> With homebrew, you can have Brewfile that can serve as declarative source of truth.

for homebrew, while Nix configuration is for everything. I never used a Brewfile before, so looked at https://github.com/Lissy93/Brewfile/blob/master/Brewfile but it just looks like a list of packages. What about the configuration for those packages? Or your own custom patches for them? Runtime parameters? Environment variables?

There is so much more going on in the typical developer environment that it doesn't seem like (to me, an uneducated fool) Brewfile would be enough to actually serve as a declarative source of truth, except for Homebrew-specific things.

Versions? Compatibilities? Just pulling latest doesn't cut it.