What are the use cases for this?

Worried that we're over-engineering /etc/hosts.

@edolstra: The main point here is to improve on mergability of the options defined in networking.hosts, because right now if you want to distinguish between the canonical host name and aliases, you have to use mkBefore to force a particular canonical hostname.

So let's say you have the following definition:

{
  networking.hosts."1.2.3.4" = [ "foo" "bar" ];
}

This leads to the canonical hostname foo and the alias bar. Now let's say you want to set the canonical host name to xyz and still keep aliases defined somewhere else, you could do something like this:

{ lib, ... }: {
  networking.hosts."1.2.3.4" = lib.mkBefore [ "xyz" ];
}

Now we have 1.2.3.4 xyz foo bar, but we'd need to use mkOrder 400 if we want to have another canonical hostname. If we want to replace the canonical name it gets even worse and we can only mkForce the whole definition.

@volth: What exactly are you referring to?

Edit: Ah, didn't see your comment on the referenced PR. That's the reason why I've added coercedTo to the type, so that it's possible to still use the list form instead. Right now the coercion here is rather simplistic and always uses the first element of the list as the canonical hostname.

So if there is some interest in this PR, the idea would be to merge the list form into aliases if a canonical name is already defined.

Any update on this pull request?

@mmahut: Hm, I guess I won't pursue this further, hence closing.