But that's the whole point of helpers, no? What do you suggest?

@dblock, you see, we want to add helper module to several endpoints and also we want to add unique resource method to each of these endpoints

it is possible with

helpers do
  include MyHelperModule

  def resource
    ...
  end
end

but grape allows us to do it with

helpers MyHelperModule do
  def resource
    ...
  end
end

and with that code resource method is added to MyHelperModule twice and the last added resource method is used in both endpoints

I suggest to always create anonymous module and include module passed in new_mod in that anonymous module. https://github.com/ruby-grape/grape/blob/master/lib/grape/dsl/helpers.rb#L31

I can create a request if you prefer.

Ok that makes total sense @vsorlov. I wonder whether this is a feature through, in Ruby if you write module MyHelperModule you'd expect it to reopen a previous one. On the other hand, we could consider modules namespaces, and maybe what you suggest has less of a surprise. I think you should make a pull request either way.