---
elements:
    - type: Hidden
      name: count

    - type: Repeatable
      counter_name: count
      elements:
        - name: foo
          constraints:
            - type: Required
              only_on_reps: 1

        - name: bar
          constraints:
            - type: Required
              only_on_reps: 2

        - name: buz
          constraints:
            - type: Required
              only_on_reps: [1, 3]

        - name: moo
          constraints:
            - type: Required