If you truly needs user-configurable setting, maybe TOML is for you.
That is…not remotely the holy grail. You’re really throwing out the baby with the bathwater on that one. User-configurable settings are important for many, many applications.
In the narrow case that you’re working on, say, a monorepo for closed-source code that only runs on your own servers, maybe in source code is fine provided there’s no host-level differences that would require a config file.
But for any other circumstance…yeah you need some type of configurability.
1. You hardcode settings in python using a multiline TOML string
2. Users may have multiple configs at the usual config folders
3. The configs override the hardcoded defaults wherever fields are present
4. Configs override each other in order of directories (when we are talking about xdg-directories) and within them in alphabetical order wherever fields are present
This allows you to have good defaults, override some fields at will and add something like 99-debug.toml that you can just rename to 99-debug.toml.invalid if you don't need it anymore. The module also provides an install/edit cli and functions for printing the final resulting config and which configs it read on the way to that final config. At some point I have to publish it.
If you need anything more than TOML because your use case is so crazy, then consider either writing a domain specific language or use a scripting language like lua, python, js, ...
Something like
server {
port = 8080
addr = "127.0.0.1"
development = true
}
db {
url = $DB_URL
user = "app"
password = include(".secrets/dbpass.txt")
}