Terraform Dynamic Object Generation

Question

I have a scaffolding module that I have created to auto-generate some of the files that we need across our environments and projects - it automatically creates the backend file, providers file and variables file.

I have this config that generates a variables file:

resource "local_file" "generated_variables" {
  for_each = { for kv in local.distinct_envs_and_regions : "${kv.env}.${kv.region}" => kv }
  content  = <<EOF
variable "supported_regions" { default = ${jsonencode(distinct([
      for region in var.regions : 
        "rg-${each.value.env}-${var.project}-${region.region_short} = ${region.region_name}"
      
    ]
  ))
} }
variable "region_info" { default = "${each.value.region}" }
variable "project" { default = "${var.project}" }
variable "environment" { default = "${each.value.env}" }
variable "tenant_id" { default = "${var.tenant_id}" }
variable "subscription_id" { default = "${var.subscription_id}" }

variable "common_tags" {
  default = {
    environment = "${each.value.env}"
    project     = "${var.project}"
    managed_by  = "terraform"
  }
}
 EOF
  filename = "../${var.project}-iac/environments/category/${var.environment_category}/${each.value.env}/core/variables_generated.tf"
}

However, I cannot get the supported_regions variable in the format that I need - I need it to look something like this:

variable "supported_regions" { 
  default = { 
    rg-prd-adm-suk = "uksouth",
    rg-prd-adm-wuk = "ukwest" 
  }
}

Instead the output looks something like this:

variable "supported_regions" { default = ["rg-prd-adm-suk = uksouth","rg-prd-adm-wuk = ukwest"] }

I am sure I am missing something in the for loop but cannot work out what that is... Any ideas?

Answer 1

EDIT A better solution using string templates

  content = <<EOF
variable "supported_regions" {
  default = {
    %{ for region in var.regions ~}
       rg-${each.value.env}-${var.project}-${region.region_short} = "${region.region_name}"
    %{ endfor ~}
}
EOF

Output:

variable "supported_regions" {
  default = {
           rg-dev-prd-adm-suk = "uksouth"
           rg-dev-prd-adm-wuk = "ukwest"
    }
}

Full working main.tf:

# providers
terraform {
  required_providers {
    local = {
      source = "hashicorp/local"
      version = "2.4.0"
    }
  }
}


locals {
  distinct_envs_and_regions = [
    {
      env    = "dev",
      region = "us-east-1",
    },
    {
      env    = "dev",
      region = "us-west-2",
    },
    {
      env    = "prod",
      region = "us-west-2",
    },
    {
      env    = "test",
      region = "us-east-1",
    },
    # Add more environments and regions as needed
  ]
}


resource "local_file" "generated_variables" {
  for_each = {
    for kv in local.distinct_envs_and_regions: "${kv.env}.${kv.region}" => kv
  }
  content = <<EOF
variable "supported_regions" {
  default = {
    %{ for region in var.regions ~}
       rg-${each.value.env}-${var.project}-${region.region_short} = "${region.region_name}"
    %{ endfor ~}
}
EOF
  filename = "variables_generated.tf"
}


variable "project" {
    default = "prd-adm"
}
variable "regions" {
  type = list(object({
    env          = string
    region_short = string
    region_name  = string
  }))
  default = [
    {
    env          = "dev"
    region_short = "suk"
    region_name  = "uksouth"
    },
    {
    env          = "dev"
    region_short = "wuk"
    region_name  = "ukwest"
    }
  ]
}

This should also do it (note that I had to substitute "=" to ":" in the output of jsonencode (which is a string):

content = <<EOF
variable "supported_regions" {
  default = ${
    replace(
      jsonencode({
        for region in var.regions :
          "rg-${each.value.env}-${var.project}-${region.region_short}" => region.region_name
      }),
      ":", "="
    )
  }
}
EOF

Output:

variable "supported_regions" {
    default = {"rg-prod-prd-adm-suk"="uksouth","rg-prod-prd-adm-wuk"="ukwest"}
  }