# 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. `https://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) { }

- Non-Symbol keys in a keyword arguments hash cause an exception.

- 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]

### Core classes updates (outstanding ones only)¶ ↑

`Array`
  New methods

    - Added `Array#union` and `Array#difference` instance methods. [Feature #14097]

  Modified method

    - `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 method

    - 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

    - Added `Dir#each_child` and `Dir#children` instance methods. [Feature #13969]

`Enumerable`
  New method

    - `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 method

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

  Aliased method

    - `Enumerable#filter` is a new alias for `Enumerable#select`. [Feature #13784]

`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 method

    - `Enumerator::Lazy#filter` is a new alias for `Enumerator::Lazy#select`. [Feature #13784]

`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 method

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

`Exception`
  New options

    - `Exception#full_message` takes `:highlight` and `:order` options. [Bug #14324]

`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 option

    - Added new mode character `'x'` to open files for exclusive access. [Feature #11258]

`Kernel`
  Aliased method

    - `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

    - Added `Method#<<` and `Method#>>` for `Proc` composition. [Feature #6284]

`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 option

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

`NilClass`
  New method

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

`NoMethodError`
  New option

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

`Numeric`
  Incompatible changes

    - `Numeric#step` now returns an instance of the `Enumerator::ArithmeticSequence` class rather than one of the `Enumerator` class.

`OpenStruct`
  Modified method

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

`Proc`
  New methods

    - Added `Proc#<<` and `Proc#>>` for `Proc` composition. [Feature #6284]

  Incompatible changes

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

`Random`
  New method

    - Added `Random.bytes`. [Feature #4938]

`Range`
  New method

    - Added `Range#%` instance method. [Feature #14697]

  Incompatible changes

    - `Range#===` now uses the cover? instead of the include? method. [Feature #14575]

    - `Range#cover?` now accepts a `Range` object. [Feature #14473]

    - `Range#step` now returns an instance of the `Enumerator::ArithmeticSequence` class rather than one of the `Enumerator` class.

Regexp/String

  - 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::AbstractSyntaxTree.parse` parses a given string and returns AST nodes. [experimental]

    - `RubyVM::AbstractSyntaxTree.parse_file` parses a given file and returns AST nodes. [experimental]

    - `RubyVM::AbstractSyntaxTree.of` returns AST nodes of the given proc or method. [experimental]

`RubyVM`
  New method

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

`String`

  - `String#crypt` is now deprecated. [Feature #14915]

  New features

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

`Struct`
  Modified method

    - `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

    - `TracePoint#parameters` [Feature #14694]

    - `TracePoint#instruction_sequence` [Feature #15287]

    - `TracePoint#eval_script` [Feature #15287]

  Modified method

    - `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 method

    - 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

    - Add `Net::HTTPClientException` to deprecate Net::HTTPServerException, whose name is misleading. [Bug #14688]

NKF

  - Upgrade to nkf v2.1.5

`Psych`

  - Upgrade to `Psych` 3.1.0

`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

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 method

    - `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`

  - Object#=~ is deprecated. [Feature #15231]

### 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`

  - The following methods are removed.

    - BigDecimal.allocate

    - BigDecimal.ver

  - Every `BigDecimal` object is frozen. [Feature #13984]

  - BigDecimal() parses the given string similar to Float().

  - String#to_d parses the receiver string similar to `String#to_f`.

  - `BigDecimal.new` will be removed in version 2.0.

`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].

### 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