eldc

eldc (Emacs Lisp Dictionary Converter) converts Emacs Lisp data files into structured formats. Write a configuration as an alist or plist, run M-x eldc-json or M-x eldc-yaml, and the package writes a standard JSON or YAML file beside the source. It is meant for configuration that is easier to express in Lisp: package manifests, CI workflows, and other structured data.

Dynamic configuration§

The last s-expression in the file is evaluated before conversion, so output can include computed values, timestamps, environment variables, and anything else Emacs Lisp can produce. This is the point of keeping configuration in Lisp rather than editing JSON or YAML by hand.

How it works§

JSON conversion uses Emacs' built-in json-encode, so it needs no external tooling. YAML is produced by passing that JSON through eldc-j2y, a small Rust converter built on serde. JSON is always the first step, which keeps the architecture open to other formats using the same approach.

Usage§

Write the data in an .el file:

'(:name "my-app"
  :version "1.0.0"
  :dependencies (:react "^18.2.0"
                 :vite "^4.3.0"))

Then run M-x eldc-json to write my-app.json, or M-x eldc-yaml to write my-app.yaml.

Plists are recommended for nested objects, and vectors make arrays explicit. The native encoder follows Emacs' JSON conventions: t becomes true, :json-false becomes false, and nil becomes null.

Installation§

eldc is available on MELPA:

M-x package-install RET eldc RET

It requires Emacs 25.1 or newer and the deferred package. YAML conversion also needs eldc-j2y: run M-x eldc-download-binary to fetch a prebuilt release, or install it from source with cargo install --git https://github.com/gicrisf/eldc eldc-j2y.

Hooks§

Before- and after-export hooks for both formats make it possible to validate data, format the output, or commit generated files. The before hooks receive the data and output path; the after hooks receive the output path.

License§

eldc is licensed under GPL-3.0-or-later. See the license.