Terraform: Looping through a list of nest objects to return and combine lists of maps

Terraform
1

I’m trying to loop through a list of complex objects with lists of objects inside to find a few specific lists of maps. I’m using local variables to return the lists and then combine them into a single list of maps. I’ve put together some logic but all I’m getting is an empty list of strings, and I can’t figure out where the problem is.

locals {
  group_names = distinct([for group in var.existing_groups : group.name])

  requestors = [
    for ap in var.assignment_policies: ap.requestor_settings.requestor
    ]
      

  primary_approvers = [
      for ap in var.assignment_policies: [
        # Primary Approvers
        for as in ap.approval_settings.approval_stage: [
          as.primary_approver
        ]
      ]
    ]

  alternative_approvers = try(
     [
      for ap in var.assignment_policies: [
        # Alternative Approvers
        for as in ap.approval_settings.approval_stage: [
          as.alternative_approver
        ]
      ]
    ], []
  )

  approvers = concat(local.primary_approvers, local.alternative_approvers)

  requestors_and_approvers = concat(local.requestors, local.approvers)
  reviewer_groups = distinct([for object_id, subject_type in local.requestors_and_approvers : object_id if subject_type == "groupMembers"])
  reviewer_users  = distinct([for object_id, subject_type in local.requestors_and_approvers : object_id if subject_type == "singleUser"])

  groups_map = zipmap(data.azuread_groups.reviewer_groups.display_names, data.azuread_groups.reviewer_groups.object_ids)
  users_map = zipmap(data.azuread_users.reviewer_users.user_principal_names, data.azuread_users.reviewer_users.object_ids)
  reviewers_map = merge(local.groups_map, local.users_map)

}

data "azuread_groups" "reviewer_groups" {
  display_names = local.reviewer_groups
}

data "azuread_users" "reviewer_users" {
  user_principal_names = local.reviewer_users
}


module "access_package" {

  assignment_policies = [
    {
      requestor_settings = {
        requestor = [
          {
            object_id    = "test-grp-3"
            subject_type = "groupMembers"
          },
          {
            object_id    = "test-grp-4"
            subject_type = "groupMembers"
          {
        ]
      }

      approval_settings = {
        approval_stage = [
          {
            primary_approver = [
              {
                object_id    = "test-grp-5"
                subject_type = "groupMembers"
              },
              {
                object_id    = "example@example.com"
                subject_type = "singleUser"
              },
              {
                object_id    = "example2@example.com"
                subject_type = "singleUser"
              }
            ]
            alternative_approver = [
              {
                object_id    = "test-grp-6"
                subject_type = "groupMembers"
              },
              {
                object_id    = "example3@example.com"
                subject_type = "singleUser"
              },
              {
                object_id    = "example4@example.com"
                subject_type = "singleUser"
              }
            ]
          }
        ]
      }
    }
  ]
}

I tried running terraform plan with the above code but got the following:

local.reviewers_map is empty map of string