default.nix

{ config, lib, pkgs, ... }:

with lib;

let
  cfg = config.services.wal;

  servers = {
    nginx = import ./nginx.nix;
  };

  walOpts = { config, options, name, ... }: {
    options = {
      enable = mkOption {
        type = types.bool;
        default = true;
        description = ''
          Whether this config should be activated.
        '';
      };
      name = mkOption {
        type = types.str;
        description = ''
          Name (defaults to attr name).
        '';
      };
      config = mkOption {
        type = types.attrs;
        description = ''
          Config.
        '';
      };
      server = mkOption {
        type = types.enum [ "nginx" ];
        description = ''
          Web server type.
        '';
      };
      enableSSL = mkOption {
        type = types.bool;
        default = false;
        description = ''
          Whether to enable SSL for this Nginx server block.
        '';
      };
      sslCertificate = mkOption {
        type = types.path;
        default = null;
        description = ''
          Whether to set SSL certificate for this Nginx server block.
        '';
      };
      sslCertificateKey = mkOption {
        type = types.path;
        default = null;
        description = ''
          Whether to set SSL key for this Nginx server block.
        '';
      };
      listenAddress = mkOption {
        type = types.str;
        default = "localhost:80";
        description = ''
          Listen address.
        '';
      };
      listenPort = mkOption {
        type = types.str;
        default = "localhost:80";
        description = ''
          Listen port.
        '';
      };
      root = mkOption {
        type = types.str;
        example = "/var/lib/www";
        description = ''
          Root directory.
        '';
      };
      serverName = mkOption {
        type = types.str;
        default = "localhost";
        description = ''
          Domain name for the app.
        '';
      };
      extraConfig = mkOption {
        type = types.str;
        default = "";
        description = ''
          Extra configuration.
        '';
      };
      preStart = mkOption {
        type = types.str;
        default = "";
        description = ''
          Pre start script.
        '';
      };
      after = mkOption {
        type = types.listOf types.str;
        default = [];
        description = ''
          Run preStart after this services.
        '';
      };
    };
    config = {
      name = mkDefault name;
    };
  };

  mkWalConfig = server: options:
    ((servers.${server}) { inherit lib pkgs options; }).config;

  mapWalConfigs = set:
    (map (attr: mkWalConfig "nginx" set.${attr}) (attrNames set));
in {
  options = {
    services.wal = mkOption {
      description = "The web abstraction layer.";
      default = { };
      type = types.attrsOf (types.submodule walOpts);
    };
  };
  # this works
  config = mkIf (cfg != {}) (mkMerge [
    (mkWalConfig "nginx" cfg.owncloud7)
  ]);

  # this does not
  /*config = mkIf (cfg != {}) (mkMerge (mapWalConfigs cfg));*/
}

mysuperservice.nix

/*
I am working on a web server abstraction layer,
and since I have nix file for each server - like.. plugins.
Inside nginx.nix file I enable services.nginx ...

the default.nix basicaly looks like this (this is an example,
please bear with me):




after adding
  ./services/mysuperservice.nix to module-list.nix
and this to configuration.nix
  services = {
      mysuperservice.foo = { services.ntp.enable = true; };
  };
*/
{ config, lib, pkgs, ... }:

with lib;

let
  cfg = config.services.mysuperservice;
  mysuperserviceOpts = { config, options, name, ... }: {
    options = {
      configuration = mkOption {
        type = types.attrs;
        description = ''
          Activate this nixos configuration.
        '';
      };
    };
  };
in {
  options = {
    services.mysuperservice = mkOption {
      description = "The mysuperservice.";
      default = { };
      type = types.attrsOf (types.submodule mysuperserviceOpts);
    };
  };
  config = mkIf (cfg != {}) (
    mkMerge
      [
        { services.nginx.enable = true; }
      ] ++ (map (name: cfg.${name}.configuration) (attrNames cfg))
  );
}

/*
there is an error when I run this code...
and accessing `cfg.mysuperservice.foo` inside a mkMerge .. does not fail
it seems that I can not map through services.mysuperservice entries without infinite recursion

$ sudo nixos-rebuild switch --fast
building the system configuration...
error: while evaluating the attribute ‘config.system.build.toplevel’ at "/home/matej/workarea/nixpkgs/nixos/lib/eval-config.nix":26:5:
while evaluating the attribute ‘config’ at "/home/matej/workarea/nixpkgs/lib/modules.nix":38:25:
while evaluating ‘yieldConfig’ at "/home/matej/workarea/nixpkgs/lib/modules.nix":25:29, called from "/home/matej/workarea/nixpkgs/lib/modules.nix":24:16:
while evaluating the attribute ‘environment.checkConfigurationOptions.value’ at "/home/matej/workarea/nixpkgs/lib/modules.nix":206:9:
while evaluating the option `environment.checkConfigurationOptions':
while evaluating ‘id’ at "/home/matej/workarea/nixpkgs/lib/trivial.nix":9:8, called from "/home/matej/workarea/nixpkgs/lib/modules.nix":204:15:
while evaluating ‘fold’ at "/home/matej/workarea/nixpkgs/lib/lists.nix":20:19, called from "/home/matej/workarea/nixpkgs/lib/modules.nix":187:12:
while evaluating ‘fold'’ at "/home/matej/workarea/nixpkgs/lib/lists.nix":23:15, called from "/home/matej/workarea/nixpkgs/lib/lists.nix":27:8:
while evaluating ‘filterOverrides’ at "/home/matej/workarea/nixpkgs/lib/modules.nix":277:21, called from "/home/matej/workarea/nixpkgs/lib/modules.nix":182:20:
while evaluating ‘concatMap’ at "/home/matej/workarea/nixpkgs/lib/lists.nix":54:18, called from "/home/matej/workarea/nixpkgs/lib/modules.nix":284:8:
while evaluating ‘concatMap’ at "/home/matej/workarea/nixpkgs/lib/lists.nix":54:18, called from "/home/matej/workarea/nixpkgs/lib/modules.nix":110:20:
while evaluating ‘concatMap’ at "/home/matej/workarea/nixpkgs/lib/lists.nix":54:18, called from "/home/matej/workarea/nixpkgs/lib/modules.nix":86:8:
while evaluating anonymous function at "/home/matej/workarea/nixpkgs/lib/modules.nix":86:19, called from undefined position:
while evaluating ‘pushDownProperties’ at "/home/matej/workarea/nixpkgs/lib/modules.nix":227:24, called from "/home/matej/workarea/nixpkgs/lib/modules.nix":86:75:
while evaluating ‘pushDownProperties’ at "/home/matej/workarea/nixpkgs/lib/modules.nix":227:24, called from "/home/matej/workarea/nixpkgs/lib/modules.nix":231:52:
while evaluating the attribute ‘content’ at "/home/matej/workarea/nixpkgs/lib/modules.nix":324:14:
while evaluating ‘yieldConfig’ at "/home/matej/workarea/nixpkgs/lib/modules.nix":25:29, called from "/home/matej/workarea/nixpkgs/lib/modules.nix":24:16:
while evaluating the attribute ‘environment.checkConfigurationOptions.value’ at "/home/matej/workarea/nixpkgs/lib/modules.nix":206:9:
infinite recursion encountered
*/