Pkl

Pkl is a typed configuration and data language by Apple. From Pkl's User Manual:

What Pkl is for

Pkl allows developers to express structured configurations in a concise and typed dialect (that's Pkl), which can be rendered into things like JSON, YAML, TOML, and more.

Pkl can also generate code in various languages to interface with these definitions.

Why Elide supports Pkl

Have you ever gotten totally lost writing Kubernetes YAMLs, or perhaps been forced to push to GitHub repeatedly until your CI jobs stop choking on syntax?

Pkl is an end-to-end answer for this problem, and many others. By allowing developers to express data models, or even actual data, in a typed and concise meta-format, JSON and other formats become checkable, interchangeable, formattable, and gain many other desirable attributes.

Usage

Elide integrates with Pkl in several ways:

Command-line Pkl

The entirety of Pkl's command line is embedded and supported within Elide; you can find it at elide pkl:

Usage: elide pkl [OPTIONS] COMMAND [ARGS]...

Options:
  -v, --version  Show the version and exit
  -h, --help     Show this message and exit

Commands:
  eval              Render pkl module(s)
  repl              Start a REPL session
  test              Run tests within the given module(s)
  project           Run commands related to projects
  download-package  Download package(s)
  analyze           Commands related to static analysis

For example, to render Pkl's own CircleCI configuration into YAML:

> elide pkl eval ./pkl/.circleci/config.pkl | head -n4

# Generated from CircleCI.pkl. DO NOT EDIT.
version: '2.1'
orbs:
  pr-approval: apple/pr-approval@0.1.0

Last modified: 15 March 2025