I've increasingly found myself drawn to writing declarations as programs, not as config in any plain textual format. Whether it's going all the way in the dire

I've increasingly found myself drawn to writing declarations as programs, not as config in any plain textual format. Whether it's going all the way in the direction of supporting general purpose languages like Pulumi does, or with a niche but still Turing-complete language like Nix's expression language, or even Dhall, which other commentators have mentioned. That isn't to say there is no place for simple, human readable schema. I think these tools need a fallback to something simpler. Nothing these tools do couldn't be emulated by manual processes of hand-writing complex makefiles or YAML or whatever, but what is striking to me is the use of general purpose languages, usually with tooling to do type-checking and IDE assistance to writing these things, which lowers the barrier to entry and empowers someone who "just knows (Python|JavaScript|Go|...)" to contribute in a familiar environment. A couple more examples: Envoy: I have had the displeasure, recently, of writing by-hand a configuration for the Envoy load balancer. Envoy uses a "typed config language", which is often represented as YAML or JSON, but it's very painful to write by hand. On the other hand, if you have the protocol buffers/gRPC schema available in code, it's vastly less painful to use any programming language to build the typed objects and then export to plain text. The xDS protocol is designed for being interacted with via programs, not plaintext. GitLab CI: GitLab supports writing a program, which runs as part of the CI/CD job, to generate the configuration for a subsequent pipeline. This makes writing complex jobs, or repetitive monorepo tasks much simpler. A 10 line Python program that effectively does "for each folder in `python`, emit this block of YAML" is incredibly powerful. That last example is salient to me: markup languages are really easy to parse, but challenging to read when they're dynamic. Wouldn't it be nice to be able to mix and match? YAML/JSON where it makes sense and the intent and meaning is self-evident, and to write code where you need dynamism? Full disclosure: I work for Pulumi, opinions are my own, etc.