Invalid index with local variable

Terraform
1

Hello,

My terraform is displaying this error message and I don’t know exactly why …

Error: Invalid index
│
│ on .terraform/modules/grafana_user/main.tf line 40, in locals:
│ 40: ])[0]
│ ├────────────────
│ │ data.ldap_object.ldap_user_attributes.attributes is set of map of string with 1 element

Here is the code to create the local variables:

locals {                                                                                            
  grafana_users = toset([                                                                           
    for item in local.groups.grafana_users :                                                        
    split(":", item)[0]                                                                             
  ])                                                                                                
}

When I am displaying the value with an output, I have this:

test = [
+ “toto1”,
+ “toto2”,
+ “toto3”,
+ “toto4”,
+ “toto5”,
+ “toto6”,
]

But when I want to use this local variable in the code below, I have the error Invalid index:

module "grafana_user" {                                                                             
  for_each   = { for user in local.grafana_users : user => user }                                   
  source     = "git@...:terraform-modules/terraform-grafana-user.git?ref=v1.1.0"      
  ldap_login = each.value                                                                           
}

Any help is welcome …