Configuration

The Watt TF blueprint file (typically blueprint.yaml) is the core definition of your infrastructure transformations. It follows a declarative structure that maps input data to Terraform resources.

Top Level Structure

Key	Type	Description
variables	map	A map of variables for use in interpolations and CEL expressions
plugins	array	A list of external plugins to hook into the transformation lifecycle.
transform	array	The sequence of transformation rules applied to your resources.
include	array	A list of other blueprint files to include and process as part of this blueprint.

The transform Block

Key	Type	Description
target	string	The path where the value will be placed (e.g., resource.aws_s3_bucket.main).
value	any	The payload or configuration data to set at the target.
if	string	An optional CEL expression that determines if this block should execute.
for_each	string	An optional CEL expression that iterates over a collection.

The plugins Block

Key	Type	Description
name	string	A unique identifier for the plugin.
version	string	The version string of the plugin.
on	string	The lifecycle event: beforeTransform or afterTransform.
cmd	string	The base command to execute (e.g., python, node, ./script.sh).
args	array	A list of arguments passed to the command (e.g., ["plugin.py"]).

Example Blueprint

plugins:
  - name: my-custom-plugin
    version: 1.0.0
    on: beforeTransform
    cmd: python
    args: ["plugin.py"]

include:
  - "another-blueprint.yaml"

transform:
  # Example of conditional resource creation
  - if: input.environment == "prod"
    target: resource.aws_instance.web
    value:
      instance_type: "t3.large"
      monitoring: true

  # Example of loop-based resource creation
  - for_each: input.subnets
    target: resource.aws_subnet.${item.name}
    value:
      cidr_block: "${item.cidr}"

You can find the full JSON schema for the blueprint configuration here: Blueprint Schema.

In case you want to learn more about the key concepts of Watt TF, check out the Core Concepts guide.