Add dag library to config.lib

[rycee]

Also replace all imports of dag.nix by the entry in config.lib.

[infinisil]

I think we could use this opportunity to make it possible to add more general purpose functions to the library. Adding a lib/default.nix with

{ lib }: {
  dag = import ./dag { inherit lib; };
  ...
}

Then config.lib = import ./lib { inherit lib; }; (or config.lib.home = ...)

This also calls for a DAG library refactor, such that you can use config.lib.dag.entryAfter instead of config.lib.dag.dagEntryAfter, etc.

[rycee]

Yeah, I was thinking about the function renaming. Unfortunately it would break the configuration of anybody who uses the dag functions directly.

I'm now thinking the config.lib.dag entries actually should be different from the dag.nix file. I.e., to have config.lib.dag = { …; entryAfter = dagEntryAfter; … }; etc. The old dag.nix could be deprecated and removed in the future.

Also agree on the use of lib/default.nix.

[infinisil]

Good idea regarding the slow deprecation

[rycee]

Force-pushed updated code.

[infinisil]

Apparently it also works to just use actual modules, for some reason I don't get recursion when I do this: infinisil@efc486b

This also enables having the file-types.nix in config.lib and seems generally nicer

[rycee]

Hmm, when I switch

with config.lib;
with lib;

to

with lib;
with config.lib;

e.g. in systemd.nix I get

error: infinite recursion encountered, at /home/rycee/devel/nixpkgs-17.09/lib/modules.nix:62:71

with or without your changes. I tried to track this down but unfortunately couldn't find the cause.

[rycee]

Replaced all use of with config.lib to instead explicitly bind dag = config.lib.dag in the let. This seems to resolve all recursion problems.