Check if a certificate validation record in Route 53 already exists before plan

main.tf

variable "zoneid" {
  type    = string
  default = "YOURZONEID"
}

variable "certificate_url" {
  type    = string
  default = "fqdn.example.com."
}

data "external" "record_checker" {
  program = ["bash", "script.sh"]
  query = {
    zoneid  = var.zoneid
    certurl = var.certificate_url
  }
}

output "is_there_one_already" {
  description = "Is there a record already?"
  value       = "${data.external.record_checker.result.number > 0}"
}

script.sh

#!/usr/bin/env bash
set -e

eval "$(jq -r '@sh "ZONEID=\(.zoneid) CERTURL=\(.certurl)"')"

NUMRECORDS=$(aws route53 list-resource-record-sets --hosted-zone-id $ZONEID --query "length(ResourceRecordSets[?ends_with(Name, '$CERTURL') && Type == 'CNAME' && ends_with(ResourceRecords[0].Value, 'acm-validations.aws.')])")

jq -n --arg number "$NUMRECORDS" '{"number":$number}'

The script format I found in https://www.terraform.io/docs/providers/external/data_source.html