Backport ruby 2.7.0-xx released articles to /ko

Author: Sangyong Sim

ko/news/_posts/2019-11-23-ruby-2-7-0-preview3-released.md

@@ -0,0 +1,364 @@
+---
+layout: news_post
+title: "Ruby 2.7.0-preview3 Released"
+author: "naruse"
+translator:
+date: 2019-11-23 12:00:00 +0000
+lang: en
+---
+
+We are pleased to announce the release of Ruby 2.7.0-preview3.
+
+A preview version is released to gather feedback for the final release
+planned for December.
+This preview3 is mainly released to confirm the compatibility of
+keyword arguments.
+
+It also introduces a number of new features and performance improvements,
+most notably:
+
+* Compaction GC
+* Pattern Matching
+* REPL improvement
+* Separation of positional and keyword arguments
+
+## 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 friendly.
+[[Feature #15626]](https://bugs.ruby-lang.org/issues/15626)
+
+## Pattern Matching [Experimental]
+
+Pattern matching, a widely used feature in functional programming languages,
+is introduced as an experimental feature.
+[[Feature #14912]](https://bugs.ruby-lang.org/issues/14912)
+
+It can traverse a given object and assign its value if it matches a pattern.
+
+{% highlight ruby %}
+require "json"
+
+json = <<END
+{
+  "name": "Alice",
+  "age": 30,
+  "children": [{ "name": "Bob", "age": 2 }]
+}
+END
+
+case JSON.parse(json, symbolize_names: true)
+in {name: "Alice", children: [{name: "Bob", age: age}]}
+  p age #=> 2
+end
+{% endhighlight %}
+
+For more details, please see
+[Pattern matching - New feature in Ruby 2.7](https://speakerdeck.com/k_tsj/pattern-matching-new-feature-in-ruby-2-dot-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 pure Ruby implementation.
+It also provides rdoc integration. In `irb` you can display the reference
+for a given class, module, or method.
+[[Feature #14683]](https://bugs.ruby-lang.org/issues/14683),
+[[Feature #14787]](https://bugs.ruby-lang.org/issues/14787),
+[[Feature #14918]](https://bugs.ruby-lang.org/issues/14918)
+
+Besides, source lines shown at `binding.irb` and inspect results
+for core-class objects are now colorized.
+
+<video autoplay="autoplay" controls="controls" muted="muted" width="576" height="259">
+  <source src="https://cache.ruby-lang.org/pub/media/irb_improved_with_key_take2.mp4" type="video/mp4">
+</video>
+
+## 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]](https://bugs.ruby-lang.org/issues/14183)
+
+* 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.
+
+  {% highlight ruby %}
+  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
+  {% endhighlight %}
+
+* 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.
+
+  {% highlight ruby %}
+  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
+  {% endhighlight %}
+
+* 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.
+
+  {% highlight ruby %}
+  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
+  {% endhighlight %}
+
+* 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.
+
+  {% highlight ruby %}
+  def foo(opt={});  end; foo( key: 42 )   # OK
+  {% endhighlight %}
+
+* Non-symbols are allowed as keyword argument keys if the method accepts
+  arbitrary keywords.
+  [[Feature #14183]](https://bugs.ruby-lang.org/issues/14183)
+
+  {% highlight ruby %}
+  def foo(**kw); p kw; end; foo("str" => 1) #=> {"str"=>1}
+  {% endhighlight %}
+
+* `**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]](https://bugs.ruby-lang.org/issues/14183)
+
+  {% highlight ruby %}
+  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
+  {% endhighlight %}
+
+* 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]](https://bugs.ruby-lang.org/issues/14183)
+
+  {% highlight ruby %}
+  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)    # {}
+  {% endhighlight %}
+
+NOTE: Too many deprecation warnings about keyword argument incompatibility
+have been pointed out to be too verbose.  Currently, two possible solutions
+are discussed; disabling deprecation warnings by default
+([#16345](https://bugs.ruby-lang.org/issues/16345))
+or suppressing duplicated warnings
+([#16289](https://bugs.ruby-lang.org/issues/16289)).
+The final decision is not made, but will be fixed by the official release.
+
+## Other Notable New Features
+
+* A method reference operator, `.:`, was introduced
+  as an experimental feature in earlier previews, but was reverted.
+  [[Feature #12125]](https://bugs.ruby-lang.org/issues/12125),
+  [[Feature #13581]]( https://bugs.ruby-lang.org/issues/13581),
+  [[Feature #16275]](https://bugs.ruby-lang.org/issues/16275)
+
+* Numbered parameter as the default block parameter is introduced
+  as an experimental feature.
+  [[Feature #4475]](https://bugs.ruby-lang.org/issues/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]](https://bugs.ruby-lang.org/issues/14799)
+
+  {% highlight ruby %}
+  ary[..3]  # identical to ary[0..3]
+  rel.where(sales: ..100)
+  {% endhighlight %}
+
+* `Enumerable#tally` is added.  It counts the occurrence of each element.
+
+  {% highlight ruby %}
+  ["a", "b", "c", "b"].tally
+  #=> {"a"=>1, "b"=>2, "c"=>1}
+  {% endhighlight %}
+
+* Calling a private method on `self` is now allowed.
+  [[Feature #11297]](https://bugs.ruby-lang.org/issues/11297),
+  [[Feature #16123]](https://bugs.ruby-lang.org/issues/16123)
+
+  {% highlight ruby %}
+  def foo
+  end
+  private :foo
+  self.foo
+  {% endhighlight %}
+
+* `Enumerator::Lazy#eager` is added.
+  It generates a non-lazy enumerator from a lazy enumerator.
+  [[Feature #15901]](https://bugs.ruby-lang.org/issues/15901)
+
+  {% highlight ruby %}
+  a = %w(foo bar baz)
+  e = a.lazy.map {|x| x.upcase }.map {|x| x + "!" }.eager
+  p e.class               #=> Enumerator
+  p e.map {|x| x + "?" }  #=> ["FOO!?", "BAR!?", "BAZ!?"]
+  {% endhighlight %}
+
+## 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.
+
+* ~~`Symbol#to_s`, `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]](https://bugs.ruby-lang.org/issues/16150)~~ reverted
+
+* The performance of `CGI.escapeHTML` is improved.
+  [GH-2226](https://github.com/ruby/ruby/pull/2226)
+
+* The performance of Monitor and MonitorMixin is improved.
+  [[Feature #16255]](https://bugs.ruby-lang.org/issues/16255)
+
+## Other notable changes since 2.6
+
+* Some standard libraries are updated.
+  * Bundler 2.1.0.pre.3
+    ([History](https://github.com/bundler/bundler/blob/2-1-stable/CHANGELOG.md#210pre3-november-8-2019))
+  * RubyGems 3.1.0.pre.3
+    ([History](https://github.com/rubygems/rubygems/blob/3.1/History.txt))
+  * CSV 3.1.2
+    ([NEWS](https://github.com/ruby/csv/blob/v3.1.2/NEWS.md))
+  * Racc 1.4.15
+  * REXML 3.2.3
+    ([NEWS](https://github.com/ruby/rexml/blob/v3.2.3/NEWS.md))
+  * RSS 0.2.8
+    ([NEWS](https://github.com/ruby/rss/blob/v0.2.8/NEWS.md))
+  * StringScanner 1.0.3
+  * Some other libraries that have no original version are also updated.
+
+* Promote stdlib to default gems
+  * The following default gems were published on rubygems.org
+    * 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 rubygems.org.
+    * monitor
+    * observer
+    * timeout
+    * tracer
+    * uri
+    * yaml
+
+* `Proc.new` 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 errs.
+
+* Update Unicode version and Emoji version from 11.0.0 to 12.0.0.
+  [[Feature #15321]](https://bugs.ruby-lang.org/issues/15321)
+
+* Update Unicode version to 12.1.0,
+  adding support for U+32FF SQUARE ERA NAME REIWA.
+  [[Feature #15195]](https://bugs.ruby-lang.org/issues/15195)
+
+* `Date.jisx0301`, `Date#jisx0301`, and `Date.parse` support the
+  new Japanese era.
+  [[Feature #15742]](https://bugs.ruby-lang.org/issues/15742)
+
+* Require compilers to support C99
+  [[Misc #15347]](https://bugs.ruby-lang.org/issues/15347)
+  * Details of our dialect:
+    <https://bugs.ruby-lang.org/projects/ruby-master/wiki/C99>
+
+* ~~`Regexp#match{?}` with `nil` raises TypeError as String, Symbol.
+  [[Feature #13083]](https://bugs.ruby-lang.org/issues/13083)~~ reverted
+
+3895 files changed, 213426 insertions(+), 96934 deletions(-)
+
+See [NEWS](https://github.com/ruby/ruby/blob/v2_7_0_preview3/NEWS)
+or [commit logs](https://github.com/ruby/ruby/compare/v2_6_0...v2_7_0_preview3)
+for more details.
+
+With those changes,
+[stat](https://github.com/ruby/ruby/compare/v2_6_0...v2_7_0_preview3)
+since Ruby 2.6.0!
+
+Enjoy programming with Ruby 2.7!
+
+## Download
+
+{% assign release = site.data.releases | where: "version", "2.7.0-preview3" | first %}
+
+* <{{ release.url.bz2 }}>
+
+      SIZE: {{ release.size.bz2 }}
+      SHA1: {{ release.sha1.bz2 }}
+      SHA256: {{ release.sha256.bz2 }}
+      SHA512: {{ release.sha512.bz2 }}
+
+* <{{ release.url.gz }}>
+
+      SIZE: {{ release.size.gz }}
+      SHA1: {{ release.sha1.gz }}
+      SHA256: {{ release.sha256.gz }}
+      SHA512: {{ release.sha512.gz }}
+
+* <{{ release.url.xz }}>
+
+      SIZE: {{ release.size.xz }}
+      SHA1: {{ release.sha1.xz }}
+      SHA256: {{ release.sha256.xz }}
+      SHA512: {{ release.sha512.xz }}
+
+* <{{ release.url.zip }}>
+
+      SIZE: {{ release.size.zip }}
+      SHA1: {{ release.sha1.zip }}
+      SHA256: {{ release.sha256.zip }}
+      SHA512: {{ release.sha512.zip }}
+
+## 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.