Comment by newobj

if you get into a config system that's complicated enough, and has modularization or inheritance, you'll know that the semantics of "remove this" "add that", override this, default to this, this stuff is hard to express in most config languages, or worse, you start enforcing application level semantics. when you have turing complete language you just ... do those things. we reduced the configuration data of a tool suite once by 90%+ by moving from json to python. there was a tremendous amount of duplication and overlap, with tons of TINY exceptions and variations. it was so hard to see those differences, brittle to maintain, things would get stale, ... moving to python you basically had the "base" thing expressed in one file, and a bunch of tiny delta files encoding the exact deviations. All those deviations were of the forms I described above. Adding a thing to a list. Removing a thign from a list. Overriding a whole list. Do a thing if not already done. And so on. It's also then easy to build all kinds of diagnostics, validators, etc, right into the same framework, without having to munge the data into some other form first.