given arg_one require arg_two of array -> auto passes empty string to array when empty array is given

[dejoma]

desc 'Breaking Grape', security: [jwt: []], success: { code: 201, model: SomeRepresenter }
      params do
        with documentation: { param_type: 'body' } do
          requires :arg_one, type: String, values: %w[one two three]
          given arg_one: ->(type) { type == 'two' } do
            requires :arg_two, type: Array[String], allow_blank: false
          end
        end
      end
end

POST to that endpoint with { "arg_one": "two", "arg_two": [] } and somehow the array will contain an empty string. Fails both with allow_blank false and allow_blank.

How does the empty string end up there? How does it not fail when allow_blank false?

[dblock]

1. Does it work if type is not an array (e.g. String)?
2. Does it work without given?
3. Confirm the version of Grape and Rack, could be related to https://github.com/ruby-grape/grape/issues/2298.

Probably a bug in some combination. Would appreciate a unit test that reproduces the problem in a pull request.