Terraform for_each key chain value

Question

I am using the for_each meta argument to create the IAM roles. Is there a way to set a default value for the object if it's not defined in one of the key map?

For example, If the key map does not contain the value chain defined for create_custom_role_trust_policy, it's should take the default value as false.

module "iam_assumable_roles" {
  for_each = local.iam_roles
  source   = "terraform-aws-modules/iam/aws//modules/iam-assumable-role"
  version  = "v5.41.0"

  create_role       = true
  role_requires_mfa = false

  role_name                       = each.key
  custom_role_policy_arns         = each.value.custom_role_policy_arns
  custom_role_trust_policy        = each.value.custom_role_trust_policy
  create_custom_role_trust_policy = each.value.create_custom_role_trust_policy
  trusted_role_arns               = each.value.trusted_role_arns
  trusted_role_services           = each.value.trusted_role_services
}

locals {
iam_roles = {
    "${terraform.workspace}_arn_lookup" = {
      trusted_role_arns = formatlist(
        "arn:aws:iam::%s:root",
        local.acceptor_account_ids
      )
      trusted_role_services = []
      custom_role_policy_arns = [
        module.iam_policies["permit_role_anywhere_id_lookup_policy"].id
      ]
    },
    "ssm_hybrid_role" = {
      trusted_role_arns     = []
      trusted_role_services = ["ssm.amazonaws.com"]
      custom_role_policy_arns = [
        "arn:aws:iam::aws:policy/AmazonSSMManagedInstanceCore",
        module.iam_policies["ssm_cwl_iam_policy"].id
      ]
    },
    "developer_test" = {
      create_custom_role_trust_policy = "true"
      custom_role_trust_policy        = data.aws_iam_policy_document.custom_trust_policy.json
      custom_role_policy_arns = [
        module.iam_policies["ssm_session_access"].arn
      ]
    }
}

Answer 1

You could use the lookup function:

lookup retrieves the value of a single element from a map, given its key. If the given key does not exist, the given default value is returned instead.

So something like that

create_custom_role_trust_policy = lookup(each.value, "create_custom_role_trust_policy", false)