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Mixins

The mixins key in component.yaml allows you to download additional files and overlay them on the vendored component. This is useful for adding or replacing files that are not part of the original component source.

Schema​

spec:
  mixins:
    - uri: https://raw.githubusercontent.com/cloudposse/terraform-null-label/0.25.0/exports/context.tf
      filename: context.tf
    - uri: https://raw.githubusercontent.com/cloudposse/terraform-aws-components/{{.Version}}/modules/datadog-agent/introspection.mixin.tf
      version: 1.398.0
      filename: introspection.mixin.tf

Attributes​

uri

The URL to download the mixin file from. Supports the same protocols as the source.uri attribute: HTTP, HTTPS, Git, S3, GCP, and OCI.

Golang templates are supported in the URI. If version is provided, {{.Version}} will be replaced with the version value.

version

Optional version to substitute into {{.Version}} placeholders in the uri. Each mixin can have its own version independent of the main source version.

filename

The filename to save the downloaded file as in the component directory. This allows you to rename files or ensure they have the correct name.

Mixins override files from source with the same filename (e.g. context.tf will override context.tf from the source).

How Mixins Work​

Mixins are processed after the main source is downloaded. All mixins are processed in the order they are declared in the list.

This means:

  1. The component source files are downloaded first
  2. Each mixin file is downloaded and placed in the component directory
  3. If a mixin has the same filename as a source file, the mixin overwrites the source file

Example: Replacing context.tf​

A common use case is to replace the context.tf file from a component with a newer version:

apiVersion: atmos/v1
kind: ComponentVendorConfig
metadata:
  name: vpc-flow-logs-bucket-vendor-config
  description: Source and mixins config for vendoring of 'vpc-flow-logs-bucket' component
spec:
  source:
    uri: github.com/cloudposse/terraform-aws-components.git//modules/vpc-flow-logs-bucket?ref={{.Version}}
    version: 1.398.0
    included_paths:
      - "**/*.tf"
      - "**/*.tfvars"
      - "**/*.md"
    # Exclude context.tf since we'll replace it with a mixin
    excluded_paths:
      - "**/context.tf"

  mixins:
    # Download a newer version of context.tf
    - uri: https://raw.githubusercontent.com/cloudposse/terraform-null-label/0.25.0/exports/context.tf
      filename: context.tf

Example: Adding Multiple Mixins​

You can add multiple mixin files to a component:

spec:
  source:
    uri: github.com/cloudposse/terraform-aws-components.git//modules/vpc?ref={{.Version}}
    version: 1.398.0

  mixins:
    # Add context.tf
    - uri: https://raw.githubusercontent.com/cloudposse/terraform-null-label/0.25.0/exports/context.tf
      filename: context.tf

    # Add an introspection mixin from another component
    - uri: https://raw.githubusercontent.com/cloudposse/terraform-aws-components/{{.Version}}/modules/datadog-agent/introspection.mixin.tf
      version: 1.398.0
      filename: introspection.mixin.tf

    # Add a custom providers configuration
    - uri: https://example.com/terraform/providers.tf
      filename: providers.tf
tip

When using mixins, consider excluding the files you intend to replace in the excluded_paths of the source configuration. This makes your intent clear and avoids downloading files that will be overwritten.