doc/NEWS/NEWS-3.1.0.md
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.
The block argument can now be anonymous if the block will only be passed to another method. [Feature #11256]
def foo(&)
bar(&)
end
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.
Parentheses can be omitted in one-line pattern matching. [Feature #16182]
[0, 1] => _, x
{y: 2} => y:
x #=> 1
y #=> 2
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:
foobar[]= called on the result of fooIn Ruby before 3.1.0, multiple assignment did not follow this evaluation order. With this code:
foo[0], bar.baz = a, b
Versions of Ruby before 3.1.0 would evaluate in the following order
abfoo[]= called on the result of foobarbaz= called on the result of barStarting in Ruby 3.1.0, the evaluation order is now consistent with single assignment, with the left-hand side being evaluated before the right-hand side:
foobarab[]= called on the result of foobaz= called on the result of barValues 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.
Non main-Ractors can get instance variables (ivars) of classes/modules if ivars refer to shareable objects. [Feature #17592]
A command syntax is allowed in endless method definitions, i.e.,
you can now write def foo = puts "Hello".
Note that private def foo = puts "Hello" does not parse.
[Feature #17398]
--disable-gems is now explicitly declared as "just for debugging".
Never use it in any real-world codebase.
[Feature #17684]Note: We're only listing outstanding class updates.
Array
Class
Class#subclasses, which returns an array of classes directly inheriting from the receiver, not including singleton classes. [Feature #18273]
class A; end
class B < A; end
class C < B; end
class D < A; end
A.subclasses #=> [D, B]
B.subclasses #=> [C]
C.subclasses #=> []
Enumerable
Enumerable#compact is added. [Feature #17312]
Enumerable#tally now accepts an optional hash to count. [Feature #17744]
Enumerable#each_cons and each_slice to return a receiver. [GH-1509]
[1, 2, 3].each_cons(2){}
# 3.0 => nil
# 3.1 => [1, 2, 3]
[1, 2, 3].each_slice(2){}
# 3.0 => nil
# 3.1 => [1, 2, 3]
Enumerator::Lazy
File
GC
"GC.measure_total_time = true" enables the measurement of GC. Measurement can introduce overhead. It is enabled by default. GC.measure_total_time returns the current setting. GC.stat[:time] or GC.stat(:time) returns measured time in milli-seconds. [[Feature #10917]]
GC.total_time returns measured time in nano-seconds. [[Feature #10917]]
Integer
Kernel
Marshal
freeze: true option.
All returned objects are frozen except for Class and
Module instances. Strings are deduplicated. [Feature #18148]MatchData
MatchData#match is added [Feature #18172]
MatchData#match_length is added [Feature #18172]
Method / UnboundMethod
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]
Module#private, #public, #protected, and #module_function will now return their arguments. If a single argument is given, it is returned. If no arguments are given, nil is returned. If multiple arguments are given, they are returned as an array. [Feature #12495]
Process
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]
String#unpack and String#unpack1 now accept an offset: keyword
argument to start the unpacking after an arbitrary number of bytes
have been skipped. If offset is outside of the string bounds
ArgumentError is raised. [Feature #18254]
Thread
Thread::Backtrace
--backtrace-limit command line option, is added.
[Feature #17479]Thread::Queue
Time
Time.new now accepts optional in: keyword argument for the
timezone, as well as Time.at and Time.now, so that is now
you can omit minor arguments to Time.new. [Feature #17485]
Time.new(2021, 12, 25, in: "+07:00")
#=> 2021-12-25 00:00:00 +0700
At the same time, time component strings are converted to integers more strictly now.
Time.new(2021, 12, 25, "+07:30")
#=> invalid value for Integer(): "+07:30" (ArgumentError)
Ruby 3.0 or earlier returned probably unexpected result
2021-12-25 07:00:00, not 2021-12-25 07:30:00 nor
2021-12-25 00:00:00 +07:30.
Time#strftime supports RFC 3339 UTC for unknown offset local
time, -0000, as %-z. [Feature #17544]
TracePoint
$LOAD_PATH
Fiber Scheduler
Add support for Addrinfo.getaddrinfo using address_resolve hook.
[Feature #17370]
Introduce non-blocking Timeout.timeout using timeout_after hook.
[Feature #17470]
Introduce new scheduler hooks io_read and io_write along with a
low level IO::Buffer for zero-copy read/write. [Feature #18020]
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
include and prepend are deprecated, and import_methods is added
instead. [Bug #17429]The following default gem are updated.
The following bundled gems are updated.
The following default gems are now bundled gems.
The following gems has been removed from the Ruby standard library.
Coverage measurement now supports suspension. You can use Coverage.suspend
to stop the measurement temporarily, and Coverage.resume to restart it.
See [Feature #18176] in detail.
Random::Formatter is moved to random/formatter.rb, so that you can
use Random#hex, Random#base64, and so on without SecureRandom.
[Feature #18190]
Note: 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]ERB#initialize warns safe_level and later arguments even without -w.
[Feature #14256]
lib/debug.rb is replaced with debug.gem
Kernel#pp in lib/pp.rb uses the width of IO#winsize by default.
This means that the output width is automatically changed depending on
your terminal size. [Feature #12913]
Psych 4.0 changes Psych.load as safe_load by the default.
You may need to use Psych 3.3.2 for migrating to this behavior.
[Bug #17866]
Documented. [GH-4815]
rb_gc_force_recycle is deprecated and has been changed to a no-op.
[Feature #18290]
Inline cache mechanism is introduced for reading class variables. [Feature #17763]
instance_eval and instance_exec now only allocate a singleton class when
required, avoiding extra objects and improving performance. [GH-5146]
The performance of Struct accessors is improved. [GH-5131]
mandatory_only? builtin special form to improve performance on
builtin methods. [GH-5112]
Experimental feature Variable Width Allocation in the garbage collector.
This feature is turned off by default and can be enabled by compiling Ruby
with flag USE_RVARGC=1 set. [Feature #18045] [Feature #18239]
--jit to --mjit, and alias --jit to --yjit
on non-Windows x86-64 platforms and to --mjit on others.The default --mjit-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.
--mjit-verbose and --mjit-warning output "JIT cancel" when JIT-ed
code is disabled because TracePoint or GC.compact is used.
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 benchmarks based on real-world software, up to 22% on railsbench, 39% on liquid-render.
Fast warm-up times.
Limited to Unix-like x86-64 platforms for now.
Generics type parameters can be bounded (PR).
# `T` must be compatible with the `_Output` interface.
# `PrettyPrint[String]` is ok, but `PrettyPrint[Integer]` is a type error.
class PrettyPrint[T < _Output]
interface _Output
def <<: (String) -> void
end
attr_reader output: T
def initialize: (T output) -> void
end
Type aliases can be generic. (PR)
# Defines a generic type `list`.
type list[T] = [ T, list[T] ]
| nil
type str_list = list[String]
type int_list = list[Integer]
rbs collection has been introduced to manage gems’ RBSs.
Many signatures for built-in and standard libraries have been added/updated.
It includes many bug fixes and performance improvements too.
See the CHANGELOG.md for more information.
A new debugger debug.gem is bundled.
debug.gem is a 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.
A built-in gem called error_highlight has been introduced. It shows fine-grained error locations in the backtrace.
Example: title = json[:article][:title]
If json is nil, it shows:
$ ruby test.rb
test.rb:2:in `<main>': undefined method `[]' for nil:NilClass (NoMethodError)
title = json[:article][:title]
^^^^^^^^^^
If json[:article] returns nil, it shows:
$ ruby test.rb
test.rb:2:in `<main>': undefined method `[]' for nil:NilClass (NoMethodError)
title = json[:article][:title]
^^^^^^^^
This feature is enabled by default.
You can disable it by using a command-line option --disable-error_highlight.
See the repository in detail.
The IRB now has an autocomplete feature, where you can just type in the code, and the completion candidates dialog will appear. You can use Tab and Shift+Tab to move up and down.
If documents are installed when you select a completion candidate, the documentation dialog will appear next to the completion candidates dialog, showing part of the content. You can read the full document by pressing Alt+d.
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 purposes. Do not use this in production.
[Feature #17762]
Now exceptions raised in finalizers will be printed to STDERR, unless
$VERBOSE is nil. [Feature #17798]
ruby -run -e httpd displays URLs to access. [Feature #17847]
Add ruby -run -e colorize to colorize Ruby code using
IRB::Color.colorize_code.