[ruby-core:109608] [Ruby master Feature#18959] Handle gracefully nil kwargs eg. **nil

Issue #18959 has been updated by sawa (Tsuyoshi Sawada).


In my opinion, putting the whole subhash `{id: id}` within a condition like that is redundant and ugly. 

That is one (but not the only) reason that I had asked for `Hash#compact`in #11818 (which is available). Using this, your code can be rewritten as:

```ruby
{
  some: 'value',
  id: id if id.present?,
}
.compact
```

although I would actually do:

```ruby
{
  some: 'value',
  id: id.presence,
}
.compact
```


----------------------------------------
Feature #18959: Handle gracefully nil kwargs eg. **nil
https://bugs.ruby-lang.org/issues/18959#change-98792

* Author: LevLukomskyi (Lev Lukomskyi)
* Status: Open
* Priority: Normal
----------------------------------------
The issue:

```ruby
def qwe(a: 1) end

qwe(**nil) #=> fails with `no implicit conversion of nil into Hash (TypeError)` error

{ a:1, **nil } #=>  fails with `no implicit conversion of nil into Hash (TypeError)` error
```

Reasoning:

I found myself that I often want to insert a key/value to hash if a certain condition is met, and it's very convenient to do this inside hash syntax, eg.:

```ruby
{
  some: 'value',
  **({ id: id } if id.present?),
}
```

Such syntax is much more readable than:

```ruby
h = { some: 'value' }
h[:id] = id if id.present?
h
```

Yes, it's possible to write like this:

```ruby
{
  some: 'value',
  **(id.present? ? { id: id } : {}),
}
```

but it adds unnecessary boilerplate noise.

I enjoy writing something like this in ruby on rails:

```ruby
content_tag :div, class: [*('is-hero' if hero), *('is-search-page' if search_page)].presence
```

If no conditions are met then the array is empty, then converted to nil by `presence`, and `class` attribute is not rendered if it's nil. It's short and so convenient! There should be a similar way for hashes!

I found this issue here: https://bugs.ruby-lang.org/issues/8507 where "consistency" thing is discussed. While consistency is the right thing to do, I think the main point here is to have fun with programming, and being able to write stuff in a concise and readable way.

Please, add this small feature to the language, that'd be so wonderful! 



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