Array params with at_least_one_of having custom validation message

When we have array as a params with elements and a validation like at_least_one_of, mutually_exclusive, ... the generated JSON has an extra field which is undesired. This field is present only when we have a custom message filed passed in the validation (message: 'is missing')

params do
  requires :my_top_arr, type: Array, allow_blank: false do
    optional :my_elem1,
             type: Float
    optional :my_elem2,
             type: String
    at_least_one_of :my_elem2,
                    :status,
                    message: 'is missing'
  end
end

The generated JSON is:

[
  [0] {
    "description": null,
             "in": "formData",
          "items": {
      "type": "float"
    },
           "name": "my_top_arr[][my_elem1]",
       "required": false,
           "type": "array"
  },
  [1] {
    "description": null,
             "in": "formData",
          "items": {
      "type": "string"
    },
           "name": "my_top_arr[][my_elem2]",
       "required": false,
           "type": "array"
  },
  [2] {
    "description": null,
             "in": "formData",
          "items": {
      "type": "string"
    },
           "name": "my_top_arr[][my_top_arr]",
       "required": false,
           "type": "array"
  },
  [3] {
    "description": null,
             "in": "formData",
          "items": {
      "type": "string"
    },
           "name": "my_top_arr[][{:message=>\"is missing\"}]",
       "required": false,
           "type": "array"
  }
]

The last field my_top_arr[][{:message=>\"is missing\"}] seems to be extra generated.

This field is generated only when i pass message: 'is missing' to the at_least_one_of validation.
*The message key is used by grape for custom validation message.

Start by reproducing the params definition and inspect the code that turns validation options into generated formData parameters. Confirm that supplying a custom message creates the extra parameter name, then verify that the unwanted field is absent while the valid array element parameters remain.