How can I prevent a positional argument from being expanded into keyword arguments?

Question

I'd like to have a method that accepts a hash and an optional keyword argument. I tried defining a method like this:

def foo_of_thing_plus_amount(thing, amount: 10)
  thing[:foo] + amount
end

When I invoke this method with the keyword argument, it works as I expect:

my_thing = {foo: 1, bar: 2}
foo_of_thing_plus_amount(my_thing, amount: 20) # => 21

When I leave out the keyword argument, however, the hash gets eaten:

foo_of_thing_plus_amount(my_thing) # => ArgumentError: unknown keywords: foo, bar

How can I prevent this from happening? Is there such a thing as an anti-splat?

Answer 1

This is a bug that was fixed in Ruby 2.0.0-p247, see this issue.

Answer 2

What about

def foo_of_thing_plus_amount(thing, opt={amount: 10})
  thing[:foo] + opt[:amount]
end

my_thing = {foo: 1, bar: 2}   # {:foo=>1, :bar=>2}
foo_of_thing_plus_amount(my_thing, amount: 20)   # 21
foo_of_thing_plus_amount(my_thing)   # 11

?