# atmos.Resolve

The `atmos.Resolve` template function evaluates an [Atmos YAML function](/functions/yaml) 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

```yaml
# 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`](/functions/yaml/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`:

```yaml
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`](/functions/template/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.