.25.4
• power_assert 2.0.4
• rake 13.2.1
• test-unit 3.6.4
• rexml 3.3.9
• rss 0.3.1
• net-ftp 0.3.8
• net-imap 0.5.1
• net-smtp 0.5.0
• prime 0.1.3
• rbs 3.7.0
• typeprof 0.21.11
• debug 1.9.2
• racc 1.8.1

The following bundled gems are promoted from default gems.

• mutex_m 0.3.0
• getoptlong 0.2.1
• base64 0.2.0
• bigdecimal 3.1.8
• observer 0.1.2
• abbrev 0.1.2
• resolv-replace 0.1.1
• rinda 0.2.0
• drb 2.2.1
• nkf 0.2.0
• syslog 0.1.2
• csv 3.3.0

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

• Object#singleton_method now returns methods in modules prepended to or included in the receiver's singleton class. [Bug #20620]

  o = Object.new
  o.extend(Module.new{def a = 1})
  o.singleton_method(:a).call #=> 1
  

Stdlib compatibility issues

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) is used in Socket.tcp. To disable it, use the keyword argument fast_fallback: false. [Feature #20108]

• Happy Eyeballs version 2 (RFC8305) is implemented in TCPSocket.new. To enable it, use the keyword argument fast_fallback: true. (This entry is temporary. It should be merged with the above entry after it becomes settled) [Feature #20782]

• Array#each is rewritten in Ruby for better performance [Feature #20182].

• Alternative GC implementations can be loaded dynamically. Configure Ruby --with-modular-gc to enable. Alternative GC libraries can be loaded at runtime using the environment variable RUBY_GC_LIBRARY. [Feature #20351], [Feature #20470]

• An experimental GC library is provided based on MMTk. Configure Ruby --with-modular-gc, build as normal, then build the GC library: make modular-gc MODULAR_GC=mmtk. Enable with RUBY_GC_LIBRARY=mmtk. This requires a working Rust compiler, and Cargo on the build machine. [Feature #20860]

JIT

Miscellaneous changes

• Passing a block to a method which doesn't use the passed block will show a warning on verbose mode (-w). [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]