The CFG configuration format is a text format for configuration files which is similar to, and a superset of, the JSON format. It's not new - it dates from well before its first announcement in 2008 - and has the following aims:

* Allow a hierarchical configuration scheme with support for key-value mappings and lists.

* Support cross-references between one part of the configuration and another.

* Provide a string interpolation facility to easily build up configuration values from other configuration values.

* Provide the ability to compose configurations (using include and merge facilities).

* Provide the ability to access real application objects safely, where supported by the platform.

* Be completely declarative.

It's similar to newer formats such as JSON5, HJSON, HOCON and similar but offers a number of features [0] which they don't, as indicated by the above list. It's not intended to occupy the niche where you find things like Cue, Jsonnet, Dhall and similar.

It was just never especially publicised when first implemented for use in Python projects, but it now also has implementations for the JVM, .NET, Go, Rust, D, JavaScript [1], Ruby and Elixir (all BSD-3-Clause licensed) and it would be great to get feedback on the project from the HN community.

[0]: https://docs.red-dove.com/cfg/intro.html - description of features and comparison with other similar systems

[1]: https://docs.red-dove.com/cfg/playground.html - uses the JS implementation to create an interactive playground