CODEWITHSUNDEEP
terraformterraform-provider-awsterraform0.12+
user6826691
user6826691

Reputation: 2011

How to ignore a value in list?

I've a list of string and I want to ignore certain elements in that list. For example my list

variable domain_names = {
  type = list(string)
}

domain_names = ["foo.com","*.foo.com","*.foo2.com","bar.co.in"]

output = [ "foo.com","bar.co.in"]

I want to ignore anything that starts with * and create a new list out of it. How can i achieve this?

I was trying to make this module more robust to handle multiple domain names 

locals {
  distinct_domain_name = distinct(var.domain_names)
}

resource "aws_acm_certificate" "main" {
  count                     = length(local.distinct_domain_name)
  domain_name               = local.distinct_domain_name[count.index]
  subject_alternative_names = [slice(var.domain_names, 1, length(var.domain_names))]
  validation_method         = var.validation_method
  tags {
    Name      = local.distinct_domain_name[count.index]
    owner     = "xxx"
    terraform = "true"
  }
}

Upvotes: 2

Views: 3427

Answers (1)

Martin Atkins
Martin Atkins

Reputation: 74109

When our goal is to filter a list, the usual place to start is a for expression with an if clause. That allows us to make a decision for each element, but raises the question of what expression to use to make that decision.

For the question of "how can we detect if a string has a particular prefix?" I think there are at least a few different ways to get that done but probably the most concise would be to use a regular expression, via regexall, and return true if there is at least one match:

length(regexall("^\\*\\.", domain_name)) > 0

I used regexall rather than regex here because regex is defined to return an error if there is no match -- it expects at least one -- whereas regexall lets us handle the zero-matches case ourselves.

Combining that with a for expression would give us the following:

[ for domain_name in var.domain_names : domain_name if length(regexall("^\\*\\.", domain_name)) > 0 ]

The above produces a list of the ones that do have *. as a prefix. We can negate that expression to produce the opposite subset:

[ for domain_name in var.domain_names : domain_name if length(regexall("^\\*\\.", domain_name)) == 0 ]

Upvotes: 4

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