It’s a deterministic subset of Python. This means that if you have complex or repetitive configurations, you can use loops and functions to structure them. But it’s impossible to write an infinite loop or recursion.
As a sysadmin, YAML seems nice until you have actually done anything more advanced with it. See Julien Pivotto's presentation about some of its pitfalls: https://www.slideshare.net/roidelapluie/yaml-magic?next_slid... Btw. Jsonnet doesn't seem too bad either: https://www.youtube.com/watch?v=LiQnSZ4SOnw and here some examples: https://jsonnet.org/ but in my book, EDN still wins.
Or if you really must, then simply interrupt processes that loop infinitely, and fix the bugs that caused it.
You know, like you already do when you have an infinite loop.
Infinite loops are not the end of the world, you know. Processes can be interrupted, and computers have reset buttons.
It's still resources to detect loops, it often involves introspection or privileged views; it's simply easier to prevent loops.
The underlying conundrum is:
- systems need to be configured,
- human-readability is obviously necessary at some level,
- configuration is often very "compressible" (needs loops, needs variables to be maintainable), but
- system-writers don't know the structure of your data, the axes on which you'd want to compress things, the best abstractions for you.
Templating languages are an obvious direction, but they're uniformly bad. If they have limited expressiveness you'll run into the limits. Maybe there are templating languages with good unit testing frameworks, but I haven't seen them. "Look at the expanded diff" doesn't scale. And generating gobs of human-readable "data" (in a format that supports comments!) is very wasteful.
If it has first-class functions, how can you avoid infinite recursion? Like, what stops me from running the omega combinator in it? This is why Meson (a similar language) does not allow those kinds of shenanigans, to keep the language non-Turing-complete.
It's a cool idea to do configuration in a subset of Python but now you have to go implement that subset in every language.
I will look into this further.
Starlark is indeed deterministic and guaranteed to terminate (the Go implementation has a flag that allows recursion, but it's off by default), but these are two orthogonal properties.