pkl

pkl

Pkl is a new configuration language created by Apple. It is capable of serializing to other formats like YAML, so it's possible to write a CloudFormation template with pkl.

https://pkl-lang.org/index.html

The following is a basic example of a pkl CloudFormation template.

AWSTemplateFormatVersion: String = "2010-09-09"
Description = "My template"
Parameters {
    ["Name"] {
        ["Type"] = "String"
    }
}
Resources {
    ["MyBucket"] {
        ["Type"] = "AWS::S3::Bucket"
        ["Properties"] {
            ["BucketName"] {
                ["Ref"] = "Name"
            }
        }
    }
}

Running pkl eval -f yaml on this file results in the following:

AWSTemplateFormatVersion: 2010-09-09
Description: My template
Parameters:
  Name:
    Type: String
Resources:
  MyBucket:
    Type: AWS::S3::Bucket
    Properties:
      BucketName:
        Ref: Name

In pkl it's possible to define type-safe configurations, which gives you syntax validation and IDE support. Rain can generate pkl classes based on the CloudFormation registry, and the repository hosts pkl modules that you can import into your own projects.

Here's an example of a file you could write using these modules:

(TODO: replace local paths with https URIs)

amends "modules/template.pkl"
import "modules/cloudformation.pkl" as cfn
import "modules/aws/s3/bucket.pkl" as bucket

Description = "Create a bucket"

Metadata { 
    ["Foo"] = "bar"
}

Parameters {
    ["Name"] {
        Type = "String"
        Default = "baz"
    }
}

Resources {
    ["TypedBucket"] = new bucket.Bucket {
        BucketName = cfn.Ref("Name")
    }
}