Can't access attributes on a list of objects in terraform

January 31, 2023

Trying to create a dynamic block based on a list of objects.

Here is the attempt

data "vault_policy_document" "this" {

  dynamic "rule" {
    for_each = {
      for p in var.policy : format("%s-%s", p.path, join(",", p.capabilities)) => p
    }

    content {
      path         = rule.value.path
      capabilities = rule.value.capabilities
    }
  }
}

and here is the input var.policy


policy-test-1 = [
  {
      capabilities = [
          "create",
          "read",
      ]
      path         = "/foo/lala"
  },
  {
      capabilities = [
          "create",
          "read",
      ]
      path         = "/bar/lala"
  },
]

Its declaration

variable "policy" {
  description = "The policy to be created"
  type = map(list(object({
    path = string
    capabilities = set(string)
  })))

Why does this fail with

5:       for p in var.policy : format("%s-%s", p.path, join(",", p.capabilities)) => p
│
│ Can't access attributes on a list of objects.

Isn’t each item in the list (i.e. the p in the for loop) an object with paths and capabilities attributes?

>Solution :

You need double four loop, because you have a map of lists, along with the merge to flatten it:

    for_each = merge([
             for p in var.policy: {
                for statement in p: 
                   format("%s-%s", statement.path, join(",", statement.capabilities)) => statement
             }   
         ]...)