ruby--ruby/NEWS.md

NEWS for Ruby 3.1.0

This document is a list of user visible feature changes since the 3.0.0 release, except for bug fixes.

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

Language changes

• Pin operator now takes an expression. [Feature #17411]

  Prime.each_cons(2).lazy.find_all{_1 in [n, ^(n + 2)]}.take(3).to_a
  #=> [[3, 5], [5, 7], [11, 13]]
  

• Pin operator now supports instance, class, and global variables. [Feature #17724]

  @n = 5
  Prime.each_cons(2).lazy.find{_1 in [n, ^@n]}
  #=> [3, 5]
  

• One-line pattern matching is no longer experimental.

• Multiple assignment evaluation order has been made consistent with single assignment evaluation order. With single assignment, Ruby uses a left-to-right evaluation order. With this code:

  foo[0] = bar
  

  The following evaluation order is used:

  1. foo
  2. bar
  3. []= called on the result of foo

  In Ruby before 3.1.0, multiple assignment did not follow this evaluation order. With this code:

  ```ruby
  foo[0], bar.baz = a, b
  ```
  

  Versions of Ruby before 3.1.0 would evaluate in the following order

  1. a
  2. b
  3. foo
  4. []= called on the result of foo
  5. bar
  6. baz= called on the result of bar

  Starting in Ruby 3.1.0, evaluation order is now consistent with single assignment, with the left hand side being evaluated before the right hand side:

  1. foo
  2. bar
  3. a
  4. b
  5. []= called on the result of foo
  6. baz= called on the result of bar

  [Bug #4443]

• Values in Hash literals and keyword arguments can be omitted. [Feature #14579]

  For example,

  • {x:, y:} is a syntax sugar of {x: x, y: y}.
  • foo(x:, y:) is a syntax sugar of foo(x: x, y: y).

  Constant names, local variable names, and method names are allowed as key names. Note that a reserved word is considered as a local variable or method name even if it's a pseudo variable name such as self.

Command line options

Core classes updates

Outstanding ones only.

• Array

  • Array#intersect? is added. [Feature #15198]

• Enumerable

  • Enumerable#compact is added. [Feature #17312]

  • Enumerable#tally now accepts an optional hash to count. [Feature #17744]

• Enumerator::Lazy

  • Enumerator::Lazy#compact is added. [Feature #17312]

• File

  • File.dirname now accepts an optional argument for the level to strip path components. [Feature #12194]

• Integer

  • Integer.try_convert is added. [Feature #15211]

• MatchData

  • MatchData#match is added [Feature #18172]

  • MatchData#match_length is added [Feature #18172]

• Module

  • Module#prepend now modifies the ancestor chain if the receiver already includes the argument. Module#prepend still does not modify the ancestor chain if the receiver has already prepended the argument. [Bug #17423]

• Struct

  • Passing only keyword arguments to Struct#initialize is warned. You need to use a Hash literal to set a Hash to a first member. [Feature #16806]

  • StructClass#keyword_init? is added [Feature #18008]

• String

  • Update Unicode version to 13.0.0 [Feature #17750] and Emoji version to 13.0 [Feature #18029]

• Queue

  • Queue#initialize now accepts an Enumerable of initial values. [Feature #17327]

• Thread

  • Thread#native_thread_id is added. [Feature #17853]

• Thread::Backtrace

  • Thread::Backtrace.limit, which returns the value to limit backtrace length set by --backtrace-limit command line option, is added. [Feature #17479]

• $LOAD_PATH

  • $LOAD_PATH.resolve_feature_path does not raise. [Feature #16043]

• Fiber Scheduler

  • Add support for Addrinfo.getaddrinfo using address_resolve hook. [Feature #17370]

  • Introduce non-blocking Timeout.timeout using timeout_after hook. [Feature #17470]

  • IO hooks io_wait, io_read, io_write, receive the original IO object where possible. [Bug #18003]

  • Make Monitor fiber-safe. [Bug #17827]

  • Replace copy coroutine with pthread implementation. [Feature #18015]

• Refinement

  • New class which represents a module created by Module#refine. include and prepend are deprecated, and import_methods is added instead. Bug #17429

Stdlib updates

• The following default gem are updated.
  • RubyGems
  • Bundler
  • RDoc 6.4.0
  • ReLine
  • JSON 2.6.0
  • Psych 4.0.2
  • FileUtils 1.6.0
  • Fiddle
  • StringIO 3.0.1
  • IO::Console 0.5.9
  • IO::Wait 0.2.0
  • CSV
  • Etc 1.3.0
  • Date 3.2.0
  • Zlib 2.1.1
  • StringScanner
  • IpAddr
  • Logger 1.4.4
  • OStruct 0.5.0
  • Irb
  • Racc 1.6.0
  • Delegate 0.2.0
  • Benchmark 0.2.0
  • CGI 0.3.0
  • Readline(C-ext) 0.1.3
  • Timeout 0.2.0
  • YAML 0.2.0
  • URI 0.11.0
  • OpenSSL
  • DidYouMean
  • Weakref 0.1.1
  • Tempfile 0.1.2
  • TmpDir 0.1.2
  • English 0.7.1
  • Net::Protocol 0.1.2
  • Net::Http 0.2.0
  • BigDecimal
  • OptionParser 0.2.0
  • Set
  • Find 0.1.1
  • Rinda 0.1.1
  • Erb
  • NKF 0.1.1
  • Base64 0.1.1
  • OpenUri 0.2.0
  • SecureRandom 0.1.1
  • Resolv 0.2.1
  • Resolv::Replace 0.1.0
  • Time 0.2.0
  • PP 0.2.1
  • Prettyprint 0.1.1
  • Drb 2.1.0
  • Pathname 0.2.0
  • Digest 3.1.0.pre2
  • Un 0.2.0
• The following bundled gems are updated.
  • minitest 5.14.4
  • power_assert 2.0.1
  • rake 13.0.6
  • test-unit 3.5.0
  • rbs 1.6.2
  • typeprof 0.20.0
• The following default gems are now bundled gems.
  • net-ftp
  • net-imap
  • net-pop
  • net-smtp
  • matrix
  • prime

Compatibility issues

Excluding feature bug fixes.

• rb_io_wait_readable, rb_io_wait_writable and rb_wait_for_single_fd are deprecated in favour of rb_io_maybe_wait_readable, rb_io_maybe_wait_writable and rb_io_maybe_wait respectively. rb_thread_wait_fd and rb_thread_fd_writable are deprecated. [Bug #18003]

Stdlib compatibility issues

• ERB#initialize warns safe_level and later arguments even without -w. [Feature #14256]

• lib/debug.rb is replaced with debug.gem

C API updates

• Documented. [GH-4815]

Implementation improvements

JIT

• The default --jit-max-cache is changed from 100 to 10000.

• JIT-ed code is no longer cancelled when a TracePoint for class events is enabled.

• The JIT compiler no longer skips compilation of methods longer than 1000 instructions.

• --jit-verbose and --jit-warning output "JIT cancel" when JIT-ed code is disabled because TracePoint or GC.compact is used.

• RubyVM::MJIT is renamed to RubyVM::JIT. [Feature #17490]

YJIT: New experimental in-process JIT compiler

New JIT compiler available as an experimental feature. Feature #18229

See this blog post introducing the project.

• Disabled by default, use --yjit command-line option to enable YJIT.

• Performance improvements on most real-world software, up to 22% on railsbench, 39% on liquid-render.

• Fast warm-up times.

• Limited to macOS & Linux on x86-64 platforms for now.

Static analysis

RBS

TypeProf

• Experimental IDE support has been implemented.
• Many bug fixes and performance improvements since Ruby 3.0.0.

Debugger

• A new debugger debug.gem is bundled. debug.gem is fast debugger implementation and it provides many features like remote debugging, colorful REPL, IDE (VSCode) integration and more. It replaces lib/debug.rb standard library.

• rdbg command is also installed into bin/ directory to start and control debugging execution.

error_highlight

A built-in gem, error_highlight, has been introduced. It includes fine-grained error location in backtrace:

$ ruby test.rb
test.rb:1:in `<main>': undefined method `time' for 1:Integer (NoMethodError)

1.time {}
 ^^^^^
Did you mean?  times

This gem is enabled by default. You can disable it by using a command-line option --disable-error_highlight. See the repository in detail.

Miscellaneous changes

• lib/objspace/trace.rb is added, which is a tool for tracing the object allocation. Just by requiring this file, tracing is started immediately. Just by Kernel#p, you can investigate where an object was created. Note that just requiring this file brings a large performance overhead. This is only for debugging purpose. Do not use this in production. [Feature #17762]

• Now exceptions raised in finalizers will be printed to STDERR, unless $VERBOSE is nil. [Feature #17798]