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atmos.Resolve

The atmos.Resolve template function evaluates an Atmos YAML function string — such as !git.repository, !exec, !store, or !terraform.output — at template-render time and returns the resolved value. It lets you compose the result of a YAML function with other strings and template variables in a single value, which a bare YAML tag cannot do because a tag owns the entire scalar.

Usage​

# Resolve a YAML-function string and combine it with other text
key: '{{ atmos.Resolve "!git.repository" }}/something'

# Resolve a value that is stored elsewhere in the stack
key: '{{ atmos.Resolve .settings.context.repo }}'

Arguments​

input
An Atmos YAML-function string to evaluate (for example, "!git.repository" or "!env API_KEY"). A plain (untagged) string is returned unchanged.

Why It's Needed​

Atmos evaluates Go templates before it evaluates YAML functions. As a result, a bare YAML tag cannot be combined with other text on the same line, and referencing a YAML function through an intermediate variable in a plain template does not work — at template time the value is still the unresolved tag string (e.g. "!git.repository").

atmos.Resolve bridges this gap: it runs the YAML-function processor on demand during template rendering, so the resolved value is available inside the template where you can concatenate it with other strings and template expressions.

Examples​

Prefix a workspace_key_prefix with the repository slug​

A common use case is prefixing the Terraform workspace_key_prefix (or any other value) with the repository slug returned by !git.repository:

settings:
  context:
    repo: "!git.repository"

components:
  terraform:
    vpc:
      backend:
        s3:
          workspace_key_prefix: '{{ atmos.Resolve .settings.context.repo }}/{{ or .metadata.name .metadata.component }}'

In a repository whose origin remote is https://github.com/cloudposse/atmos.git, the workspace_key_prefix resolves to cloudposse/atmos/vpc.

Resolve any YAML function inline​

atmos.Resolve works with every Atmos YAML function, so you can compose values that previously required shelling out through !exec:

vars:
  # Combine an environment variable with a static suffix
  bucket: '{{ atmos.Resolve "!env BUCKET_PREFIX" }}-state'

Considerations​

  • atmos.Resolve runs during the template phase (before the eager YAML-function pass), giving it the same evaluation semantics as atmos.Component. Avoid using it for expensive functions (e.g. !terraform.output) when a plain YAML tag would suffice.
  • A plain (untagged) string is returned unchanged, so it is safe to pass values that may or may not contain a YAML function.