Grape::Exceptions::UnknownValidator

I have the following files:

# app/controllers/api/v2/base.rb
module Api
  module V2
    class Base < Grape::API
      mount V2::Jobs
    end
  end
end

# app/controllers/api/v2/jobs.rb
module Api
  module V2
    class Jobs < Grape::API
      resources :jobs do
        params do
          requires :id, type: String, uuid: true
        end
        get ':id' do
        end
      end
    end
  end
end

# app/controllers/api/v2/validators/uuid.rb
module Api
  module V2
    module Validators
      class Uuid < ::Grape::Validations::Base

        REGEX = %r{[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}}

        def validate_param!(attr_name, params)
          unless (params[attr_name] =~ REGEX).zero?
            fail ::Grape::Exceptions::Validation, params: [@scope.full_name(attr_name)], message: 'must be a valid UUID'
          end
        end

      end
    end
  end
end

If I want the above to work, I have to manually require the validator class in base.rb file, like so:

require_relative './validators/uuid'

which result in throwing warnings:

app/controllers/api/v2/validators/uuid.rb:6: warning: already initialized constant Api::V2::Validators::Uuid::REGEX
app/controllers/api/v2/validators/uuid.rb:6: warning: previous definition of REGEX was here

since rails will automatically require the validator as well. Any idea why grape is not able to pick up the custom validator? Looks like a require order issue or something. Any clue?

Thanks

Start by comparing app/controllers/api/v2/base.rb, jobs.rb, and validators/uuid.rb with Rails' automatic loading behavior and Grape's custom validator lookup. Reproduce the UUID validation path without the manual require, then confirm the validator is discovered once and no duplicate-constant warning is emitted.