How to use ellipsis (...) in nested for loop

[khandujaniket]

Is it possible to use ellipsis in a nested for loop as shown below

    existing_nsg_rules = {
    for key, rules in data.azurerm_network_security_group.subnet_nsg :
    key => {
      for rule_key in rules.security_rule : key=> key...{
         priority = rule_key.priority
        name     = rule_key.name
  }}}

I see this error Invalid ‘for’ expression: Extra characters after the end of the ‘for’ expression.

[apparentlymart]

Hi @khandujaniket,

The ... modifier for a for expression must be placed after the expression that represents the value for each element. In your case I think that would look like this:

    existing_nsg_rules = {
      for key, rules in data.azurerm_network_security_group.subnet_nsg : key => {
        for rule_key in rules.security_rule : key => {
          priority = rule_key.priority
          name     = rule_key.name
        }...
      }
    }

Alternatively, if it’s the outer of the two that you want to use in the grouping, you’d place the ... after the inner for expression, like this:

    existing_nsg_rules = {
      for key, rules in data.azurerm_network_security_group.subnet_nsg : key => {
        for rule_key in rules.security_rule : key => {
          priority = rule_key.priority
          name     = rule_key.name
        }
      }...
    }

If neither of these matches what you want to achieve, it’d help if you could share an example of what data structure you are trying to generate, using some example values.

[adamwshero]

Can you add some additional context @apparentlymart in the case where you also need to flatten first? For example when we are creating a database on an existing RDS instance and want to configure each database using a yaml config file. The example below works fine for one database but will not work for multiples because the lack of grouping, hence duplicate keys will be found.

databases:
  - name: my_db
    namespace: dev
    readonly_users:
      - name: app_reader
        password: my_32_char_password
    crud_users:
      - name: app_writer
        password: my_32_char_password
    migration_users:
      - name: migration_user
        password: my_32_char_password

  readonly_users = flatten([
    for db in var.bootstrap_config.databases : [
      for user in db.readonly_users : {
        username = "${db.namespace}_${user.name}"
        password = user.password
        db_name  = "${db.name}_${db.namespace}"
      }
    ]
  ])
  crud_users = flatten([
    for db in var.bootstrap_config.databases : [
      for user in db.crud_users : {
        username = "${db.namespace}_${user.name}"
        password = user.password
        db_name  = "${db.name}_${db.namespace}"
      }
    ]
  ])
  migration_users = flatten([
    for db in var.bootstrap_config.databases : [
      for user in db.migration_users : {
        username = "${db.namespace}_${user.name}"
        password = user.password
        db_name  = "${db.name}_${db.namespace}"
      }
    ]
  ])

In the above example, we won’t be able to use grouping ellipses when building a tuple. Is it then required to group first, and then flatten?

[apparentlymart]

Hi @adamwshero,

This is a very old topic. Please start a new topic for your new question. Thanks!