Create a set from a string of elements in Rego

Question

How to create a set from a string in Rego Open Policy Agent language?

I've a string of elements like "values": "pvc-volume,emptydir-volume,hostPath,ConfigMaps" which elements need to be validated against a given set of admitted values

valid_backup_profiles := {
      "pvc-volume",
      "emptydir-volume"
    }

for example using intersection

valid_backup_profiles & elements_coming_from_string_above

I know the split(string, ",") function returning an array of elements but the array cannot be intersected with a set. Is there any smart way to generate a set from a string instead of an array?

Answer 1

The trick is to use a set comprehension:

s := {x |
  some i
  parts := split(string, ",")
  x := parts[i]
}

You can do it on one line like this if you want:

s := {x | x := split(string, ",")[_]}

Obviously this is nice and compact, but the form above is a bit easier to read. If you want to make the logic reusable, just define a function:

split_csv_set(str) = {x |
  some i
  parts := split(str, ",")
  x := parts[i]
}