How to transfer a powershell list variable to terraform by using Azure Devops?

Question

I have a list which is filled with addressprefixes like 192.168.1.0/24

$listOfSubnetsToBeCreated = @() 
Write-Host "##vso[task.setvariable variable=availableSubnetList]$listOfSubnetsToBeCreated"

created in a powershell and transferred to azure devops pipeline variable that i have already defined in Azure Devops. I am using this variable which is set on the run with

terraform apply -var="availableSubnetList=$(availableSubnetList)"

in my Terraform task to create a subnet. Here below is the tf script:

variable "availableSubnetList" {
  type = list(string)
  default = [""]
}
resource "azurerm_subnet" "Subnet-lab" {
    count = var.project_subnet_number
    name = join("-", ["${var.LabRGName}","subnet", "${count.index + 1}"])
    resource_group_name = var.AdminRGName
    virtual_network_name = var.lab_vnet
    address_prefix = var.availableSubnetList[count.index]
}

When i executed the pipeline, i am having the following error on terraform apply task:

2020-05-25T14:39:52.5509261Z [0m  on <value for var.availableSubnetList> line 1:
2020-05-25T14:39:52.5510090Z   (source code not available)
2020-05-25T14:39:52.5510378Z 
2020-05-25T14:39:52.5510814Z This character is not used within the language.
2020-05-25T14:39:52.5511149Z [0m[0m
2020-05-25T14:39:52.5511412Z [31m
2020-05-25T14:39:52.5512135Z [1m[31mError: [0m[0m[1mInvalid expression[0m
2020-05-25T14:39:52.5512438Z 
2020-05-25T14:39:52.5512833Z [0m  on <value for var.availableSubnetList> line 1:
2020-05-25T14:39:52.5513301Z   (source code not available)
2020-05-25T14:39:52.5513582Z 
2020-05-25T14:39:52.5513977Z Expected the start of an expression, but found an invalid expression token.
2020-05-25T14:39:52.5514566Z [0m[0m

Afaik, the variables in Azure Devops are strings. Do you have any idea on how to transfer a powershell list correctly to terraform by using Azure Devops?

Mathias R. Jessen · Accepted Answer · 2020-05-25 16:01:00Z

3

Output a comma-separated string of subnets from the PowerShell script:

Write-Host "##vso[task.setvariable variable=availableSubnetList]$($listOfSubnetsToBeCreated -join ',')"

Then split it into a list again when invoking terraform:

terraform apply -var='availableSubnetList=${split(",", $(availableSubnetList))}'

Or change the way you resolve each subnet in terraform:

address_prefix = split(",", var.availableSubnetList)[count.index]

edited May 25, 2020 at 16:01

answered May 25, 2020 at 10:58

Mathias R. Jessen

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8 Comments

MoonHorse Over a year ago

i have applied it and got this error: 2020-05-25T12:21:07.2672860Z [1m[31mError: [0m[0m[1mInvalid reference[0m 2020-05-25T12:21:07.2674089Z 2020-05-25T12:21:07.2675081Z [0m on network.tf line 8, in resource "azurerm_subnet" "Subnet-lab": 2020-05-25T12:21:07.2676095Z 8: address_prefix = [4mavailableSubnetList[0m[count.index] 2020-05-25T12:21:07.2676984Z [0m 2020-05-25T12:21:07.2700114Z A reference to a resource type must be followed by at least one attribute 2020-05-25T12:21:07.2701181Z access, specifying the resource name.

MoonHorse Over a year ago

here $(availableSubnetList) seems empty at the logs: the terraform.exe plan -var=LabRGName=rg-deniztest3-87719dccbe -var=project_subnet_number=3 "-var=availableSubnetList=${split(,, )}" Although i enter -var="availableSubnetList=${split(",", $(availableSubnetList))}"

MoonHorse Over a year ago

i noticed that i made an error in tf script: address_prefix = availableSubnetList[count.index] . It should be var.availableSubnetList[count.index]

Mathias R. Jessen Over a year ago

@MoonHorse I'm not 100% sure the ${split()} expression works when passed at the command line, you might need to do it in the task itself

Mathias R. Jessen Over a year ago

@MoonHorse That's great (sorry I couldn't be of more help with tf, not my strongsuit). I've updated my answer to reflect your solution as well :)

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