masp / cfnpkl

Write Cloud Formation templates using the Pkl configuration language

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://github.com/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.