Terraform count using bool?

February 23, 2022

count is a great meta-argument for being able to provision resources conditionally in Terraform. From my previous experience, we do something like my_var = "1" and use this to programmatically control resource creation with count.

Since count in that case takes in a string "1", but can also interpret a number type (e.g. 1), I’m wondering:

a) What is Terraform’s count doing under the hood; is it parsing the string as a number first?
b) Can it also accept other data types e.g. bool?

I’m hoping to have a .tfvars which has a my_var = true in it, which is then passed into the count meta-argument on affected resources e.g count = var.my_var. Is this possible?

I also kindly request some information which goes into generally how data types are interpreted in Terraform for "truthiness". If you have docs or a blog post to share it’d be much appreciated!

>Solution :

a). In Terraform string representation of numeric values are automatically converted to numbers. From the docs:

Terraform automatically converts number and bool values to strings when needed. It also converts strings to numbers or bools, as long as the string contains a valid representation of a number or bool value.

true converts to "true", and vice-versa

false converts to "false", and vice-versa

15 converts to "15", and vice-versa

This is valid:

resource "aws_s3_bucket" "s3" {
  bucket = "bucket-name"
  count = "1"
}

This is also valid:

resource "aws_s3_bucket" "s3" {
  bucket = "bucket-name"
  count = 1
}

b). In Terraform booleans are not considered to be numeric values. Numbers are not automatically converted to booleans, which means this is NOT valid:

resource "aws_s3_bucket" "s3" {
  bucket = "asd"
  count = false
}

It will throw the following error:

╷
│ Error: Incorrect value type
│
│   on main.tf line 9, in resource "aws_s3_bucket" "s3":
│    9:   count = false
│
│ Invalid expression value: number required.
╵