Speaking personally, there are essentially two distinct reasons I like having programmable config languages:

- For personal application config (window manager, shell, text editor, etc), I find I often want to have site-specific configuration, but I also want identical configuration files at every workstation. My laptop probably needs slightly different keybindings than my desktop, my $PATH and text editor needs to be configured a bit differently for work than for personal use, etc. When the configuration is done with a real programming language, this is always straightforward, when it's done via a json/yml/toml file, it's usually a huge pain in the ass.

- You want templating for your configuration, to improve readability, reduce typos and configuration drift, &c, but if you give programmers an inch with any sort of templating system, they will eventually take a mile and figure out how to smuggle Turing-completeness (or, at least, for-loops and variable binding and probably closures) into their configs. If you have a real programming language, this is fine, because the programming language was designed to make loops and conditionals and function calls readable, and probably has decent tooling to boot, but if they're doing it with, say, Mustache-templated YAML, you will have an unreadable mess that is extremely unpleasant to work with.

Lua was specifically designed to be a configuration language https://www.lua.org/history.html

Lots of people start out with a non-programmable config format. But, as their situation becomes more complicated, they end up shoehorning in programmable-ish features until they realize they are running straight into https://en.wikipedia.org/wiki/Greenspun%27s_tenth_rule and decide to do it properly.

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.

If you look at hyprland config, you can see why they went with it.

Much like vim/neovim config, people want to do things like register a callback that fires to determine the window title and things that are much more advanced than that, like layout management.

When I was using sway, I was using its IPC or worse (https://github.com/johnae/persway) to do advanced things, and Lua scripting in the first class config would have been a much better UX.

All these window managers have a Turing complete configuration language, because you need to do things in response to events (keyboard hotkeys etc). It's just that for most of them, the "Turing completeness" happens through passing around strings with shell snippets. Might as well be a Lua callback function.

I have switched from FVWM to awesome because of Lua. Many years later, I have switched to i3 because it's not using a programming language for configuration. It's fine to have a configuration language if you have time to maintain, but your configuration can become quite complex and difficult to evolve. And it is also far more subject to breakage when upgrading.

I think I've found balance by using a Python daemon as a "companion" for my i3 configuration. It listens and react to event. It enhances the configuration, so when it's broken, it's not a big deal. And the interface exposed by i3 is smaller, so less risk of breakage. https://vincent.bernat.ch/en/blog/2021-i3-window-manager#i3-...

Half of me agrees with you. As someone who used to tinker with neovim all day I've had to learn just because you can program the problem doesn't mean you should and stick to a relatively minimal config.

Still, its a valid design choice with different design decisions compared to sway. But that's the point you get to choose.

Hyprland is much more "build your workspace with legos" so having a full lang like lua makes sense to properly integrate the various pieces.

Hyprland config break is usually syntax changes or reallocated features. Never had an instance where hyprland broke beyond repair or was hard to fix, even before LLMs were a thing. But yeah, its a 0.x software so if you aren't keen on fixing small stuff it's better to wait indeed. My point is that hyprland is easy to fix.

there is a converter: https://eiontusk.github.io/hyprlang2lua/

I don't dislike it but I do think it's interesting that a number of minimalist WMs seem to have converged on the idea of code as config. I have used AwesomeWM for years and love its Lua configuration for providing infinite flexibility. When I was recently looking for something like AwesomeWM but in Wayland I toyed with the idea of moving to something with a simpler config format (and Hyprland was one of the options I considered). I can see the benefit of the simplicity but I guess for the kinds of users that use these WMs, maximum configurability probably trumps everything else. (Currently I am using SomeWM which is just an attempt to get something as close as possible to AwesomeWM in Wayland.)

Personally I have grown a bit frustrated with Lua as a language, but at the same time can see why it would be a good choice for this use case.

I have to agree. There are things that I want to do with my sway scratchpad that are just not possible because the config vocab is so limited. I might port my config to hyprland and give it a shot.

It is good to keep a configuration simple enough that it doesn't need to be a programming language.

The absolute moment you find yourself thinking of putting conditional logic, or string substitution, or anything like that, in your pure config format, switch to a real programming language, before you end up managing several times the complexity of one with only some of the benefits. No need to end up contemplating some sort of for-loop macro with another key referencing the loop variable, when you can just have a for loop.

I find TOML, in addition to being very readable, to be great at automatically restricting config complexity by making nested lists of tables miserable. If your config sucks at being TOML, it should be JS or Python. (Not a fan of Lua.)

So you don't like using programming languages as config languages, so you:

1. Use a declarative-style format for config, which is fine, I guess; 2. ... and when that inevitably fails, you... use a programming language?

Some people -- not all, but some -- may prefer to skip the first step and go straight for the second option. Particularly if it's a complex thing indeed like a build system and not, y'know, configuring your blog.

I think the problem is with people downloading perfect configs from other people, I put the time to make my own, not overly complicated, basic window rules, nothing fancy. And it just werks, haven't changed it for 4 months (outside of rewriting it in lua, which took 30min and was quite fun).

My first hyprland experience was with ML4W (nothing against the guy) but as soon as you download it you get 10 config errors and you don't know where to begin. I took the same philosophy as arch, I install only what I understand, and this way my config grew over time, my games where spawning in 2nd monitor? I look up manual and fix it, etc..

python is terrible for embedding, starlark is the way to go. Very easy to embed.

The theoretical difference in power between a non-Turing complete declarative language and a turing complete one is irrelevant in practice. Datalog is an decidable, declarative subset of Turing-complete Prolog. It's also EXPTIME complete. I don't think we exclude any real use cases by prohibiting super-exponential algorithms.

The problem is shitty config languages. I wouldn't group xaml in the same category as dhall for example.

It was my own config, I just felt annoying because a fundamental part of my system didn't work. I end upf fixing it later but it was veryannoying