[ruby-core:79448] [Ruby trunk Bug#13196] Improve keyword argument errors when non-keyword arguments given

Issue #13196 has been updated by Robert A. Heiler.


I guess the error-reporting there did not yet account for the possibility that keyword arguments can be
mandatory too, so I agree that the message "wrong number of arguments (given 1, expected 0)" appears to
be incorrect, since one indeed has to pass a mandatory argument to that method. I assume that when
keyword args were added, this behaviour was probably not yet been noticed. I have not seen code like
"foo:" in any method definition yet either, though.

----------------------------------------
Bug #13196: Improve keyword argument errors when non-keyword arguments given
https://bugs.ruby-lang.org/issues/13196#change-62880

* Author: Olivier Lacan
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
* ruby -v: 
* Backport: 2.2: UNKNOWN, 2.3: UNKNOWN, 2.4: UNKNOWN
----------------------------------------
Given the following method definition:


```ruby
def explode(code:)
  puts "Boom!"
end
```

If a Ruby user doesn't provide any arguments when calling the `explode` method, the following helpful feedback is given:

```ruby
explode
ArgumentError: missing keyword: code
```

But when a Ruby user mistakenly provides a regular argument, the exception message is obtuse and unhelpful: 

```ruby
explode "1234"
ArgumentError: wrong number of arguments (given 1, expected 0)
```

This does not provide information to properly recover from the error. Worse, it's incorrect. It is not true that the method expected 0 arguments. The method expected 1 keyword argument.

Instead, Ruby should respond something like: 

```ruby
explode "1234"
ArgumentError: missing keyword: code, given "1234" which is not a keyword argument.
```

One could argue that this situation would call for a different error class, perhaps a `KeywordArgumentError` that would inherit from `ArgumentError`, but that would extend the scope of this feature request a bit too far in my mind. 



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