Terraform create variable array from tfvars

Question

I am still getting used to using Terraform and have the following question.

I have an array in a TFVARS file; extproviders = [ "production" , "support" ]

i am using thisto call a module

module userpoolclientN {
   count = length(var.extproviders)
   source =  "../modules/cognito"
   basename = var.extproviders[count.index]
}

what i would like to do is create a new array that attaches 'odd' 'even' to each variable. I dont want the user to input this as the extproviders is used elsewhere in the code.

extproviders_new = [ "production_odd" ,"production_even" , "support_odd", "support_even" ]


module userpoolclientN {
   count = length(var.extproviders_new)
   source =  "../modules/cognito"
   basename = var.extproviders_new[count.index]
}

I am still learning Terraform, understand i cant use a for loop to accomplish this. Is there another way?

Would you consider updating the usage to for_each so that the for expression can be used directly as the module argument (also could then remove basename argument)? It would simplify and stabilize the usage and answer. — Matthew Schuchard
– Matthew Schuchard, Commented Dec 21, 2022 at 15:41

Will · Accepted Answer · 2022-12-21 15:09:33Z

3

Using for and foreach :

variable "extproviders" {
  default = ["production", "support"]
}

locals {
  extproviders_new  = flatten([ for e in var.extproviders : tolist(["${e}odd","${e}even"])])
}


module userpoolclientN {
   for_each = toset(local.extproviders_new)
   source =  "../modules/cognito"
   basename = each.value
}

Explaining the locals :

For each element on the input list returns a list made of that element + odd suffix and element + even suffix. Then flatten those list into a single one

flatten() will transform multilevel lists into a single one

[for] will returns a list containing two lists

"${e}odd" and "${e}even" is a simple string concatenation

edited Dec 21, 2022 at 15:09

answered Dec 21, 2022 at 15:03

Will

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