ruby/NEWS.md

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# NEWS for Ruby 2.8.0 (tentative; to be 3.0.0)
This document is a list of user visible feature changes
since the **2.7.0** release, except for bug fixes.
Note that each entry is kept so brief that no reason behind or reference
information is supplied with. For a full list of changes with all
sufficient information, see the ChangeLog file or Redmine
(e.g. `https://bugs.ruby-lang.org/issues/$FEATURE_OR_BUG_NUMBER`).
## Language changes
* Keyword arguments are now separated from positional arguments.
Code that resulted in deprecation warnings in Ruby 2.7 will now
result in ArgumentError or different behavior. [[Feature #14183]]
* Procs accepting a single rest argument and keywords are no longer
subject to autosplatting. This now matches the behavior of Procs
accepting a single rest argument and no keywords.
[[Feature #16166]]
```ruby
pr = proc{|*a, **kw| [a, kw]}
pr.call([1])
# 2.7 => [[1], {}]
# 3.0 => [[[1]], {}]
pr.call([1, {a: 1}])
# 2.7 => [[1], {:a=>1}] # and deprecation warning
# 3.0 => [[[1, {:a=>1}]], {}]
```
* $SAFE is now a normal global variable with no special behavior.
[[Feature #16131]]
* yield in singleton class definitions in methods is now a SyntaxError
instead of a warning. yield in a class definition outside of a method
is now a SyntaxError instead of a LocalJumpError. [[Feature #15575]]
* Rightward assignment statement is added. [EXPERIMENTAL]
[[Feature #15921]]
```ruby
fib(10) => x
```
* Endless method definition is added. [EXPERIMENTAL]
[[Feature #16746]]
```ruby
def square(x) = x * x
```
## Command line options
### `--help` option
When the environment variable `RUBY_PAGER` or `PAGER` is present and has
non-empty value, and the standard input and output are tty, `--help`
option shows the help message via the pager designated by the value.
[[Feature #16754]]
## Core classes updates
Outstanding ones only.
* Dir
* Modified method
* Dir.glob and Dir.[] now sort the results by default, and
accept `sort:` keyword option. [[Feature #8709]]
* Hash
* Modified method
* Hash#transform_keys now accepts a hash that maps keys to new
keys. [[Feature #16274]]
* Kernel
* Modified method
* Kernel#clone when called with `freeze: false` keyword will call
#initialize_clone with the `freeze: false` keyword.
[[Bug #14266]]
* Kernel#eval when called with two arguments will use "(eval)"
for `__FILE__` and 1 for `__LINE__` in the evaluated code.
[[Bug #4352]]
* Module
* Modified method
* Module#include now includes the arguments in modules and
classes that have already included or prepended the receiver,
mirroring the behavior if the arguments were included in the
receiver before the other modules and classes included or
prepended the receiver. [[Feature #9573]]
* Symbol
* Modified method
* Symbol#to_proc now returns a lambda Proc.
[[Feature #16260]]
## Stdlib updates
Outstanding ones only.
* Net::HTTP
* New method
* Add Net::HTTP#verify_hostname= and Net::HTTP#verify_hostname
to skip hostname verification. [[Feature #16555]]
* Modified method
* Net::HTTP.get, Net::HTTP.get_response, and Net::HTTP.get_print can
take request headers as a Hash in the second argument when the first
argument is a URI.
## Compatibility issues
Excluding feature bug fixes.
* Regexp literals are frozen [[Feature #8948]] [[Feature #16377]]
```ruby
/foo/.frozen? #=> true
```
* Bundled gems
* net-telnet and xmlrpc have been removed from the bundled gems.
If you are interested in maintaining them, please comment on
your plan to https://github.com/ruby/xmlrpc
or https://github.com/ruby/net-telnet.
* EXPERIMENTAL: Hash#each consistently yields a 2-element array [[Bug #12706]]
* Now `{ a: 1 }.each(&->(k, v) { })` raises an ArgumentError
due to lambda's arity check.
* This is experimental; if it brings a big incompatibility issue,
it may be reverted until 2.8/3.0 release.
* When writing to STDOUT redirected to a closed pipe, no broken pipe
error message will be shown now. [[Feature #14413]]
* `TRUE`/`FALSE`/`NIL` constants are no longer defined.
## Stdlib compatibility issues
Excluding feature bug fixes.
## C API updates
* C API functions related to $SAFE have been removed.
[[Feature #16131]]
* C API header file `ruby/ruby.h` was split. [[GH-2991]] Should have no implact
on extension libraries, but users might experience slow compilations.
## Implementation improvements
* The number of hashes allocated when using a keyword splat in
a method call has been reduced to a maximum of 1, and passing
a keyword splat to a method that accepts specific keywords
does not allocate a hash.
## Miscellaneous changes
* Methods using `ruby2_keywords` will no longer keep empty keyword
splats, those are now removed just as they are for methods not
using `ruby2_keywords`.
* Taint deprecation warnings are now issued in regular mode in
addition to verbose warning mode. [[Feature #16131]]
[Bug #4352]: https://bugs.ruby-lang.org/issues/4352
[Feature #8709]: https://bugs.ruby-lang.org/issues/8709
[Feature #8948]: https://bugs.ruby-lang.org/issues/8948
[Feature #9573]: https://bugs.ruby-lang.org/issues/9573
[Feature #14183]: https://bugs.ruby-lang.org/issues/14183
[Bug #14266]: https://bugs.ruby-lang.org/issues/14266
[Feature #14413]: https://bugs.ruby-lang.org/issues/14413
[Feature #15575]: https://bugs.ruby-lang.org/issues/15575
[Feature #16131]: https://bugs.ruby-lang.org/issues/16131
[Feature #16166]: https://bugs.ruby-lang.org/issues/16166
[Feature #16260]: https://bugs.ruby-lang.org/issues/16260
[Feature #16274]: https://bugs.ruby-lang.org/issues/16274
[Feature #16377]: https://bugs.ruby-lang.org/issues/16377
[Bug #12706]: https://bugs.ruby-lang.org/issues/12706
[Feature #15921]: https://bugs.ruby-lang.org/issues/15921
[Feature #16555]: https://bugs.ruby-lang.org/issues/16555
[Feature #16746]: https://bugs.ruby-lang.org/issues/16746
[Feature #16754]: https://bugs.ruby-lang.org/issues/16754
[GH-2991]: https://github.com/ruby/ruby/pull/2991