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Read One Component Label with an Optional Default

· 2 min read
Erik Osterman
Erik Osterman
Founder @ Cloud Posse

A component can have several labels, while a variable may need only one value. The !labels function now accepts a key to read a single component label, with an optional fallback when that label is absent.

The Problem​

Individual labels are already accessible through Go templates, such as {{ .metadata.labels.owner }}. The !labels function previously returned only the full map and accepted no key or fallback argument.

The Fix​

Use !labels key [default] to retrieve a string from the component’s resolved metadata labels. An absent key uses the explicit default or produces an error if none was supplied. Existing empty-string values are preserved. Bare !labels continues to return the full map.

How to Use It​

components:
  terraform:
    vpc:
      metadata:
        labels:
          cost-center: platform
      vars:
        cost_center: !labels cost-center
        owner: !labels owner "Platform Team"

Here cost_center resolves to platform. If the resolved metadata has no owner label after stack defaults and component inheritance, owner resolves to the explicit fallback, Platform Team. An inherited owner label supplies its value instead.

Keys are literal, including dots, slashes, and hyphens. Quote fallback values containing spaces; use "" when the fallback should be an empty string. Values reflect stack defaults and component inheritance.

See the label lookup reference for full-map access and Go template equivalents.

Get Involved​

Share your label lookup use cases in Atmos discussions.