Pkl¶

Pkl is a configuration language from Apple. cfnrain can read templates written in Pkl, and can write templates as Pkl.

Requirements¶

cfnrain runs Pkl through the pkl command line tool. Install it from the Pkl website and make sure that it is on your PATH.

Read Pkl templates¶

pkg, deploy and fmt accept a file with the .pkl extension. cfnrain evaluates it to YAML first, and then works with the YAML.

cfnrain fmt template.pkl
cfnrain deploy template.pkl my-stack

diff, merge and tree do not read Pkl files. Run cfnrain fmt template.pkl > template.yaml first.

A Pkl template that uses the cloudformation-pkl package:

amends "package://github.com/aws-cloudformation/cloudformation-pkl/releases/download/cloudformation@0.1.1/cloudformation@0.1.1#/template.pkl"
import "package://github.com/aws-cloudformation/cloudformation-pkl/releases/download/cloudformation@0.1.1/cloudformation@0.1.1#/cloudformation.pkl" as cfn
import "package://github.com/aws-cloudformation/cloudformation-pkl/releases/download/cloudformation@0.1.1/cloudformation@0.1.1#/aws/s3/bucket.pkl" as bucket

Description = "Create a bucket"

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

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

The cloudformation-pkl package is an AWS project. cfnrain does not maintain it.

Write Pkl¶

cfnrain fmt -p converts a YAML or JSON template to Pkl:

cfnrain fmt -p template.yaml > template.pkl

--pkl-basic and --pkl-package change the Pkl output. See fmt.

cfnrain build --pkl-class <type> writes a Pkl class for a resource type.

A full example is in test/webapp, in webapp.pkl.