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# NEWS for Ruby 3.1.0
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.
## Language changes
* Pin operator now takes an expression. [[Feature #17411]]
```ruby
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]]
```ruby
@n = 5
Prime.each_cons(2).lazy.find{_1 in [n, ^@n]}
#=> [3, 5]
```
* One-line pattern matching is no longer experimental.
* 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:
```ruby
foo[0] = bar
```
The following evaluation order is used:
1. `foo`
2. `bar`
3. `[]=` called on the result of `foo`
In Ruby before 3.1.0, multiple assignment did not follow this
evaluation order. With this code:
```ruby
foo[0], bar.baz = a, b
```
Versions of Ruby before 3.1.0 would evaluate in the following
order
1. `a`
2. `b`
3. `foo`
4. `[]=` called on the result of `foo`
5. `bar`
6. `baz=` called on the result of `bar`
Starting in Ruby 3.1.0, evaluation order is now consistent with
single assignment, with the left hand side being evaluated before
the right hand side:
1. `foo`
2. `bar`
3. `a`
4. `b`
5. `[]=` called on the result of `foo`
6. `baz=` called on the result of `bar`
[[Bug #4443]]
* Values 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`.
## Command line options
## Core classes updates
Outstanding ones only.
* Array
* Array#intersect? is added. [[Feature #15198]]
* Enumerable
* Enumerable#compact is added. [[Feature #17312]]
* Enumerable#tally now accepts an optional hash to count. [[Feature #17744]]
* Enumerator::Lazy
* Enumerator::Lazy#compact is added. [[Feature #17312]]
* File
* File.dirname now accepts an optional argument for the level to
strip path components. [[Feature #12194]]
* Integer
* Integer.try_convert is added. [[Feature #15211]]
* MatchData
* MatchData#match is added [[Feature #18172]]
* MatchData#match_length is added [[Feature #18172]]
* 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]]
* 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]]
* Queue
* Queue#initialize now accepts an Enumerable of initial values.
[[Feature #17327]]
* Thread
* Thread#native_thread_id is added. [[Feature #17853]]
* Thread::Backtrace
* Thread::Backtrace.limit, which returns the value to limit backtrace
length set by `--backtrace-limit` command line option, is added.
[[Feature #17479]]
* $LOAD_PATH
* $LOAD_PATH.resolve_feature_path does not raise. [[Feature #16043]]
* Fiber Scheduler
* Add support for `Addrinfo.getaddrinfo` using `address_resolve` hook.
[[Feature #17370]]
* Introduce non-blocking `Timeout.timeout` using `timeout_after` hook.
[[Feature #17470]]
* 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]]
## Stdlib updates
Outstanding ones only.
## Compatibility issues
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]]
## Stdlib compatibility issues
* `ERB#initialize` warns `safe_level` and later arguments even without -w.
[[Feature #14256]]
## C API updates
* Documented. [[GH-4815]]
## Implementation improvements
### JIT
* The default `--jit-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.
* `--jit-verbose` and `--jit-warning` output "JIT cancel" when JIT-ed
code is disabled because TracePoint or GC.compact is used.
* `RubyVM::MJIT` is renamed to `RubyVM::JIT`. [[Feature #17490]]
## Static analysis
### RBS
### TypeProf
## Miscellaneous changes
* 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 purpose. Do not use this in production.
[[Feature #17762]]
* Now exceptions raised in finalizers will be printed to `STDERR`, unless
`$VERBOSE` is `nil`. [[Feature #17798]]
[Bug #4443]: https://bugs.ruby-lang.org/issues/4443
[Feature #12194]: https://bugs.ruby-lang.org/issues/12194
[Feature #14256]: https://bugs.ruby-lang.org/issues/14256
[Feature #14579]: https://bugs.ruby-lang.org/issues/14579
[Feature #15198]: https://bugs.ruby-lang.org/issues/15198
[Feature #15211]: https://bugs.ruby-lang.org/issues/15211
[Feature #16043]: https://bugs.ruby-lang.org/issues/16043
[Feature #16806]: https://bugs.ruby-lang.org/issues/16806
[Feature #17312]: https://bugs.ruby-lang.org/issues/17312
[Feature #17327]: https://bugs.ruby-lang.org/issues/17327
[Feature #17411]: https://bugs.ruby-lang.org/issues/17411
[Bug #17423]: https://bugs.ruby-lang.org/issues/17423
[Feature #17479]: https://bugs.ruby-lang.org/issues/17479
[Feature #17490]: https://bugs.ruby-lang.org/issues/17490
[Feature #17724]: https://bugs.ruby-lang.org/issues/17724
[Feature #17744]: https://bugs.ruby-lang.org/issues/17744
[Feature #17762]: https://bugs.ruby-lang.org/issues/17762
[Feature #17798]: https://bugs.ruby-lang.org/issues/17798
[Bug #18003]: https://bugs.ruby-lang.org/issues/18003
[Feature #17370]: https://bugs.ruby-lang.org/issues/17370
[Feature #17470]: https://bugs.ruby-lang.org/issues/17470
[Feature #17750]: https://bugs.ruby-lang.org/issues/17750
[Feature #17853]: https://bugs.ruby-lang.org/issues/17853
[Bug #17827]: https://bugs.ruby-lang.org/issues/17827
[Feature #18008]: https://bugs.ruby-lang.org/issues/18008
[Feature #18015]: https://bugs.ruby-lang.org/issues/18015
[Feature #18029]: https://bugs.ruby-lang.org/issues/18029
[Feature #18172]: https://bugs.ruby-lang.org/issues/18172
[GH-4815]: https://github.com/ruby/ruby/pull/4815
|
