Package aliases

[ericzbeard]

It would be nice if we could alias package imports.

What I do now:

amends "package://github.com/aws-cloudformation/rain/releases/download/v1.8.2-alpha1/cloudformation@1.8.2-alpha1#/template.pkl"
import "package://github.com/aws-cloudformation/rain/releases/download/v1.8.2-alpha1/cloudformation@1.8.2-alpha1#/aws/s3/bucket.pkl"

Description = "testing imports"
Resources {
    ["Foo"] = new {
        Type = "AWS::S3::Bucket"
    }
    ["Bar"] = new bucket.Bucket {
        BucketName = "my-bucket-name"
    }
}

What I would like to do:

use "package://github.com/aws-cloudformation/rain/releases/download/v1.8.2-alpha1/cloudformation@1.8.2-alpha1" as cfn

amends "cfn/template.pkl"
import "cfn/aws/s3/bucket.pkl"

or

amends cfn.template
import cfn.aws.s3.bucket

...

[bioball]

You can do this by declaring them as project dependencies. See docs here: https://pkl-lang.org/main/current/language-reference/index.html#project-dependencies

By the way: package URIs should only have the version once in their path, after the last @. This is because Pkl uses the base path to determine what the name of the package is. It then uses the package name to resolve dependencies.

If you are publishing packages as GitHub releases, a path you can take is:

1. Create a tag and release called <name>@<version> to hold the package assets
2. Use package://pkg.pkl-lang.org/github.com/<org>/<repo>/<name>@<version> as the package URI. This is a redirect server that redirects back to github.com.

For example, here's how we manage the releases for pkl-go: https://github.com/apple/pkl-go/releases. We create two GitHub releases for every release; one as the Go release, and one as the Pkl package release.

[ericzbeard]

I struggled with figuring out the right format for the PklProject file. I think I'm complicating the issue by releasing this package as a part of a larger repo, so it's not the only thing being released. See the assets in this release. Maybe it would be better to put this in a repo by itself, but it makes development a bit easier having it all together.

[ericzbeard]

And thank you, the code is much cleaner now!

amends "@cfn/template.pkl"
import "@cfn/aws/s3/bucket.pkl"

Description = "testing imports"
Resources {
    ["Foo"] = new {
        Type = "AWS::S3::Bucket"
    }
    ["Bar"] = new bucket.Bucket {
        BucketName = "my-bucket-name"
    }
}

[bioball]

Something else you can do here is to deploy these assets elsewhere, e.g. to an S3 bucket (and then maybe CNAME'd so the url is shorter). Pkl doesn't actually care where these packages come from, only that they are accessible via HTTPS.

Some notes about the PklProject:

• you can define the version in an external file if you'd like, and read it in. This lets you avoid doing some string replacing before you do your packaging.
• to help Pkl with stack traces, it's nice to provide sourceCode and sourceCodeUrlScheme.
• Typically, the package's name should be the last segment of the base uri.

amends "pkl:Project"

package {
  name = "cloudformation"
  baseUri = "package://example.com/\(name)"
  version = read("path/to/some/version.txt").text.trim()
  packageZipUrl = "https://github.com/aws-cloudformation/rain/releases/download/v\(version)/cloudformation@\(version).zip"
  sourceCode = "https://github.com/aws-cloudformation/rain"
  sourceCodeUrlScheme = "\(sourceCode)/blob/v\(version)/pkl%{path}#L%{line}-%{endLine}"
}