cfnpkl

cfnpkl is bindings for the Pkl language to generate CloudFormation templates instead of using JSON or YAML. Pkl provides features like:

• Type safety
• Code completion
• Support for reusing templates
• Defining functions for transforming templates
• Modeling inputs to templates instead of the clunk Ref syntax

Getting Started

Prerequisites

• Install Pkl

Create an S3 bucket template

PklProject

dependencies {
  ["cfn"] { uri = "package:/masp/cfnpkl" }
}

mybucket.pkl

import "@cfn/aws/s3/Bucket.pkl"

Resources {
    ["Bucket"] = new Bucket {
        Properties {
            BucketName = "mybucket"
            AccelerateConfiguration {
                AccelerationStatus = "Enabled"
            }
        }
    }
}

Running pkl eval mybucket.pkl -f json will generate the following CloudFormation template:

{
  "Resources": {
    "Bucket": {
      "Type": "AWS::S3::Bucket",
      "Properties": {
        "BucketName": "mybucket",
        "AccelerateConfiguration": {
          "AccelerationStatus": "Enabled"
        }
      }
    }
  }
}

You can also generate the output in YAML:

Resources:
  Bucket:
    Type: AWS::S3::Bucket
    Properties:
      BucketName: mybucket
      AccelerateConfiguration:
        AccelerationStatus: Enabled

cfnpkl can warn you ahead of time if there's a typo in a property name or if you're missing a required property:

test.pkl

Resources {
    ["Bucket"] = new Bucket {
        Properties {
            BucketName = "mybucket"
            AccelerateConfiguration {
                AccelerationStatus = "Enable" // ERROR: only "Enabled" or "Disabled" allowed!
            }
        }
    }
}

Output

> pkl eval -f json examples/bucket.pkl
–– Pkl Error ––
Expected value of type `"Enabled"|"Suspended"`, but got `"Enable"`.

65 | AccelerationStatus: "Enabled" | "Suspended"
                         ^^^^^^^^^^^^^^^^^^^^^^^

TODO

• Add support for all standard AWS resource providers. See AWS Resource Types
• Add support for inputs to templates and calculated values
• Add examples of reusable templates
• Add automated testing to verify all generated templates are correct and produce valid CloudFormation templates.