From: "zverok (Victor Shepelev) via ruby-core" <ruby-core@...>
Date: 2024-05-26T11:45:23+00:00
Subject: [ruby-core:118019] [Ruby master Feature#20508] Explicit access to *, **, &, and ...

Issue #20508 has been updated by zverok (Victor Shepelev).


Regardless of the rest of the proposal,

> I'm not sure how to access the `&` variable, unless I name it. 

There is a way:

```ruby
def show_block(&)
  p proc(&)
end

show_block {} #=> #<Proc:0x00007f485eb07e28 anon_block.rb:5>
show_block &-> {} #=> #<Proc:0x00007f485eb07c98 anon_block.rb:6 (lambda)>
show_block &:to_i #=> #<Proc:0x00007f485eb07ba8(&:to_i) (lambda)>
show_block &method(:puts) #=> #<Proc:0x00007f485eb07a18 (lambda)>
show_block #=> in `proc': tried to create Proc object without a block (ArgumentError)
```

Depending on the goals, that might be enough for some introspection.

----------------------------------------
Feature #20508: Explicit access to *, **, &, and ...
https://bugs.ruby-lang.org/issues/20508#change-108439

* Author: bradgessler (Brad Gessler)
* Status: Open
----------------------------------------
I find debugging and certain meta-programming tasks challenging because there's no explicit APIs for accessing certain types of arguments in Ruby.

Here's some example code:

```ruby
def splats(one, *, two: nil, **, &)
  # These work
  p(*)
  p(**)
  # But the block doesn't show a proc.
  p(&)

  # This would show [:one, :two, :_]
  p binding.local_variables
end

splats(:arg, two: true) do
  42
end
```

I'm not sure how to access the `&` variable, unless I name it. The same applies to endless ruby methods.

I'd like to see a way to explicitly call bindings for those methods. Something like this (not sure if binding is the right place for it):

```ruby
def splats(one, *, true: nil, **, &)
  binding.arguments # Returns an array
  binding.keyword_arguments # Returns a hash
  binding.block_argument # Returns a block
end
```

These methods would give me access to the values used to call the method.




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