Target Path Resolution

The target property in a transformation block tells Watt TF exactly where to place your evaluated payload in the final Terraform JSON structure.

By utilizing a flexible dot-notated string syntax, Watt TF acts as an automated structural architect—building deeply nested objects on the fly without requiring you to pre-define the parent object trees.

Dynamic Object Creation

When Watt TF processes a target path like resource.aws_s3_bucket.main, it evaluates the string from left to right:

1. It checks if the top-level object resource exists. If not, it creates it.
2. It moves to the next segment (aws_s3_bucket) and inserts it as a nested map inside resource.
3. It resolves the final leaf node (main) and assigns your value payload directly to it.

Because this evaluation happens dynamically in memory, you can safely write to any deep path without worrying about initializing empty parent blocks.

Dynamic Targets (via Interpolation)

The target path itself fully supports variable interpolation using the ${...} syntax. This allows you to namespace resources dynamically based on developer input or loop variables (item).

transform:
  # Stamping out a resource named exactly after the input service
  - target: resource.aws_instance.${input.service_name}
    value:
      ami: "ami-123456"

  # Using a loop variable to generate multiple unique resource keys
  - for_each: input.topics
    target: "resource.aws_sns_topic.${item}"
    value:
      name: ${item}

If you want to learn more about interpolation, visit the Interpolation section.

Handling Special Characters (Escaping Dots)

Terraform frequently utilizes dots or slashes inside property keys—especially when dealing with resource tags, Kubernetes labels, or AWS integration configurations (e.g., tags.kubernetes.io/cluster/main).

If you write a path like resource.aws_instance.web.tags.company.com, Watt TF will interpret it as a deeply nested structure: tags -> company -> com.

To enforce a literal dot inside a single path segment, wrap that specific segment in backticks (`) or double quotes (depending on your preference/engine version):

transform:
  # The backticks ensure "company.com" remains a single JSON key
  - target: resource.aws_instance.web.tags.`[company.com/managed-by](https://company.com/managed-by)`
    value: "Watt TF"
    
  # Useful for complex cloud annotations
  - target: resource.kubernetes_deployment.api.metadata.annotations.`cert-manager.io/cluster-issuer`
    value: "letsencrypt-prod"

The compiled output correctly preserves the dot-notation inside the key name:

{
  "resource": {
    "aws_instance": {
      "web": {
        "tags": {
          "[company.com/managed-by](https://company.com/managed-by)": "Watt TF"
        }
      }
    }
  }
}