We use (abuse, arguably) the nixos module system for typechecking. Un
the plus side, it gives us documentation of the options and their
expected types. On the downside, the error message doesn't tell us
the file in which the error was encountered.
(This is subject to change, if I can find a better way)
The objective here is that services which depend on global config
(e.g. kernel config or busybox options or static paths in the
filesystem) now live under config.system.service, and are added
to that collection by the module that defines the necessary state.
This is a first step: the services will be configured by a typechecked
attr set instead of the arbitrary arguments that
pkgs.liminix.networking.pppoe accepts
New rules: everything under "config" that isn't actually configuration
(e.g. build products) will in future live in config.system. This is
the first step.
Runs fennel using a Lua compiled with the same options as the
host system, and with packages set up so it can find all the local
Lua packages
To shorten the dev feedback loop further, allows FENNEL_PATH to be set
on the command line so you can point directly it at the Fennel sources
for some library you're working against instead of having to run
nix-build and compile them to Lua
Previously: the service wrote a timestamp and the receiver
read and parsed it to see if there was new data
Now: the service writes and removes a .lock file to prevent
the receiver reading partial data. The receiver is responsible
for remembering the *previous* state and only updating if it's changed
