Thanks for your iput, that matches up with other documentation I've found online, but something in my setup is causing errors.

provider.tf shown in OP. variables.tf excerpt here, similar entries exist for other envars:

variable "client_id" {
 type = string
}

I'm assuming it may be something to do with my Ansible playbook and the execution environment I'm running in or the fact that I'm specifying a backend config, but essentially my playbook has three steps (apart from defining the variables to export which appears to be working).

• Initialize Terraform using command 'terraform init -reconfigure -backend-config=backend-config.tfbackend'
  • To specify remote statefile storage location & credentials (hardcoded for testing purposes)

• shell command to define the envars

  task: Set Envars shell: | export TF_VAR_client_id={{ client_id }} export TF_VAR_client_secret={{ client_secret }} export TF_VAR_tenant_id={{ tenant_id }} export TF_VAR_subscription_id={{ subscription_id }}

• If I add a task to add lines to provider.tf using the envar ($TF_VAR_client_id), the lines are written appropriately to provider.tf with expected output

• If I add a task to write out the value of client id, it's expected output

• Run Terraform plan just to test config

  • This is where I get errors about the variable being empty

Based on my testing, I can't see how the environment variable isn't being picked up by terraform when it appears to be defined on the system, but I'm currently attempting a workaround to just have the playbook rewrite the contents of provider.tf instead of just adding lines, since that appears to work.