NEWS for Ruby 2.4.0

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 2.3.0 release

Language changes

  • Multiple assignment in conditional expression is now allowed.

    Feature #10617
  • Refinements is enabled at method by Symbol#to_proc. [Feature #9451]

  • Refinements is enabled with Kernel#send and BasicObject#__send__.

    Feature #11476
  • Rescue modifier now applicable to method arguments.

    Feature #12686
  • Toplevel return is now allowed. [Feature #4840]

Core classes updates (outstanding ones only)

Stdlib updates (outstanding ones only)

Compatibility issues (excluding feature bug fixes)

  • Array#sum and Enumerable#sum are implemented. [Feature #12217] Ruby itself has no compatibility problem because Ruby didn't have sum method for arrays before Ruby 2.4. However many third party gems, activesupport, facets, simple_stats, etc, defines sum method. These implementations are mostly compatible but there are subtle differences. Ruby's sum method should be mostly compatible but it is impossible to be perfectly compatible with all of them.

  • Fixnum and Bignum are unified into Integer [Feature #12005] Fixnum class and Bignum class is removed. Integer class is changed from abstract class to concrete class. For example, 0 is an instance of Integer: 0.class returns Integer. The constants Fixnum and Bignum is bound to Integer. So obj.kind_of?(Fixnum) works as obj.kind_of?(Integer). At C-level, Fixnum object and Bignum object should be distinguished by FIXNUM_P(obj) and RB_TYPE_P(obj, T_BIGNUM). RUBY_INTEGER_UNIFICATION can be used to detect this feature at C-level. 0.class == Integer can be used to detect this feature at Ruby-level. The C-level constants, rb_cFixnum and rb_cBignum, are removed. They can cause compilation failure.

  • String/Symbol#upcase/downcase/swapcase/capitalize(!) now work for all of Unicode, not only for ASCII. [Feature #10085] No change is needed if the data is in ASCII anyway or if the limitation to ASCII was only tolerated while waiting for a more extensive implementation. A change (using the :ascii option) is needed in cases where Unicode data is processed, but the operation has to be limited to ASCII only. A good example of this are internationalized domain names.

  • TRUE / FALSE / NIL These constants are now obsoleted. [Feature #12574] Use true / false / nil resp. instead.

Stdlib compatibility issues (excluding feature bug fixes)

  • DateTime

  • Psych

  • RDoc

    • Update to RDoc 5.0.0

  • RubyGems

    • Update to RubyGems 2.6.8

  • shellwords

    • Shellwords.shellwords (shellsplit) treats the backslash as escape character only when followed by one of the following characters: $ ` “ \ <newline>

      Bug #10055
  • Time

  • thread

    • the extension library is removed. Till 2.0 it was a pure ruby script “thread.rb”, which has precedence over “thread.so”, and has been provided in $LOADED_FEATURES since 2.1.

  • Tk

  • XMLRPC

  • Zlib

C API updates

  • ruby_show_version() will no longer exits the process, if RUBY_SHOW_COPYRIGHT_TO_DIE is set to 0. This will be the default in the future.

  • rb_gc_adjust_memory_usage() [Feature #12690]

Supported platform changes

  • FreeBSD < 4 is no longer supported

Implementation improvements

  • In some condition, `[x, y].max` and `[x, y].min` are optimized so that a temporal array is not created. The concrete condition is an implementation detail: currently, the array literal must have no splat, must have at least one expression but literal, the length must be <= 0x100, and Array#max and min must not be redefined. It will work in most casual and real-life use case where it is written with intent to `Math.max(x, y)`.

  • Thread deadlock detection now shows their backtrace and dependency. [Feature #8214]

  • st_table (st.c) internal data structure is improved. [Feature #12142]

  • Rational is extensively optimized. [Feature #12484]

Miscellaneous changes

  • ChangeLog is removed from the repository. It is generated from commit messages in Subversion by `make dist`. Also note that now people should follow Git style commit message. The template is written at [Short (50 chars or less) summary of changes](git-scm.com/book/ch5-2.html).

    Feature #12283