This fixes an unnecessary evaluation dependency that prevented the
custom and much appreciated primaryUser error from popping up.
Specifically:
… while evaluating the option `system.build':
… while evaluating definitions from `/nix/store/lc6n4bhxj9255kzfn9pnpx65583a8cgc-source/modules/environment':
… while evaluating definitions from `/nix/store/lc6n4bhxj9255kzfn9pnpx65583a8cgc-source/modules/nix':
… while evaluating the option `environment.darwinConfig':
… while evaluating the option `system.primaryUserHome':
error: expected a string but found null: null
at /nix/store/lc6n4bhxj9255kzfn9pnpx65583a8cgc-source/modules/system/primary-user.nix:26:30:
25| default =
26| config.users.users.${config.system.primaryUser}.home or "/Users/${config.system.primaryUser}";
| ^
27| };
While it did have some indication as to the cause, it lets the good
error message go to waste.
**Context**
`lazyAttrsOf` is the better choice when you use an attrset as individual
variables instead of in aggregate (e.g. `attrNames`, `toJSON`).
The reason is that an expression like `a.b` is strict in `a`, which
entails the evaluating the _whole_ set of attribute _names_ in `a`.
In the `attrsOf` this means evaluating all `mkIf` conditions, which
in turn also means evaluating all the regular definitions to the
smallest degree (WHNF) to determine that they're not `mkIf`s.
`lazyAttrsOf` simply assumes that all attributes aren't `mkIf false`,
and throws an error in the attribute value if necessary.
This would be a problem with `toJSON` and such, but is completely
fine when the attributes are treated as variables of a lazy program,
as is the case here.
**NixOS**
NixOS made `system.build` a submodule with a `freeformType`, allowing
the things inside of it to be declared, and for them to have niceties
like documentation and merging behavior.
nix-darwin could probably adopt this.
acf6b46011