pass list(strings) as a terraform variable - amazon-web-services

Question

While defining my module, I do this:
module "activate_alarms" {
source = "../_modules/aws/.."
config = module.config
alarm_arns = ["arn:aws:cloudwatch:eu-central-123:test-alarm"]
}
variable "alarm_arns" {
type = list(string)
}
resource "aws_lambda_function" "processing_lambda" {
filename = data.archive_file.lambda_zip.output_path
function_name = local.processing_lambda_name
handler = "enable_disable_alarms.lambda_handler"
source_code_hash = data.archive_file.lambda_zip.output_base64sha256
role = aws_iam_role.lambda_role.arn
runtime = "python3.9"
tags = var.config.tags
environment {
variables = {
alarm_arns = local.alarm_arns
}
}
}
However, I get an error:
Error: Incorrect attribute value type
│
│ on ../_modules/aws/enable_disable_alarms/processing_lambda.tf line 20, in resource "aws_lambda_function" "processing_lambda":
│ 20: variables = {
│ 23: alarm_arns = local.alarm_arns
│ 30: }
│ ├────────────────
│ │ local.alarm_arns is a list of string, known only after apply
│
│ Inappropriate value for attribute "variables": element "alarm_arns": string required.
What's the correct way to pass a list of strings?
Edit:
locals {
config = var.config
alarm_arns = "${var.alarm_arns}"
}

Answer 1

You can't pass list(string) directly as environment into lambda. You have to make it into string first, e.g.:
environment {
variables = {
alarm_arns = jsonencode(var.alarm_arns)
}
}
Then in your lambda you would have to convert it back to list of strings according to your programming language.