Mark fields with a prefix as non-preferred

metadata.json

{
  "name": "Mark non-preferred",
  "kind": "script",
  "description": "Given a dataset, mark as non-preferred fields starting with a prefix",
  "source_code": "script.whizzml",
  "imports":[
    ],
  "inputs":[
    {
      "name": "dataset-id",
      "type": "dataset-id",
      "description": "The dataset whose fields we want to mark"
    },
    {
      "name": "prefix",
      "type": "string",
      "description": "The prefix of the fields' names to mark"
    }],
  "outputs":[
    {
      "name": "result",
      "type": "dataset-id",
      "description": "The input dataset, now with marked fields"
    }]
}

script.whizzml

(define (mark-fields ds-id prefix)
  (let (fields (resource-fields ds-id)
        ids (keys fields)
        len (count prefix)
        flags (for (f (values fields))
                {"preferred" (not (= prefix (subs (f "name") 0 len)))}))
    (update ds-id {"fields" (make-map ids flags)})))

(define result (mark-fields dataset-id prefix))