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# -*- rdoc -*-

NEWS for Ruby 2.6.0

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. bugs.ruby-lang.org/issues/$FEATURE_OR_BUG_NUMBER)

Changes since the 2.5.0 release

Language changes

  • $SAFE now is a process global state and can be set to 0 again. [Feature #14250]

  • Refinements take place at block passing. [Feature #14223]

  • Refinements take place at Kernel#public_send. [Feature #15326]

  • Refinements take place at Kernel#respond_to?. [Feature #15327]

  • else without rescue now causes a syntax error. [EXPERIMENTAL] [Feature #14606]

  • Constant names may start with a non-ASCII capital letter. [Feature #13770]

  • Endless ranges are introduced. You can use a Range that has no end, like (0..) (or similarly (0…)). [Feature #12912]

    The following shows typical use cases:

    ary[1..]                              # identical to ary[1..-1]
(1...).each {|index| block }          # infinite loop from index 1
ary.zip(1..) {|elem, index| block }   # ary.each.with_index(1) { }

  • The “shadowing outer local variable” warning is removed. [Feature #12490]

    You can now write the following without warning:

    user = users.find {|user| cond(user) }

  • Print cause of the exception if the exception is not caught and printed its backtraces and error message. [Feature #8257]

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

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

Core classes updates (outstanding ones only)

Array
New methods
Modified methods

  • Array#to_h now accepts a block that maps elements to new key/value pairs. [Feature #15143]

Aliased methods

  • Array#filter is a new alias for Array#select. [Feature #13784]

  • Array#filter! is a new alias for Array#select!. [Feature #13784]

Binding
New methods

  • Added Binding#source_location. [Feature #14230]

    This method returns the source location of the binding, a 2-element array of __FILE__ and __LINE__. Traditionally, the same information could be retrieved by eval(“[__FILE__, __LINE__]”, binding), but we are planning to change this behavior so that Kernel#eval ignores binding’s source location [Bug #4352]. So, users should use this newly-introduced method instead of Kernel#eval.

Dir
New methods
Enumerable
New methods

  • Enumerable#chain returns an enumerator object that iterates over the elements of the receiver and then those of each argument in sequence. [Feature #15144]

Modified methods

  • Enumerable#to_h now accepts a block that maps elements to new key/value pairs. [Feature #15143]

Aliased methods
Enumerator::ArithmeticSequence

  • This is a new class to represent a generator of an arithmetic sequence, that is a number sequence defined by a common difference. It can be used for representing what is similar to Python’s slice. You can get an instance of this class from Numeric#step and Range#step.

Enumerator::Chain

  • This is a new class to represent a chain of enumerables that works as a single enumerator, generated by such methods as Enumerable#chain and Enumerator#+.

Enumerator::Lazy
Aliased methods
Enumerator
New methods

  • Enumerator#+ returns an enumerator object that iterates over the elements of the receiver and then those of the other operand. [Feature #15144]

ENV
Modified methods

  • ENV.to_h now accepts a block that maps names and values to new keys and values. [Feature #15143]

Exception
New options
Hash
Modified methods

  • Hash#merge, Hash#merge!, and Hash#update now accept multiple arguments. [Feature #15111]

  • Hash#to_h now accepts a block that maps keys and values to new keys and values. [Feature #15143]

Aliased methods

  • Hash#filter is a new alias for Hash#select. [Feature #13784]

  • Hash#filter! is a new alias for Hash#select!. [Feature #13784]

IO
New options

  • Added new mode character ‘x’ to open files for exclusive access. [Feature #11258]

Kernel
Aliased methods

  • Kernel#then is a new alias for Kernel#yield_self. [Feature #14594]

New options

  • Kernel#Complex, Kernel#Float, Kernel#Integer, and Kernel#Rational take an :exception option to specify the way of error handling. [Feature #12732]

  • Kernel#system takes an :exception option to raise an exception on failure. [Feature #14386]

Incompatible changes

  • Kernel#system and Kernel#exec do not close non-standard file descriptors (the default of the :close_others option is changed to false, but we still set the FD_CLOEXEC flag on descriptors we create). [Misc #14907]

KeyError
New options

  • KeyError.new accepts :receiver and :key options to set receiver and key in Ruby code. [Feature #14313]

Method
New methods
Module
Modified methods

  • Module#method_defined?, Module#private_method_defined?, and Module#protected_method_defined? now accept the second parameter as optional. If it is true (the default value), it checks ancestor modules/classes, or checks only the class itself. [Feature #14944]

NameError
New options

  • NameError.new accepts a :receiver option to set receiver in Ruby code. [Feature #14313]

NilClass
New methods

  • NilClass#=~ is added for compatibility. [Feature #15231]

NoMethodError
New options

  • NoMethodError.new accepts a :receiver option to set receiver in Ruby code. [Feature #14313]

Numeric
Incompatible changes
OpenStruct
Modified methods

  • OpenStruct#to_h now accepts a block that maps keys and values to new keys and values. [Feature #15143]

Proc
New methods
Incompatible changes

  • Proc#call doesn’t change $SAFE any more. [Feature #14250]

Random
New methods

  • Added Random.bytes. [Feature #4938]

Range
New methods

  • Added Range#% instance method. [Feature #14697]

Incompatible changes
Regexp/String

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

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

  • Update Unicode version from 10.0.0 to 11.0.0. [Feature #14802]

    This includes a rewrite of the grapheme cluster (/X/) algorithm and special-casing for Georgian MTAVRULI on String#downcase.

  • Update Emoji version from 5.0 to 11.0.0 [Feature #14802]

RubyVM::AbstractSyntaxTree
New methods
RubyVM
New methods

  • RubyVM.resolve_feature_path identifies the file that will be loaded by “require(feature)”. [experimental] [Feature #15230]

String
New features

  • String#split yields each substring to the block if given. [Feature #4780]

Struct
Modified methods

  • Struct#to_h now accepts a block that maps keys and values to new keys and values. [Feature #15143]

Aliased method

  • Struct#filter is a new alias for Struct#select. [Feature #13784]

Time
New features

  • Time.new and Time#getlocal accept a timezone object as well as a UTC offset string. Time#+, Time#-, and Time#succ also preserve the timezone. [Feature #14850]

TracePoint
New features

  • “script_compiled” event is supported. [Feature #15287]

New methods
Modified methods

  • TracePoint#enable accepts new keywords “target:” and “target_line:”.

    Feature #15289

Stdlib updates (outstanding ones only)

BigDecimal

Update to version 1.4.0. This version includes several compatibility issues, see Compatibility issues section below for details.

Modified methods

  • BigDecimal() accepts the new keyword “exception:” similar to Float().

Note for the differences among recent versions

You should want to know the differences among recent versions of bigdecimal. Please select the suitable version of bigdecimal according to the following information.

  • 1.3.5 has BigDecimal.new without “exception:” keyword. You can see the deprecation warning of BigDecimal.new when you specify “-w” option. BigDecimal(), BigDecimal.new, and Object#to_d methods are the same.

  • 1.4.0 has BigDecimal.new with “exception:” keyword. You always see the deprecation warning of BigDecimal.new. Object#to_d method is different from BigDecimal() and BigDecimal.new.

  • 2.0.0 will be released soon after releasing Ruby 2.6.0. This version will not have the BigDecimal.new method.

Bundler

  • Add Bundler to Standard Library. [Feature #12733]

  • Use 1.17.2, the latest stable version.

Coverage

A oneshot_lines mode is added. [Feature #15022]

This mode checks “whether each line was executed at least once or not”, instead of “how many times each line was executed”. A hook for each line is fired at most once, and after it is fired the hook flag is removed, i.e., it runs with zero overhead.

New options

  • Add :oneshot_lines keyword argument to Coverage.start.

  • Add :stop and :clear keyword arguments to Coverage.result. If clear is true, it clears the counters to zero. If stop is true, it disables coverage measurement.

New methods

  • Coverage.line_stub, which is a simple helper function that creates the “stub” of line coverage from a given source code.

CSV

  • Upgrade to 3.0.2. This includes performance improvements especially for writing. Writing is about 2 times faster. See github.com/ruby/csv/blob/master/NEWS.md.

ERB
New options

  • Add :trim_mode and :eoutvar keyword arguments to ERB.new. Now non-keyword arguments other than the first one are softly deprecated and will be removed when Ruby 2.5 becomes EOL. [Feature #14256]

  • erb command’s -S option is deprecated, and will be removed in the next version.

FileUtils
New methods

  • FileUtils#cp_lr. [Feature #4189]

Matrix
New methods

  • Matrix#antisymmetric?, Matrix#skew_symmetric?

  • Matrix#map!, Matrix#collect! [Feature #14151]

  • Matrix#[]=

  • Vector#map!, Vector#collect!

  • Vector#[]=

Net
New options

  • Add :write_timeout keyword argument to Net::HTTP.new. [Feature #13396]

New methods

  • Add Net::HTTP#write_timeout and Net::HTTP#write_timeout=. [Feature #13396]

New constant
Net::IMAP

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

NKF

  • Upgrade to nkf v2.1.5

Psych
RDoc

  • Become about 2 times faster.

  • Use SOURCE_DATE_EPOCH to generate files.

  • Fix method line number that slipped off.

  • Enable –width, –exclude, and –line-numbers that were ignored.

  • Add support for blockquote by “>>>” in default markup notation.

  • Add support for “Raises” lines in TomDoc notation.

  • Fix syntax error output.

  • Fix many parsing bugs.

REXML

  • Upgrade to REXML 3.1.9. See github.com/ruby/rexml/blob/master/NEWS.md.

Improved some XPath implementations

  • concat() function: Stringify all arguments before concatenating.

  • string() function: Support context node.

  • string() function: Support processing instruction node.

  • Support “*:#{ELEMENT_NAME}” syntax in XPath 2.0.

Fixed some XPath implementations

  • “//#{ELEMENT_NAME}[#{POSITION}]” case

  • string() function: Fix function(document) returns nodes that are out of root elements.

  • “/ #{ELEMENT_NAME} ” case

  • “/ #{ELEMENT_NAME} [ #{PREDICATE} ]” case

  • “/ #{AXIS}::#{ELEMENT_NAME}” case

  • “#{N}-#{M}” case: One or more white spaces were required before “-”

  • “/child::node()” case

  • “#{FUNCTION}()/#{PATH}” case

  • “@#{ATTRIBUTE}/parent::” case

  • “name(#{NODE_SET})” case

CSV

  • Upgrade to 3.0.9. See github.com/ruby/csv/blob/master/NEWS.md.

Date

  • Date.jisx0301, Date#jisx0301, and Date.parse provisionally support the new Japanese era as an informal extension, until the new JIS X 0301 is issued. [Feature #15742]

RSS
New options

  • RSS::Parser.parse now accepts options as Hash. :validate , :ignore_unknown_element , :parser_class options are available.

RubyGems

  • Upgrade to RubyGems 3.0.1

  • blog.rubygems.org/2018/12/19/3.0.0-released.html

  • blog.rubygems.org/2018/12/23/3.0.1-released.html

Set
Aliased methods

  • Set#filter! is a new alias for Set#select!. [Feature #13784]

URI
New constant

  • Add URI::File to handle the file URI scheme. [Feature #14035]

Compatibility issues (excluding feature bug fixes)

Dir

  • Dir.glob with ‘0’-separated pattern list will be deprecated, and is now warned. [Feature #14643]

File

  • File.read, File.binread, File.write, File.binwrite, File.foreach, and File.readlines do not invoke external commands even if the path starts with the pipe character ‘|’. [Feature #14245]

Object

Stdlib compatibility issues (excluding feature bug fixes)

  • These standard libraries have been promoted to default gems.

    • e2mmap

    • forwardable

    • irb

    • logger

    • matrix

    • mutex_m

    • ostruct

    • prime

    • rexml

    • rss

    • shell

    • sync

    • thwait

    • tracer

BigDecimal
Pathname

  • Pathname#read, Pathname#binread, Pathname#write, Pathname#binwrite, Pathname#each_line and Pathname#readlines do not invoke external commands even if the path starts with the pipe character ‘|’. This follows [Feature #14245].

C API updates

Implementation improvements

  • Speedup Proc#call because we don’t need to care about $SAFE any more. [Feature #14318]

    With lc_fizzbuzz benchmark which uses Proc#call many times we can measure x1.4 improvements. [Bug #10212]

  • Speedup block.call where block is passed block parameter. [Feature #14330]

    Ruby 2.5 improves block passing performance. [Feature #14045]

    Additionally, Ruby 2.6 improves the performance of passed block calling.

  • Introduce an initial implementation of a JIT (Just-in-time) compiler. [Feature #14235] [experimental]

    • --jit command line option is added to enable JIT. --jit-verbose=1 is good for inspection. See ruby --help for others.

    • To generate machine code, this JIT compiler uses the C compiler used for building the interpreter. Currently GCC, Clang, and Microsoft Visual C++ are supported for it.

    • --disable-mjit-support option is added to configure. This is added for JIT debugging, but if you get an error on building a header file for JIT, you can use this option to skip building it as a workaround.

    • rb_waitpid reimplemented on Unix-like platforms to maintain compatibility with processes created for JIT [Bug #14867]

  • VM generator script renewal; makes the generated VM more optimized. [GH-1779]

  • Thread cache enabled for pthreads platforms (for Thread.new and Thread.start). [Feature #14757]

  • timer thread is eliminated for platforms with POSIX timers. [Misc #14937]

  • Transient Heap (theap) is supported. [Bug #14858] [Feature #14989]

    theap is a managed heap for short-living memory objects. For example, making a small and short-living Hash object is x2 faster. With rdoc benchmark, we measured 6-7% performance improvement.

  • Native implementations (arm32, arm64, ppc64le, win32, win64, x86, amd64) of coroutines to improve performance of Fiber significantly. [Feature #14739]

Miscellaneous changes

  • On macOS, shared libraries no longer include a full version number of Ruby in their names. This eliminates the burden of each teeny upgrade on the platform that users need to rebuild every extension library.

    Before

    • libruby.2.6.0.dylib

    • libruby.2.6.dylib -> libruby.2.6.0.dylib

    • libruby.dylib -> libruby.2.6.0.dylib

    After

    • libruby.2.6.dylib

    • libruby.dylib -> libruby.2.6.dylib

  • Extracted misc/*.el files to github.com/ruby/elisp

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