Data module terraform - How to use conditioanl block

Question

I have a data module where I am creating "aws_iam_policy_document" "trust-policy and would like to add conditions only for certain modules, not all.

For example:

data "aws_iam_policy_document" "trust-policy" {
  statement {
    actions = [var.action]

    principals {
      type        = var.type
      identifiers = concat(var.trusted_arns)
    }
    count        = var.git ? 1 : 0
    condition {
      test     = "StringEquals"
      variable = "abc"
      values   = ["sts.amazonaws.com"]
    }
    condition {
      test     = "StringLike"
      variable = "dcf"
      values   = ["repo:var.org_name/var.repo_name:ref:refs/heads/var.branch_name"]
    }

  }
}

I want to run the condition blocks only if module is git. But with count , it fails with below error:

 An argument named "count" is not expected here.

Answer 1

You can use a dynamic block. For example, declare a new variable trust_policy_conditions like this:

variable "trust_policy_conditions" {
  description = "A list of trust policy conditions"
  type = list(object({
    test     = string
    variable = string
    values   = list(string)
  }))
  default = []
}

Then add the dynamic block to the data source:

data "aws_iam_policy_document" "trust-policy" {
  statement {
    actions = [var.action]

    principals {
      type        = var.type
      identifiers = concat(var.trusted_arns)
    }

    dynamic "condition" {
      for_each = var.git == true ? { for index, policy in var.trust_policy_conditions : index => policy } : {}
      content {
        test     = condition.value.test
        variable = condition.value.variable
        values   = condition.value.values
      }
    }
  }
}

Note that the index is the key as there may be a scenario where multiple conditions share the same test or variable attribute.