Arguments wrapper

arguments.rb

require "ostruct"

class Arguments
  def initialize(arguments)
    @whiny     = arguments.delete(:whiny) || false
    @arguments = arguments
    @delegee   = OpenStruct.new(@arguments)
  end

  def method_missing(method, *args)
    @delegee.send(method, *args)
  rescue NoMethodError
    if whiny?
      raise ArgumentError.new("No argument matches '#{method}': available arguments '#{@arguments.keys.join(', ')}'")
    end
  end

  private

  def whiny?
    !!@whiny
  end
end

arguments_spec.rb

require "rubygems"
require "rspec"
require "arguments"

describe Arguments do
  let(:args) do
    { foo: "bar" }
  end

  subject(:arguments) { Arguments.new(args) }

  it { expect(arguments.foo).to eq "bar" }
  it { expect(arguments.foo_b).to be_nil }

  context "when whiny" do
    subject(:arguments) { Arguments.new(args.merge(whiny: true)) }
    it { expect { arguments.foo_b }.to raise_error }
  end
end