[ruby-core:117996] [Ruby master Bug#20505] Reassigning the block argument in method body keeps old block when calling super with implicit arguments

24 May 2024

      Issue #20505 has been updated by Earlopain (A S).

mame (Yusuke Endoh) wrote in #note-3:
...
Actually, `super` is totally confusing. Do you know that `super()` passes the block argument? I have been using Ruby for 20 years and never knew about it until recently.
```
class A
  def foo
    yield
  end
end
class B < A
  def foo
    super() # delegates the given block!
  end
end
B.new.foo { puts "Hello" } #=> Hello
```
As for `super`, I don't think it is a good idea to change the behavior based on only partial consistency.
My personal preference is to deprecate no-argument `super`, if possible. We have `super(...)` now, which looks much better to me.
I believe super always passes the block along, unless you explitly do `&nil`. I guess it works out most of the time but it is one of the things I wish Ruby didn't do. But changing that would be hugely disruptive I think.

This goes along with all methods accepting a block without declaring they do so, and in that context always passing it along does make sense since the method may not even have a block arg to exicitly pass along.

----------------------------------------
Bug #20505: Reassigning the block argument in method body keeps old block when calling super with implicit arguments
https://bugs.ruby-lang.org/issues/20505#change-108418

* Author: Earlopain (A S)
* Status: Open
* ruby -v: 3.3.1
* Backport: 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN
----------------------------------------
You can call super without arguments and parenthesis to pass along all the enclosing method arguments to the parent method.

You can modify positional and keyword arguments before the call to super, and the parent method will recieve these modified values. With the block arg however that isn't the case:

```rb
class A
  def positional_arg(a)
    puts a
  end

  def block_arg(&block)
    yield
  end
end

class B < A
  def positional_arg(a = nil)
    a = 'b'
    super
  end

  def block_arg(&block)
    block = proc { puts 'b' }
    super
  end
end

B.new.positional_arg('a')
B.new.positional_arg
B.new.block_arg { puts 'a' }
B.new.block_arg
```

I would expect this snippet to print `b` four times. The actual output is `b` `b` `a` and `LocalJumpError`. To get the desired output I must pass the block along explicitly with `super(&block)`.

I hope my example explains the issue good enough. I have looked through issues here and searched for documentation and haven't found any mention of this behaviour. Sorry if I missed something somewhere.

-- 
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