skylark VS libyaml

My stance is that YAML is a good format for configuration management and generation -- it's wonderful at filling gaps as your deployment model increases in complexity to provide a mechanism to "render" your configuration -- much like Skylark [1] does (derived from Google's internal GCL).

YAML ends up being a powerfully declarative model [2] for the state of a data structure, rather than a straight representation, ironically often enough being used in turn for an imperative model like in Ansible [3]. Definitely friendlier than JSON. But personally, I really like YAML because it lets me compose using a traits/mixins-like model using & and , which allows for verbose, structured configuration inputs but concise configuration files.

docker-compose YAML files extension fields [4], imo, are a great example of this type of model in action. When you leave this much pre-deserialization flexibility in your configuration representation, it makes building cool stuff like docker-compose ECS support x-aws- extension keys [5] and other plugin system-type capabilities much more straightforward than, for example, adding a new language feature to HCL.

[1]: https://github.com/google/skylark

Currently, my main concern with YAML is that, by the spec, comments are not attached to a particular node (see https://yaml.org/spec/1.2/spec.html#id2767100). As a result, a lot of YAML parsers (like https://github.com/yaml/libyaml and https://github.com/chyh1990/yaml-rust) only filter out the comments during the parsing phase. This makes it less than ideal for a use-case where the configuration file is expected to be modified by both programs and humans.

TOML makes it more trivial to associate comments with a node. This is mainly because the language is simpler though, as the spec is not explicit about that (https://github.com/chyh1990/yaml-rust).