Terraform: TF_VAR_ prefixed environment variable ignored by Terraform in Azure DevOps

[guywood13]

Running a Terraform build with the following code and environment variable set on the pipeline. It ignores the environment variable and uses default. Works fine locally with PowerShell. Seen lots of similar bugs reported in this area but not beyond the realms that I'm doing something wrong.

variable "testvar" {
default = "meh"
}

variable "testenvvar" {
    type = "string"
    default = "fml"
}

output "printvar" {
value = "${var.testvar}"
}

output "printenvvar" {
value = "${var.testenvvar}"
}

Output:

Of course, I'm expecting printenvvar = meow instead.

-Terraform 0.12.13
-Agent Pool: Azure Pipelines (hosted)
-Agent Spec: vs2017-win2016

I have workaround -var testenvvar=meow on plan but this should work, is my preferred and seems to be Terraform best practice.

Thanks
Guy

[hashibot]

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[teamterraform]

Hi @guywood13!

It looks like you might be running into the problem described in microsoft/azure-pipelines-agent#1645: it seems that Azure DevOps doesn't allow setting environment variables containing lowercase letters or periods, and so it's likely converting your variable to be named TF_VAR_TESTENVVAR and thus Terraform (whose variable names are case sensitive) is not looking at it.

It sounds like the Azure team is still considering how to support mixed-case environment variable names in that issue, but in the mean time you might be able to work around it by naming your Terraform variable with an uppercase name so that it won't get altered by the Azure Pipelines Agent. Alternatively, as you've seen you can use the -var and -var-file command line arguments to set variables in a way that isn't subject to transformation by the Azure Pipelines Agent.

If you have any questions about this, please feel free to start a new topic in the community forum. Thanks!

[guywood13]

I've tested this and you're correct. Thank you for pointing me at the root cause.

[hashibot[bot]]

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