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Bug #11967

closed

Mixing kwargs with optional parameters changes way method parameters are parsed

Added by markus_d (Markus Doits) about 8 years ago. Updated about 8 years ago.

Status:
Rejected
Target version:
-
ruby -v:
ruby 2.3.0p0 (2015-12-25 revision 53290) [x86_64-darwin15]
[ruby-core:72763]

Description

I have the following method:

def test(first_param = nil, keyword_arg: nil)
  puts "first_param: #{first_param}"
  puts "keyword_arg: #{keyword_arg}"
end

All the following calls do what I expect them to do:

test(:something)
#=> first_param: something
#   keyword_arg:

test(nil, keyword_arg: :keyword_arg)
#=> first_param:
#   keyword_arg: keyword_arg

test({ first_param: :is_a_hash }, keyword_arg: :is_still_working)
#=> first_param: {:first_param=>:is_a_hash}
#   keyword_arg: is_still_working

But omitting the optional keyword_arg and passing a hash as first argument gives me an error:

test(first_param: :is_a_hash)
#=> test.rb:1:in `test': unknown keyword: first_param (ArgumentError)
#           from test.rb:12:in `<main>'

I'd expect it to set first_param to { first_param: :is_hash } and keyword_arg being nil.

It seems it is interpreting every hash as keyword arg:

test(keyword_arg: :should_be_first_param)
#=> first_param:
#   keyword_arg: should_be_first_param

This should have set first_param to { keyword_arg: :should_be_first_param }, leaving keyword_arg nil in my opinion.

Making the first parameter mandatory and everything works like I'd expect to:

def test(first_param, keyword_arg: nil)
  puts "first_param: #{first_param}"
  puts "keyword_arg: #{keyword_arg}"
end

test(first_param: :is_a_hash)
#=> first_param: {:first_param=>:is_a_hash}
#   keyword_arg:

test(keyword_arg: :should_be_first_param)
#=> first_param: {:keyword_arg=>:should_be_first_param}
#=> keyword_arg:

I'd expect making a parameter optional does not change the way parameters are parsed.

Is this a parser oddity or expected behaviour?


Related issues 1 (0 open1 closed)

Related to Ruby master - Feature #14183: "Real" keyword argumentClosedActions
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