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!labels

The !labels YAML function returns the current component's own metadata.labels as a typed map (map[string]string), without the !template '{{ toJson .metadata.labels }}' boilerplate normally needed to get a properly-typed value out of a template expression.

Usage​

The !labels function takes no parameters:

components:
  terraform:
    vpc:
      metadata:
        labels:
          cost-center: platform
          compliance: sox
      vars:
        labels: !labels

Arguments​

This function takes no arguments. It reads metadata.labels from the component it's used on.

How It Works​

When processing the !labels YAML function, Atmos reads the labels field from the component's own metadata section (the same metadata.labels used for atmos list components --labels filtering) and returns it as a map[string]string. If metadata.labels is unset, !labels returns an empty map rather than an error, consistent with labels being optional everywhere in Atmos.

Bridging metadata.labels into vars.tags​

The most common use of !labels is to bridge Atmos's own metadata.labels (used for CLI categorization and filtering) into the map-shaped vars.tags/vars.labels that terraform-null-label-style modules expect for actual cloud resource tagging:

stack.yaml
components:
  terraform:
    vpc:
      metadata:
        tags: [production, networking]
        labels:
          Namespace: eg
          Environment: prod
          cost-center: platform
      vars:
        # var.tags (map, AWS/terraform-null-label convention) <- metadata.labels
        tags: !labels
Why vars.tags: !labels isn't a typo

Terraform/AWS-style modules call their map-shaped resource-tagging input tags (var.tags map(string)) — the same "AWS calls a map a tag" naming that Atmos's tags-vs-labels standard distinguishes: a list is a tag, a map is a label. So !labels — which returns the map — is what belongs in a module's tags variable. !tags returns Atmos's own []string list and is for a different shape of consumer entirely.

Examples​

Bridging into a Terraform module​

stack.yaml
components:
  terraform:
    vpc:
      metadata:
        labels:
          cost-center: platform
          compliance: sox
      vars:
        tags: !labels

No Labels Set​

stack.yaml
components:
  terraform:
    rds:
      vars:
        # labels will be {} (empty map, not an error)
        labels: !labels
  • !tags - Get the current component's own metadata.tags as a list
  • !labels.keys - Get the current component's metadata.labels keys
  • !labels.values - Get the current component's metadata.labels values