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# -*- rdoc -*-

NEWS for Ruby 2.7.0

This document is a list of user visible feature changes made between releases 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)

Changes since the 2.6.0 release

Language changes

Pattern matching

  • Pattern matching is introduced as an experimental feature. [Feature #14912]

    case [0, [1, 2, 3]]
in [a, [b, *c]]
pa#=> 0pb#=> 1pc#=> [2, 3]endcase {a:0, b:1}
in {a:0, x:1}
:unreachablein {a:0, b:var}
pvar#=> 1endjson = <<END{
"name": "Alice",
"age": 30,
"children": [{ "name": "Bob", "age": 2 }]
}ENDifJSON.parse(json, symbolize_names:true) in
{name:"Alice", children: [{name:"Bob", age:age}]}
page#=> 2end

  • See the following slides in detail

The spec of keyword arguments is changed towards 3.0

  • Automatic conversion of keyword arguments and positional arguments is deprecated, and conversion will be removed in Ruby 3. [Feature #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 as keywords, add a double splat operator to avoid the warning and ensure correct behavior in Ruby 3.

      deffoo(key:42); end; foo({key:42}) # warneddeffoo(**kw); end; foo({key:42}) # warneddeffoo(key:42); end; foo(**{key:42}) # OKdeffoo(**kw); end; foo(**{key:42}) # OK

    • 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.

      deffoo(h, **kw); end; foo(key:42) # warneddeffoo(h, key:42); end; foo(key:42) # warneddeffoo(h, **kw); end; foo({key:42}) # OKdeffoo(h, key:42); end; foo({key:42}) # OK

    • 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.

      deffoo(h={}, key:42); end; foo("key"=>43, key:42) # warneddeffoo(h={}, key:42); end; foo({"key"=>43, key:42}) # warneddeffoo(h={}, key:42); end; foo({"key"=>43}, key:42) # OK

    • 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.

      deffoo(opt={}); end; foo( key:42 ) # OK

  • Non-symbols are allowed as a keyword argument keys if method accepts arbitrary keywords. [Feature #14183]

    • Non-Symbol keys in a keyword arguments hash were prohibited in 2.6.0, but are now allowed again. [Bug #15658]

      deffoo(**kw); pkw; end; foo("str"=>1) #=> {"str"=>1}

  • **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]

    deffoo(h, **nil); end; foo(key:1) # ArgumentErrordeffoo(h, **nil); end; foo(**{key:1}) # ArgumentErrordeffoo(h, **nil); end; foo("str"=>1) # ArgumentErrordeffoo(h, **nil); end; foo({key:1}) # OKdeffoo(h, **nil); end; foo({"str"=>1}) # OK

  • 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]

    h = {}; deffoo(*a) aend; foo(**h) # []h = {}; deffoo(a) aend; foo(**h) # {} and warningh = {}; deffoo(*a) aend; foo(h) # [{}]h = {}; deffoo(a) aend; foo(h) # {}

Numbered parameter

  • Numbered parameter as the default block parameter is introduced as an experimental feature. [Feature #4475]

    [1, 2, 10].map { _1.to_s(16) } #=> ["1", "2", "a"]

    You can still define a local variable named _1 and so on, and that is honored when present, but renders warning.

    _1 = 0
[1].each { p _1 } # prints 0 instead of 1, but also warns.

proc/lambda without block is deprecated

  • Proc.new and Kernel#proc with no block in a method called with a block is warned now.

    deffooprocendfoo { puts"Hello" } #=> warning: Capturing the given block using Proc.new is deprecated; use `&block` instead

  • Kernel#lambda with no block in a method called with a block raises an exception.

    defbarlambdaendbar { puts"Hello" } #=> tried to create Proc object without a block (ArgumentError)

Other miscellaneous changes

  • A beginless range is experimentally introduced. It might not be as useful as an endless range, but would be good for DSL purpose. [Feature #14799]

    ary[..3] # identical to ary[0..3]where(sales:..100)

  • Setting $; to non-nil value is warned now. Use of it in String#split is warned too.

  • Setting $, to non-nil value is warned now. Use of it in Array#join is warned too.

  • Quoted here-document identifier must end within the same line.

    <<"EOS
" # This had been warned since 2.4; Now it raises a SyntaxError
EOS

  • The flip-flop syntax deprecation is reverted. [Feature #5400]

  • Comment lines can be placed between fluent dot now.

    foo# .bar
.baz# => foo.baz

  • Calling a private method with a literal self as the receiver is now allowed. [Feature #11297] [Feature #16123]

  • Modifier rescue now operates the same for multiple assignment as single assignment:

    a, b = raiserescue [1, 2]
# Previously parsed as: (a, b = raise) rescue [1, 2]# Now parsed as: a, b = (raise rescue [1, 2])

  • yield in singleton class syntax is warned and will be deprecated later [Feature #15575].

    def foo
class << Object.new
yield
end
end
foo { p :ok } #=> warning: `yield' in class syntax will not be supported from Ruby 3.0.

  • Argument forwarding by (...) is introduced. [Feature #16253]

    deffoo(...)
bar(...)
end

    All arguments to foo are forwarded to bar, including keyword and block arguments. Note that the parentheses are mandatory. ‘bar …` is parsed as an endless range.

  • Access and setting of $SAFE is now always warned. $SAFE will become a normal global variable in Ruby 3.0. [Feature #16131]

  • Object#{taint,untaint,trust,untrust} and related functions in the C-API no longer have an effect (all objects are always considered untainted), and are now warned in verbose mode. This warning will be disabled even in non-verbose mode in Ruby 3.0, and the methods and C functions will be removed in Ruby 3.2. [Feature #16131]

Core classes updates (outstanding ones only)

Array
New method

  • Added Array#intersection. [Feature #16155]

Comparable
Modified method

  • Comparable#clamp now accepts a Range argument. [Feature #14784]

    -1.clamp(0..2) #=> 01.clamp(0..2) #=> 13.clamp(0..2) #=> 2
Complex
New method

  • Added Complex#<=>. So 0 <=> 0i will not raise NoMethodError. [Bug #15857]

Dir
Modified methods

  • Dir.glob and Dir.[] no longer allow NUL-separated glob pattern. Use Array instead. [Feature #14643]

Encoding
New encoding

  • Added new encoding CESU-8 [Feature #15931]

Enumerable
New methods

  • Added Enumerable#filter_map. [Feature #15323]

    [1, 2, 3].filter_map {|x|x.odd??x.to_s:nil } #=> ["1", "3"]

  • Added Enumerable#tally. [Feature #11076]

    ["A", "B", "C", "B", "A"].tally#=> {"A"=>2, "B"=>2, "C"=>1}
Enumerator
New methods

  • Added Enumerator.produce to generate Enumerator from any custom data-transformation. [Feature #14781]

    require'date'dates = Enumerator.produce(Date.today, &:succ) #=> infinite sequence of datesdates.detect(&:tuesday?) #=> next tuesday

  • Added Enumerator::Lazy#eager that generates a non-lazy enumerator from a lazy enumerator. [Feature #15901]

    a = %w(foo bar baz)e = a.lazy.map {|x|x.upcase }.map {|x|x+"!" }.eagerpe.class#=> Enumeratorpe.map {|x|x+"?" } #=> ["FOO!?", "BAR!?", "BAZ!?"]

  • Added Enumerator::Yielder#to_proc so that a Yielder object can be directly passed to another method as a block argument. [Feature #15618]

Fiber
New method

  • Added Fiber#raise that behaves like Fiber#resume but raises an exception on the resumed fiber. [Feature #10344]

File
Modified method

  • File.extname now returns a dot string at a name ending with a dot on non-Windows platforms. [Bug #15267]

    File.extname("foo.") #=> "."
FrozenError
New method

  • Added FrozenError#receiver to return the frozen object that modification was attempted on. To set this object when raising FrozenError in Ruby code, pass it as the second argument to FrozenError.new. [Feature #15751]

GC
New method

  • Added GC.compact method 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]

    Details on the algorithm and caveats can be found here: bugs.ruby-lang.org/issues/15626

IO
New method

  • Added IO#set_encoding_by_bom to check the BOM and set the external encoding. [Bug #15210]

Integer
Modified method

  • Integer#[] now supports range operation. [Feature #8842]

    0b01001101[2, 4] #=> 0b0011
0b01001100[2..5] #=> 0b0011
0b01001100[2...6] #=> 0b0011
^^^^
Method
Modified method

  • Method#inspect shows much information. [Feature #14145]

Module
New methods

  • Added Module#const_source_location to retrieve the location where a constant is defined. [Feature #10771]

  • Added Module#ruby2_keywords for marking a method as passing keyword arguments through a regular argument splat, useful when delegating all arguments to another method in a way that can be backwards compatible with older Ruby versions. [Bug #16154]

Modified methods

  • Module#autoload? now takes an inherit optional argument, like as Module#const_defined?. [Feature #15777]

  • Module#name now always returns a frozen String. The returned String is always the same for a given Module. This change is experimental. [Feature #16150]

NilClass / TrueClass / FalseClass
Modified methods

  • NilClass#to_s, TrueClass#to_s and FalseClass#to_s now always return a frozen String. The returned String is always the same for each of these values. This change is experimental. [Feature #16150]

ObjectSpace::WeakMap
Modified method

  • ObjectSpace::WeakMap#[]= now accepts special objects as either key or values. [Feature #16035]

Regexp
Modified method

  • Regexp#match and Regexp#match? with a nil argument are deprecated and will raise a TypeError in the next release. [Feature #13083]

RubyVM
Removed method

  • RubyVM.resolve_feature_path moved to $LOAD_PATH.resolve_feature_path. [Feature #15903] [Feature #15230]

String
Unicode

  • Update Unicode version and Emoji version from 11.0.0 to 12.0.0. [Feature #15321]

  • Update Unicode version to 12.1.0, adding support for U+32FF SQUARE ERA NAME REIWA. [Feature #15195]

  • Update Unicode Emoji version to 12.1 [Feature #16272]

Symbol
New methods

  • Added Symbol#start_with? and Symbol#end_with? method. [Feature #16348]

Time
New methods

  • Added Time#ceil method. [Feature #15772]

  • Added Time#floor method. [Feature #15653]

Modified method

  • Time#inspect is separated from Time#to_s and it shows its sub second. [Feature #15958]

UnboundMethod
New method

  • Added UnboundMethod#bind_call method. [Feature #15955]

    umethod.bind_call(obj, ...) is semantically equivalent to umethod.bind(obj).call(...). This idiom is used in some libraries to call a method that is overridden. The added method does the same without allocation of intermediate Method object.

    classFoodefadd_1(x)
x+1endendclassBar<Foodefadd_1(x) # overridex+2endendobj = Bar.newpobj.add_1(1) #=> 3pFoo.instance_method(:add_1).bind(obj).call(1) #=> 2pFoo.instance_method(:add_1).bind_call(obj, 1) #=> 2
$LOAD_PATH
New method

  • Added $LOAD_PATH.resolve_feature_path. [Feature #15903] [Feature #15230]

Stdlib updates (outstanding ones only)

Bundler
CGI
CSV
Date

  • Date.jisx0301, Date#jisx0301, and Date.parse support the new Japanese era. [Feature #15742]

Delegator

  • Object#DelegateClass accepts a block and module_evals it in the context of the returned class, similar to Class.new and Struct.new.

ERB

  • Prohibit marshaling ERB instance.

IRB

  • Introduce syntax highlight inspired by pry.gem to Binding#irb source lines, REPL input, and inspect output of some core-class objects.

  • Introduce multiline mode by Reline.

  • Show documents when completion.

  • Enable auto indent and save/load history by default.

Net::FTP

  • Add Net::FTP#features to check available features, and Net::FTP#option to enable/disable each of them. [Feature #15964]

Net::HTTP

  • Add ipaddr optional parameter to Net::HTTP#start to replace the address for TCP/IP connection [Feature #5180]

Net::IMAP

  • Add Server Name Indication (SNI) support. [Feature #15594]

open-uri

  • Warn open-uri’s “open” method at Kernel. Use URI.open instead. [Misc #15893]

  • The default charset of text/* media type is UTF-8 instead of ISO-8859-1. [Bug #15933]

OptionParser

  • Now show “Did you mean?” for unknown option. [Feature #16256]

    test.rb:

    require'optparse'OptionParser.newdo|opts|opts.on("-f", "--foo", "foo") {|v| }
opts.on("-b", "--bar", "bar") {|v| }
opts.on("-c", "--baz", "baz") {|v| }
end.parse!

    example:

    $ ruby test.rb --baa
Traceback (most recent call last):
test.rb:7:in `<main>': invalid option: --baa (OptionParser::InvalidOption)
Did you mean? baz
bar
Pathname

  • Delegates 3 arguments from Pathname.glob to Dir.glob to accept base: keyword.

Racc

  • Merge 1.4.15 from upstream repository and added cli of racc.

Reline

  • New stdlib that is compatible with readline stdlib by pure Ruby and also has a multiline mode.

REXML
RSS
RubyGems
StringScanner

Compatibility issues (excluding feature bug fixes)

  • The following libraries are no longer bundled gems. Install corresponding gems to use these features.

    • CMath (cmath gem)

    • Scanf (scanf gem)

    • Shell (shell gem)

    • Synchronizer (sync gem)

    • ThreadsWait (thwait gem)

    • E2MM (e2mmap gem)

Proc

  • Proc#to_s format was changed. [Feature #16101]

Stdlib compatibility issues (excluding feature bug fixes)

  • Promote stdlib to default gems

    • The following default gems was published at rubygems.org

      • benchmark

      • cgi

      • delegate

      • getoptlong

      • net-pop

      • net-smtp

      • open3

      • pstore

      • singleton

    • The following default gems only promoted ruby-core, Not yet published at rubygems.org.

      • monitor

      • observer

      • timeout

      • tracer

      • uri

      • yaml

pathname

  • Kernel#Pathname when called with a Pathname argument now returns the argument instead of creating a new Pathname. This is more similar to other Kernel methods, but can break code that modifies the return value and expects the argument not to be modified.

profile.rb, Profiler__

  • Removed from standard library. No one maintains it from Ruby 2.0.0.

C API updates

  • Many *_kw functions have been added for setting whether the final argument being passed should be treated as keywords. You may need to switch to these functions to avoid keyword argument separation warnings, and to ensure correct behavior in Ruby 3.

  • The : character in rb_scan_args format string is now treated as keyword arguments. Passing a positional hash instead of keyword arguments will emit a deprecation warning.

  • C API declarations with ANYARGS are changed not to use ANYARGSgithub.com/ruby/ruby/pull/2404

Implementation improvements

Fiber

  • Allow selecting different coroutine implementation by using --with-coroutine=, e.g.

    ./configure --with-coroutine=ucontext
./configure --with-coroutine=copy

  • Replace previous stack cache with fiber pool cache. The fiber pool allocates many stacks in a single memory region. Stack allocation becomes O(log N) and fiber creation is amortized O(1). Around 10x performance improvement was measured in micro-benchmarks.

File

  • File.realpath now uses realpath(3) on many platforms, which can significantly improve performance.

Hash

  • Change data structure of small Hash objects. [Feature #15602]

Monitor

  • Monitor class is written in C-extension. [Feature #16255]

Thread

  • VM stack memory allocation is now combined with native thread stack, improving thread allocation performance and reducing allocation related failures. ~10x performance improvement was measured in micro-benchmarks.

JIT

  • 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.

  • Default value of --jit-max-cache is changed from 1,000 to 100

  • Default value of --jit-min-calls is changed from 5 to 10,000

Miscellaneous changes

  • Support for IA64 architecture has been removed. Hardware for testing was difficult to find, native fiber code is difficult to implement, and it added non-trivial complexity to the interpreter. [Feature #15894]

  • Require compilers to support C99 [Misc #15347]

  • Ruby’s upstream repository is changed from Subversion to Git.

    • git.ruby-lang.org/ruby.git

    • RUBY_REVISION class is changed from Integer to String.

    • RUBY_DESCRIPTION includes Git revision instead of Subversion’s one.

  • Support built-in methods in Ruby with __builtin_ syntax. [Feature #16254] Some methods are defined in *.rb (such as trace_point.rb). For example, it is easy to define a method which accepts keyword arguments.