NEWS for Ruby 3.4.0

This document is a list of user-visible feature changes since the 3.3.0 release, except for bug fixes.

Note that each entry is kept to a minimum, see links for details.

Language changes

String literals in files without a frozen_string_literal comment now emit a deprecation warning when they are mutated. These warnings can be enabled with -W:deprecated or by setting Warning[:deprecated] = true. To disable this change, you can run Ruby with the --disable-frozen-string-literal command line argument. [Feature #20205]
it is added to reference a block parameter. [Feature #18980]
Keyword splatting nil when calling methods is now supported. **nil is treated similarly to **{}, passing no keywords, and not calling any conversion methods. [Bug #20064]
Block passing is no longer allowed in index assignment (e.g. a[0, &b] = 1). [Bug #19918]
Keyword arguments are no longer allowed in index assignment (e.g. a[0, kw: 1] = 2). [Bug #20218]
GC.config added to allow setting configuration variables on the Garbage Collector. [Feature #20443]
GC configuration parameter rgengc_allow_full_mark introduced. When false GC will only mark young objects. Default is true. [Feature #20443]

Note: We're only listing outstanding class updates.

Exception
- Exception#set_backtrace now accepts arrays of Thread::Backtrace::Location. Kernel#raise, Thread#raise and Fiber#raise also accept this new format. [Feature #13557]
Range
- Range#size now raises TypeError if the range is not iterable. [Misc #18984]
- Range#step now consistently has a semantics of iterating by using + operator for all types, not only numerics. [Feature #18368]
```
(Time.utc(2022, 2, 24)..).step(24*60*60).take(3)
#=> [2022-02-24 00:00:00 UTC, 2022-02-25 00:00:00 UTC, 2022-02-26 00:00:00 UTC]
```
RubyVM::AbstractSyntaxTree
- Add RubyVM::AbstractSyntaxTree::Node#locations method which returns location objects associated with the AST node. [Feature #20624]
- Add RubyVM::AbstractSyntaxTree::Location class which holds location information. [Feature #20624]
Fiber::Scheduler
- An optional Fiber::Scheduler#blocking_region hook allows blocking operations to be moved out of the event loop in order to reduce latency and improve multi-core processor utilization. [Feature #20855]

Tempfile
- The keyword argument anonymous: true is implemented for Tempfile.create. Tempfile.create(anonymous: true) removes the created temporary file immediately. So applications don't need to remove the file. [Feature #20497]
win32/sspi.rb
- This library is now extracted from the Ruby repository to ruby/net-http-sspi. [Feature #20775]

The following default gem is added.

The following default gems are updated.

The following bundled gem is added.

The following bundled gems are updated.

The following bundled gems are promoted from default gems.

See GitHub releases like GitHub Releases of Logger or changelog for details of the default gems or bundled gems.

Error messages and backtrace displays have been changed.
- Use a single quote instead of a backtick as an opening quote. [Feature #16495]
- Display a class name before a method name (only when the class has a permanent name). [Feature #19117]
- Kernel#caller, Thread::Backtrace::Location’s methods, etc. are also changed accordingly.
  
  Old:
```
test.rb:1:in `foo': undefined method `time' for an instance of Integer
        from test.rb:2:in `<main>'
```
  New:
```
test.rb:1:in 'Object#foo': undefined method 'time' for an instance of Integer
        from test.rb:2:in '<main>'
```
Hash#inspect rendering have been changed. [Bug #20433]
- Symbol keys are displayed using the modern symbol key syntax: "{user: 1}"
- Other keys now have spaces around =>: '{"user" => 1}', while previously they didn't: '{"user"=>1}'

rb_newobj and rb_newobj_of (and corresponding macros RB_NEWOBJ, RB_NEWOBJ_OF, NEWOBJ, NEWOBJ_OF) have been removed. [Feature #20265]
Removed deprecated function rb_gc_force_recycle. [Feature #18290]

Passing a block to a method which doesn't use the passed block will show a warning on verbose mode (-w). [Feature #15554]
Redefining some core methods that are specially optimized by the interpreter and JIT like String#freeze or Integer#+ now emits a performance class warning (-W:performance or Warning[:performance] = true). [Feature #20429]