This helps with troubleshooting exceptions in config values, which were hard
to track down for options with many definitions.
The trace will look like:
error: while evaluating the attribute 'config.foo' at undefined position:
[...]
while evaluating the option `foo':
[...]
while evaluating definitions from `/home/user/mymod.nix':
while evaluating 'dischargeProperties' at /home/user/nixpkgs/lib/modules.nix:464:25, called from /home/user/nixpkgs/lib/modules.nix:392:137:
while evaluating the attribute 'value' at /home/user/nixpkgs/lib/modules.nix:277:44:
Value error!
where the `/home/user/mymod.nix` module is
{ lib, ... }: {
options.foo = lib.mkOption {
type = lib.types.lines;
};
config.foo = builtins.throw "Value error!";
}
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