Hash as last argument leads to unnecessary object creation

[sfdcdoug]

Describe the bug

Dry::Transaction::Callable seems overly aggressive in its attempt to address a shift in the ruby language around hashes passed to methods. Within Callable is the following documentation on ruby_27_last_arg_hash?:

Ruby 2.7 gives a deprecation warning about passing a hash of parameters as the last argument to a method. Ruby 3.0 outright disallows it.

This isn't 100% true. The ruby documentation around converting arrays into arguments states (emphasis mine):

If the method accepts keyword arguments [...] Note that this behavior is currently deprecated and will emit a warning. This behavior will be removed in Ruby 3.0.

As far as I can tell, the emphasized portion is not accounted for in Dry::Transaction::Callable. This may not seem like a big deal, but from a behavior standpoint it turns calls into call-by-value instead of call-by-reference, which can lead to issues when side-effects are expected.

To Reproduce

require "dry-transaction"

class Txn
  include Dry::Transaction

  step :do_something

  def do_something(input)
    input[:side_effect] *= 2
    Success()
  end
end

input = {side_effect: 1}
Txn.new.call(input)
puts "This should be 2 => #{input[:side_effect]}"

Expected behavior

In my example input should be passed without generating a copy, allowing any modifications to the hash to be seen outside of the transaction. Locally, I have put this patch in place to address the issue:

class Dry::Transaction::Callable
  alias_method :original_ruby_27_last_arg_hash?, :ruby_27_last_arg_hash?
  def ruby_27_last_arg_hash?(args)
    parameters = operation.instance_of?(Method) ? operation.parameters : operation.method(:call).parameters
    operation_uses_kwargs = parameters.any? { |(type, _)| %i[key keyrest].include?(type) }
    operation_uses_kwargs && original_ruby_27_last_arg_hash?(args)
  end
end

I won't argue that this is the right way to do this, but it seems to work for my situation.

My environment

• Affects my production application: No. A workaround (listed above) is available.
• Ruby version: 3.3.4
• OS: macOS 13.6.9 (22G830)