nixos/nixos-option: fix evaluator to render a full submodule entry

When running e.g. `nixos-option users.users.ma27`, the evaluation breaks
since `ma27` is the attribute name in `attrsOf (submodule {})`, but not
a part of the option tree and therefore breaks with the following
errors:

```
error: At 'ma27' in path 'users.users.ma27': Attribute not found
An error occurred while looking for attribute names. Are you sure that 'users.users.ma27' exists?
```

This happens since the option evaluator expects that either the option
exists or the option is a submodule and the "next" token in the
attribute path points to an option (e.g. `users.users.ma27.createHome`).

This patch checks in the `Attribute not found` condition if the attribute-path
actually exists in the config tree. If that's true, a dummy-attrset is created
which contains `{_type = "__nixos-option-submodule-attr";}`, in that case, the
entire entry of the submodule will be displayed.

0 files changed, 0 insertions, 0 deletions