Ruby 2.7.0 Released

We are pleased to announce the release of Ruby 2.7.0.

It introduces a number of new features and performance improvements, most notably:

  • Pattern Matching
  • REPL improvement
  • Compaction GC
  • Separation of positional and keyword arguments

Pattern Matching [Experimental]

Pattern matching, a widely used feature in functional programming languages, is introduced as an experimental feature. [Feature #14912]

It can traverse a given object and assign its value if it matches a pattern.

require "json"

json = <<END
  "name": "Alice",
  "age": 30,
  "children": [{ "name": "Bob", "age": 2 }]

case JSON.parse(json, symbolize_names: true)
in {name: "Alice", children: [{name: "Bob", age: age}]}
  p age #=> 2

For more details, please see Pattern matching - New feature in Ruby 2.7.

REPL improvement

irb, the bundled interactive environment (REPL; Read-Eval-Print-Loop), now supports multi-line editing. It is powered by reline, a readline-compatible library implemented in pure Ruby. It also provides rdoc integration. In irb you can display the reference for a given class, module, or method. [Feature #14683], [Feature #14787], [Feature #14918]

Besides, source lines shown by Binding#irb and inspect results for core-class objects are now colorized.

Compaction GC

This release introduces Compaction GC which can defragment a fragmented memory space.

Some multi-threaded Ruby programs may cause memory fragmentation, leading to high memory usage and degraded speed.

The GC.compact method is introduced for compacting the heap. This function compacts live objects in the heap so that fewer pages may be used, and the heap may be more CoW (copy-on-write) friendly. [Feature #15626]

Separation of positional and keyword arguments

Automatic conversion of keyword arguments and positional arguments is deprecated, and conversion will be removed in Ruby 3. [Feature #14183]

See the article “Separation of positional and keyword arguments in Ruby 3.0” in detail. Only the changes are as follows.

  • When a method call passes a Hash at the last argument, and when it passes no keywords, and when the called method accepts keywords, a warning is emitted. To continue treating the hash as keywords, add a double splat operator to avoid the warning and ensure correct behavior in Ruby 3.

    def foo(key: 42); end; foo({key: 42})   # warned
    def foo(**kw);    end; foo({key: 42})   # warned
    def foo(key: 42); end; foo(**{key: 42}) # OK
    def foo(**kw);    end; foo(**{key: 42}) # OK
  • When a method call passes keywords to a method that accepts keywords, but it does not pass enough required positional arguments, the keywords are treated as a final required positional argument, and a warning is emitted. Pass the argument as a hash instead of keywords to avoid the warning and ensure correct behavior in Ruby 3.

    def foo(h, **kw); end; foo(key: 42)      # warned
    def foo(h, key: 42); end; foo(key: 42)   # warned
    def foo(h, **kw); end; foo({key: 42})    # OK
    def foo(h, key: 42); end; foo({key: 42}) # OK
  • When a method accepts specific keywords but not a keyword splat, and a hash or keywords splat is passed to the method that includes both Symbol and non-Symbol keys, the hash will continue to be split, and a warning will be emitted. You will need to update the calling code to pass separate hashes to ensure correct behavior in Ruby 3.

    def foo(h={}, key: 42); end; foo("key" => 43, key: 42)   # warned
    def foo(h={}, key: 42); end; foo({"key" => 43, key: 42}) # warned
    def foo(h={}, key: 42); end; foo({"key" => 43}, key: 42) # OK
  • If a method does not accept keywords, and is called with keywords, the keywords are still treated as a positional hash, with no warning. This behavior will continue to work in Ruby 3.

    def foo(opt={});  end; foo( key: 42 )   # OK
  • Non-symbols are allowed as keyword argument keys if the method accepts arbitrary keywords. [Feature #14183]

    def foo(**kw); p kw; end; foo("str" => 1) #=> {"str"=>1}
  • **nil is allowed in method definitions to explicitly mark that the method accepts no keywords. Calling such a method with keywords will result in an ArgumentError. [Feature #14183]

    def foo(h, **nil); end; foo(key: 1)       # ArgumentError
    def foo(h, **nil); end; foo(**{key: 1})   # ArgumentError
    def foo(h, **nil); end; foo("str" => 1)   # ArgumentError
    def foo(h, **nil); end; foo({key: 1})     # OK
    def foo(h, **nil); end; foo({"str" => 1}) # OK
  • Passing an empty keyword splat to a method that does not accept keywords no longer passes an empty hash, unless the empty hash is necessary for a required parameter, in which case a warning will be emitted. Remove the double splat to continue passing a positional hash. [Feature #14183]

    h = {}; def foo(*a) a end; foo(**h) # []
    h = {}; def foo(a) a end; foo(**h)  # {} and warning
    h = {}; def foo(*a) a end; foo(h)   # [{}]
    h = {}; def foo(a) a end; foo(h)    # {}

If you want to disable the deprecation warnings, please use a command-line argument -W:no-deprecated or add Warning[:deprecated] = false to your code.

Other Notable New Features

  • Numbered parameters as default block parameters are introduced. [Feature #4475]

  • A beginless range is experimentally introduced. It might not be as useful as an endless range, but would be good for DSL purposes. [Feature #14799]

    ary[..3]  # identical to ary[0..3]
    rel.where(sales: ..100)
  • Enumerable#tally is added. It counts the occurrence of each element.

    ["a", "b", "c", "b"].tally
    #=> {"a"=>1, "b"=>2, "c"=>1}
  • Calling a private method with a literal self as the receiver is now allowed. [Feature #11297], [Feature #16123]

    def foo
    private :foo
  • Enumerator::Lazy#eager is added. It generates a non-lazy enumerator from a lazy enumerator. [Feature #15901]

    a = %w(foo bar baz)
    e = {|x| x.upcase }.map {|x| x + "!" }.eager
    p e.class               #=> Enumerator
    p {|x| x + "?" }  #=> ["FOO!?", "BAR!?", "BAZ!?"]

Performance improvements

  • JIT [Experimental]

    • JIT-ed code is recompiled to less-optimized code when an optimization assumption is invalidated.

    • Method inlining is performed when a method is considered as pure. This optimization is still experimental and many methods are NOT considered as pure yet.

    • The default value of --jit-min-calls is changed from 5 to 10,000.

    • The default value of --jit-max-cache is changed from 1,000 to 100.

  • Fiber’s cache strategy is changed and fiber creation is speeded up. GH-2224

  • Module#name, true.to_s, false.to_s, and nil.to_s now always return a frozen String. The returned String is always the same for a given object. [Experimental] [Feature #16150]

  • The performance of CGI.escapeHTML is improved. GH-2226

  • The performance of Monitor and MonitorMixin is improved. [Feature #16255]

  • Per-call-site method cache, which has been there since around 1.9, was improved: cache hit rate raised from 89% to 94%. See GH-2583

  • RubyVM::InstructionSequence#to_binary method generates compiled binary. The binary size is reduced. [Feature #16163]

Other notable changes since 2.6

  • Some standard libraries are updated.
  • The following libraries are no longer bundled gems. Install corresponding gems to use these features.
    • CMath (cmath gem)
    • Scanf (scanf gem)
    • Shell (shell gem)
    • Synchronizer (sync gem)
    • ThreadsWait (thwait gem)
    • E2MM (e2mmap gem)
  • profile.rb was removed from standard library.

  • Promote stdlib to default gems
    • The following default gems were published on
      • benchmark
      • cgi
      • delegate
      • getoptlong
      • net-pop
      • net-smtp
      • open3
      • pstore
      • singleton
    • The following default gems were only promoted at ruby-core, but not yet published on
      • monitor
      • observer
      • timeout
      • tracer
      • uri
      • yaml
  • and proc with no block in a method called with a block is warned now.

  • lambda with no block in a method called with a block raises an exception.

  • Update Unicode version and Emoji version from 11.0.0 to 12.0.0. [Feature #15321]

  • Update Unicode version to 12.1.0, adding support for U+32FF SQUARE ERA NAME REIWA. [Feature #15195]

  • Date.jisx0301, Date#jisx0301, and Date.parse support the new Japanese era. [Feature #15742]

  • Require compilers to support C99. [Misc #15347]

See NEWS or commit logs for more details.

With those changes, 4190 files changed, 227498 insertions(+), 99979 deletions(-) since Ruby 2.6.0!

Merry Christmas, Happy Holidays, and enjoy programming with Ruby 2.7!



    SIZE: 14703381
    SHA1: b54f4633174dbc55db77d9fd6d0ef90cc35503af
    SHA256: 7aa247a19622a803bdd29fdb28108de9798abe841254fe8ea82c31d125c6ab26
    SHA512: 8b8dd0ceba65bdde53b7c59e6a84bc6bf634c676bfeb2ff0b3604c362c663b465397f31ff6c936441b3daabb78fb7a619be5569480c95f113dd0453488761ce7

    SIZE: 16799684
    SHA1: 6f4e99b5556010cb27e236873cb8c09eb8317cd5
    SHA256: 8c99aa93b5e2f1bc8437d1bbbefd27b13e7694025331f77245d0c068ef1f8cbe
    SHA512: 973fc29b7c19e96c5299817d00fbdd6176319468abfca61c12b5e177b0fb0d31174a5a5525985122a7a356091a709f41b332454094940362322d1f42b77c9927

    SIZE: 11990900
    SHA1: 943c767cec037529b8e2d3cc14fc880cad5bad8d
    SHA256: 27d350a52a02b53034ca0794efe518667d558f152656c2baaf08f3d0c8b02343
    SHA512: dd5690c631bf3a2b76cdc06902bcd76a89713a045e136debab9b8a81ff8c433bbb254aa09e4014ca1cf85a69ff4bcb13de11da5e40c224e7268be43ef2194af7

    SIZE: 20571744
    SHA1: fbebdd3a2a641f9a81f7d8db5abd926acea27e80
    SHA256: 8bf2050fa1fc76882f878fd526e4184dc54bd402e385efa80ef5fd3b810522e0
    SHA512: 5060f2dd3bfd271ef255b17589d6d014260d7ec2d97b48112b717ee01c62fe125c3fe04f813e02d607cea3f0a2a812b14eb3a28d06c2551354dfeff5f4c3dd6b

What is Ruby

Ruby was first developed by Matz (Yukihiro Matsumoto) in 1993, and is now developed as Open Source. It runs on multiple platforms and is used all over the world especially for web development.