getting error 'Keyword "optional" is not a valid type constructor' in terraform with terraform version ">= 0.15" - apache-kafka

Question

In the current terraform pipeline, I am passing topics as a list
locals {
test_topics = [
{
name = "topic1"
is_public = true
version = 1
is_cleanup_policy_compact = true
max_message_bytes = "-1"
partition_count = 3
},
{
name = "topic2"
is_public = true
version = 1
is_cleanup_policy_compact = true
max_message_bytes = "-1"
partition_count = 4
},
{
name = "topic3"
is_public = true
version = 1
is_cleanup_policy_compact = true
max_message_bytes = "-1"
partition_count = 5
},
{
name = "topic4"
is_public = true
version = 1
is_cleanup_policy_compact = true
max_message_bytes = "-1"
},
{
name = "topic5"
is_public = true
version = 1
is_cleanup_policy_compact = true
max_message_bytes = "-1"
partition_count = 5
}
]
}
# example create topic it automatically assigns READ WRITE access to the service account and READ access to all PUBLIC topics
module "test_topics" {
source = "../kafka_topic"
topics = "${local.test_topics}"
environment = var.environment
data_domain = var.data_domain
service_account = var.service_account
}
and declaring variables in child modules like below
variable "topics" {
type = list(object({
name = string
is_public = bool
is_cleanup_policy_compact = bool
version = number
max_message_bytes = number
partition_count = number
}))
description = "list of topics with their configuration"
default = null
}
and in child main.tf we are creating the topics using following code
resource "kafka_topic" "topic" {
count = length(var.topics)
name = "${lookup(var.topics[count.index], "is_public") ? "public" :"private"}_${var.environment}_${var.data_domain}_${lookup(var.topics[count.index], "name")}_${lookup(var.topics[count.index], "version")}"
partitions = lookup(var.topics[count.index], "partition_count") == null ? 6 : "${lookup(var.topics[count.index], "partition_count")}"
replication_factor = 3
config = {
"cleanup.policy" = lookup(var.topics[count.index], "is_cleanup_policy_compact") ? "compact" : "delete"
"max.message.bytes" = lookup(var.topics[count.index], "max_message_bytes") != -1 ? "${lookup(var.topics[count.index], "max_message_bytes")}" : 1000012
}
}
but when running terraform plan I am getting following exception
attribute "partition_count" is required.
Note : I also used partition_count = optional(number) in declaring the variable in variable.tf (to keep that attribute as a optional field) but getting following error
Keyword "optional" is not a valid type constructor
as it might be due to the terraform version currently I am using which is ">= 0.12" but when I tried with the ">= 0.15" version, got the same error 'Keyword "optional" is not a valid type constructor' error.
Is there any way I can fix this issue?

Answer 1

Try to add this:
terraform {
experiments = [module_variable_optional_attrs]
}