module GraphQL::BackwardsCompatibility

def get_arity(callable) 

def get_arity(callable)
  case callable
  when Method, Proc
    callable.arity
  else
    callable.method(:call).arity
  end
end

def wrap_arity(callable, from:, to:, name:, last: false)

If `last`, then use the last arguments to call the function.

If a wrapper is applied, warn the application with `name`.
it can be called with `to` arguments.
check its arity, and if needed, apply a wrapper so that
Given a callable whose API used to take `from` arguments, 
def wrap_arity(callable, from:, to:, name:, last: false)
  arity = get_arity(callable)
  if arity == to || arity < 0
    # It already matches, return it as is
    callable
  elsif arity == from
    # It has the old arity, so wrap it with an arity converter
    message ="#{name} with #{from} arguments is deprecated, it now accepts #{to} arguments, see:"
    backtrace = caller(0, 20)
    # Find the first line in the trace that isn't library internals:
    user_line = backtrace.find {|l| l !~ /lib\/graphql/ }
    warn(message + "\n" + user_line + "\n")
    wrapper = last ? LastArgumentsWrapper : FirstArgumentsWrapper
    wrapper.new(callable, from)
  else
    raise "Can't wrap #{callable} (arity: #{arity}) to have arity #{to}"
  end
end