ruby-core

We are pleased to announce the release of Ruby 3.0.0-preview1.

It introduces a number of new features and performance improvements.

## RBS

RBS is a language to describe the types of Ruby programs.
Type checkers including type-profiler and other tools supporting RBS
will understand Ruby programs much better with RBS definitions.

You can write down the definition of classes and modules: methods
defined in the class, instance variables and their types, and
inheritance/mix-in relations.
The goal of RBS is to support commonly seen patterns in Ruby programs
and it allows writing advanced types including union types, method
overloading, and generics. It also supports duck typing with
_interface types_.

Ruby 3.0 ships with `rbs` gem, which allows parsing and processing
type definitions written in RBS.

The following is a small example of RBS.

```rbs
module ChatApp
  VERSION: String

  class Channel
    attr_reader name: String
    attr_reader messages: Array[Message]
    attr_reader users: Array[User | Bot]              # `|` means
union types, `User` or `Bot`.

    def initialize: (String) -> void

    def post: (String, from: User | Bot) -> Message   # Method
overloading is supported.
            | (File, from: User | Bot) -> Message
  end
end
```

See [README of rbs gem](https://github.com/ruby/rbs) for more detail.

## Ractor (experimental)

Ractor is an Actor-model like concurrent abstraction designed to
provide a parallel execution feature without thread-safety concerns.

You can make multiple ractors and you can run them in parallel. Ractor
enables to make thread-safe parallel programs because ractors can not
share normal objects. Communication between ractors are supported by
message passing.

To limit sharing objects, Ractor introduces several restrictions to
the Ruby's syntax (without multiple Ractors, there is no changes).

The specification and implmentation are not matured and changed in
future, so this feature is marked as experimental and show the
experimental feature warning if Ractor is created.

The following small program calculates `prime?` in parallel with two
ractors and about x2 times faster with two or more cores than
sequential program.

```ruby
require 'prime'

# n.prime? with sent integers in r1, r2 run in parallel
r1, r2 = *(1..2).map do
  Ractor.new do
    n = Ractor.recv
    n.prime?
  end
end

# send parameters
r1.send 2**61 - 1
r2.send 2**61 + 15

# wait for the results of expr1, expr2
p r1.take #=> true
p r2.take #=> true
```

see [doc/ractor.md](https://github.com/ruby/ruby/blob/master/doc/ractor.md)
for more detail.

## Scheduler (Experimental)

`Thread#scheduler` is introduced for intercepting blocking operations.
This allows for light-weight concurrency without changing existing
code.

Currently supported classes/methods:

- `Mutex#lock`, `Mutex#unlock`, `Mutex#sleep`
- `ConditionVariable#wait`
- `Queue#pop`, `SizedQueue#push`
- `Thread#join`
- `Kernel#sleep`
- `IO#wait`, `IO#read`, `IO#write` and related methods (e.g.
`#wait_readable`, `#gets`, `#puts` and so on).
- `IO#select` is *not supported*.

The current entry point for concurrency is `Fiber.schedule{...}`
however this is subject to change by the time Ruby 3 is released.

Currently, there is a test scheduler available in
[`Async::Scheduler`](https://github.com/socketry/async/pull/56). See
[`doc/scheduler.md`](https://github.com/ruby/ruby/blob/master/doc/scheduler.md)
for more details. [Feature #16786]

**CAUTION**: This feature is strongly experimental. Both the name and
feature will change in next preview release.

## Other Notable New Features

* Rightward assignment statement is added.
  ```ruby
  fib(10) => x
  p x #=> 55
  ```

* Endless method definition is added.
  ```ruby
  def square(x) = x * x
  ```

* Find pattern is added.
  ```ruby
  case ["a", 1, "b", "c", 2, "d", "e", "f", 3]
  in [*pre, String => x, String => y, *post]
    p pre  #=> ["a", 1]
    p x    #=> "b"
    p y    #=> "c"
    p post #=> [2, "d", "e", "f", 3]
  end
  ```

* `Hash#except` is now built-in.
  ```ruby
  h = { a: 1, b: 2, c: 3 }
  p h.except(:a) #=> {:b=>2, :c=>3}
  ```

* Memory view is added as an experimental feature

    * This is a new C-API set to exchange a raw memory area, such as a
numeric array and a bitmap image, between extension libraries.  The
extension libraries can share also the metadata of the memory area
that consists of the shape, the element format, and so on.  Using
these kinds of metadata, the extension libraries can share even a
multidimensional array appropriately.  This feature is designed by
referring to Python's buffer protocol.

## Performance improvements

* Many improvements were implemented in MJIT. See NEWS in detail.

## Other notable changes since 2.7

* Keyword arguments are separated from other arguments.
  * In principle, code that prints a warning on Ruby 2.7 won't work.
See the [document](https://www.ruby-lang.org/en/news/2019/12/12/separation-of-positional-and-keyword-arguments-in-ruby-3-0/)
in detail.
  * By the way, arguments forwarding now supports leading arguments.
    ```ruby
    def method_missing(meth, ...)
      send(:"do_#{ meth }", ...)
    end
    ```

* The feature of `$SAFE` was completely removed; now it is a normal
global variable.

* The order of backtrace had been reversed at Ruby 2.5, but it was
cancelled.  Now it behaves like Ruby 2.4; an error message and the
line number where the exception occurs are printed first, and its
callers are printed later.

* Some standard libraries are updated.
  * RubyGems 3.2.0.rc.1
  * Bundler 2.2.0.rc.1
  * IRB 1.2.6
  * Reline 0.1.5

* The following libraries are no longer bundled gems.
  Install corresponding gems to use these features.
  * net-telnet
  * xmlrpc

* Promote default gems to bundled gems.
  * rexml
  * rss

* Promote stdlib to default gems. The following default gems were
published on rubygems.org
  * abbrev
  * base64
  * English
  * erb
  * find
  * io-nonblock
  * io-wait
  * net-ftp
  * net-http
  * net-imap
  * net-protocol
  * nkf
  * open-uri
  * optparse
  * resolv
  * resolv-replace
  * rinda
  * securerandom
  * set
  * shellwords
  * tempfile
  * time
  * tmpdir
  * tsort
  * weakref

See [NEWS](https://github.com/ruby/ruby/blob/v3_0_0/NEWS)
or [commit logs](https://github.com/ruby/ruby/compare/v2_7_0...v3_0_0)
for more details.


With those changes, [3385 files changed, 150159 insertions(+), 124949
deletions(-)](https://github.com/ruby/ruby/compare/v2_7_0...v3_0_0)
since Ruby 2.7.0!

Please try Ruby 3.0.0-preview1, and give us any feedback!

## Download

* <https://cache.ruby-lang.org/pub/ruby/3.0/ruby-3.0.0-preview1.tar.bz2>

      SIZE: 15538340
      SHA1: 032697f3ace0a697cd72f68bac0032c31a8328d4
      SHA256: 013bdc6e859d76d67a6fcd990d401ed57e6e25896bab96d1d0648a877f556dbb
      SHA512: 3a6a6458d9c5f06555ab8705160f6b071f4dbe9d2a91cd7848852633657b495c480d74e4b2ff2cebddda556118d26bbb271160c989bc970bb1b5cb234e868d2f

* <https://cache.ruby-lang.org/pub/ruby/3.0/ruby-3.0.0-preview1.tar.gz>

      SIZE: 17747808
      SHA1: 2842d2af2568d74c8d4071f5f536889a6b149202
      SHA256: ce8bd7534e7ec2a870b24d2145ea20e9bbe5b2d76b7dfa1102dbee5785253105
      SHA512: b94892951f842a1538f4b99022606ac2c0b5031f1ede7eef3833a8caa9ed63e9b22868509173bfefb406f263c65211db75597b152b61f49e5ba2a875fce63a27

* <https://cache.ruby-lang.org/pub/ruby/3.0/ruby-3.0.0-preview1.tar.xz>

      SIZE: 12703060
      SHA1: 91d9fbe87504924148deeec90199d6ff4d7dcf56
      SHA256: aa7cce0c99f4ea2145fef9b78d74a44857754396790cd23bad75d759811e7a2a
      SHA512: dca5dcc965c434371947c100864090e29e649e19ae24b8bb2e88a534ebd8220c5a086035a999b1e8b1cd5ec154a6985a8d8dfea56095d712d62aeea7a2054f7d

* <https://cache.ruby-lang.org/pub/ruby/3.0/ruby-3.0.0-preview1.zip>

      SIZE: 22002645
      SHA1: 4b5b61066373daf0a947d3fafe2645788504a164
      SHA256: a39a48ed9a8ca2c83d65d225a1bb3db331c6587a77ba156c20e630c1b4bfc23b
      SHA512: 10f6f28715a52093d7d9da82d1678147091b45e2f279e463626adea8efbf181485daa42565e5086057ffb45a097ffb8ff395c572b247b6b5da27d85933cf58a8

## 3.0.0-preview2 trailer

We plan to include
["type-profiler"](https://github.com/mame/ruby-type-profiler) that is
a static type analysis feature.  Stay tuned!

## 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.

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